CONFORMATIONAL FEATURES OF GALACTURONANS .2. CONFIGURATIONAL STATISTICS OF PECTIC POLYMERS

The unperturbed dimensions of poly-alpha-D-galacturonic acid (PGA) as a function of the degree of polymerization (n) and degree of ionizatio n (%GalA(-)) have been determined by molecular mechanics and Monte Car lo methods. Chain extensions appear to depend substantially on contrib utions arising from local redistributions of charge on charged and unc harged galacturonic acid residues. Inclusion of methyl-esterified gala cturonic acid units results in increased chain extensions. Incorporati on of alpha-(1 --> 2)-L-rhamnose units causes abrupt changes in chain propagation and a reduction in calculated chain extension.