Book of Abstracts: Albany 2009

category image Albany 2009
Conversation 16
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 the values of induced CD spectra (at 400-470 nm) for complexes tRNA with TOEPyP4 and CuTOEPyP4 there is an optimum concentration of porphyrins (r = 0.2 - 0.25) at which the anisotropy of system is maximal. Increase of concentration leads to decrease of anisotropy of system, may be as a result of aggregations. At r = 0.4 the visible aggregation of a solution takes place.

    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.
References and Footnotes
  1. Y. B. Dalyan, S. G. Haroutiunian, G. V. Ananyan, V. I. Vardanyan, D. Y. Lando, V. N.Madakyan, R. K.Kazaryan, L. Messori, P.-L. Orioli, A. S. Benight. J of Biomol Structure & Dynamics 18, 677-687 (2001).
  2. A. Ghazaryan, Y. Dalyan, S. Haroutiunian, A. Tikhomirova, N. Taulier, J. W. Wells, T. V. Chalikian. J Amer Chem Soc 128, 6, 1914-1921 (2006).
  3. Correia, J. J., Chaires, J. B. Methods in Enzymology 240, 593-614 (1994).

Y. Dalyan*
I. Vardanyan
A. Chavushyan

Yerevan State University
Faculty of Physics
Molecular Physics Department
1, A.Manoogian St.
0025, Yerevan, Armenia

*Phone:+(374 10)554341
Fax: +(374 10)577689
Email: yeva@ysu.am