title: Fluorescence label studies of the phase transitions of T7.
abstract: Optical density, fluorescence intensity, polarization and lifetime measurements were performed to analyze the temperature-induced phase transitions of phage T7 in several buffers. For labelling the intraphage DNA, ethidium bromide, proflavine and rivanol were applied for the proteins 1,6-diphenyl-1,3,5-hexatriene (DPH). In the temperature range of 20 degrees C-100 degrees C several structural changes of T7 were detected. Making corrections for light scattering by using integrating spheres and analyzing the fluorescence signals, the phase transition of intraphage DNA below 60 degrees C was interpreted as a superhelical relaxation phenomenon. The structural changes found by optical density at higher temperatures could be assigned to a change in the phage DNA or to a change in its protein part on the basis of fluorescence-melting results concerning DNA and protein labels. The effects of ionic strength and environment on the structural changes were studied.
mesh_terms: D000891:Anti-Infective Agents, Local; D004279:DNA, Viral / Q000032:analysis; D004161:Diphenylhexatriene; D004975:Ethacridine / Q000031:analogs & derivatives; D004996:Ethidium; D007700:Kinetics; D011370:Proflavine; D013050:Spectrometry, Fluorescence; D013604:T-Phages / Q000648:ultrastructure*; D013696:Temperature; D014764:Viral Proteins / Q000032:analysis
chemical_list: D000891:Anti-Infective Agents, Local; D004279:DNA, Viral; D014764:Viral Proteins; D004161:Diphenylhexatriene; D011370:Proflavine; D004996:Ethidium; D004975:Ethacridine