Viruses and Raman spectroscopy: determination of secondary structures of viral capsids and chromosomes by difference methods

摘要

Vibrational spectra of the double-stranded DNA genome of an icosahedral virus (P22) in packaged and unpackaged states have been accurately compared by digital difference Raman spectroscopy. The difference Raman spectrum, which is sensitive to structural changes at the level of $LS 2% of a given nucleotide type, reveals the effects of packaging upon sugar pucker, glycosyl orientation, phosphodiester geometry, base pairing, base stacking and the electrostatic environment of DNA phosphate groups. At the experimental conditions employed, the B form secondary structure of unpackaged P22 DNA is minimally perturbed by packaging the viral genome in the virion capsid. However, the electrostatic environment of DNA phosphates is dramatically altered with packaging. The present results suggest a simple model for organization of the condensed dsDNA chromosomes of icosahedral viruses.