物理化学学报 >> 2001, Vol. 17 >> Issue (07): 645-650.doi: 10.3866/PKU.WHXB20010715

研究简报 上一篇    下一篇

水溶液中氨基酸与甲脲的焓相互作用

邵爽;林瑞森;胡新根;方文军;应晓虹   

  1. 浙江大学化学系,杭州 310027;浙江教育学院化学系,杭州 310012
  • 收稿日期:2000-12-04 修回日期:2001-02-15 发布日期:2001-07-15
  • 通讯作者: 邵爽 E-mail:shaoshuang@mail.hz.zj.cn

Enthalpic Interactions of Some Amino Acids with Monomethylurea in Aqueous Solutions at 298.15 K

Shao Shuang;Lin Rui-Sen;Hu Xin-Gen;Fang Wen-Jun;Ying Xiao-Hong   

  1. Department of Chemistry,Zhejiang University,Hangzhou 310027;Department of Chemistry,Zhejiang Education Institute,Hangzhou 310012
  • Received:2000-12-04 Revised:2001-02-15 Published:2001-07-15
  • Contact: Shao Shuang E-mail:shaoshuang@mail.hz.zj.cn

摘要: 用LKB-2277精密微热量计测定了298.15 K时甘氨酸、L-丙氨酸、L-丝氨酸、L-缬 氨酸、L-苏氨酸和L-脯氨酸六种α-氨基酸分别与甲脲分子在水溶液中的混合过程焓变及 这些溶质分子在水溶液中的稀释焓.实验数据根据McMillan-Mayer理论进行回归分析,得到 各级交叉焓相互作用系数.讨论了不同氨基酸与甲脲分子的相互作用机制.结果表明,氨基酸 的两性离子部分、α-碳上的非极性脂肪侧基、极性的羟基侧基和五元吡咯环结构对交叉焓 对作用系数hxy具有不同贡献.与尿素相比,甲脲分子中-CH3基团的引入明显增强了分子的 疏水性.

关键词: α-氨基酸, 甲脲(MMU), 交叉焓相互作用

Abstract: The enthalpies of mixing of monomethylurea(MMU)with six kinds of ami no acids (glycine,L-alanine,L-serine,L-proline,L-threonine,L-valine) in aqu eous solutions have been determined by the LKB-2277 flow microcalorimetric syst em at 298.15 K.These results along with enthalpies of dilution of these solutes for the initial solutions were used to determine the enthalpic interaction coeff icients (hxy,hxxy,etc.) in terms of the McMillan-Mayer theory.The pairwise cros s interaction coefficients (hxy) of amino acids and MMU have been discussed.The results show that different side-groups of amino acids have different contribut ions to hxy.The hydrophobic-hydrophobic interactions of glycine,L-alanine and L-valine with MMU increase with the number of -CH2- groups on α-carbon.The hydroxyl group gives a negative contribution to hxy.The five-membered pyrolidin e ring in proline exhibits some hydrophobicity.The introduction of CH3 makes the hydrophobicity of MMU stronger than that of urea.

Key words: α-amino acid, Monomethylurea (MMU), Enthalpic interaction