Lentinan is an antitumor homoglucan' isolated from Lentinus edodes, an edible mushroom popular in Japan, and it has a backbone constituted mainly of a chain of P-D-( 1+3)-linked D-glucopyranosyl residues2*3. Its molecular weight was recently reported4 to be 3 x 10' to 8 x 105. Its hydrodynamic characteristics are, however, not yet known precisely.
We have now performed quasielastic light-scattering measurements on lentinan solutions, in order to study their hydrodynamic behavior, and to establish the relationship between the molecular weight (M) and the diffusion coefficient (D) of lentinan molecules. Because lentinan samples are highly polydisperse, and quasielastic light-scattering experiments on such samples are difficult to interpret, we employed polydispersity information provided by gel-permeation chromatographic data for the samples in our analysis'.
Lentinan samples were isolated and purified by the method reported by Chihara et aL6. Gel-permeation chromatographic study was conducted by one of the authors (K.S.) and his colleagues4. Some of the gel-permeation chromatograms of lentinan samples used in the present study are shown in Fig. 1.
After being clarified by centrifuging at 10,OOOg for 1 h at room temperature, lentinan solutions (0.1%) in 0.12~ borate buffer, pH 10, were carefully placed in a light-scattering cell. The fluctuation in the intensity of the scattered light was measured at various scattering-angles by means of single-photon counting, all measurements being conducted at 20".
The light-scattering profiles of the lentinan solutions did not change for over 48 h, which shows that Ientinan molecules are stable, and have little tendency to form aggregates. The measured autocorrelation functions of the scattered light were *Dedicated to Professor Sumio Umezawa on the occasion of his 73rd birthday and the 25th anniversary of the Microbial Chemistry Research Foundation.