Divalent cation interactions with oligogalacturonides

The conformational properties of high and low molecular weight galacturonid es were investigated in relation to the ability of oligomers with degree of polymerization > 10 to act as elicitors of plant defense mechanisms. Oligo mers from polygalacturonate were obtained by means of enzymatic hydrolysis. Two fractions exhibiting high and low average degrees of polymerization we re isolated by solvent fractionation and characterized by means of electros pray mass spectrometry. The conformational behaviors of the two fractions w ere investigated in the presence of different divalent cations using circul ar dichroism. Calcium, copper, and zinc ions were able to induce a conforma tional transition in both fractions. When in the presence of the high molec ular weight fraction, copper and zinc ions were much more effective than ca lcium ions, whereas the efficiency was much reduced with low molecular weig ht oligomers.