Solid-state NMR studies of collagen-based parchments and gelatin

Historical collagen-based parchments have been studied by solid-state NMR. In addition, new parchment (produced according to traditional methods) and gelatin from bovine skin were also studied. Wideline H-1 and MAS C-13 measurements were carried out directly on intact parchments. A simple approach is proposed for evaluation of the extent of parchment degradation based on the linewidth changes in the C-13 CPMAS spectra relative to new parchment and gelatin. Structural (bound) water content was estimated from wideline H-1 NMR lineshape and relaxation time measurements. It was found that the relative water content in parchments correlates linearly with C-13 MAS linewidths. Its decrease on parchment degradation indicates that structural water molecules are of primary importance in stabilizing higher order collagen structures. Backbone and side chain dynamics of collagen in parchments were compared to those of gelatin based on the C-13 dipolar-dephased experiments. Carbonyl C-13 chemical shift anisotropies were measured to deduce the geometry of the collagen backbone motion. Unlike previous studies, we found that the collagen backbone motion is similar to that found in other proteins and occurs primarily via small-angle librations about internal bond directions. (C) 2005 Wiley Periodicals, Inc.