title: A new physical assay method for tobacco mosaic virus using a radioactive virus recovery standard and the first derivative of the ultraviolet absorption spectrum.
abstract: A new physical assay method for tobacco mosaic virus is described which incorporates two improvements on previous procedures. Losses of up to 75% of virus during extraction are corrected by adding a trace of radioactive virus to leaf samples before homogenization, and determining percentage recovery of radioactivity in final virus preparations. Estimation of virus concentration in partially purified preparations is from the first derivative (dA/d lambda) of the ultraviolet absorption spectrum, using a pronounced signal from the tryptophan fine-structure absorption band at 285-293 nm. This method is highly insensitive to ultraviolet-absorbing contaminants, which cause errors and increase variation between replicates, when estimation of virus concentration is by normal measurement of ultraviolet absorption (A260). The method can be applied to at least some other viruses.
mesh_terms: D012367:RNA, Viral / Q000032:analysis; D013056:Spectrophotometry, Ultraviolet; D014027:Tobacco Mosaic Virus / Q000302:isolation & purification*; D014316:Tritium; D014364:Tryptophan / Q000032:analysis; D014764:Viral Proteins / Q000032:analysis
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins; D014316:Tritium; D014364:Tryptophan