胶束溶液中某些氨基酸和二肽的解离常数

Effect of SDS Micelle on the Protonation Constants of some Aminoacids and Dipeptide

用pH电位法测定了在SDS(十二烷基磺酸钠)胶束溶液中甘氨酰丙氨酸和六种氨基酸(甘氨酸、丙氨酸、缬氨酸、亮氨酸、异亮氨酸、苯丙氨酸)的两级酸解离常数 pKa1 和 pKa2,发现与水溶液相比 ,pKa 值均显著增加 ,即SDS胶束形成强烈抑制质子解离.结合1HNMR测定结果 ,讨论了pKa1和 pKa2

The protonation constants of six aminoacids (glycine,analine,valine,leucine,isoleucine,and phenylalanine)and alycylalanine in SDS micelle solution have been determined by potentiometric pH titration technique at 25.0+0.1℃and at 0.10 mol·dm-3 ionic strength(NaNO3).It is found that all of the protonation constants in SDS solution increase remarkably as compare with these in aqueous solution.This means that SDS micelle depresses strongly the dissociation of proton.The reasons leading to the results and the rule of change of the protonation constants pKa1 and pKa2 with the concentration of SDS and the structure of these aminoacids and dipeptide are discussed by the pH titration data and 1H NMR research results.