ORGANIZATION PROCESSES OF A PYROPHEOPHORBIDE-SPERMIDINE CONJUGATE IN THE PRESENCE OR ABSENCE OF DNA

The spectroscopic properties of a pyropheophorbide-spermidine conjugat e, a new chemical photonuclease, are described in the absence and in t he presence of DNA, The strong variations in the absorption, emission and circular dichroism spectra of this pyropheophorbide, induced by ch anging the solvent ethanol for phosphate buffer, indicate the occurren ce of an aggregation process in aqueous solution, Addition of calf thy mus (CT) DNA to a phosphate buffer solution of dye promotes biphasic v ariations on both the UV absorption and fluorescence spectra, These da ta are accounted for by an increase in the pyropheophorbide organizati on due to a template effect at low DNA concentrations (Dye/DNA > 1) an d a redistribution of the dye on the DNA backbone at high DNA concentr ations (Dye/DNA < 1). A model of the reorganization of the pyropheopho rbide in the presence of DNA is proposed on the basis of a mathematica l framework.