Potential mechanisms of photodynamic inactivation of virus by methylene blue. I. RNA-protein crosslinks and other oxidative lesions in Q beta bacteriophage

Photochem Photobiol. 1998 Mar;67(3):350-7.


A spectrum of oxidative lesions was observed in a bacteriophage-based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Q beta were exposed to methylene blue plus light (MB + L), inactivating events, or "hits" occurred that were oxygen-dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8-oxo-7,8-dihydroguanine (8-oxoGua), and (3) single-strand breaks (ssb) in the RNA genome and (4) RNA-protein crosslinks. Formation of carbonyl groups associated with protein in the Q beta phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Q beta genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full-length Q beta RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8-oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB + L, crosslink formation between Q beta RNA and protein was observed by virtue of the location of RNA at the interface of phenol-aqueous extractions of phage suspensions. A significant increase over background of RNA-protein complexes (including full-length Q beta RNA) was observed at the lowest concentration of MB tested (0.5 microM), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Q beta inactivation and its expected lethality, RNA-protein crosslink formation may be important as an inactivating lesion in bacteriophage Q beta following MB + L exposure.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Allolevivirus / drug effects*
  • Allolevivirus / radiation effects
  • Coloring Agents / pharmacology*
  • Guanine / analogs & derivatives
  • Guanine / metabolism
  • Light
  • Methylene Blue / pharmacology*
  • Oxidative Stress
  • Photochemistry
  • Photosensitizing Agents / pharmacology*
  • RNA, Viral / drug effects*
  • RNA, Viral / metabolism
  • RNA, Viral / radiation effects
  • Viral Proteins / metabolism*


  • Coloring Agents
  • Photosensitizing Agents
  • Qbeta ribonucleic acid
  • RNA, Viral
  • Viral Proteins
  • 8-hydroxyguanine
  • Guanine
  • Methylene Blue