Book of Abstracts: Albany 2009
June 16-20 2009
© Adenine Press (2008)
Peculiarities of Interaction of Porphyrins with tRNA
The interaction of meso-tetra-(4N-oxyethylpyridyl)porphyrin (TOEPyP4) and its Zn(II), Cu(II), Mn(III)-metallocomplexes with DNA and RNA duplexes are well investigated (1, 2). It was established that the binding mode of porphyrins and metalloporphyrins with nucleic acids duplexes depend both on the type of central metal, and of peripheral substituent of porphyrins. In this work the interaction of these porphyrins with single stranded tRNA from E.Coli was studied using UV/Vis spectrophotometry and Circular Dichroism (CD) methods.
All measurements were performed in 0.1 BPSE buffer (1BPSE = 6 mM Na2HPO4 + 2 mM NaH2PO4 + 185 mM NaCl + 1 mM Na2EDTA), μ = 0.02.
The binding parameters were calculated using the absorption data and the equation (3):
where Cf is the free porphyrins concentration in solution, r = Cb/CN, Cb is the concentration of bound porphyrins, CN is the concentration of nucleotides, Kb is the binding constant and n is the number of binding sites per nucleotide.
General conclusion: these porphyrins interact stronger with single stranded tRNA than double stranded DNA or RNA.
The following peculiarities of the interaction of different porphyrins with tRNA were observed:
For complexes of ZnTOEPyP4 with tRNA the induced CD spectra are essentially different. The induced CD spectra of complex change a sign and continue to grow (remaining negative) starting from a certain relative concentration. It is possible that at high relative concentration of porphyrins the liquid crystal form may be generated from the solution.
The binding constant of ZnTOEPyP4 with tRNA is 10 times greater than with DNA. The number of nucleotides, which become inaccessible as a result of binding of one porphyrin molecule (n = 4) is higher for tRNA, than for DNA. We assume that on tRNA there are specific places for porphyrin binding.
Yerevan State University