Conformational dynamics of hyaluronan in solution. 1. A C-13 NMR study of oligomers

Conformational dynamic properties of a series of hyaluronan oligomers (UA)( n), with degree of polymerization n = 2-6, have been investigated through e xtensive NMR experiments. Dynamic parameters T-1, NOEF (by gated decoupling experiments), and T-2 (by line broadening experiments) on these samples ha ve been collected and analyzed in terms of several averaging procedures aim ed at discriminating the ring position in the chain and the carbon type in the ring units U and A. Trends of these parameters and changes of carbon re sonance pattern as a function of the oligomer degree of polymerization n ha ve been interpreted in terms of changes in the local dynamics of the probe in the conformational fluctuations mainly due to the soft torsional angles at the glycosidic linkages. Preliminary molecular dynamics results on two o ligomers (UA)(2) and (UA)(4) are used to disclose the complex variations wh ich affect the dynamic features of the oligomers, upon increasing degree of polymerization.