Effect of compensatory organic osmolytes on resistance to freeze-drying of L929 cells and of their isolated chromatin.

(1) Compensatory organic osmolytes are stabilizers of macromolecular structures. During acclimation to dehydration or high salinity, they accumulate in cells and effectively protect them against disruption that might otherwise result from increased inorganic ion concentrations. (2) Circular and electric dichroism, analysis of the kinetics of digestion by micrococcal nuclease, and UV spectra between 190 and 305 nm were used to investigate the resistance to dehydration upon freezing or freeze-drying that could confer such compounds to chromatin isolated from cultured L929 cells.

Interaction of DNA-threading peptide-amsacrine conjugates with DNA and chromatin.

The SPKK peptide motif which functions as a DNA minor groove binding unit in various chromosomal and gene regulatory proteins has been attached to the antitumour drug amsacrine in order to reinforce interaction with DNA. Two bifunctional molecules in which an amsacrine-4-carboxamide derivative is linked to one or two SPKK motifs via a diaminopropyl tether have been designed and synthesized. We have applied various spectroscopic methods (absorption, circular and linear dichroism) to delineate the role of the peptide moiety as opposed to the chromophoric acridine moiety in the interaction of the conjugates with both DNA and chromatin.

Interaction of a DNA-threading netropsin-amsacrine combilexin with DNA and chromatin.

Combilexins are a group of DNA ligands having a sequence-specific minor groove binding element combined with an intercalating chromophore which stabilizes the DNA complex and can interfere with topoisomerases. In this study, complementary methods of spectroscopy (absorption, circular dichroism, electric linear dichroism) and biochemistry (viscometry, footprinting) have been applied to explore the nature of the complex formed between a new amsacrine-4-carboxamide-netropsin combilexin and DNA or chromatin. Collectively, the structural and kinetic data concur that the conjugate threads through the DNA double helix so as to intercalate its acridine chromophore, leaving the netropsin moiety and the methanesulfonanilino group positioned within the minor and major grooves of the double helix, respectively.