Albany 2013: Book of Abstracts
June 11-15 2013
©Adenine Press (2012)
The melting of DNA in the presence of meso-tetra-pyridyl Porphyrins with different peripheral substituents
The influence of water soluble cationic 3N- and 4N-pyridyl porphyrins with different peripheral substituents (oxyethyl, buthyl, allyl, metallyl) on melting parameters of DNA has been studied.
Results indicate that the presence of porphyrin changes the shape and parameters of DNA melting curve. The increase of porphyrins concentration results in the increase of the melting temperature (Tm) and melting interval (ΔT) of DNA.
At the porphyrin-DNA concentration ratio r = 0.01, changes of melting temperature have not been observed. The melting intervals almost don’t change upon adding of the 4N- porphyrins, while the decrease of ΔT, in the presence of 3N-porphyrins, is observed. Because of the intercalation binding mechanism occurs in GC-rich regions of DNA we assume that 3N-porphyrins intercalated in GC-rich regions, reduce the thermal stability of these sites, bringing them closer to the thermal stability of the AT-sites, which is the reason for the decrease melting interval.
While at the relative concentration r = 0.01 for 4-N porphyrins already the external binding mechanism “turns on” and destabilizing effect of porphyrins on GC-pairs compensates stabilizing effect on AT-pairs, as a result of which change in the melting of DNA upon complexation with these porphyrins is not observed. The decrease of the hypochromic effect also indicates the intercalation of investigated porphyrins in the DNA structure, which weakens staking interaction of base pairs of DNA.
The increase of the hypochromic effect of DNA upon binding with porphyrin depends on the type of peripheral substituents of the porphyrin. The results show that porphyrins with buthyl and allyl substituens weaken staking interaction of base pairs less than porphyrins with other substituents. The largest change was observed for metallyl porphyrins. It can be the result of bulky peripheral substituents, which makes significant local changes in DNA structure.
1 Department of Molecular Physics