Photochemistry of Heparin‐acridine Orange Complexes in Solution: Photochemical Changes Occurring in the Dye and Polymer on Fluorescence Fading

Photolysis of acridine‐orange‐heparin complexes in N 2 ‐ and O 2 ‐saturated solution results in permanent photooxidation of AO with little or no concomitant change in the heparin moiety. The major photoproduct is mono‐ N ‐demethylated acridine orange; in O 2 ‐saturated solution an additional minor oxygenated product, most likely the 10‐oxide (N‐oxide) or the 9‐acridanone (acridone) is also formed. The results suggest an intermolecular electron transfer between adjacently adsorbed dye molecules. The heparin moiety plays a significant role in the photochemistry by bringing dye molecules into favorable geometric orientation for biomolecular reaction and by means of specific dye‐polymer interactions.