title: [Physico-chemical properties of the RNA of Sendai virus. III. Interaction with proflavin].
abstract: The binding isotherms of the Sendai virus single- and double-stranded RNA-proflavine complexes have been studied. The existence of two regions on the binding curves, corresponding to two subtypes of the strong complex (I1 and I2) has been demonstrated. The association constants and the numbers of binding sites for both subtypes were determined as a function of ionic strength. Both of the single- and for the double-stranded RNA the association constant for I1 complex were higher than those for I2 complex under all ionic strengths conditions. For the double-stranded RNA the variation of the ionic strength is more importance in case of the I1 complex formation. The total number of binding sites increases with a decrease of ionic strength. At low ionic strength (10(-4) M NaCl) the number of binding sites for single- and double-stranded RNA is practically the same and is equal to the number of binding sites for DNA at high ionic strength (1 molecule of proflavine per 3 nucleotides pairs). The heat denaturation of the RNA-proflavine complexes under different ionic conditions has been also investigated. The melting curves for double-stranded RNA-proflavine complex had two waves at high and low ionic strengths. For the single-stranded RNA the high temperature wave occured only at the high ionic strength. The dependence of heat denaturation of single-stranded RNA on ionic strength was examined for the evaluation of RNA structure. In these experiments a significant decrease of the width of melting interval under low ionic strength conditions was observed. It may reflect the existance in the RNA molecule of long helical regions. The occurence of such structures is likely to be responsible for an increase in the number of binding sites at low ionic strength and also for the appearance of the second wave on the melting curves of the single-stranded RNA-proflavine complexes at high ionic strength.
mesh_terms: D000166:Acridines; D055598:Chemical Phenomena; D002621:Chemistry; D004279:DNA, Viral; D006358:Hot Temperature; D008956:Models, Chemical; D009691:Nucleic Acid Denaturation; D009994:Osmolar Concentration; D010222:Parainfluenza Virus 1, Human / Q000032:analysis*; D011370:Proflavine; D012367:RNA, Viral; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000166:Acridines; D004279:DNA, Viral; D012367:RNA, Viral; D011370:Proflavine
vernacular_title: Fiziko-khimicheskie svoĭstva RNK virusa Sendaĭ. III. Vzaimodeĭstvie s proflavinom.