Conformational features of galacturonans. II. 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 ionization (%GalA-) have been determined by molecular mechanics and Monte Carlo methods. Chain extensions appear to depend substantially on contributions arising from local redistributions of charge on charged and uncharged galacturonic acid residues. Inclusion of methyl-esterified galacturonic acid units results in increased chain extensions. Incorporation of alpha-(1-->2)-L-rhamnose units causes abrupt changes in chain propagation and a reduction in calculated chain extension.