The interactions of Morin (2', 3, 4', 5, 7-pentahydroxyflavone) and its Zn-
complex, ZnL2. 3H(2)O [L = Morin (2'-OH group deprotonated)], with calf thy
mus DNA have been studied using fluorimetric and electrochemical methods. Z
nL2. 3H(2)O has different spectral characteristics and electrochemical beha
vior from that of Morin in the presence of DNA. Increasing fluorescence is
seen for ZnL2. 3H(2)O with DNA addition whereas decreased fluorescence is o
bserved for Morin. An isosbestic point appears at 560 nm for the DNA-ZnL2.
3H(2)O system with ethidium bromide (EB) addition while no isosbestic point
is detectable for Morin. Quenching fluorescence is observed for DNA-EB sys
tem when ZnL2. 3H(2)O is added whereas no quenched fluorescence is seen for
DNA-EB system with Morin addition. The above results suggest that Morin an
d ZnL2. 3H(2)O can both bind to DNA, but the binding mode is different. The
complex binds to DNA mainly by intercalation, while Morin binds in a non-i
ntercalating mode. The binding constant and binding site sizes are derived
from electrochemical methods. For ZnL2. 3H(2)O, the binding constant is 5.0
x 10(4) 1 mol(-1) at 20 degrees C, and the binding site size n(s) is 5. (C
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