Spectroscopic Studies on the Interaction of Aristololactam-â-D-Glucoside with DNA and RNA Double and Triple Helices: A Comparative Study
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Spectroscopic Studies on the Interaction of Aristololactam-â-D-Glucoside with DNA
and RNA Double and Triple Helices: A Comparative Study
Kumar, G Suresh
The interaction of aristololactam-â-D-glucoside (ADG), a DNA intercalating alkaloid, with
the DNA triplexes, poly(dT)âpoly(dA)�poly(dT) and poly(dC)âpoly(dG)�poly(dC+), and the RNA triplex
poly(rU)âpoly(rA)�poly(rU) was investigated by circular dichroic, UV melting profile, spectrophotometric,
and spectrofluorimetric techniques. Comparative interaction with the corresponding Watson-Crick duplexes
has also been examined under identical experimental conditions. Triplex formation has been confirmed
from biphasic thermal melting profiles and analysis of temperature-dependent circular dichroic measurements.
The binding of ADG to triplexes and duplexes is characterized by the typical hypochromic and
bathochromic effects in the absorption spectrum, quenching of steady-state fluorescence intensity, a decrease
in fluorescence quantum yield, an increase or decrease of thermal melting temperatures, and perturbation
in the circular dichroic spectrum. Scatchard analysis indicates that ADG binds both to the triplexes and
the duplexes in a noncooperative manner. Binding parameters obtained from spectrophotometric
measurements are best fit by the neighbor exclusion model. The binding affinity of ADG to the DNA
triplexes is substantially stronger than to the RNA triplex. Thermal melting study further indicates that
ADG stabilizes the Hoogsteen base-paired third strand of the DNA triplexes whereas it destabilizes the
same strand of RNA triplex but stabilizes its Watson-Crick strands. Comparative data reveal that ADG
exhibits a stronger binding to the triple helical structures than to the respective double helical structures.
American Chemical Society
Roy, A and Kumar, G Suresh and Das, S and Maiti, Motilal (1999) Spectroscopic Studies on the Interaction of Aristololactam-â-D-Glucoside with DNA and RNA Double and Triple Helices: A Comparative Study. Biochemistry, 38 (19). pp. 6239-6247.