Circular Dichroism Studies on Southern Bean Mosaic Virus

Circular dichroism spectra showed that the RNA of southern bean mosaic virus (SBMV) has considerable base pairing and that the protein subunit has a higher proportion of -structure than of α-helix. A specific feature of the circular dichroism (CD) spectra of SBMV at 230 nm appears to be related to the binding of divalent cations to the virion; Ca²⁺ affects this CD spectral feature at a lower concentration than does Mg²⁺ or Sr²⁺. The CD spectra are compared with those of turnip rosette virus (TRosV), another member of the SBMV group.