SOLUTION CONFORMATION OF A PECTIC ACID FRAGMENT BY H-1-NMR AND MOLECULAR-DYNAMICS

H-1-NMR and molecular dynamics simulations in vacuo and in water of (1 --> 4)-alpha-D-galacturono-disaccharide were performed. The results of the molecular dynamics simulations showed that the molecule fluctuates between two conformations characterized by different values of torsion angles around the glycosidic linkage and two different intramolecular hydrogen bonds. When these conformations are extrapolated to a regular polymeric structure, they generate pectic acid compatible with a 2(1)- or a right-handed 3(1)-helix. (C) 1994 John Wiley & Sons, Inc.