STUDY OF COMPLEX-FORMATION BETWEEN ETHIDI UM-BROMIDE AND THE SELF-COMPLEMENTARY DESOXYTETRANUCLEOTIDE 5'-D(APGPCPT) BY UNI-DIMENSIONAL AND 2-DIMENSIONAL H-1-NMR SPECTROSCOPY
An. Veselkov et al., STUDY OF COMPLEX-FORMATION BETWEEN ETHIDI UM-BROMIDE AND THE SELF-COMPLEMENTARY DESOXYTETRANUCLEOTIDE 5'-D(APGPCPT) BY UNI-DIMENSIONAL AND 2-DIMENSIONAL H-1-NMR SPECTROSCOPY, Biofizika, 40(6), 1995, pp. 1189-1201
Complex formation of ethidium bromide (3,8-diamino-6-phenyl-5-ethyl-ph
enanthridine) with the self-complementary desoxytetraribonucleosidetri
phosphate d(ApGpCpT) was studied in aqueous solution by uni- and two-d
imensional H-1 NMR spectroscopy (500 and 600 MHz). The concentration d
ependence of the chemical shifts of protons of the complex at a fixed
temperature (T=308 K) were measured. The schemes of complexing of the
dye with the tetranucleotide which take into account eventual molecula
r associates in solution are discussed. Equilibrium constants of the r
eactions and the limiting values for the chemical shifts of the proton
s of ethidium bromide incorporating into the complex were calculated.
Relative contents of different complex types were analyzed. The relati
onship between the dynamic equilibrium and dye/tetranucleotide concent
ration ratio was examined. The conclusion is made that, as with the co
mplex of proflavine with the d(AGCT) examined earlier, ethidium bromid
e is intercalated essentially into the G-C site of the tetranucleotide
being in the duplex form. The difference in intercalation between eth
idium bromide and proflavine lies in the fact that ethidium bromide in
corporate on the side of the narrow groove, whereas proflavine is buil
t in on the side of the large groove. Based on the calculated values o
f the induced chemical shift of ethidium bromide protons and 2-d NOE s
pectal data, an adequate model (1:2) of the complex of the dye with te
tranucleotide in solution was constructed.