Bhat R, Ahluwalia J C
Department of Chemistry, Indian Institute of Technology, New Delhi.
Int J Pept Protein Res. 1987 Aug;30(2):145-52. doi: 10.1111/j.1399-3011.1987.tb03323.x.
Partial molar heat capacities (CP2 degrees) and volumes (V2 degrees) for some amino acids and peptides were measured in 1 M aqueous calcium chloride solutions at 298.15 degrees K using a Picker flow microcalorimeter and an oscillating-tube digital density meter. Using the data for these amino acids and peptides in water, the corresponding partial molar heat capacities of transfer (CP2,tr degree) and volumes (V2,tr degree) from water to 1 M aqueous calcium chloride were deduced. These thermodynamic parameters are significantly positive, indicating that strong interactions occur between the ions of calcium chloride and the charged centres of these amino acids and peptides. A comparison has been made with a similar transfer of these compounds to sodium chloride solutions. The thermodynamic parameters of the transfer of peptide group (-CONH) are much more positive in calcium chloride than in sodium chloride solutions. The implication of this result for the ability of calcium chloride to act as a stronger destabilizer of protein conformation is discussed.
使用Picker流动微量热计和振荡管数字密度计，在298.15 K下于1 M氯化钙水溶液中测量了一些氨基酸和肽的偏摩尔热容（(C_{P2}^{\circ})）和体积（(V_{2}^{\circ})）。利用这些氨基酸和肽在水中的数据，推导出了它们从水转移至1 M氯化钙水溶液时相应的偏摩尔转移热容（(C_{P2,tr}^{\circ})）和体积（(V_{2,tr}^{\circ})）。这些热力学参数显著为正，表明氯化钙离子与这些氨基酸和肽的带电中心之间发生了强相互作用。已将这些化合物转移至氯化钠溶液的类似情况进行了比较。肽基（-CONH）转移的热力学参数在氯化钙中比在氯化钠溶液中要正得多。讨论了该结果对于氯化钙作为蛋白质构象更强破坏剂能力的意义。
