PEROXIDASE‐GENERATED TRIPLET INDOLE‐3‐ALDEHYDE ADDS TO URIDINE BASES AND EXCITES THE 4‐THIOURIDINE GROUP IN t‐RNAPhe

Abstract
Triplet indole‐3‐aldehyde generated by the peroxidase catalyzed aerobic oxidation of indole‐3‐acetic acid adds to t‐RNAphe with an efficiency which can reach 20% of the theoretical value based upon the substrate. The reaction occurs with uridine groups and is of the Paterno‐Büchi type. Magnesium ions reduced addition and increased the sensitized emission from the 4‐thiouridine group. Our results, coupled with available biological data obtained with selectively labeled indole‐3‐acetic acid, support the hypothesis that formation of triplet indole‐3‐aldehyde is at the root of the biological effects of indole‐3‐acetic acid.