Origin of the residual NMR linewidth of a peptide bound to a resin under magic angle spinning

The tetrapeptide Ala-lle-Gly-Met bound to a Wang resin via the methionine residue was studied by NMR under MAS conditions and compared to the same peptide in solution. The bound peptide exhibits average linewidths superior to those observed for the peptide in solution, The origin of the residual NMR linewidth observed for the bound form was investigated, The dynamics of the peptide is shown to be only marginally responsible for the increased linewidth; the major cause of the line broadening appears to be nonaveraged magnetic susceptibility differences. (C) 1999 academic Press.