Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films
The blue-light photo-reduction (conversion of oxidized flavin quinone via flavin semiquinone to fully reduced flavin hydroquinone) and dark re-oxidation of the flavins riboflavin and lumiflavin in starch (α-amylose) films was studied by absorption and luminescence spectroscopy. Blue-light photo-exci...
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| Format: | Article |
| Language: | English |
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MDPI AG
2012-07-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | http://www.mdpi.com/1422-0067/13/7/9157 |
| _version_ | 1811266788568072192 |
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| author | Alfons Penzkofer |
| author_facet | Alfons Penzkofer |
| author_sort | Alfons Penzkofer |
| collection | DOAJ |
| description | The blue-light photo-reduction (conversion of oxidized flavin quinone via flavin semiquinone to fully reduced flavin hydroquinone) and dark re-oxidation of the flavins riboflavin and lumiflavin in starch (α-amylose) films was studied by absorption and luminescence spectroscopy. Blue-light photo-excitation caused an absorption, fluorescence, and phosphorescence decrease which recovered in the dark. The photo-reduction dark-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 a long time of storage in the dark increased beyond the initial flavin quinone fluorescence efficiency. Flavin photo-excitation is thought to cause starch-flavin restructuring (static fluorescence quenching center formation), enabling enhanced photo-induced starch to flavin electron transfer with subsequent flavin reduction and starch oxidation. In the dark, after light switch-off, thermal reversion of flavin reduction and starch oxidation occurred. |
| first_indexed | 2024-04-12T20:49:42Z |
| format | Article |
| id | doaj.art-e4f7f38c5d6e455f94385b7d7cbaa02a |
| institution | Directory Open Access Journal |
| issn | 1422-0067 |
| language | English |
| last_indexed | 2024-04-12T20:49:42Z |
| publishDate | 2012-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | International Journal of Molecular Sciences |
| spelling | doaj.art-e4f7f38c5d6e455f94385b7d7cbaa02a2022-12-22T03:17:10ZengMDPI AGInternational Journal of Molecular Sciences1422-00672012-07-011379157918310.3390/ijms13079157Reduction–Oxidation Photocycle Dynamics of Flavins in Starch FilmsAlfons PenzkoferThe blue-light photo-reduction (conversion of oxidized flavin quinone via flavin semiquinone to fully reduced flavin hydroquinone) and dark re-oxidation of the flavins riboflavin and lumiflavin in starch (α-amylose) films was studied by absorption and luminescence spectroscopy. Blue-light photo-excitation caused an absorption, fluorescence, and phosphorescence decrease which recovered in the dark. The photo-reduction dark-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 a long time of storage in the dark increased beyond the initial flavin quinone fluorescence efficiency. Flavin photo-excitation is thought to cause starch-flavin restructuring (static fluorescence quenching center formation), enabling enhanced photo-induced starch to flavin electron transfer with subsequent flavin reduction and starch oxidation. In the dark, after light switch-off, thermal reversion of flavin reduction and starch oxidation occurred.http://www.mdpi.com/1422-0067/13/7/9157riboflavinlumiflavinstarchoxystarchflavin photo-reduction cyclestarch photo-oxidation cyclestatic fluorescence quenchingphoto-induced starch restructuringphosphorescencedelayed fluorescence |
| spellingShingle | Alfons Penzkofer Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films International Journal of Molecular Sciences riboflavin lumiflavin starch oxystarch flavin photo-reduction cycle starch photo-oxidation cycle static fluorescence quenching photo-induced starch restructuring phosphorescence delayed fluorescence |
| title | Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films |
| title_full | Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films |
| title_fullStr | Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films |
| title_full_unstemmed | Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films |
| title_short | Reduction–Oxidation Photocycle Dynamics of Flavins in Starch Films |
| title_sort | reduction oxidation photocycle dynamics of flavins in starch films |
| topic | riboflavin lumiflavin starch oxystarch flavin photo-reduction cycle starch photo-oxidation cycle static fluorescence quenching photo-induced starch restructuring phosphorescence delayed fluorescence |
| url | http://www.mdpi.com/1422-0067/13/7/9157 |
| work_keys_str_mv | AT alfonspenzkofer reductionoxidationphotocycledynamicsofflavinsinstarchfilms |