Journal of Physical Chemistry B, Vol.115, No.12, 2924-2930, 2011
Interaction of an Antituberculosis Drug with a Nanoscopic Macromolecular Assembly: Temperature-Dependent Forster Resonance Energy Transfer Studies on Rifampicin in an Anionic Sodium Dodecyl Sulfate Micelle
In this contribution, we report studies on the nature of binding of a potent antituberculosis drug, Rifampicin (RE) with a model drug delivery system, sodium dodecyl sulfate (SDS) micelle. Temperature dependent dynamic light scattering (DLS), conductometry, and circular dichroism (CD) spectroscopy have been employed to study the binding interaction of the drug with the micelle. The absorption spectrum of the drug RE in the visible region has been employed to study Forster resonance energy transfer (FRET) from another fluorescent drug Hoechst 33258 (H33258), bound to the micelle. Picosecond-resolved FRET studies at room temperature confirm the simultaneous binding of the two drugs to the micelle and the distance between the donor acceptor pair is found to be 341 The temperature dependent FRET study also confirms that the location and efficiency of drug binding to the micelle changes significantly at the elevated temperature. The energy transfer efficiency of the donor H33258, as measured from lime-resolved studies, decreases significantly from 76% at 20 degrees C to 60% at 55 degrees C. This reveals detachment of some amount of the drug molecules from the micelles and increased donor acceptor distance at elevated temperatures. The estimated donor acceptor distance increases from a value of 33 angstrom at 20 degrees C to 37 angstrom at 55 degrees C. The picosecond resolved FRET studies on a synthesized DNA bound H33258 in RP solution have been performed to explore the interaction between the two. Our studies are expected to find relevance in the exploration of a potential vehicle for the vital drug rifampicin.