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  • The lipid composition affects Trastuzumab adsorption at monolayers at the air-water interface
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2020-01-15
    Andrei Sakai; Ana Paula de Sousa Mesquista; Helena B. Nader; Carla Cristina Lopes; Waka Nakanishi; Katsuhiko Ariga; Luciano Caseli
    更新日期:2020-01-15
  • Effect of ergosterol on the interlamellar spacing of deuterated yeast phospholipid multilayers
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2020-01-09
    Alessandra Luchini; Robin Delhom; Viviana Cristiglio; Wolfgang Knecht; Hanna Wacklin-Knecht; Giovanna Fragneto
    更新日期:2020-01-09
  • 更新日期:2020-01-09
  • Effect of the fluorination degree of partially fluorinated octyl-phosphocholine surfactants on their interfacial properties and interactions with purple membrane as a membrane protein model
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2020-01-07
    Teruhiko Baba; Toshiyuki Takagi; Kimio Sumaru; Toshiyuki Kanamori

    Interfacial properties and membrane protein solubilization activity of a series of partially fluorinated octyl-phosphocholine (PC) surfactants were investigated from the viewpoint of the fluorination degree of the hydrophobic chain. The critical micelle concentration (CMC), surface tension lowering activity, molecular occupied area at the CMC and free energy changes of micellization as well as adsorption to the air-water interface for each PC surfactant were estimated from surface tension measurements at 25 °C. The PCs with higher degree of fluorination exhibited low CMC and high surface activity, while the single trifluoromethyl group at the end of the chain appeared to enhance the hydrophilicity of the surfactant molecule. Under conditions where conventional short-chain surfactants, n-octyl-β-glucoside, Triton X-100 and dioctanoylphosphatidylcholine significantly solubilize purple membranes (PM), none of the fluorinated-PCs solubilized PM. This suggests that fluorinated-PCs are low-invasive enough to maintain the structure of lipids/protein assemblies like PM.

    更新日期:2020-01-07
  • Antibacterial effect of indene on Helicobacter pylori correlates with specific interaction between its compound and dimyristoyl-phosphatidylethanolamine
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2020-01-07
    Kiyofumi Wanibuchi; Motoki Takezawa; Kouichi Hosoda; Avarzed Amgalanbaatar; Kentaro Tajiri; Yuki Koizumi; Sakura Niitsu; Hisashi Masui; Yuki Sakai; Mitsuru Shoji; Takashi Takahashi; Yoshikazu Hirai; Hirofumi Shimomura
    更新日期:2020-01-07
  • Role of Cholesterol-mediated Effects in GPCR Heterodimers
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-12-19
    Xavier Prasanna; Madhura Mohole; Amitabha Chattopadhyay; Durba Sengupta

    G protein-coupled receptors (GPCRs) are transmembrane receptors that mediate a large number of cellular responses. The organization of GPCRs into dimers and higher-order oligomers is known to allow a larger repertoire of downstream signaling events. In this context, a crosstalk between the adenosine and dopamine receptors has been reported, indicating the presence of heterodimers that are functionally relevant. In this paper, we explored the effect of membrane cholesterol on the adenosine2A (A2A) and dopamine D3 (D3) receptors using coarse-grain molecular dynamics simulations. We analyzed cholesterol interaction sites on the A2A receptor and were able to reproduce the sites indicated by crystallography and previous atomistic simulations. We predict novel cholesterol interaction sites on the D3 receptor that could be important in the reported cholesterol sensitivity in receptor function. Further, we analyzed the formation of heterodimers between the two receptors. Our results suggest that membrane cholesterol modulates the relative population of several co-existing heterodimer conformations. Both direct receptor-cholesterol interaction and indirect membrane effects contribute toward the modulation of heterodimer conformations. These results constitute one of the first examples of modulation of GPCR hetero-dimerization by membrane cholesterol, and could prove to be useful in designing better therapeutic strategies.

    更新日期:2019-12-19
  • Ferrihydrite nanoparticles interaction with model lipid membranes
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-12-11
    Claudia G. Chilom, Bogdan Zorilă, Mihaela Bacalum, Maria Bălăşoiu, Roman Yaroslavtsev, Sergey V. Stolyar, Sergey Tyutyunnicov

    In recent years was observed an increased interest towards the use of metal nanoparticles for various biomedical applications, such as therapeutics, delivery systems or imaging. As biological membranes are the first structures with which the nanoparticles interact, it is necessary to understand better the mechanisms governing these interactions. In the present paper we aim to characterize the effect of three different ferrihydrite nanoparticles (simple or doped with cooper or cobalt) on the fluidity of model lipid membranes. First we evaluated the physicochemical properties of the nanoparticles: size and composition. Secondly, their effect on lipid membranes was also evaluated using Laurdan, TMA-DPH and DPH fluorescence. Our results can help better understand the mechanisms involved in nanoparticles and membrane interactions.

    更新日期:2019-12-11
  • Differential Sensitivity of pHLIP to Ester and Ether Lipids
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-12-10
    Bhagyashree D. Rao, Hirak Chakraborty, Arunima Chaudhuri, Amitabha Chattopadhyay
    更新日期:2019-12-11
  • NEW 20-HYDROXYCHOLESTEROL-LIKE COMPOUNDS WITH FLUORESCENT NBD OR ALKYNE LABELS: SYNTHESIS, IN SILICO INTERACTIONS WITH PROTEINS AND UPTAKE BY YEAST CELLS
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-12-10
    Yaroslav V. Faletrov, Vera S. Efimova, Matvey S. Horetski, Kristina V. Tugaeva, Nina S. Frolova, Quingquing Lin, Ludmila V. Isaeva, Michael A. Rubtsov, Nikolai N. Sluchanko, Ludmila A. Novikova, Vladimir M. Shkumatov

    20-hydroxycholesterol is a signaling oxysterol with immunomodulating functions and, thus, structural analogues with reporter capabilities could be useful for studying and modulating the cellular processes concerned. We have synthesized three new 20-hydroxycholesterol-like pregn-5-en-3β-ol derivatives with fluorescent 7-nitrobenzofurazan (NBD) or Raman-sensitive alkyne labels in their side-chains. In silico computations demonstrated the compounds possess good membrane permeability and can bind within active sites of known 20-hydroxycholesterol targets (e.g. Smoothened and yeast Osh4) and some other sterol-binding proteins (human LXRβ and STARD1; yeast START-kins Lam4S2 and Lam2S2). Having found good predicted membrane permeability and binding to some yeast proteins, we tested the compounds on microorganisms. Fluorescent microscopy indicated the uptake of the steroids by both Saccharomyces cerevisiae and Yarrowia lipolytica, whereas only S. cerevisiae demonstrated conversion of the compounds into 3-O-acetates, likely because 3-O-acetyltransferase Atf2p is present only in its genome. The new compounds provide new options to study the uptake, intracellular distribution and metabolism of sterols in yeast cells as well as might be used as ligands for sterol-binding proteins.

    更新日期:2019-12-11
  • Starch aided synthesis of giant unilamellar vesicles
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-11-26
    Mohammad Maoyafikuddin, Meenakshi Pundir, Rochish Thaokar

    Synthesis of giant unilamellar vesicles (GUVs) of charged and uncharged lipids at physiological salt concentration is presented using the starch hydrogel method as an example of the gel assisted synthesis method. The swelling of the gel is assisted by the presence of a high amount of amylopectin in starch and yields giant-sized vesicles, which are unilamellar in nature. This method holds promise since starch is a commonly available cheap bio-compatible material. This work indicates that native starch yields vesicles of better size range as compared to the acid-treated starch. It is demonstrated that contrary to the common belief, pre-hydration of bilayers is not critical to the success of this method. The synthesis of GUVs in physiological salt concentrations is possible since the salt does not produce any osmotic effect on its own. At low starch concentration, the size of the vesicles is found to correlate with the swelling factor. The conjugate effect of the starch concentration and ion leads to the change in the swelling factor of the gel and thereby influence the size and architecture of the vesicles. Also, interactions between starch and lipid play an important role in the formation of the giant vesicles.

    更新日期:2019-11-26
  • An overview of current knowledge in biological functions and potential theragnostic applications of exosomes
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-10-31
    Shima Rahmati, Fereshteh Shojaei, Ali Shojaeian, Leila Rezakhani, Mehdi Banitalebi Dehkordi

    Exosomes are cup-shaped structures, made of two lipid layers. Their size is in the range of 30–150 nm. Exosomes are excreted to the extracellular space and function in local and systemic cellular communication. Based on their primary origins, they can contain substantial amounts of RNA, protein, and miRNA; the horizontal transfer of these contents significantly determines the exosome's biological effects. The endosomal origins of exosomes can be deduced based on their surface protein markers. The use of exosomes as a diagnostic biomarker and therapeutic tool, has numerous advantages because they do not pose risks such as aneuploidy and transplant rejection. This - overview highlights the recent findings in exosome development and current knowledge in exosome-based therapies.

