THE MECHANISM OF THE FLAVIN SENSITIZED PHOTODESTRUCTION OF INDOLEACETIC ACID*

B. Nathanson, M. Brody, S. Brody, S. B. Broyde

Research output: Contribution to journalArticlepeer-review

Abstract

Abstract— A detailed in vitro study was made of the flavin sensitized photoinactivation of indoleacetic acid, using primarily riboflavin as sensitizer. The dependence of the quantum yield on reactant concentrations, pH, presence of oxygen, viscosity, temperature, KI concentration, and solvent was determined. The involvement of a limiting dark reaction was demonstrated, using an intermittent light technique. The results are consistent with a mechanism involving a metastable state of riboflavin as the photochemically reactive species. The calculated rate constant for intersystem crossing to this state was found to be 2.5 times 108/sec. Riboflavin, in the metastable state, is believed to oxidize indoleacetic acid to indolealdehyde, with subsequent recovery of riboflavin by autoxidation. The maximum quantum yield of the photoinactivation of IAA is 0.71, indicating a highly efficient process, approaching 100% when energy loss due to riboflavin fluorescence is taken into account. Both carotenoids and pure chlorophyll‐a were found to be inactive as sensitizers.

Original languageEnglish (US)
Pages (from-to)177-187
Number of pages11
JournalPhotochemistry and photobiology
Volume6
Issue number3
DOIs
StatePublished - Mar 1967

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

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