Gj. Lee et al., EFFECT OF ETHIDIUM ON THE FORMATION OF POLY(DA)CENTER-DOT[POLY(DT)](2) TRIPLEX - A KINETIC-STUDY BY OPTICAL SPECTROSCOPIC METHODS, Bulletin of the Korean Chemical Society, 19(4), 1998, pp. 444-449
The kinetics of the formation of tripler poly(dA).[poly(dT)](2) from p
oly(dA).poly(dT) and poly(dT) is examined by various optical spectrosc
opic methods, including absorption, circular and linear dichroism (LD)
spectroscopy. In the pseudo first order condition, where the poly(dT)
concentration is kept lower than that of duplex, the association of t
he poly(dT) is enhanced by the presence of ethidium; the rate constant
is proportional to the amount of ethidium in the mixture. When the co
ncentration of the duplex and the single strand is the same, a spectra
l change is explained by double exponential curves, indicating that at
least two steps are involved, the fast association and slow rearrange
ment steps. In contrast to the pseudo first order kinetics, the associ
ation step in an equimolar condition is not affected by the presence o
f ethidium. In the rearrangement step, the magnitude of LD decreases w
ith an increase in ethidium concentration, suggesting that the bending
of polynucleotide around the intercalation site occurs in the rearran
gement step.