    更新日期:2019-11-18
  • Oxidative modification of skin lipids by cold atmospheric plasma (CAP): A standardizable approach using RP-LC/MS2 and DI-ESI/MS2
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-06-20
    Johanna Striesow, Jan-Wilm Lackmann, Zhixu Ni, Sebastian Wenske, Klaus-Dieter Weltmann, Maria Fedorova, Thomas von Woedtke, Kristian Wende

    Cold atmospheric plasma (CAP) is an emerging source for the locally defined delivery of reactive species, and its clinical potential has been identified in the control of inflammatory processes, such as acute and chronic wounds, or cancerous lesions. Lipids, due to their localization and chemical structure as ideal targets for oxidative species, are relevant modifiers of physiological processes. Human forehead lipids collected on a target were treated by an argon plasma jet and immediately analyzed by direct-infusion high-resolution tandem mass spectrometry (DI-MS2) or liquid chromatography-tandem MS (RP-LC/MS2). Subsequent data analysis was performed by LipidHunter (University of Leipzig), LipidXplorer (Max Planck Institute of Molecular Cell Biology and Genetics, Dresden), and LipidSearch (Thermo Scientific). With either MS method, all major lipid classes of sebum lipids were detected. Significant differences regarding triacylglycerols (predominantly identified in RP-LC/MS2) and ceramides (predominantly identified in DI-MS2) indicate experimental- or approach-inherent distinctions. A CAP-driven oxidation of triacyclglycerols, ceramides, and cholesteryl esters was detected such as truncations and hydroperoxylations, but at a significantly lower extent than expected. Scavenging of reactive species due to naturally present antioxidants in the samples and the absence of a liquid interphase to allow reactive species deposition by the CAP will have contributed to the limited amount of oxidation products observed. In addition, limitations of the software’s capability of identifying unexpected oxidized lipids potentially led to an underestimation of the CAP impact on skin lipids, indicating a need for further software development. With respect to the clinical application of CAP, the result indicates that intact skin with its sebum/epidermal lipid overlay is well protected and that moderate treatment will yield limited (if any) functional consequences in the dermal tissue.

    更新日期:2019-11-18
  • Methylene volumes in monoglyceride bilayers are larger than in liquid alkanes
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-11-16
    Brian C. Seper, Anthony Ko, Aaron F. Abma, Andrew D. Folkerts, Stephanie Tristram-Nagle, Paul E. Harper

    The densities as a function of temperature of four fully hydrated saturated monoglycerides with even chain lengths ranging from eight to fourteen were determined by vibrating tube densitometry and their phase transition temperatures were determined by differential scanning calorimetry (DSC). We find the volume of a methylene group in a monoglyceride bilayer is 2 percent larger than in liquid alkanes at physiological temperatures, similar to the methylene group volumes found in phosphatidylcholine (PC) bilayers. Additionally, we carefully consider the traditional method of calculating component volumes from experimental data and note potential difficulties in this approach. In the literature, the ratio of terminal methyl volume (CH3) to methylene (CH2) volumes is typically assumed to be 2. By analysis of literature alkane data, we find this ratio actually ranges from 1.9 to 2.3 for temperatures ranging from 0 °C to 100 °C. For a rough sense of scale, we note that to effect a 2 percent reduction in volume requires of order 200 atmospheres of pressure, and pressures of this magnitude are biologically relevant. For instance, this amount of pressure is sufficient to reverse the effect of anesthesia. The component volumes obtained are an important parameter used for determining the structure of lipid bilayers and for molecular dynamics simulations.

    更新日期:2019-11-18
  • Characterization of glycerophospholipid molecular species in muscles from three species of cephalopods by direct infusion-tandem mass spectrometry
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-11-06
    Yan Shen, Hong-Kai Xie, Zhong-Yuan Liu, Ting Lu, Zhuo-Liang Yu, Li-Hua Zhang, Da-Yong Zhou, Tong Wang

    More than 200 molecular species of glycerophospholipids (GP) including glycerophosphocholine (GPC), glycerophosphoethanolamine (GPE), glycerophosphoserine (GPS), lysoglycerophosphocholine (LGPC), lysoglycerophosphoethanolamine (LGPE) and lysoglycerophosphoserine (LGPS), as well as 18 kinds of sphingomyelin (SM) were characterized by using a direct infusion-tandem mass (MS/MS) spectrometry method for lipids from the muscles of cephalopods Sepiella maindroni, Octopus ocellatus and Loligo chinensis for the first time. The majority of the GP molecular species contained long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Therefore, cephalopods can be a good possible source of dietary GP carrying n-3 LC-PUFA. The total lipids were composed of phospholipid (PL, 72.29-83.32 wt% of total lipids), cholesterol (12.70-23.60 wt% of total lipids), triacylglycerol (1.86-2.93 wt% of total lipids), diacylglycerol (0.15-1.09 wt% of total lipids), monoacylglycerol (0.06-0.18 wt% of total lipids) and free fatty acid (0.72-1.86 wt% of total lipids). For PL, phosphatidylcholine (44.47-62.30 mol%), phosphatidylethanolamine (22.57-39.08 mol%), phosphatidylserine (6.15-10.18 mol%), phosphatidylglycerol (0.68-3.11 mol%), phosphatidylinositol (2.41-7.15 mol%) and lysophosphatidylcholine (1.84-5.24 mol%) were detected. Furthermore, the total lipids from the muscles of cephalopods Sepiella maindroni, Octopus ocellatus and Loligo chinensis contained 41.80-50.02 mol% of saturated fatty acids, 11.53-21.54 mol% of monounsaturated fatty acids and 36.67-40.82 mol% of PUFA, whilst DHA (15.25-26.71 mol%) and EPA (6.29-16.57 mol%) were found to account for the majority of the PUFA. With these data presented, cephalopod muscle can be considered as a healthy food for humans.

    更新日期:2019-11-06
  • Lipid Nanocarriers for microRNA Delivery
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-11-02
    Marcel Scheideler, Ivan Vidakovic, Ruth Prassl

    Non-coding RNAs (ncRNAs) like microRNAs (miRNAs) or small interference RNAs (siRNAs) with their power to selectively silence any gene of interest enable the targeting of so far ‘undruggable’ proteins and diseases. Such RNA molecules have gained much attention from biotech and pharmaceutical companies, which led to the first Food and Drug Administration (FDA) approved ncRNA therapeutic in 2018. However, the main barrier in clinical practice of ncRNAs is the lack of an effective delivery system that can protect the RNA molecules from nuclease degradation, deliver them to specific tissues and cell types, and release them into the cytoplasm of the targeted cells, all without inducing adverse effects. For that reason, drug delivery approaches, formulations, technologies and systems for transporting pharmacological ncRNA compounds to achieve a diagnostic or therapeutic effect in the human body are in demand. Here, we review the development of therapeutic lipid-based nanoparticles for delivery of miRNAs, one class of endogenous ncRNAs with specific regulatory functions. We outline challenges and opportunities for advanced miRNA-based therapies, and discuss the complexity associated with the delivery of functional miRNAs. Novel strategies are addressed how to deal with the most critical points in miRNA delivery, such as toxicity, specific targeting of disease sites, proper cellular uptake and endosomal escape of miRNAs. Current fields of application and various preclinical settings involving miRNA therapeutics are discussed, providing an outlook to future clinical approaches. Following the current trends and technological developments in nanomedicine exciting new delivery systems for ncRNA-based therapeutics can be expected in upcoming years.

