Thermodynamic view of hydrophobic association of side chains of aromatic amino acids

Abstract

The hydrophobic association constants, K. for the side chains of phenylalanine, tyrosin and tryptophan betains have been evaluated employing the difference in the mode of self-association of the optically pure -betains and their -mixtures and using the equation of Rose and Drago. The corresponding association free energy, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>G</em>, values for benzyl-, <em>p</em>-hydroxybenzyl- and (3-indolyl)methyl groups have been determined as - 15.90, - 19.92 and - 20.21 kJmol^-1 respectively, after correcting for partial overlap of aromatic ring in <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-<img src='http://www.niscair.res.in/jinfo/small.gif' border=0>/<img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0> - <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0> dimers.