Ultraviolet absorption spectra and difference spectra of barley stripe mosaic and tobacco mosaic viruses in buffer and sodium dodecyl sulfate.

Ultraviolet absorption spectra and difference spectra were determined for barley stripe mosaic virus (BSMV) virions and protein and for tobacco mosaic virus (TMV) virions and protein in buffer and in sodium dodecyl sulfate (SDS). The absorbance at 260 nm of BSMV virions disrupted in SDS was 92% of that of intact virions after correction for light scattering. The corresponding value for TMV was 76%. The decrease in A(260) for BSMV virions upon disruption in SDS was almost entirely due to loss of partial hyperchromocity of RNA in the virion. However, both the protein and the RNA of TMV were hyperchromic in the virion at 260 nm compared to their light absorption after disruption in SDS. The turbidity resulting from light scattering was not a linear function of virion concentration above 2 mg/ml.