    更新日期:2019-11-04
  • Editorial.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-08-11
    Sebastian Jaksch,Thomas Gutberlet,Maikel Rheinstädter

    更新日期:2019-11-01
  • Editorial.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2019-08-11
    Sebastian Jaksch,Thomas Gutberlet,Maikel Rheinstädter

    更新日期:2019-11-01
  • A simple supported tubulated bilayer system for evaluating protein-mediated membrane remodeling.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2018-07-18
    Noah A Schenk,Peter J Dahl,Michael G Hanna,Anjon Audhya,Gregory G Tall,Jefferson D Knight,Arun Anantharam

    Fusion and fission of cellular membranes involve dramatic, protein-mediated changes in membrane curvature. Many of the experimental methods useful for investigating curvature sensing or generation require specialized equipment. We have developed a system based on supported lipid bilayers (SLBs) in which lipid tubules are simple to produce and several types of membrane remodeling events can be readily imaged using widely available instrumentation (e.g., tubule fission and/or membrane budding). Briefly, high ionic strength during lipid bilayer deposition results in incorporation of excess lipids in the SLB. After sequentially washing with water and physiological ionic strength buffer solutions, lipid tubules form spontaneously. We find that tubule formation results from solution-dependent spreading of the SLB; washing from water into physiological ionic strength buffer solution leads to expansion of the bilayer and formation of tubules. Conversely, washing from physiological buffer into water results in contraction of the membrane and loss of tubules. We demonstrate the utility of these supported tubulated bilayers, termed "STuBs," with an investigation of Sar1B, a small Ras family G-protein known to influence membrane curvature. The addition of Sar1B to STuBs results in dramatic changes in tubule topology and eventual tubule fission. Overall, STuBs are a simple experimental system, useful for monitoring protein-mediated effects on membrane topology in real time, under physiologically relevant conditions.

    更新日期:2019-11-01
  • Factors affecting DNA binding and stability of association to cationic liposomes.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2012-06-21
    Simcha Even-Chen,Rivka Cohen,Yechezkel Barenholz

    Lipoplexes are complexes formed between cationic liposomes (L(+)) and polyanionic nucleic acids (P(-)). They are commonly used in vitro and in vivo as a nucleic acid delivery system. Our study aims are to investigate how DOTAP-based cationic liposomes, which vary in their helper lipid (cholesterol or DOPE) and in media of different ionic strengths affect the degree, mode of association and degree of condensation of pDNA. This was determined by ultracentrifugation and gel electrophoresis, methods based on different physical principles. In addition, the degree of pDNA condensation was also determined using the ethidium bromide (EtBr) intercalation assay. The results suggest that for cationic lipid compositions (DOTAP/DOPE and DOTAP/cholesterol), 1.5 M NaCl, but not 0.15 M NaCl, both prevent lipoplex formation and/or induce partial dissociation between lipid and DNA of preformed lipoplexes. The higher the salt concentration the greater is the similarity of DNA condensation (monitored by EtBr intercalation) between lipoplex DNA and free DNA. As determined by ultracentrifugation and agarose gel electrophoresis, 30-90% of the DNA is uncondensed. SDS below its critical micellar concentration (CMC) induced "de-condensation" of DNA without its physical release (assessed by ultracentrifugation) for both DOTAP/DOPE and DOTAP/cholesterol lipoplexes. As was assessed by agarose gel electrophoresis SDS induced release of 50-60% of DNA from the DOTAP/cholesterol lipoplex but not from the DOTAP/DOPE lipoplex. This study shows that there are conditions under which DNA is still physically associated with the cationic lipids but undergoes unwinding to become less condensed. We also proved that the helper lipid affects level and strength of the L(+) and DNA(-) electrostatic association; these interactions are weaker for DOTAP/cholesterol than for DOTAP/DOPE, despite the fact that the positive charge and surface pH of DOTAP/cholesterol and DOTAP/DOPE are similar.

    更新日期:2019-11-01
  • Dynamics and ordering of lipid spin-labels along the coexistence curve of two membrane phases: an ESR study.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2012-05-16
    Andrew K Smith,Jack H Freed

    An analysis of electron spin resonance (ESR) spectra from compositions along the liquid-ordered (L(o)) and liquid-disordered (L(d)) coexistence curve from the brain-sphingomyelin/dioleoylphosphatidylcholine/cholesterol (SPM/DOPC/Chol) model lipid system was performed to characterize the dynamic structure on a molecular level of these coexisting phases. We obtained 200 continuous-wave ESR spectra from glycerophospholipid spin-labels labeled at the 5, 7, 10, 12, 14, and 16 carbon positions of the 2nd acyl chain, a sphingomyelin spin-label labeled at the 14 carbon position of the amide-linked acyl chain, a headgroup-labeled glycerophospholipid, a headgroup-labeled sphingomyelin, and the cholesterol analogue spin-label cholestane all within multi-lamellar vesicle suspensions at room temperature. The spectra were analyzed using the MOMD (microscopic-order macroscopic-disorder) model to provide the rotational diffusion rates and order parameters which characterize the local molecular dynamics in these phases. The analysis also incorporated the known critical point and invariant points of the neighboring three-phase triangle along the coexistence curve. The variation in the molecular dynamic structures of coexisting L(o) and L(d) compositions as one moves toward the critical point is discussed. Based on these results, a molecular model of the L(o) phase is proposed incorporating the "condensing effect" of cholesterol on the phospholipid acyl chain dynamics and ordering and the “umbrella model” of the phospholipid headgroup dynamics and ordering.

    更新日期:2019-11-01
  • A new method for determining phospholipase D activity using the monomolecular film technique.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 1996-03-29
    A Abousalham,M G Ivanova,I Douchet,R Verger

    A versatile and continuous assay for phospholipase D (PL D) activity was developed using the monomolecular film technique. For this purpose, a two-step enzymatic reaction was used. First, PL D hydrolysis of stable 1,2-diacyl-sn-glycero-3-phosphocholine (PC) films by PL D generated a stable 1,2-diacyl-sn-glycero-3-phosphate (PA) film and water-soluble choline. Secondly, the latter acidic phospholipid, in contrast to the initial PC molecule, was further hydrolysed under the action of porcine pancreatic lipase (PPL) in order to give rise to lysophosphatidic acid and fatty acid, which were rapidly desorbed from the interface. With this new procedure, it is possible to obtain continuous and accurate kinetic measurements of the PL D-catalyzed reaction with phospholipid monolayers as substrates. The PLD kinetics were linear with time and the velocities recorded were directly dependent upon the amount of PL D used. In a preliminary study, we investigated the effects of the surface pressure on the PL D activity.

    更新日期:2019-11-01
  • Biomimetic nitration of the linoleic acid metabolite 13-hydroxyoctadecadienoic acid: isolation and spectral characterization of novel chain-rearranged epoxy nitro derivatives.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2008-03-06
    Paola Manini,Emanuela Camera,Mauro Picardo,Alessandra Napolitano,Marco d'Ischia

    Nitration of unsaturated fatty acids is a (patho)physiologically important pathway of lipid modification induced by nitric oxide-derived species. We report herein on the unexpected chain rearrangement undergone by (13S,9Z,11E)-13-hydroxyoctadeca-9,11-dienoic acid (1), a linoleic acid metabolite, when exposed to nitrating agents of biological relevance. At pH 7.4 and at room temperature, reaction of 1 with peroxynitrite (ONOO-) as well as Fe2+-EDTA/H2O2/NO2- and horseradish peroxidase/H2O2/NO2- led to the formation of two nitration products, which could be isolated as the methyl esters and were identified as diastereoisomeric methyl (12S)-10,11-epoxy-12-hydroxy-9-nitromethylheptadecanoates by extensive 1H, 13C, 15N NMR and MS analysis.

    更新日期:2019-11-01
  • 更新日期:2019-11-01
  • Effects of lysophosphatidic acid on melanogenesis.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Dong-Seok Kim,Seo-Hyoung Park,Sun-Bang Kwon,Sang-Woong Youn,Kyoung-Chan Park

    In this study, we investigated the effects of lysophosphatidic acid (LPA) on melanogenesis in Mel-Ab cells. We found that LPA significantly attenuates melanin synthesis, and reduces the activity of tyrosinase, the rate-limiting melanogenic enzyme. Interestingly, LPA was also found to induce the activation of a 90 kDa ribosomal S6 kinase (RSK-1), which is known to phosphorylate microphthalmia-associated transcription factor (MITF) at serine 409. Though it has been previously reported that the phosphorylation of MITF is followed by the degradation of MITF, we found that LPA significantly inhibited MITF promoter activity, and that this reduced MITF and tyrosinase protein production. Our results indicate that LPA contributes to reduced melanin synthesis via the down-regulation of MITF.

    更新日期:2019-11-01
  • Photoinduced interaction of riboflavin dye with different reducing agents in aqueous and liposome media.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Benoy B Bhowmik,Arpita Sil

    The photoelectrochemical and spectral studies of riboflavin have been carried out in aqueous and phosphatidylcholine (PC) liposome media in presence of different reducing agents such as I-, Br-, Cl-, Fe2+, Fe(CN)6(4-) and Cu+. The results from both the studies support the photoinduced electron transfer from the reducing agent to the excited riboflavin dye. Moreover, a good correlation between photovoltages/Stern-Volmer quenching constants versus reduction potentials of the reducing agents also confirms the above electron transfer in the photoexcited state. An alternative method has been developed to determine the Stern-Volmer quenching constant.

