柠檬黄与玉米醇溶蛋白的相互作用研究

Interaction Between Tartrazine and Zein

为了对玉米醇溶蛋白的改性研究及柠檬黄色素的安全使用评估提供理论依据,借助于荧光光谱法、紫外光谱法、全内反射-傅里叶红外光谱(ATR-FTIR)自去卷积计算及核磁共振氢谱研究了人工合成色素柠檬黄对玉米醇溶蛋白构象的影响。结果表明,柠檬黄对玉米醇溶蛋白有明显的荧光猝灭作用,猝灭机理较复杂。柠檬黄可以与玉米醇溶蛋白结合,分子间主要以疏水作用力结合,利用Stern-Volmer方程和Van’t Hoff公式计算获得结合比为1∶1,结合常数Ka值较大。通过FTIR的自去卷积计算分析,这种结合反应导致玉米蛋白二级结构中α螺旋结构、β折叠和β转角均发生显著改变。核磁共振氢谱分析表明由于玉米醇溶蛋白具有两亲性,当溶剂为二甲基亚砜时,混合溶液为低极性环境,化学位移略向高磁场移动;当溶剂为重水D2O时,化学位移明显地向低磁场移动,而且这种作用与反应时间长短无关。进一步说明在极性和低极性的环境下柠檬黄都会引起玉米醇溶蛋白构象的改变。

The effect of tartrazine on the zein conformation was studied by fluorescence spectroscopy, UV spectroscopy, ATR-FTIR self-deconvolution calculations and 1H NMR spectroscopy, in order to provide a theoretical basis for the modification study of zein and the safe use assessment of tartrazine. The results showed that tartrazine had obvious fluorescence quenching effect on zein, and the quenching mechanism was complicated. Tartrazine can bind to zein, and the molecules were mainly combined by hydrophobic interaction. Using the Stern-Volmer equation and Van’t Hoff formula, their binding ratio was calculated to be 1 ∶1 and the binding constant K a value was larger. By self-deconvolution analysis of Fourier transform infrared spectroscopy, this binding reaction resulted in significant changes in the α-helix structure,β-folding and β-turn angle in the secondary structure of zein. Nuclear magnetic resonance spectroscopy indicated that due to the amphipathic nature of zein, when the solvent was dimethyl sulfoxide, the mixed solution was in a low-polarity environment, the chemical shift shifted slightly to a high magnetic field;when the solvent was heavy water D2O, chemical shifts significantly shift to low magnetic fields, and this effect was independent of the length of reaction time. It was further illustrated that tartrazine can cause changes in the zein conformation in a polar and low polarity environment.