Department of Chemistry, Karnatak University, Dharwad 580003, India.
J Pharm Biomed Anal. 2012 Feb 5;59:102-8. doi: 10.1016/j.jpba.2011.09.013. Epub 2011 Sep 22.
Serum albumin (SA) is the principal extra cellular protein with higher concentration in the blood plasma and acts as a carrier for many drugs to different molecular targets. The present work is designed to investigate the mechanism of interaction between the protein and an anti-tubercular drug, ethionamide (ETH) at the physiological pH by different molecular spectroscopic techniques viz., fluorescence, UV absorption, CD and FTIR. The interaction of SA with ETH was studied by following the quenching of intrinsic fluorescence of protein by ETH at different temperatures. The Stern-Volmer quenching constant, binding constant and the binding site numbers were calculated from fluorescence results. The results indicated the presence of static quenching mechanism in both HSA-ETH and BSA-ETH systems. The distances of separation between the acceptor and donor were calculated based on the theory of fluorescence resonance energy transfer and were found to be 2.35 nm and 2.18 nm for HSA-ETH and BSA-ETH systems, respectively. The conformational changes in protein were confirmed from UV absorption, CD and FTIR spectral data. Displacement experiments with different site probes revealed that the site I was the main binding site for ETH in protein. Effect of some metal ions was also investigated.
血清白蛋白（SA）是细胞外的主要蛋白质，在血液中的浓度较高，是许多药物向不同分子靶标输送的载体。本工作旨在通过不同的分子光谱技术，即荧光、紫外吸收、CD 和 FTIR，研究 SA 与抗结核药物乙硫异烟胺（ETH）在生理 pH 值下的相互作用机制。通过在不同温度下观察 ETH 对蛋白质固有荧光的猝灭，研究了 SA 与 ETH 的相互作用。从荧光结果计算了 Stern-Volmer 猝灭常数、结合常数和结合位点数。结果表明，在 HSA-ETH 和 BSA-ETH 体系中均存在静态猝灭机制。根据荧光共振能量转移理论计算了受体和供体之间的分离距离，分别为 HSA-ETH 和 BSA-ETH 体系的 2.35nm 和 2.18nm。从紫外吸收、CD 和 FTIR 光谱数据证实了蛋白质构象的变化。用不同的位点探针进行的置换实验表明，位点 I 是 ETH 在蛋白质中的主要结合位点。还研究了一些金属离子的影响。
