Complementarity of infrared linear dichroism and X-ray diffraction analysis as demonstrated by the study of a DNA-drug complex.

Infrared linear dichroism and X-ray diffraction analysis on oriented films and fibres, respectively, were used simultaneously to elucidate structural characteristics of a DNA-drug complex (the drug was the anticancer antibiotic violamycin BI, an anthracycline derivative). First, the parameters accessible by the two methods are briefly explained; then, attempts to inter-correlate the data from both lines of investigations are made, which demonstrate that they support and supplement each other favourably concerning several structural aspects. This holds, in particular, for results regarding the conformational flexibility of DNA in complexes and the relative amounts of intercalated and outside-bound drug molecules. Thus, the study represents an example for a successful combined application of two physical methods to one biochemical problem.