STRUCTURAL-PROPERTIES OF NATIVE AND SONICATED CINEREAN, A BETA-(1-]3)(1-]6)-D-GLUCAN PRODUCED BY BOTRYTIS-CINEREA

Cinerean, the extracellular beta-(1-->3) (1-->6)-D-glucan of the fungu s Botrytis cinerea was studied. Electron micrographs of the native pol ysaccharide revealed;quasi-endless fibrils with an estimated diameter of ca. 1.5 nm. A particle mass of 10(9)-10(10) daltons was determined from dilute solutions by low-angle laser light scattering. Sonication of increasing duration led to fragmentation of the native polymer with an approximately exponential decrease of mass in the range of average molecular masses between 250 000 and 50 000 daltons. Shadowed by plat inum, cinerean fibril fragments with a weight-average molecular mass o f 172 000 +/- 3000 daltons could be characterized from electron microg raphs as a distribution of rods of most probable length of 45 nm and a n average length of 72 nm. Small-angle X-ray scattering confirmed the fibrillar structure of the native cinerean and the rodlike structure o f sonicated cinerean. A rod diameter of 1.9 +/- 0.2 nm and a mass per unit length of 2250 +/- 490 daltons/nm were found. The latter is in ag reement with the value of 1830 daltons/nm calculated from the length d istribution determined from the electron micrographs. These data - esp ecially the mass per unit length - suggest a quaternary structure for the polysaccharide. Such a structure would explain the rigidity of the rods which, in turn, is responsible for the characteristic phase sepa ration behaviour in aqueous solutions observed by nephelometry and vis cometry.