    更新日期:2019-11-01
  • Insights on the interaction of met-enkephalin with negatively charged membranes--an infrared and solid-state NMR spectroscopic study.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Isabelle Marcotte,Marise Ouellet,Michèle Auger

    Enkephalins are pentapeptides found in the human nervous system, where they are involved in the relief of pain. The interaction of these neuropeptides with the nerve cell membranes would be a key-step in the receptor binding. We have used both Fourier-transform infrared and solid-state NMR spectroscopies to shed light on the interactions responsible for the association of enkephalins with negatively charged membranes. More specifically, we have investigated the interaction of methionine-enkephalin (Menk) with DMPG and DMPS vesicles. Our results suggest that Menk interacts electrostatically with both model membranes via its terminal NH3+ group. However, the peptide induced the formation of elongated DMPG vesicles in the magnetic field. On the other hand, the association of Menk with DMPS bilayers was concentration-dependent and disrupted the membrane at high peptide concentrations. The different effect of methionine-enkephalin with the two types of anionic membranes is most likely related to the different fluidity of these systems.

    更新日期:2019-11-01
  • Solid-liquid phase behavior of binary fatty acid mixtures. 2. Mixtures of oleic acid with lauric acid, myristic acid, and palmitic acid.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Tohru Inoue,Yusuke Hisatsugu,Ruri Ishikawa,Masao Suzuki

    Solid-liquid phase behavior was investigated for binary fatty acid mixtures composed of oleic acid (OA; cis-9-octadecenoic acid) and saturated fatty acids, lauric acid (LA; dodecanoic acid), myristic acid (MA; tetradecanoic acid), and palmitic acid (PA; hexadecanoic acid), by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). When the mixture was heated immediately after the solidification from the melt, the heat effect due to the gamma-to-alpha transformation of OA varied depending on the composition of the mixture. However, the mixture subjected to an annealing at the temperature slightly below the melting temperature provided the transformation at constant temperature which corresponds to the gamma-to-alpha transformation temperature of pure OA. This suggests that a solid phase formed by cooling of the melt of the mixture is not in an equilibrium state, but it relaxes to a stable solid during the annealing process. The T-X phase diagrams of these mixtures constructed from the DSC measurements demonstrate that the two fatty acid species are completely immiscible in a solid phase regardless of the type of polymorphs of OA, alpha- or gamma-form. According to a thermodynamic analysis of liquidus line basing on the regular solution model for the melt, the non-ideality of mixing tends to increase with the decrease in the acyl chain length of the saturated fatty acid, although the mixing is rather close to ideal.

    更新日期:2019-11-01
  • The kinetics and mechanism of the formation of crystalline phase of dipalmitoylphosphatidylethanolamine dispersed in aqueous dimethyl sulfoxide solutions.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Lin Chen,Xin Xie,Zhi-Wu Yu,Peter J Quinn

    The phase transition kinetics and mechanism of formation of a lamellar-crystalline phase of dipalmitoylphosphatidylethanolamine (DPPE) dispersed in different concentrations of aqueous dimethyl sulfoxide (DMSO) during cooling have been examined by differential scanning calorimetry and synchrotron X-ray diffraction techniques. In dispersions containing mole fractions of DMSO (x<0.22), the phase transition sequence of the phospholipid is from lamellar liquid-crystal phase to lamellar-gel phase. Increasing the mole fraction of DMSO to 0.220.5 resulted in a direct transition from liquid-crystal phase to lamellar crystal phase with no detectable intermediate gel phase. A temperature versus DMSO concentration phase diagram was constructed based on calorimetric data with phase assignments made using synchrotron X-ray diffraction measurements. The non-isothermal formation kinetics of the lamellar crystal phase, which is expressed as the half time of the transformation process, was found to depend on DMSO concentration. The inducement of lamellar crystal phase in DPPE by DMSO is discussed in terms of the dehydration effect of DMSO and competitive molecular interactions between DMSO, water, and the phospholipid.

    更新日期:2019-11-01
  • Solid-liquid phase behavior of binary fatty acid mixtures. 1. Oleic acid/stearic acid and oleic acid/behenic acid mixtures.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Tohru Inoue,Yusuke Hisatsugu,Reiri Yamamoto,Masao Suzuki

    Solid-liquid phase behavior of binary fatty acid mixtures was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) for the mixture composed of oleic acid (OA) and stearic acid (SA) and that composed of OA and behenic acid (BA). The DSC results provided a monotectic type T-X phase diagram for these mixtures, from which it was suggested that the two fatty acid species are completely immiscible in a solid phase regardless of the two polymorphs of OA, i.e., alpha-form or gamma-form. The solid phase immiscibility was confirmed by the FT-IR observation that the spectra obtained for the mixtures correspond to the superposition of the two spectra for respective components. Thermodynamic analysis of liquidus line demonstrated that OA and SA form an ideal mixture in a liquid phase, whereas the mixing of OA and BA in a liquid phase is slightly non-ideal.

    更新日期:2019-11-01
  • Effect of phytosterols and phytostanols on the solubilization of cholesterol by dietary mixed micelles: an in vitro study.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-17
    Sergey M Mel'nikov,Jack W M Seijen ten Hoorn,Astrid P A M Eijkelenboom

    The effect of a plant sterol, beta-sitosterol (SI), and a plant stanol, sitostanol (SS), on the solubilization of cholesterol (CH) by model dietary mixed micelles was examined under in vitro conditions with the use of gas chromatography, isothermal titration calorimetry, NMR spectroscopy and cryogenic transmission electron microscopy techniques. Free SI and SS were shown to reduce the concentration of CH in dietary mixed micelles via a dynamic competition mechanism. CH, SI and SS affect the microstructure of lipid vesicles and influence the process of amphiphilic self-assembly of nutrients in the gut with the formation of dietary mixed micelles in a similar manner. Therefore, substitution of CH by phytosterols and phytostanols in the diet does not lead to the notable changes in the mechanism of dietary mixed micelle formation and does not affect the process of the intestinal transport of nutrients and drugs via the micellar diffusion mechanism. Our experimental findings demonstrate that the introduction of plant sterols and plant stanols into the diet is clearly beneficial for the reduction of the intestinal uptake of cholesterol. Due to the limited capacity of dietary mixed micelles to embody hydrophobic sterol/stanol molecules, the micellar concentration of cholesterol is reduced and hence, its transport towards the intestinal brush border membrane decreases.

    更新日期:2019-11-01
  • Determination of liposomal encapsulation efficiency using proton NMR spectroscopy.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Xian-Man Zhang,Anant B Patel,Robin A de Graaf,Kevin L Behar

    A rapid and simple approach using 1H NMR was developed for determination of liposomal encapsulation efficiency without the need for physical separation of entrapped and non-entrapped marker. Measurements were made using a marker (homocarnosine) with a pH-sensitive 1H chemical shift in the presence of a pH gradient across the phospholipid vesicle membrane, or by addition of the chemical shift reagent, thulium(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra-(methylene phosphonic acid sodium salt) (TmDOTP5-). The measured encapsulation efficiencies for the liposomal dispersions prepared from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) through extrusion using 50, 200 and 1000 nm polycarbonate membranes were found to be identical using the two different experimental approaches.

    更新日期:2019-11-01
  • The effect of increasing concentrations of precipitating salts used to crystallize proteins on the structure of the lipidic Q224 cubic phase.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Rodolfo Vargas,Leonardo Mateu,Antonio Romero

    A major obstacle to elucidating the structure of membrane proteins at high resolution is the difficulty of preparing these proteins as well as to grow well-ordered crystals. During the last few years several groups have considered the use of three-dimensional bicontinuous lipidic cubic phases as a possible crystallization matrix for such molecules. In a few cases these studies have been successfully approached by other laboratories, however, a number of questions remain, particularly in regard to the effects of solutes on the phase diagrams of lipid-water systems. In the present work we report the structural behavior of the lipidic Q224 (Pn3m), Q230 (Ia3d) and HII phases systematically studied in the presence of a range of concentrations of various salts and precipitating agents at various pH values. Some of the results reported here have been presented elsewhere Vargas et al. (2000) [Strategies in membrane protein crystallization. Chemical Prospectives in Crystallography of Molecular Biology. International School of Crystallography, NATO-ASI course, Erice (Italy)].

