Book of Abstracts: Albany 2009

category image Albany 2009
Conversation 16
June 16-20 2009
© Adenine Press (2008)

Cooperative Effect of EtBr on DNA-cis-DDPt Complexes

In the current series of investigations the effects of EtBr on cis-DDP-DNA complexes was studied. The experiments were conducted within the relative cis-DDP/DNA concentration ranging between 1·10-5 to 5·10-2. The concentrations of EtBr were chosen in the lowers range to insure low levels of DNA saturation. The conditions were optimized to obtain isotherm of adsorption of EtBr with cis-DDP-DNA complexes within the linear region in the Sketchard?s coordinates. The linear isotherm of DNA-ligand binding allow to determine characteristic parameters of binding such as the binding constant (K) and the number of biding sites (n) on DNA for a ligand (i.g. EtBr) (1,2). Experimental results show that both binding constant and number of biding sites change with the relative concentration of cis-DDP/DNA complex.

At low cis-DDP/DNA relative concentration, the molecule of DNA undergoes fundamental changes in which cis-DDP forms pseudo circular structure in DNA, which, in turn, allows EtBr to intercalation into the dsDNA with greater ease in the circular regions of DNA. As a result the value of K increases. Simultaneously the value of n is readily reduced. At high cis-DDP/DNA relative concentration value of K deceases as a result of single and double strand brakes in DNA. With decrease in dsDNA, predominating mode of interaction of EtBr with DNA becomes semi intercalation. Farther increase in cis-DDP/DNA relative concentration, values of both K and n increase because with increase in concentration of cis-DDP the amount of double strand brake increases which results in formation of short dsDNA fragments. Under such conditions (high cis-DDP concentrations) interaction of EtBr with cis-DDP/DNA complex mainly occurs via the intercalation mode.

References and Footnotes
  1. Bloomfield, V.A., Crothers, D.M., Tinoco I. Nucleic Acids. Structures, Properties and Functions. University Science Books, Sausalito, California, (1999). (ISBN 0-935702-49-0).
  2. Arakelyan, V.B., Babayan, Yu.S., Tairyan, V.I., Arakelyan, A.V., Parsadanyan, M.A., Vardevanyan, P.O. J. Biomol. Str. Dyn. 23, 479-483 (2006).

Poghos O. Vardevanyan1*
Anush V.Arakelyan1
Ara P. Antonyan1
Lilit S.Baghdasaryan1
Gor S. Sarkisyan2

1Dept. of Biophysics
Yerevan State University
Yerevan, 0025, Armenia
2The Scripps Research Inst.
10550 N. Torrey Pines Rd.
La Jolla, CA 92037