Book of Abstracts: Albany 2009
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
Poghos O. Vardevanyan1*
1Dept. of Biophysics