TITLE:
Zn Ions Change Binding Mode of TOEPyP4 with DNA and Cause DNA Transition from B to C and Zn-Like Conformations
AUTHORS:
Jamlet Monaselidze, Maya Gorgoshidze, David Khachidze, Maya Kiladze, Vasil Bregadze, Eugene Kiziria, Hakob Margaryan, Nune Hakobyan
KEYWORDS:
CD; Porphyrin; TOEPyP4; TMPyP4; B-C Transition; B-Z Transition
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.4 No.12,
December
16,
2013
ABSTRACT: It is known that at low concentrations of TMPyP4, this porphyrin
predominantly intercalates between GC pairs at GC-rich sites of duplex DNA and G-quadruplexes
of various constructions, and stabilizes these structures. However, there are still
some arguable suggestions about the exact binding sites and modes of TMPyP4 to GC-rich
regions of DNA in case of helation of divalent ions with help of the porphrin, which
makes porphyrin structure asymmetric. We examined TOEPyP4—analogue of TMPyP4—and
studied interaction of TOEPyP4 into the calf thymus DNA at presence of nanomole
concentrations of one of the most important microelements in cell vital function—Zn
ion. On the basis of CD and absorption spectra of the DNA-TOEPyP4 mixture, it was
determined that nanomole concentrations of Zn ions changed porphyrin intercalative
binding mode to some external binding modes, which initiated transition of the canonic
B conformation of DNA into C-like conformation, and incubation of the (DNA-TOEP4)
+ Zn mixture at 37?C caused B-Z-like transition, but no transition was observed
for the DNA-TOEPyP4 mixture. In particular, at 10 mM?NaCl, TOEPyP4/DNA
= 0.02, the binding mode change was observed in the concentration range from 150
to 300 nM?Zn, and the B-C-like transition occurred from 150 to 600 nM?Zn. The B-Z
transition at TOEPyP4/DNA = 0.015, Zn/DNA = 0.015, NaCI 10 mM, T = 37?C
was observed within incubation time interval from 0.3 to 20 hours, and maximal percent
of Z-like form was seen when incubation time interval was from 5 to 6 hours.