We report a detailed investigation of the interaction of Cr(NN)33+ with bovine serum albumin (BSA), an important protein for the transport of drugs in blood plasma which allows us to understand further the role of Cr(NN)33+ as a sensitizer in photodynamic therapy (PDT). Chromium(III) complexes, Cr(5Cl-phen)33+, Cr(5Me-phen)33+ and Cr(5Ph-phen)33+ (where Cl = chlorine, Me = methyl and Ph = phenyl are substituents in position 5 of the phen = 1,10-phenanthroline bidentate ligand), were used for the present study. The interactions of BSA with Cr(NN)33+ were assessed employing fluorescence spectroscopy and UV-Vis absorption spectroscopy; in addition electrochemical experiments carried out at a liquid/liquid interface gave insight into the relative hydrophobicities of the complexes. We found that chromium complexes bind strongly with bovine serum albumins (BSA) with intrinsic binding constants, Kb, of (3.33 ± 0.08) × 105 M-1, (5.92 ± 0.08) × 105 M-1 and (1.64 ± 0.05) × 105 M-1 at 300.3 K. Analysis of the thermodynamic parameters ΔG, ΔH, and ΔS indicated that hydrophobic interactions played a major role in all the BSA-Cr(NN)33+ association processes. The binding distances and transfer efficiencies for BSA binding reactions were calculated according to the Förster theory of non-radiation energy transfer giving distance (r) of 2.63 nm, 2.94 nm and 3.00 nm for 5Clphen, 5Mephen and 5Ph phenanthroline complexes, respectively. All these experimental results indicate that Cr(NN)33+ binds to serum albumins, by which these proteins could act as carriers of this complex for further applications in PDT.

中文翻译：

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聚吡啶基Cr（III）配合物与牛血清白蛋白的相互作用。

我们报告了对Cr（NN）33+与牛血清白蛋白（BSA）相互作用的详细调查，牛血清白蛋白（BSA）是血浆中药物运输的重要蛋白质，可让我们进一步了解Cr（NN）33+的作用光动力疗法（PDT）中的敏化剂。铬（III）配合物Cr（5Cl-phen）33 +，Cr（5Me-phen）33+和Cr（5Ph-phen）33+（其中Cl =氯，Me =甲基和Ph =苯基是位置5的取代基的phen = 1,10-菲咯啉二齿配体）用于本研究。用荧光光谱法和紫外可见吸收光谱法评价BSA与Cr（NN）33+的相互作用。另外，在液/液界面进行的电化学实验使人们深入了解了配合物的相对疏水性。我们发现铬配合物与牛血清白蛋白（BSA）牢固结合，固有结合常数Kb为（3.33±0.08）×105 M-1，（5.92±0.08）×105 M-1和（1.64±0.05）×在300.3 K时为105 M-1。对热力学参数ΔG，ΔH和ΔS的分析表明，疏水相互作用在所有BSA-Cr（NN）33+缔合过程中均起主要作用。根据非辐射能量转移的Förster理论计算BSA结合反应的结合距离和转移效率，得出5Clphen，5Mephen和5Ph菲咯啉配合物的距离（r）分别为2.63 nm，2.94 nm和3.00 nm。所有这些实验结果表明，Cr（NN）33+与血清白蛋白结合，通过这些蛋白，这些蛋白可以充当该复合物的载体，以在PDT中进一步应用。