310.15K时蛋白质模型化合物与二元醇在水溶液中的异系焓相互作用

Heterotactic Enthalpy of the Interaction between Protein Model Compounds and Diols in Aqueous Solutions at 310.15 K

利用2277热活性检测仪的流动量热系统测量蛋白质模型化合物(甘氨酸、丙基酸、N,N-二甲基甲酰胺(DMF)和N,N-二甲基乙酰胺(DMA))与二元醇(1,3-丁二醇和2,3-丁二醇)的混合过程焓变以及各自的稀释焓;依据McMillan-Mayer理论对实验数据进行分析,获得310.15K时水溶液中蛋白质模型化合物与二元醇异构体分子的异系焓相互作用系数(hxy,hxxy,hxyy).结果表明,hxy值均为正值,此过程吸热效应占主导作用,并且hxy(DMA)>hxy(丙氨酸)>hxy(甘氨酸)>hxy(DMF)和hxy(2,3-丁二醇)>hxy(1,3-丁二醇).根据结果讨论了溶质-溶质相互作用和溶质-溶剂相互作用情况,阐明了二元醇官能团相对位置的变化对hxy值的影响,发现DMF或DMA与二元醇之间有较强的氢键作用,由于DMF分子共振结构有较好的可极化性,DMF与二元醇的氢键作用被进一步加强.

The enthalpies of mixing for model protein compounds （glycine, alanine, N,N-dimethyl formamide （DMF） and N,N-dimethyl acetamide （DMA）） with diols （1, 3-butanediol and 2, 3-butanediol） and their respective enthalpies of dilution in aqueous solutions at 310.15 K were determined by flow microcalorimetric measurements. Heterotactic enthalpic interaction coefficients （hxy, hxxy, hxyy） were obtained by analyzing these experimental results according to McMillan-Mayer theory. The results indicated that the hxy values were all positive with a dominant endothermic effect and the coefficients decreased according to the order of hxy（DMA）hxy（Ala）hxy（Gly）hxy（DMF） and hxy（2,3-butanediol） hxy（1,3-butanediol）. Based on these results, we discussed solute-solute and solute-solvent interactions with regards to the influence of the relative position of the diol functional groups on the value of hxy. We found that the hydrogen bonds between DMF or DMA and the diols were strong, and because of the good polarizability of DMF′s resonance structure, hydrogen bonds between DMF and the diols were further strengthened.