a Institute of Biochemistry and Biophysics, University of Tehran , Tehran , Iran .
J Biomol Struct Dyn. 2014;32(3):438-47. doi: 10.1080/07391102.2013.775599. Epub 2013 Apr 13.
Sodium benzoate (SB), a powerful inhibitor of microbial growth, is one of the most commonly used food preservative. Here, we determined the effects of SB on human serum albumin (HSA) structure in the presence or absence of glucose after 35 days of incubation under physiological conditions. The biochemical, biophysical, and molecular approaches including free amine content assay (TNBSA assay), fluorescence, and circular dichroism spectroscopy (CD), differential scanning calorimetry (DSC), and molecular docking and LIGPLOT studies were utilized for structural studies. The TNBSA results indicated that SB has the ability to bind Lys residues in HSA through covalent bonds. The docking and LIGPLOT studies also determined another specific site via hydrophobic interactions. The CD results showed more structural helicity for HSA incubated with SB, while HSA incubated with glucose had the least, and HSA incubated with glucose + SB had medium helicity. Fluorescence spectrophotometry results demonstrated partial unfolding of HSA incubated with SB in the presence or absence of glucose, while maximum partial unfolding was observed in HSA incubated with glucose. These results were confirmed by DSC and its deconvoluted thermograms. The DSC results also showed significant changes in HSA energetic structural domains due to HSA incubation with SB in the presence or absence of glucose. Together, our studies showed the formation of three different intermediates and indicate that biomolecular investigation are effective in providing new insight into safety determinations especially in health-related conditions including diabetes.
苯甲酸钠（SB）是一种抑制微生物生长的强力抑制剂，是最常用的食品防腐剂之一。在这里，我们在生理条件下孵育 35 天后，确定了 SB 在存在或不存在葡萄糖的情况下对人血清白蛋白（HSA）结构的影响。利用包括游离胺含量测定（TNBSA 测定）、荧光和圆二色性光谱（CD）、差示扫描量热法（DSC）以及分子对接和 LIGPLOT 研究在内的生化、生物物理和分子方法进行了结构研究。TNBSA 结果表明，SB 具有通过共价键结合 HSA 中 Lys 残基的能力。对接和 LIGPLOT 研究也通过疏水相互作用确定了另一个特定的结合位点。CD 结果表明，与 SB 孵育的 HSA 具有更多的结构螺旋性，而与葡萄糖孵育的 HSA 具有最少的螺旋性，与葡萄糖+SB 孵育的 HSA 具有中等螺旋性。荧光分光光度法结果表明，与葡萄糖存在或不存在时 SB 孵育的 HSA 部分展开，而与葡萄糖孵育的 HSA 观察到最大的部分展开。这些结果通过 DSC 及其去卷积热谱图得到了证实。DSC 结果还表明，由于 HSA 与 SB 在存在或不存在葡萄糖的情况下孵育，HSA 中能量结构域发生了显著变化。总的来说，我们的研究表明形成了三种不同的中间体，并表明生物分子研究在提供有关安全性特别是与健康相关的条件（包括糖尿病）的新见解方面是有效的。
