Acta Phys. -Chim. Sin. ›› 2006, Vol. 22 ›› Issue (08): 1034-1039.doi: 10.3866/PKU.WHXB20060825

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Study on Hydrophobic Self-association of Aliphatic α-amino Acids by Flow Microcalorimetry

HU Xin-Gen;YU Li;LIN Rui-Sen;FANG Ying-Ying;LI Wen-Bing   

  1. School of Chemistry and Materials Science, Wenzhou University Zhejiang Wenzhou 325027, P. R. China;Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, Shandong University, Jinan 250100, P. R. China;Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. China;
  • Received:2006-02-21 Revised:2006-05-08 Published:2006-08-04
  • Contact: HU Xin-Gen

Abstract: A chemical interaction model has been established for the hydrophobic self- association of aliphatic α- amino acids in aqueous solutions. In order to obtain the parameters of the model equation, dilution enthalpies of 5 aliphatic α- amino acids aqueous solutions have been measured at 298.15 K by flow microcalorimetry. The equilibrium constants (K), enthalpy change (ΔHm) and entropy change (ΔSm) have been determined for the equal- step association. It was found that between enthalpy and entropy exists a good compensation relationship. In addition, partial molar excess entropies of water in solutions (SE1) were calculated, and were discussed according to the hydration model for aliphatic α- amino acids. Noteworthily, the parameters in the model equation can be used to explain the homogeneous enthalpic interaction coefficients in McMillan- Mayer model to some extent.

Key words: α-amino acids, Hydrophobic self-association, Chemical model, Dilution enthalpy, Flow microcalorimetry