    更新日期:2019-11-01
  • Organization and dynamics of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-labeled lipids: a fluorescence approach.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Soumi Mukherjee,H Raghuraman,Sudeshna Dasgupta,Amitabha Chattopadhyay

    Lipids that are labeled with the NBD (7-nitrobenz-2-oxa-1,3-diazol-4-yl) group are widely used as fluorescent analogues of native lipids in biological and model membranes to monitor a variety of processes. NBD-labeled lipids have previously been used to monitor the organization and dynamics of molecular assemblies such as membranes, micelles and reverse micelles utilizing the wavelength-selective fluorescence approach. In this paper, we have characterized the organization and dynamics of various NBD-labeled lipids using red edge excitation shift (REES) and other fluorescence approaches which include analysis of membrane penetration depths of the NBD group using the parallax method. We show here that the environment and location experienced by the NBD group of the NBD-labeled lipids could depend on the ionization state of the lipid. This could have potentially important implications in future studies involving NBD-labeled lipids as tracers in a cellular context.

    更新日期:2019-11-01
  • Incorporation of beta-lactoglobulin in a lipid/porphyrin monolayer at the air--water interface.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Amélia M Gonçalves da Silva,Rute S Romão,Sílvia M B Costa

    A catanionic lipid/porphyrin monolayer was formed at the air-water interface by the tetra-anionic porphyrin, tetra-sodium-meso-tetra(4-sulfonatophenyl)porphine (TSPP), mixed with the cationic lipid dioctadecyldimethylammonium bromide (DODAB) in a 1:4 molar ratio. This binary mixture (TSPP/4DODAB) was used as the incorporation matrix of beta-lactoglobulin (betaLG). Binary and ternary systems (TSPP/4DODAB/zbetaLG, where z stands for the number of protein residues per TSPP) were characterized by surface pressure versus area (pi-A) measurements and by Brewster angle microscopy (BAM) observation at the air-water interface. Pi-A measurements and BAM images show that protein is incorporated in the expanded regime of the monolayer and is gradually expelled upon compression at high surface pressures. The successive compression-expansion cycles indicate that the protein under adsorbed to the floating film is reincorporated after the expansion of the monolayer. At low subphase pH, TSPP tends to aggregate decreasing the interaction with DODAB molecules. Electrostatic and hydrophobic interactions are responsible for the presence of betaLG at the interfacial film.

    更新日期:2019-11-01
  • Alkylglucosides with isoprenoid-type hydrophobic chains-effects of hydrophobic chain size on the aqueous phase behavior.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Rajesh A Salkar,Hiroyuki Minamikawa,Masakatsu Hato

    Aqueous phase diagrams were constructed for two new alkylglucosides with isoprenoid-type hydrophobic chains, viz. 1-O-beta-(3,7-dimethyloctyl)-D-glucopyranoside, beta-Glc(Ger), and 1-O-beta-(3,7,11,15-tetramethylhexadecyl)-D-glucopyranoside, beta-Glc(Phyt). In a low concentration regime, from 0.17 to 34 wt.% beta-Glc(Ger), the beta-Glc(Ger)/water system exhibits two phase, a dilute (L1dil) and a concentrated isotropic phase (L1con), coexistence region. Above about 62 wt.% beta-Glc(Ger), an Lalpha phase is formed. The extent of the L1dil + L1conc two-phase region decreases as temperature increases and totally disappears above 130 degrees C, exhibiting an upper critical temperature. The beta-Glc(Phyt)/water system exhibits an Lalpha phase above 78 wt.% surfactant below which, an Lalpha + water two-phase region appears. One notable feature of these compounds is their low values of Krafft-eutectic temperature, TK, e.g. the value of TK for beta-Glc(Phyt) is below 0 degrees C although the total number of carbon atoms in the hydrophobic chain is as large as 20.

    更新日期:2019-11-01
  • Synthesis and properties of methyl 5-(1'R,2'S)-(2-octadecylcycloprop-1-yl)pentanoate and other omega-19 chiral cyclopropane fatty acids and esters related to mycobacterial mycolic acids.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Geoffrey D Coxon,Juma'a R Al Dulayymi,Caroline Morehouse,Patrick J Brennan,Gurdyal S Besra,Mark S Baird,David E Minnikin

    A 23-26-carbon chain length range of omega-19 (1'R,2'S) cyclopropane fatty acids, related to mycobacterial mycolic acids, has been prepared. The key cyclopropyl intermediate, (1'R,2'S)-(Z)-1-formyl-2-octadecylcyclopropane, underwent Wittig chemistry with various reagents to provide vinylic precursors, which were selectively reduced to the corresponding saturated omega-19 cyclopropane fatty acids or esters. The 24-carbon omega-19 cyclopropane ester was made by chain elongation of the 23-carbon ester. Saturated and unsaturated chiral cyclopropane acids and esters were assayed, using wall extracts of Mycobacterium smegmatis; the incorporation of 14C-acetate was used to measure inhibition or stimulation of mycolic acid synthesis. Minor inhibition (2-3%) was shown by the 23- and 24-carbon saturated esters; all the other compounds were stimulants. The most effective (38-55%) stimulators of mycolate synthesis were the unsaturated esters with 23- and 26-carbons and the saturated and unsaturated 25-carbon acids.

    更新日期:2019-11-01
  • Thermotropic and lyotropic properties of long chain alkyl glycopyranosides: part III: pH-sensitive headgroups.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    G Milkereit,M Morr,J Thiem,V Vill

    As part of a series of papers, the influence of carbohydrate headgroups and aliphatic chains on the mesogenic properties of glycolipids was investigated. Alkyl glycosides with different types of aliphatic chains were synthesised. Neutral glycolipids were oxidized to their uronic acid derivatives, using the well established TEMPO-oxidation. For comparison a 6-deoxy-6-amino alkylglucopyranoside was synthesised. In addition, the thermotropic and lyotropic phase behaviour of the synthesised compounds were investigated. The thermotropism was characterised by polarising microscopy, the lyotropism by the contact preparation method.

    更新日期:2019-11-01
  • Lipid bilayers: thermodynamics, structure, fluctuations, and interactions.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Stephanie Tristram-Nagle,John F Nagle

    This article, adapted from our acceptance speech of the Avanti Award in Lipids at the 47th Biophysical Society meeting in San Antonio, 2003, summarizes over 30 years of research in the area of lipid bilayers. Beginning with a theoretical model of the phase transition (J.F.N.), we have proceeded experimentally using dilatometry and density centrifugation to study volume, differential scanning calorimetry to study heat capacity, and X-ray scattering techniques to study structure of lipid bilayers as a function of temperature. Electron density profiles of the gel and ripple phases have been obtained as well as profiles from several fluid phase lipids, which lead to many structural results that compliment molecular dynamics simulations from other groups. Using the theory of liquid crystallography plus oriented lipid samples, we are the first group to obtain both material parameters (KC and B) associated with the fluctuations in fluid phase lipids. This allows us to use fully hydrated lipid samples, as in vivo, to obtain the structure.

    更新日期:2019-11-01
  • Can cholesterol absorption be reduced by phytosterols and phytostanols via a cocrystallization mechanism?
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2004-01-07
    Sergey M Mel'nikov,Jack W M Seijen ten Hoorn,Benoit Bertrand

    The formation of mixed water-insoluble poorly absorbable crystals between cholesterol (CH) and phytosterols (PS) or phytostanols (PSS) in the intestinal lumen has been considered for a long time as a plausible mechanism of the PS/PSS-induced reduction of serum CH concentration. In this report, we demonstrated with the use of the powder X-ray diffraction (XRD) and the differential scanning calorimetry (DSC) techniques that mixed CH:beta-sitosterol (SI) crystals can be formed by recrystallization of corresponding mixtures from melts and also from mixed CH:SI solutions in triglyceride oil. Formation of mixed CH:SI crystals takes place in a wide interval of CH:SI ratios, from approximately 10 up to approximately 75 wt.% of SI in the mixture. Formation of mixed CH:sitostanol (SS) crystals from melts and solutions in triglyceride oil was also detected, but in a more narrow interval of CH:SS ratios. However, during the lipolysis of model dietary emulsions under in vitro conditions, the formation of crystalline material was not detected due to the relatively high solubility of free sterols/stanols in products of fat hydrolysis. We found that the solubility of free CH, SI, and SS raises upon the increase in the solvent polarity, i.e. free fatty acid > diglycerideoil > triglyceride oil. Therefore, we believe that the cocrystallization mechanism of phytosterol-induced serum CH lowering has relatively low importance, unless the diet is specially designed to include relatively little amounts of dietary fats. The presented experimental evidence demonstrates that it is unlikely that the formation of poorly absorbable mixed crystals largely affects the intestinal absorption of CH and, therefore, that this is a prime mechanism by which PS and PSS effect CH absorption.

