Significance of bound residual water in the DMSO solution structure of stable peptide hydrates

Abstract

Water molecules in peptide hydrates are widely known to be directly involved in the stabilization of the peptide structure in the solid state. In this work, the influence of tightly bound residual water molecules on the conformational properties of two hydrates of the L-Arg-L-Leu-Gly and Gly-L-Phe-L-Leu peptide lyophilized from water at acidic pH, has been investigated for the first time in DMSO solution by means of 1 D and 2D ¹H NMR spectroscopy. Significant conformational changes have been observed in solution as the bound residual water is gradually expelled from the peptide hydrate. These observations point out the crucial role of bound water in fine-structural determinations of peptides in solution when evaluating NMR data.