氨基酸、酰胺、多羟基醇化合物相互作用的热力学研究

【作者】 杨艳；

【导师】 孙海涛；

【作者基本信息】 曲阜师范大学 ， 物理化学， 2006， 硕士

【摘要】 氨基酸、酰胺作为重要的生物活性物质,是组成蛋白质的基本结构单位,被认为是研究中重要的生物模型化合物。糖类和多羟基化合物能够稳定球形蛋白质的天然构象,而有机溶剂对蛋白质的溶解性、变性行为、折叠和解折叠及酶的活性等都有很大影响。通过研究水溶液中氨基酸与多羟基化合物的热力学性质,既可以获得水溶液中溶剂化的溶质分子间的相互作用方面的信息,又有助于了解多羟基化合物对蛋白质的稳定机理及氨基酸在蛋白质中的构象稳定性和解折叠过程中所担当的角色。 本论文主要以六种氨基酸、酰胺与多羟基化合物为研究体系,主要由以下五个部分组成: 第一部分:概述了蛋白质模型分子体系溶液热力学的研究状况。 第二部分:310.15K（37℃）时,用2277热活性检测仪的流动混合测量系统测定了六种典型氨基酸分别与甘露醇和甘露糖的混合焓及各自的稀释焓,根据McMillan-Mayer理论关联得到各级异系焓相互作用系数,从溶质—溶质相互作用的角度,研究了氨基酸与多元醇、多元糖分子的作用机制。 第三部分:测定了310.15K（37℃）时六种氨基酸分别与三种乙酰胺在水溶液中的混合焓及各自在水溶液中的稀释焓,根据McMillan-Mayer理论得到各级焓作用系数,分析了六种氨基酸与三种酰胺分子间的异系焓对作用系数h_xy。 第四部分:经测定得到了五种酰胺与丁二醇的三种异构体在298.15K（25℃）时的各级异系焓相互作用系数,并进行了分析比较,讨论了五种乙酰胺分子与三种丁二醇分子的相互作用机制。 第五部分:采用密度泛函理论（DFT）等方法研究了甲酰胺分子分别与丁二醇的三种异构体分子以1:1的比例形成的氢键络合物,从B3LYP6-31G到6-31++G（d,p）基组水平进行了优化,利用结合能数据讨论了焓对作用系数的差别。通过理论计算较好地解释了溶液中溶质—溶质相互作用理论。更多还原

【Abstract】 Amino acids and amide, which have been used extensively as the most important biological model compounds, are not only the basic building blocks of proteins, but also the important active materials in living things. Sugars and polyols help in stabilizing the native conformation of globular proteins. There has been significant interest in the investigation on the interaction in aqueous solutions between amino acids and organic molecules present in living organisms or possessing functional group identical. The principle reasons for studying such systems are to obtain the information that contributes to the growing body of knowledge about solute solvation and solute-solute interactions in aqueous media, and a better understanding of their role played in the conformational stability and unfolding behavior of proteins.This paper mainly consists of the following five parts.The first part summarizes the general states of studies on the thermodynamic properties of systems containing protein model molecules.In the second part, enthalpies of mixing of aqueous amino acids solutions （glycine, L-alanine, L-serine, L-valine, L-proline, L-threonine） with aqueous polyols solutions （mannitol, manna saccharine） have been determined at 310.15K by 2277 flow micro calorimetric system. These results along with enthalpies of dilution of these aqueous solutions have been used to obtain the enthalpic interaction coefficients (h_xy, h_xxy, h_xyy) in terms of the McMillan-Mayer theory. The pairwise interactions between amino acids and polyols have been discussed by solute-solute interaction theory.In the third part, the enthalpic pairwise interactions between six kinds of amino acids and three N- ethane amides have been determined at 310.15K.In the forth part, the heterotactic enthalpic pairwise interaction coefficients between five amides and butanediol isomers （1,3-butanediol, 1,4-butanediol and 2,3-butanediol） at 310.15K are discussed. The change of temperature made remarkable effects on the values of h_xy.In the last part, the hydrogen bonding of 1:1 complexes formed between N-methyl amide and three kinds of isomers of butanediol have been completely investigated using B3LYP method at varied basis set levels from 6-31G to 6-31++G （d, p）. The results show that the interaction energies of hydrogen bond complexes between amino acids and butanediol isomers have great effects on the values of hxy. The stronger the interaction energy is, the smaller is the value of hxy:更多还原