Molecular weight determination of Sendai RNA by dimethyl sulfoxide gradient sedimentation

The molecular weight of the large RNA of Sendai virus has been determined by sedimentation analysis in sucrose gradients containing 99% dimethyl sulfoxide (DMSO) to be 2.3 x 10(6). Sendai RNA recovered from 99% DMSO was found to cosediment with nondenatured Sendai RNA at 46 to 48s in ordinary sucrose gradients. The molecular weight value of 2.3 x 10(6) is considerably smaller than the estimates of 6 x 10(6) to 7 x 10(6) determined under nondenaturing conditions, suggesting a unique structure for Sendai RNA.