Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 13: Biomaterials and Biopolymers I (joint session CPP/BP)

CPP 13.11: Talk

Tuesday, March 12, 2013, 12:30–12:45, H34

Reduction - oxidation photocycle dynamics of flavins in starch films — •Alfons Penzkofer — Fakultät für Physik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany

The blue-light photo-reduction and dark re-oxidation of the flavins riboflavin and lumiflavin in starch (α-amylose) films was studied by absorption and luminescence spectroscopy. Blue-light sample excitation caused an absorption, fluorescence, and phosphorescence decrease which recovered in the dark. The photo-reduction and dark re-oxidation cycle could be repeated. The efficiency of photo-reduction decreased with exposed excitation energy, and the speed of re-oxidation in the dark slowed down with time after excitation. The absorption did not fully recover. The fluorescence efficiency after long time of storage in the dark increased beyond the initial oxidized flavin fluorescence efficiency. Flavin photo-excitation is thought to cause a starch-flavin restructuring (static fluorescence quenching center formation) enabling enhanced photo-induced starch to flavin electron transfer with subsequent flavin reduction and starch oxidation (oxystarch formation). In the dark after light switch-off, thermal reversion of flavin reduction and starch oxidation occurred and fluorescence quenching decreased.