Studies on the bacteriophage MS2. XXIV. Hydrodynamic properties of the native and acid MS2 RNA structures

The molecular weight of native 26.6S MS2 RNA, of acidic 53.1S MS2 RNA and of formaldehyde‐treated 36.1S MS2 RNA was determined by light‐scattering studies. The three forms examined correspond to monomers. Also νv values were determined, and in conjunction with our previous estimates for S 20,W and [η], led again to the conclusion that formaldehyde‐cross‐linked 37S MS2 RNA is a monomer. On the basis of the experimentally observed R G , [η], S 20,W , and νv values, and taking a prolate ellipsoid as a model, the hydrodynamic volume, the solvation water and the axial ratio could be deduced for the three conformations. In the “native” 26S form the RNA occupies only 8.2% of the hydrodynamic volume. The formation of the 36S and the 53S structures correspond largely to a loss of solvation water.