Basu Anirban, Suresh Kumar Gopinatha
Biophysical Chemistry Laboratory Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology , Kolkata 700 032, India.
J Phys Chem B. 2017 Feb 16;121(6):1222-1239. doi: 10.1021/acs.jpcb.6b10465. Epub 2017 Feb 3.
Interaction of two food colorant dyes, amaranth and tartrazine, with lysozyme was studied employing multiple biophysical techniques. The dyes exhibited hypochromic changes in the presence of lysozyme. The intrinsic fluorescence of lysozyme was quenched by both dyes; amaranth was a more efficient quencher than tartrazine. The equilibrium constant of amaranth was higher than that of tartarzine. From FRET analysis, the binding distances for amaranth and tartrazine were calculated to be 4.51 and 3.93 nm, respectively. The binding was found to be dominated by non-polyelectrolytic forces. Both dyes induced alterations in the microenvironment surrounding the tryptophan and tyrosine residues of the protein, with the alterations being comparatively higher for the tryptophans than the tyrosines. The interaction caused significant loss in the helicity of lysozyme, the change being higher with amaranth. The binding of both dyes was exothermic. The binding of amaranth was enthalpy driven, while that of tartrazine was predominantly entropy driven. Amaranth delayed lysozyme fibrillation at 25 μM, while tartrazine had no effect even at 100 μM. Nevertheless, both dyes had a significant inhibitory effect on fibrillogenesis. The present study explores the potential antiamyloidogenic property of these azo dyes used as food colorants.
采用多种生物物理技术研究了两种食用色素染料苋菜红和柠檬黄与溶菌酶的相互作用。在溶菌酶存在下，染料呈现减色变化。两种染料均使溶菌酶的固有荧光猝灭；苋菜红比柠檬黄是更有效的猝灭剂。苋菜红的平衡常数高于柠檬黄。通过荧光共振能量转移（FRET）分析，计算出苋菜红和柠檬黄的结合距离分别为4.51和3.93 nm。发现这种结合主要受非聚电解质力的支配。两种染料均引起蛋白质中色氨酸和酪氨酸残基周围微环境的改变，色氨酸的改变比酪氨酸相对更高。这种相互作用导致溶菌酶的螺旋度显著降低，苋菜红引起的变化更大。两种染料的结合都是放热的。苋菜红的结合由焓驱动，而柠檬黄的结合主要由熵驱动。25 μM的苋菜红延迟了溶菌酶的纤维化，而即使在100 μM时柠檬黄也没有效果。然而，两种染料对纤维形成都有显著的抑制作用。本研究探讨了这些用作食用色素的偶氮染料潜在的抗淀粉样蛋白生成特性。
