Department of Chemistry, Islamic Azad University, Central Tehran Branch, Tehran, Iran.
J Photochem Photobiol B. 2011 Dec 2;105(3):198-202. doi: 10.1016/j.jphotobiol.2011.09.002. Epub 2011 Sep 22.
Vitamin C (L-ascorbic acid) has a major biological role as a natural antioxidant. Aspirin belongs to the nonsteroidal anti-inflammatory drugs and functions as an antioxidant via its ability to scavenge-OH radicals. Bovine serum albumin (BSA) is the major soluble protein constituent of the circulatory system and has many physiological functions including transport of a variety of compounds. In this report, the competitive binding of vitamin C and aspirin to bovine serum albumin has been studied using constant protein concentration and various drug concentrations at pH 7.2. FTIR and UV-Vis spectroscopic methods were used to analyze vitamin C and aspirin binding modes, the binding constants and the effects of drug complexation on BSA stability and conformation. Spectroscopic evidence showed that vitamin C and aspirin bind BSA via hydrophilic interactions (polypeptide and amine polar groups) with overall binding constants of K(vitamin C-BSA)=1.57×10(4)M(-1) and K(aspirin-BSA)=1.15×10(4)M(-1); assuming that there is one drug molecule per protein. The BSA secondary structure was altered with major decrease of α-helix from 64% (free protein) to 57% (BSA-vitamin C) and 54% (BSA-aspirin) and β-sheet from 15% (free protein) to 6-7% upon drug complexation, inducing a partial protein destabilization.
维生素 C（L-抗坏血酸）作为一种天然抗氧化剂具有重要的生物学作用。阿司匹林属于非甾体抗炎药，通过清除-OH 自由基发挥抗氧化作用。牛血清白蛋白（BSA）是循环系统中主要的可溶性蛋白质成分，具有许多生理功能，包括运输各种化合物。在本报告中，使用恒蛋白浓度和不同药物浓度在 pH 7.2 下研究了维生素 C 和阿司匹林与牛血清白蛋白的竞争结合。使用傅里叶变换红外光谱（FTIR）和紫外可见光谱（UV-Vis）光谱方法分析了维生素 C 和阿司匹林的结合模式、结合常数以及药物络合对 BSA 稳定性和构象的影响。光谱证据表明，维生素 C 和阿司匹林通过亲水相互作用（多肽和胺极性基团）与 BSA 结合，总结合常数为 K（维生素 C-BSA）=1.57×10(4)M(-1)和 K（阿司匹林-BSA）=1.15×10(4)M(-1)；假设每个蛋白质分子有一个药物分子。BSA 的二级结构发生了变化，主要是α-螺旋从 64%（游离蛋白）减少到 57%（BSA-维生素 C）和 54%（BSA-阿司匹林），β-折叠从 15%（游离蛋白）减少到 6-7%，导致蛋白质部分失稳。
