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Leucine on Silica: A Combined Experimental and Modeling Study of a System Relevant for Origins of Life, and the Role of Water Coadsorption
Langmuir ( IF 3.7 ) Pub Date : 2022-06-23 , DOI: 10.1021/acs.langmuir.2c00841
Hagop Abadian 1, 2 , Pauline Cornette 1 , Dominique Costa 3 , Alberto Mezzetti 1 , Christel Gervais 2 , Jean-François Lambert 1
Affiliation  

Leucine on silica constitutes an interesting system from the point of view of origins of life studies since leucine coadsorbed on SiO2 together with glutamic acid can give rise to rather long linear polypeptides upon activation. It is also an ideal system to test methods of molecular characterization of biomolecules deposited on mineral surfaces since it combines a small-scale model of peptides and proteins, which are among the most important components of biodevices, with one of the most widely used inorganic materials. We have deposited l-leucine on a high surface fumed silica in the submonolayer range and characterized it by a multipronged approach including macroscopic information (thermogravimetry, X-ray diffraction), in situ spectroscopic methods (IR, multinuclear solid-state NMR including single-pulse and CP-MAS, 2-D HETCOR), and molecular modeling by density functional theory (DFT), including calculation of NMR parameters. Specific information can be obtained on the adsorption and interaction mechanism. Leucine is rather strongly adsorbed without any covalent bonds, through the formation of a specific lattice of H-bonds that often involve coadsorbed water molecules. Its state is indeed strongly dependent on the drying procedure: insufficient drying results in liquid-like surroundings for the leucine functional groups, while vacuum drying only retains a limited number of waters (of the order of 5 per leucine molecule). The most stable models have zwitterionic leucine interacting directly with surface silanols through their ammonium group, while the carboxylate interacts through bridging waters. Experimental NMR chemical shifts are satisfactorily predicted for these models, and leucine can be viewed as a probe for specific groups of surface sites known as silanol nests.

中文翻译:

二氧化硅上的亮氨酸:与生命起源和水共吸附作用相关的系统的实验和建模研究

从生命起源研究的角度来看,二氧化硅上的亮氨酸构成了一个有趣的系统,因为与谷氨酸一起共吸附在 SiO 2上的亮氨酸可以在活化时产生相当长的线性多肽。它也是测试沉积在矿物表面上的生物分子的分子表征方法的理想系统,因为它结合了肽和蛋白质的小规模模型,肽和蛋白质是生物器件最重要的组成部分之一,也是最广泛使用的无机材料之一. 我们已存入l-亮氨酸在亚单层范围内的高表面气相二氧化硅上,并通过多管齐下的方法对其进行表征,包括宏观信息(热重分析、X 射线衍射)、原位光谱方法(IR、多核固态 NMR,包括单脉冲和 CP- MAS、2-D HETCOR) 和密度泛函理论 (DFT) 的分子建模,包括 NMR 参数的计算。可以获取关于吸附和相互作用机制的具体信息。通过形成通常涉及共吸附水分子的特定 H 键晶格,亮氨酸在没有任何共价键的情况下被相当强烈地吸附。它的状态确实强烈依赖于干燥过程:干燥不充分会导致亮氨酸官能团处于液体状环境中,而真空干燥仅保留有限数量的水(每个亮氨酸分子大约 5 个)。最稳定的模型具有两性离子亮氨酸通过其铵基直接与表面硅烷醇相互作用,而羧酸盐通过桥接水相互作用。对于这些模型,实验 NMR 化学位移得到了令人满意的预测,并且亮氨酸可以被视为对特定的表面位点组(称为硅烷醇巢)的探针。
更新日期:2022-06-23
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