Collect. Czech. Chem. Commun. 1996, 61, 1261-1266

The Effect of Small Aliphatic Alcohols on the Dissociation of Tyrosine

Vladimír Karpenkoa, Jana Horálkováa and Milan Kodíčekb

a Department of Physical and Macromolecular Chemistry, Charles University, 128 40 Prague 2, Czech Republic
b Department of Biochemistry and Microbiology, Prague Institute of Chemical Technology,166 28 Prague 6, Czech Republic


Dissociation of tyrosine was studied in aqueous solutions of methanol, ethanol, 1-propanol, and 2-propanol of various concentrations, when the permittivity of all solutions had the same value. The effect of electrostatic interactions was, consequently, equal and thus the other interactions became more pronounced. On the basis of pK values of tyrosine -OH groups these alcohols can be divided into two groups, the first one including methanol and ethanol, the second one both propanols. The observed differences can be explained only qualitatively as a result of interaction of alcohols with tyrosine and with the surrounding water.

Keywords: Tyrosine dissociation; Alcohols effect; Isopermittivity conditions.