Abstract:

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.

Key words: Protonation constant, SDS Micelle, Aminoacid, Dipeptide