A. Radzicka et al., LACK OF WATER TRANSPORT BY AMINO-ACID SIDE-CHAINS OR PEPTIDES ENTERING A NONPOLAR ENVIRONMENT, Biochemistry, 32(27), 1993, pp. 6807-6809
Water has been reported to enter cyclohexane in association with 3-met
hylindole, a model compound representing the side chain of tryptophan.
Entrainment of water would cloud the interpretation of measured parti
tion coefficients as a simple index of hydrophobicity. NMR and isotope
-exchange experiments indicate that the reported entrainment of water
resulted from unrecognized exchange of H-3 from water into the -NH- gr
oup of the indole ring. A more detailed analysis shows that no signifi
cant amounts of excess water (less than 0.1 molecule/molecule of solut
e) enter cyclohexane with molecules representing the side chains of tr
yptophan, phenylalanine, threonine, lysine, or the peptide bond itself
.