采用多光谱技术研究pH-依赖的食品色素酸性绿9(AG9)和酸性蓝9(AB9)与牛血清白蛋白(BSA)间的相互作用.BSA-AG9/AB9体系的KSV值与温度呈负相关,对应的Kq值比猝灭剂与生物分子的最大散射碰撞猝灭常数(2.0×1010 L·mol-1·s-1)高,且BSA的RLS光谱强度随AG9/AB9的加入逐渐增强,表明AG9/AB9对BSA的猝灭机制是静态猝灭而不是动态猝灭.从热力学参数ΔG0<0,ΔH0<0,ΔS0>0可以看出AG9/AB9与BSA间的结合作用是以静电力为主要驱动力的自发放热过程.所研究pH范围内,AG9/AB9在BSA上的特异性结合位点位于Trp残基(位点I,子域IIA),在相同条件下的结合亲和力遵循以下顺序:BSA-AG9>BSA-AB9.两体系在低pH溶液中的K值较大,证实AG9/AB9与BSA间结合作用的pH依赖行为:随酸性的增强而增强.此外,分析不存在和存在AG9/AB9时Hurea的变化来探讨BSA的结构稳定性.%Multiple spectroscopic techniques were employed to detect pH-dependent interaction of food colorants acid green 9 (AG9)and acid blue 9(AB9)with BSA. All the KSV values for BSA-AG9/AB9 system were negatively correlated with the tempera-ture,and their Kq values were higher than the maximum scatter collision quenching constant of quenchers with biomolecule(2. 0× 1010 L · mol-1 · s-1 );the RLS intensities of BSA were heightening with adding AG9/AB9. It suggested that the fluorescence quenching mechanism of BSA by AG9/AB9 was a static quenching rather than the dynamic one. The negativeΔG0 ,ΔH0 and positiveΔS0 values demonstrated that the binding of AG9/AB9 with BSA was a spontaneous and exothermic reaction driven by elec-trostatic force. The specific binding site of AG9/AB9 on BSA within the studied pH range is located in Trp residue(site I,subdoma-in II A),and under the same conditions,the combination affinity of BSA-AG9 system was stronger than that of BSA-AB9. The high-er K values at a lower pH for BSA-AG9/AB9 system suggested that there was a stronger binding at the higher acidity,i. e. the pH-dependent behavior. Besides,the change of Hurea in the absence and presence of AG9/AB9 was analyzed to discuss the structural stability of BSA.
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