Optical microscopy and multinuclear NMR investigation of the liquid crystalline netropsin-DNA complex

The influence of netropsin, a minor groove binder, on the organization of calf thymus DNA in cholesteric phase has been investigated by a combination of polarized light microscopy and H-2, Na-23 and P-31 NMR spectroscopy. Compared to drug-free cholesteric DNA, a significant increase of the cholesteric pitch has been observed upon complexation at room temperature, accompanied mainly by a noticeable change in the aqueous environment close to the complexed DNA. The behaviour of netropsin has been compared to that of the intercalator ethidium bromide in liquid crystalline DNA solution in the same experimental conditions and the results were discussed in terms of possible binding modes.