Basu Anirban, Kumar Gopinatha Suresh
Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology , Kolkata 700 032, India.
J Agric Food Chem. 2014 Jan 8;62(1):317-26. doi: 10.1021/jf404960n. Epub 2013 Dec 20.
The interaction of the food additive carmoisine with herring testes DNA was studied by multifaceted biophysical techniques. Carmoisine exhibited hypochromic effects in absorbance, whereas in fluorescence the intensity enhanced upon complexation with DNA. Energy transfer from the DNA base pairs to carmoisine molecules occurred upon complexation. A groove binding model of interaction was envisaged for carmoisine-DNA complexation from 4',6-diamidino-2-phenylindole (DAPI) and Hoechst displacement studies. The binding of carmoisine stabilized the DNA structure against thermal denaturation. The binding induced moderate conformational perturbations in the B-form structure of DNA. The binding affinity (10(4) M(-1)) values, calculated from absorbance and fluorescence data, and calorimetry titrations were in close agreement with each other. The binding was characterized to be exothermic and favored by small negative enthalpic and large positive entropic contributions. Salt-dependent calorimetric studies revealed that the binding reaction was dominated by nonpolyelectrolytic forces. The negative heat capacity value suggested the role of hydrophobic effect in the interaction.
采用多方面的生物物理技术研究了食品添加剂胭脂红与鲱鱼精巢DNA的相互作用。胭脂红在吸光度上表现出减色效应，而在荧光方面，与DNA络合后强度增强。络合时发生了从DNA碱基对到胭脂红分子的能量转移。通过4',6-二脒基-2-苯基吲哚（DAPI）和赫斯特位移研究，设想了胭脂红与DNA络合的沟槽结合相互作用模型。胭脂红的结合使DNA结构对热变性具有稳定性。该结合在DNA的B型结构中引起适度的构象扰动。由吸光度和荧光数据以及量热滴定法计算得到的结合亲和力（10(4) M(-1)）值彼此密切一致。该结合的特征是放热，且受到小的负焓贡献和大的正熵贡献的支持。盐依赖性量热研究表明，结合反应以非聚电解质力为主导。负的热容值表明疏水效应在相互作用中的作用。
