Relationship between conformation and biological response for (1----3)-beta-D-glucans in the activation of coagulation factor G from limulus amebocyte lysate and host-mediated antitumor activity. Demonstration of single-helix conformation as a stimulant.

The relationship between the conformation of (1----3)-beta-D-glucans in gel or hydrated form and the stimulation of two types of biological responses, namely, activation of coagulation Factor G from limulus amebocyte lysate (LAL) and host-mediated antitumor activity was examined. Both types were activated by the single-helical conformation, as revealed by high-resolution, solid-state 13C-n.m.r. spectroscopy. The potency of activation of Factor G was increased over 100-fold by treatment with a NaOH solution which leads to a complete or partial conversion from the triple to the single helix. Such a single-helix specific response was also demonstrated for the antitumor activity of curdlan, although the distinction was less pronounced for branched (1----3)-beta-D-glucans. The presence of the single-helix conformation was observed in schizophyllan gel, even though the triple helix is the most stable form of branched glucans in aqueous media.