Interaction of tobacco mosaic virus protein with synthetic polynucleotides containing a fluorescent label: optical properties of poly (A,εA) and poly (C,εC) copolymers and energy migration from the tryptophan to 1,N6or 3,N4-ethenocytosine residues in RNP

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Abstract
A spectrophotometric method for determination of the modification degrees and molar extinction coefficients for poly(A, εA) and poly(C, εC) copolymers has been developed. Dependence of some absorption and fluorescence parameters of the copolymere on the modification degree has been studied. Distribution of modified residues in copolymers differs from random and depends on modification conditions. Interaction between the TMV protein and copolymers has been investigated. The protein interacts with poly(A, εA) of low or medium modifica tion degree and displays no activity with respect to poly(εA). On the contrary, introduction of εC to the polynucleotide promotes complex formation between poly(C, εC) and TMV protein. Analysis of the fluorescence emission and excitation spectra has revealed energy transfer from tryptophan to εA or εC in the RNP to occur and permits one to estimate the average distance between Trp (presumably Trp 52) the RNA base binding region in the virus to be 17 to 20 Å.