    更新日期:2019-11-01
  • A divergent synthesis of [1-14C]-mono-E isomers of fatty acids.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    D Georgin,F Taran,C Mioskowski

    A convenient synthesis of [1-14C]-mono-trans fatty acid using olefin inversion as a key-step is described. This methodology allows for a facile synthesis of [1-14C]-labelled mono-trans analogues of oleic, linoleic and linolenic acids. As an example, only eleven steps were necessary to obtain the [1-14C]-mono-E isomers of linolenic acid from its commercial all-Z form. In the first step, Barton's decarboxylation procedure yielded a bromo intermediate. Epoxidation of this compound resulted in the formation of three monoepoxides, which could be separated by HPLC. After identification by 1H NMR and MS, the pure monoepoxides were then subjected to inversion consisting of a stereospecific deoxygenation followed by a beta-elimination step. Finally, the labelling was introduced by substitution of the bromine by a [14C]-cyano group followed by hydrolysis.

    更新日期:2019-11-01
  • Lag phase and hydrolysis mechanisms of triacylglycerol film lipolysis.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    Torben Snabe,Steffen Bjørn Petersen

    We here present novel insights into the dynamic changes of a nanosized lipid film during enzymatic degradation. When adding an aqueous solution containing a triacylglycerol lipase to an approximately 100nm thin triolein film, which is supported on a hard surface, the film thickness, elasticity, viscosity, and chemical composition were obtained continuously. Both a mechanical technique (quartz crystal microbalance with dissipation monitoring) and a spectroscopic technique (attenuated total reflection Fourier transform infrared spectroscopy) were utilised for this study. Detailed data revealed the effects of pH, Ca(2+), and catalytic rate on lipolysis, including product release from the film. It was found that under basic conditions and without Ca(2+), the lipolytic activity commence instantaneously upon addition of enzyme, whereas product release from the substrate film awaits conditions that favours release. A model for removal of degradation products from the film is introduced, including a novel interpretation of the lag phase phenomenon.

    更新日期:2019-11-01
  • Phase equilibria of model milk membrane lipid systems.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    Rianne Waninge,Tommy Nylander,Marie Paulsson,Björn Bergenståhl

    The phase behaviour of mixtures of recombined milk membrane lipids dioleoylphosphatidylcholine (DOPC), sphingomyelin (SM), dioleoylphosphatidylethanolamine (DOPE), phosphatidylinositol (PI) and dioleoylphosphatidylserine (DOPS) in 60% water was examined as a function of temperature between 5 and 90 degrees C. The aim was to examine under which lipid composition the average properties turn from balanced over to hydrophobic. The phase boundaries were determined by small angle X-ray diffraction (SAXD) and differential scanning calorimetry (DSC). The lamellar phase was dominating in the DOPC/SM/DOPE system. The phase boundary for the reversed hexagonal phase was only observed at high DOPE content within the examined temperature interval. The anionic phospholipids PI and DOPS induced a swollen lamellar phase, but no significant change of the transition between the lamellar phase and the reversed hexagonal phase was observed.

    更新日期:2019-11-01
  • Substituted p-hydroquinones as inhibitors of lipid peroxidation.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    Vitaly Roginsky,Tatyana Barsukova,Denis Loshadkin,Evgeny Pliss

    The technique based on monitoring oxygen consumption was applied to study 12 alkyl- and methoxy-substituted p-hydroquinones (QH(2)) as a chain-breaking antioxidant during the oxidation of styrene and methyl linoleate (ML) in bulk as well as ML oxidation in micellar solution of sodium dodecyl sulfate (SDS) at 37 degrees C. The antioxidant activities of QH(2) were characterized by two parameters: the rate constant k(1) for reaction of QH(2) with the peroxy radical LO(2)*: QH(2)+LO(2)*-->QH*+LOOH and the stoichiometric factor of inhibition, f, which shows how many kinetic chains may be terminated by one molecule of QH(2). In the case of styrene and ML oxidation in bulk, f values never exceed two; for the majority of QH(2), f was found to be significantly less than two due to the interaction of QH* with molecular oxygen. In the absence of superoxide dismutase (SOD), all the studied QH(2) displayed a very moderate if any antioxidant capability during ML oxidation in SDS micelles. When 20U/ml SOD was added, the majority of QH(2) showed a pronounced ability to inhibit ML oxidation, f parameter being ca. one. The features of QH(2) as an antioxidant in aqueous environment are suggested to associate with the reactivity of semiquinone (Q*(-)). Q*(-) reacts readily with molecular oxygen with formation of superoxide (O(2)*(-)); further reactions of O(2)*(-) result in fast depleting QH(2) and chain propagation. The addition of SOD results in purging a reaction mixture from O(2)*(-) and, as a corollary, in depressing undesirable reactions with the participation of O(2)*(-). With all the oxidation models, QH(2) were found to be very reactive to LO(2)*. The rate constants k(1) decreased progressively when going from the oxidation of styrene to ML oxidation in bulk and further to ML oxidation in SDS micelles.

    更新日期:2019-11-01
  • Acyl migration incidence on accuracy of a triacylglycerol regioanalysis--a theoretical evaluation.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    F Turon,F Bonnot,Y Caro,M Pina,J Graille

    We will consider the Grignard chemical deacylation to study the regioanalysis of triacylglycerols (TAGs). Using a given TAG structure, a cross-contamination model is developed and used for evaluating the incidence of the acyl migration and its influence on the accuracy of a regiospecific analysis of the molecule. Despite unavoidable isomerization, the newly formed alpha,beta-diacylglycerols are considered as most representative of the original TAG composition. In this paper, we present evidence that in conditions of limited acyl migration, the regiospecific distribution could more accurately be determined from the alpha-monoacylglycerol rather than through calculations based on the alpha,beta-diacylglycerols fraction.

    更新日期:2019-11-01
  • Nuclear magnetic resonance of lipid A--the influence of solvents on spin relaxation and spectral quality.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    Lothar Brecker

    Nuclear magnetic resonance (NMR) spectroscopy of lipid A is limited by rapid transversal relaxation and subsequent line broadening caused by the tendency of these glycolipids to form aggregates in all solvents. To examine the influence of solvents on NMR spectra, hexa-acyl lipid A from Escherichia coli F515 was investigated. Line widths at half height, longitudinal relaxation times, and transversal relaxation times were measured in different solvents, lipid A concentrations, and temperatures. Chloroform-d, dioxane-d(8), and pyridine-d(5) each mixed with 25% methanol-d(4) as well as sole DMSO-d(6) and 0.1M triethylamine-d(15) (TEA-d(15)) in D(2)O caused good spectral resolutions and allowed structure analysis. ROESY and HMBC spectra gave an insight into the influence of transversal relaxation times on spectral quality in two-dimensional spectra. Solvent depending differences of interglycosidic NOEs indicated dissimilarities of the conformations in the interglycosidic linkage and allowed conclusions about the lipid A solution state.

    更新日期:2019-11-01
  • Losartan's molecular basis of interaction with membranes and AT1 receptor.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    P Zoumpoulakis,I Daliani,M Zervou,I Kyrikou,E Siapi,G Lamprinidis,E Mikros,T Mavromoustakos

    Physicochemical methods were used to study the thermal and dynamic changes caused by losartan in the membrane bilayers. In addition, molecular modeling was implemented to explore its topography both in membranes and AT(1) receptor. Its incorporation resulted in the modification of thermal profile of dipalmitoyl phosphatidylcholine (DPPC) bilayers in a concentration dependent way up to 20mol% as it is depicted from the combination of differential scanning calorimetry (DSC) and MAS data. In particular, the presence of losartan caused lowering of the phase transition temperature and abolishment of the pretransition. T(1) experiments revealed the location of the drug into the membrane bilayers. The use of a combination of biophysical methods along with docking experiments brought out a possible two-step mechanism which involves incorporation of losartan at the interface of membrane bilayers and diffusion in the upper parts of AT(1) receptor helices IV-VII.

