[Possibility of spectrophotometric registration of conformation changes of polynucleotides in the system poly(A:U)-pyronine G].

The spectrophotometric study of poly(A:U) (90:10)-pyronine G (PG) complex formation has shown that the interaction of PG with polyriboadenylic acid pH = 6.3 is not changed despite the presence of 10% of pyrimidine bases in the single-stranded polynucleotide chain. Analysis of the dependence of complex formation versus acidity increase in the visible spectral range suggests that there are two forms of protonated double-stranded helix of poly(A:U) (90:10), as well as poly(A). PG dye does not interact with the more strongly protonated form by means of the aggregation. There is a strong resemblance between the interaction of PG with the less strongly protonated form and with the neutral single-stranded form of poly(A:U) (90:10). One can determine pH-transition ranges of the two poly(A:U) (90:10) protonated forms using the difference in their interaction with PG at low concentrations of polynucleotide.