    更新日期:2019-11-01
  • Interaction of natural polyamines and dimethylsilyl analogues with a phospholipid monolayer: a study by Brewster angle microscopy and PM-IRRAS.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-20
    Olga Berdycheva,Bernard Desbat,Michel Vaultier,Michèle Saint-Pierre-Chazalet

    This work presents an analysis of the physicochemical interactions of natural and dimethylsilyl polyamines with an anionic deuterated phospholipid monolayer, d(62)DPPG (dipalmitoyl phosphatidyl glycerol), at the air-water interface. It was motivated by previous studies, which suggested an antitumour strategy based on the accumulation of derivatives such as bis(7-amino-4-azaheptyl) dimethylsilyl (azhepSi), in order to diminish the concentration of natural polyamines (spermine and putrescine) whose metabolism is strongly activated in tumour cells. Our results, obtained by the surface-pressure technique, Brewster angle microscopy (BAM) and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), support the idea of an interaction between the polar head groups of d(62)DPPG and amino groups followed by an adsorption of polyamines up to the carbonyl group. Moreover, an insertion of the dimethylsilyl group up to the alkyl chains occurs with azhepSi, in agreement with the observation that the cohesion of the alkyl chain is lower in this case, as compared with the effect of natural polyamines.

    更新日期:2019-11-01
  • Archaeal lipids forming a low energy-surface on air-water interface.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Takahiro Kitano,T Onoue,Kiyoshi Yamauchi

    Archaea or archaebacteria are the microorganism living in extreme environments such as hot springs and salt lakes. The membrane is featured universally by lipids which possess saturated polyisoprenoid chains in the hydrophobic moiety. This paper concerns the surface properties of Langmuir membranes made of archaeal lipid models (AL) bearing a phytanyl group or (3RS, 7R, 11R)-3,7,11,15-tetramethylhexadecyl group. All of the AL provide a Langmuir membrane on an air-water interface with an abnormally low surface tension (32-37 mN/m at 20-70 degrees C), while the conventional lipids having n-alkyl chains give membranes of 54-56 mN/m. The abnormally low energy surface of AL lipids is considered to arise from the bulky and fluid polyisoprenoid chain.

    更新日期:2019-11-01
  • Interpretation of small angle X-ray measurements guided by molecular dynamics simulations of lipid bilayers.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Jonathan N Sachs,Horia I Petrache,Thomas B Woolf

    Reconstruction and interpretation of lipid bilayer structure from X-ray scattering often rely on assumptions regarding the molecular distributions across the bilayer. It is usually assumed that changes in head-head spacings across the bilayer, as measured from electron density profiles, equal the variations in hydrocarbon thicknesses. One can then determine the structure of a bilayer by comparison to the known structure of a lipid with the same headgroup. Here we examine this procedure using simulated electron density profiles for the benchmark lipids DMPC and DPPC. We compare simulation and experiment in both real and Fourier space to address two main aspects: (i) the measurement of head-head spacings from relative electron density profiles, and (ii) the determination of the absolute scale for these profiles. We find supporting evidence for the experimental procedure, thus explaining the robustness and consistency of experimental structural results derived from electron density profiles. However, we also expose potential pitfalls in the Fourier reconstruction that are due to the limited number of scattering peaks. Volumetric analysis of simulated bilayers allows us to propose an improved, yet simple method for scale determination. In this way we are able to remove some of the restrictions imposed by limited scattering data in constructing reliable electron density profiles.

    更新日期:2019-11-01
  • Synthesis and antiproliferative activity of alkylphosphocholines.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Mandy Agresta,Paola D'Arrigo,Ezio Fasoli,Daniele Losi,Giuseppe Pedrocchi-Fantoni,Simona Riva,Stefano Servi,Davide Tessaro

    Alkylphosphocholines (APC) with one or more methylene groups in the alkyl chain replaced by oxygen atoms or carbonyl groups, or both have been assembled modularly using omega-diols as central building blocks. Out of 25 new compounds of this kind, 11 were evaluated for their antiproliferative activity on four cell lines and compared with miltefosine to evaluate their hemolytic activity (HA) and cytotoxicity on non-tumoral cells (MT2), used as markers of adverse effects. Compound 13 was more active on cancer cell lines than on non-tumoral cells and the data were similar for MTT and thymidine incorporation assays. It had less HA than miltefosine. Compound 13 could therefore be a candidate for the preparation of compounds with higher cytotoxicity on cancer cells and lower general toxicity.

    更新日期:2019-11-01
  • The separation and synthesis of lipidic 1,2- and 1,3-diols from natural phenolic lipids for the complexation and recovery of boron.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    John H P Tyman,Satinderjit K Mehet

    A study has been made of the semi-synthesis of 1,3-diols (anacardic alcohols) from natural phenolic lipid resources from Anacardium occidentale and Anacardium giganteum which have given C15 and C11 derivatives, respectively. An isomeric 1,3-diol (isoanacardic alcohol) has been obtained from cardanol separated from technical cashew nut-shell liquid. Homologous 1,3-diols have been synthesised from a range of synthetic 2-alkyl-, 3-alkyl- and 4-alkylphenols and from 6-alkylsalicylic acids. The natural 1,2-diol, urushiol, from Rhus vernicifera has been purified. All these lipidic compounds have been studied for their complexation and the potential recovery of boron as boric acid.

    更新日期:2019-11-01
  • Alternative NMR method for quantitative determination of acyl positional distribution in triacylglycerols and related compounds.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    S Simova,G Ivanova,S L Spassov

    High-resolution 13C NMR spectroscopy has been used to analyze the positional distribution of fatty acids in model triacylglycerols. A novel method for quantitative determination of the positional distribution of unsaturated chains in triacylglycerols simultaneously with the ratio of saturated/unsaturated acyl chains has been proposed, utilizing the chemical shift differences of the aliphatic atoms C4, C5, and C6. The use of HSQC-TOCSY spectra allows unequivocal proof of the position of the unsaturated chain as well as complete assignment of the 13C NMR signals in tripalmitin.

    更新日期:2019-11-01
  • Effect of 2,4-dichlorophenol on DPPC/water liposomes studied by X-ray and freeze-fracture electron microscopy.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Agnes Csiszár,Erwin Klumpp,Attila Bóta,Krisztián Szegedi

    The effect of 2,4-dichlorophenol (DCP) was studied on the fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)--water liposomes. The structure and the thermotropic phase behaviour of the liposomes was examined in the presence of DCP (DCP/DPPC molar ratio, varied from 2x10(-2) up to 1) using small- and wide-angle X-ray scattering (SAXS, WAXS) and freeze-fracture electron microscopy. The structural behaviour of the DPPC/DCP/water system was strongly dependent on the concentration of the DCP. In the pretransition range the DCP molecules (at 2x10(-2) DCP/DPPC molar ratio) induced the interdigitated phase beside the parent (gel and rippled gel) phases, locally which can be form at higher DCP concentration. When the DCP/DPPC molar ratio was increased the pretransition disappeared and the main transition was shifted to lower temperatures. In the molar ratio range from 2x10(-1) up to 5x10(-1), a coexistence of different phases was observed in the wide temperature range from 20 up to 40 degrees C. With a further increase of the DCP/DPPC molar ratio (6x10(-1) to 1) only the interdigitated gel phase occurred below 25 degrees C. A schematic phase diagram of DPPC/DCP/water system was constructed to summarise the results.

    更新日期:2019-11-01
  • The first total synthesis of the marine fatty acid (+/-)-2-methoxy-13-methyltetradecanoic acid: a cytotoxic fatty acid to leukemia cells.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Néstor M Carballeira,Heidyleen Cruz,Elsie A Orellano,Fernando A González

    The recently discovered marine fatty acid (+/-)-2-methoxy-13-methyltetradecanoic acid was synthesized for the first time in six steps (26% overall yield) starting from commercially available methyl 12-methyltridecanoate. The synthetic approach provided enough material to corroborate the structure of the acid, which was recently identified in the sponge Amphimedon complanata from Aguadilla, Puerto Rico, and to test its cytotoxicity to three leukemia cell lines. The key step in the synthesis was the addition of trimethylsilyl cyanide to 12-methyltridecanal under triethylamine catalysis. Nuclear magnetic resonance data are provided for the first time for this methoxylated fatty acid and the synthetic approach utilized is of general applicability since it can be used in the synthesis of other methyl-branched 2-methoxylated fatty acids. We also report that the acid (+/-)-2-methoxy-13-methyltetradecanoic acid is cytotoxic to human chronic myelogenous leukemia K-562 (EC50=238 microM), histiocytic lymphoma U-937 (EC50=250 microM), and promielocytic leukemia HL-60 (EC50=476 microM) in RPMI 1640 medium.

    更新日期:2019-11-01
  • Stable cubic phases in codispersions of glucocerebroside and palmitoyloleoylphosphatidylethanolamine.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Ying Feng,Zhi-Wu Yu,Peter J Quinn

    The effect of glucocerebroside (GlcCer) on the structure and thermotropic phase behavior of aqueous dispersions of palmitoyloleoylphosphatidylethanolamine (POPE) has been examined using simultaneous small-angle and wide-angle X-ray diffraction methods. Binary mixtures of GlcCer:POPE in molar ratios of 2:100, 5:100, 10:100, 20:100, 30:100, and 40:100 were examined in the temperature range 20-90 degrees C. Cubic phase has been observed in binary mixtures comprised of molar ratios greater than 5:100 in the temperature range of 60-90 degrees C upon heating at a rate of 2 degrees C/min. The cubic phase is relatively stable and coexists with inverted hexagonal or lamellar phases. It persists in the codispersions throughout subsequent cooling scans to 30 degrees C. The space group of the cubic phase is determined to be Pn3m or Pn3. The lattice constant of the Pn3m cubic phase was found to be almost constant when it coexists with lamellar liquid-crystal phase. Marked temperature-dependent changes were observed when cubic phase coexists with hexagonal phase or lamellar-gel phases. This is the first report of cubic phases formed by codispersions of glycosphingolipids and phospholipids. The mechanism of cubic phase formation and the interaction between GlcCer and POPE is discussed in terms of the putative biological functions of glycolipids.

    更新日期:2019-11-01
  • Functional group analysis during ozonation of sunflower oil methyl esters by FT-IR and NMR.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Nestor U Soriano,Veronica P Migo,Masatoshi Matsumura

    Ozonation of neat sunflower oil (SFO) methyl esters was monitored by FT-IR and 1H and 13C NMR spectroscopy. During the early stage of ozonation, ozone absorption was essentially quantitative. This was accompanied by the formation of 1,2,4-trioxolane. IR and NMR spectra of ozonated samples showed that scission of ozonide to give aldehyde were minimal. 1H NMR analysis revealed that the amount of ozonide relative to aldehyde was more than 90% regardless of the extent of ozonation. Complete ozonation was attained after supplying around 0.20 g O3/ml methyl ester after which ozone absorption suddenly dropped to around 25%. At the latter part of ozonation, ozonide and aldehyde reacted with excess ozone to give carboxylic acid. Reaction products were identified according to Criegee mechanism.

    更新日期:2019-11-01
  • Ceriporic acid C, a hexadecenylitaconate produced by a lignin-degrading fungus, Ceriporiopsis subvermispora.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-11-19
    Rudianto Amirta,Kenya Fujimori,Nobuaki Shirai,Yoichi Honda,Takashi Watanabe

    A lignin-degrading basidiomycete, Ceriporiopsis subvermispora produces a series of alkyl- and alkenylitaconates (ceriporic acids). Previously, two alkylitaconic acids with tetradecyl and hexadecyl side chains were isolated and identified as 1-heptadecene-2,3-dicarboxylic acid (ceriporic acid A) and 1-nonadecene-2,3-dicarboxylic acid (ceriporic acid B). In the present study, one hexadecenylitaconate (ceriporic acid C) was isolated and its chemical structure was analyzed by glycolation and subsequent (1) trimethylsilation, or (2) acetalation with acetone and acetone-d6. Analyses of the isolated metabolite demonstrated that the hexadecenylitaconic acid was (Z)-1,10-nonadecadiene-2,3-dicarboxylic acid. The structure of the side chain in ceriporic acid C was the same as that of hexadecenylcitraconate, chaetomellic acid B. Thus, it was found that ceriporic acids share close structural similarity with alk(en)yl citraconate derivatives, chaetomellic acids and other lichen lactones, protolichesterinic, lichesterinic, and murolic acids.

    更新日期:2019-11-01
  • Comparative study of the product components of lipid oxidation in aqueous and organic systems.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-10-29
    Hidetaka Kobayashi,Mitsuru Yoshida,Kazuo Miyashita

    Ethyl esters and phosphatidylcholines (PCs) of polyunsaturated fatty acids (PUFAs) were oxidized in organic solvents, aqueous emulsions, and liposomes in the presence of a radical inducer. Oxidation products and the positional distribution of monohydroperoxide (MHP) were determined by gas chromatography-mass spectrometry (GC-MS) analysis. The total amount of the oxidation products, of PUFA ethyl esters and PCs in organic solvents, increased with an increase in the number of bis-allylic positions. However, the opposite results were obtained in an aqueous emulsion and liposomes. The distribution pattern of MHPs obtained from oxidation of the linolate and alpha-linolenate showed little difference between a chloroform solution and an aqueous emulsion or liposomes. However, there were differences between these systems with the arachidonate, the icosapentaenoate, and docosahexaenoate. These results may be due to the different rate of hydrogen abstraction from bis-allylic positions in the fatty acid moieties, and/or 1,3-cyclization of hydroperoxides in the systems.

    更新日期:2019-11-01
  • Peroxidation of liposomal palmitoyllinoleoylphosphatidylcholine (PLPC), effects of surface charge on the oxidizability and on the potency of antioxidants.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-10-29
    Sigal Gal,Ilya Pinchuk,Dov Lichtenberg

    Peroxidation of membrane phospholipids is an important determinant of membrane function. Previously we studied the kinetics of peroxidation of the polyunsaturated fatty acid (PUFA) residues in model membranes (liposomes) made by sonication of palmitoyllinoleoylphosphatidylcholine (PLPC). Since most biomembranes are negatively-charged, we have now studied the effect of negative surface charge on the kinetics of peroxidation of liposomes made of PLPC and 9% of one of the negatively-charged phospholipids phosphatidylserine (PS) or phosphatidic acid (PA). Peroxidation was initiated by either CuCl2 or AAPH and continuously monitored spectrophotometrically. The following results were obtained: (i) The negative charge had only a slight effect on AAPH-induced peroxidation, but accelerated markedly copper-induced peroxidation of the liposomes, probably by increasing the binding of copper to the membrane surface. (ii) Ascorbic acid (AA) inhibited AAPH-induced but promoted copper-induced peroxidation in all the studied liposomes, probably by enhancing the production of free radicals upon reduction of Cu(II) to Cu(I). (iii) alpha-tocopherol (Toc) inhibited AAPH-induced peroxidation in all the studied liposomes, whereas the effect of tocopherol on copper-induced peroxidation varied from being pro-oxidative in PA-containing liposomes, to being extremely anti-oxidative in PS-containing liposomes, even at very low tocopherol concentrations. The significance of the latter unusual protective effect, which we attribute to recycling of tocopherol by a PS-Cu complex, requires further investigation.

    更新日期:2019-11-01
  • Analysis of the lipid composition of bull spermatozoa by MALDI-TOF mass spectrometry--a cautionary note.
    Chem. Phys. Lipids (IF 2.536) Pub Date : 2003-10-29
    Jürgen Schiller,Karin Müller,Rosemarie Süss,Jürgen Arnhold,Claudia Gey,Andreas Herrmann,Jacqueline Lessig,Klaus Arnold,Peter Müller

    In this study we demonstrated the combination of MALDI-TOF MS and TLC as a fast and powerful tool to investigate the phospholipid (PL) composition of organic extracts of bull spermatozoa. Since phosphatidylcholine (PC) is the dominant PL species, an adequate resolution of MALDI-TOF spectra for sphingomyelin (SM) or phosphatidylethanolamine (PE) was achieved only after previous PL separation by TLC. We found a poor diversity especially for PE and PC, mainly containing ether-linked fatty acids which were 1-palmityl-2-docosahexaenoyl-PL and the corresponding alkenyl-acyl compound (plasmalogen) 1-palmitenyl-2-docosahexaenoyl-PL. For PC, both lipids were quantified after phospholipase A2 digestion to represent 44.2 and 37.2%, respectively, of the total PC. In contrast, the diacyl-PC content of bull spermatozoa was comparatively low (18.6% of total PC). In the presence of trifluoroacetic acid (TFA), which is routinely added to the MALDI-TOF matrix to improve the signal to noise ratio, a high lysophospholipid (LPL) content was detected in the PL extracts of bull spermatozoa, whereas TLC did not reveal significant amounts of LPL. The TFA mediated hydrolysis of the acid-labile alkenyl-acyl PL to the corresponding LPL was shown to cause this discrepancy. This assumption was verified by analysing the PL composition by MALDI-TOF MS before and after (i) digestion of sperm cell lipids with phospholipase A2 and (ii) exposition of spermatozoa to HCl fumes. We conclude that the analysis of samples containing alkenyl-acyl-PL by MALDI-TOF has to be performed with great caution.

    更新日期:2019-11-01
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