Fortschritte in Chemie und Molekularbiologie der Flavine und Flavocoenzyme

Hemmerich, P.; Veeger, C.; Wood, H. C. S.

doi:10.1002/ange.19650771604

Cited by 69 publications

(32 citation statements)

References 79 publications

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“…Flavins [in this work lumiflavin (6,7,9-trimethylisoalloxazine)] are amphoteric and, according to Hemmerich (1965), there are three protolytic forms (see also Dudley et ai., 1964). First publ.…”

Section: (Received 23 Maymentioning

confidence: 99%

DETERMINATION OF THE pk VALUES OF THE LUMIFLAVIN TRIPLET STATE BY FLASH PHOTOLYSIS

Schreiner

Steiner

Kramer

1975

Photochem & Photobiology

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Lumiflavin was prepared by photolysis of an alkaline aqueous solution of riboflavin (Knowles and Roe, 1968). As a solvent we used triply distilled water, as buffers (0,2 M) (Schwabe, 1958): pH 1-3'7 sodium acetate, hydrochloric acid pH 3·7-5·6 sodium acetate, acetic acid pH 6-12 potassium dihydrogen phosphate, sodium hydroxide pH 13 potassium chloride, sodium hydroxide (E. Merck. Darmstadt, Germany). RESULTSDependence of the lumiflavin triplet -triplet absorption spectrum on pH. Figure I shows the transient change in absorption when lumiflavin soJutions of pH = 2, pH = 7, and pH = 13 are flashed. From this the triplet-triplet absorption spectra of the acid (pH = 2), neutral (pH = 7), Kramer and Maute, 1972). The flash energy could be varied between 300 J and 900 J. The half duration of the flash was about 4-6 JlS (3001) and 6 JlS (900 J). The cuvette was surrounded by a Kodak-Wratten filter No. 2A which absorbs light of wavelength shorter than 400 nm. Using the flash apparatus described above (kinetic spectrophotometry) the spectra were recorded point-by-point at intervals of 10 nm (half-width value 2·5 nm) in the spectral region from 300 to 780 nm; the spectra were corrected for stray light.The high buffer concentration ensures that the protolytic equilibria in the triplet state are really established.Oxygen was removed by bubbling nitrogen (>99,9%) through the solutions for 45 min. The results with solutions treated in this way were identical to those with solutions degassed by the 'freezepump-and-thaw' procedure.The flash apparatus was the same as described earlier (Fischer, 81 S. SCHREINER, U. STEINER and H. E. A. KRAMER* Institut fuer Physikalische Chemie der Universitaet Stuttgart, Germany•Author to whom correspondence should be addressed. DETERMINATION OF THE pK VALUES OF THE LUMIFLAVIN TRIPLET STATE BY FLASH PHOTOLYSISConsequently one has to assurne the existence of at least three different protolytic forms for the excited states, too. Kavanagh and Goodwin (1948) found a marked change of f1uorescence of lumiflavin and riboflavin in the regions of pH 2-4 and 9-10'5. The pK values of the lumiflavin triplet are still unknown. For f1avins, there are only a few investigations of the triplet state with respect to variation of the pH (Shiga and Piette, 1964; Lhoste et ai., 1966;Katan et al., 1971).In this paper we present the results of our investigations on the triplet-triplet absorption spectra of the acid ('LfH2+), the neutral ('LfH) and the basic ('Ln forms of the lumiflavin triplet as detected by flash photolysis.Abstract-The triplet-triplet absorption spectra in aqueous solution of the acid ('UH,+), the neutral ('UH) and the basic ('Ln forms of lumiflavin (6,7,9-trimethylisoalloxazine) were measured by flash photolysis. The pK. values of the corresponding protolytic equilibria of the lumiflavin triplet were found to be 4,4, ± 0·1 and 9·8 ± 0·15.

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Section: (Received 23 Maymentioning

confidence: 99%

DETERMINATION OF THE pk VALUES OF THE LUMIFLAVIN TRIPLET STATE BY FLASH PHOTOLYSIS

Schreiner

Steiner

Kramer

1975

Photochem & Photobiology

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“…[18,19] The different flavin redox states are termed the quinone (oxidized), semiquinone (singly reduced radical anion or neutral radical), and hydroquinone (doubly reduced) states, and can be distinguished by their absorption spectra. [20,21] The characteristic absorption band of the quinone appears at 450 nm, and that of the semiquinone at 610 nm, whereas the hydroquinone has no absorption in the visible range (absorbs below 380 nm).…”

Section: Introductionmentioning

confidence: 99%

Redox Properties of LOV Domains: Chemical versus Photochemical Reduction, and Influence on the Photocycle

et al. 2007

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LOV (light-oxygen-voltage-sensitive) domains comprise the light-sensitive parts of many blue light photoreceptor proteins. Photoexcitation of the chromophore flavin mononucleotide (FMN) in these LOV domains leads to formation of a covalent adduct between FMN and a cysteine residue. So far, the electronically excited singlet and triplet states of FMN have been identified as the only intermediates in the photocycles of LOV domains from several organisms. Since many flavoproteins are redox-active, however, the photocycles of LOV domains might involve other redox states of FMN, and might be controlled by the external redox potential. Here we report on the redox properties of the LOV1 domain from phototropin of the green alga Chlamydomonas reinhardtii. By equilibrium-redox spectropotentiometry a redox potential [E(fq/fhq) (flavoquinone/flavohydroquinone)] of -290 mV vs. the normal hydrogen electrode (NHE) was determined for the wild-type domain (LOV1-wt). A similar value of -280 mV was found for the mutant LOV1-C57G, in which the photoreactive cysteine is replaced by glycine. The recovery kinetics (photoadduct-->ground state) in the photocycle of LOV1-wt are not influenced by a redox potential in the range between +500 and -260 mV versus NHE. No flavosemiquinone could be generated by chemical reduction with sodium dithionite. However, photoreduction of LOV1-C57G with EDTA leads exclusively to the flavosemiquinone. This semiquinone is stable against disproportionation, and the photoreduction is not mediated by free FMN.

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“…The structure is derived from the IH-NMR spectrum which shows a CH-triplet with ~5 = 5.30 ppm and J = 6.5 Hz -S indicative of a _cH~CH-N(5)-linkage... This species exhibits two pK a values, one at 7.4 arising from deprotonation of N(1) to yield FlredX-, as is normal for flavohydroquinones [7,8], and one at 3.4 due to protonation of N(5) (H,Fl,,X', &ax = 3 10 nm). Fig.…”

Section: Resultsmentioning

confidence: 99%

5‐(2‐Thiolyl)‐1,5‐dihydro‐flavin: A model of group transfer in flavin dependent substrate dehydrogenation

Knappe

Hemmerich

1971

FEBS Letters

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Fortschritte in Chemie und Molekularbiologie der Flavine und Flavocoenzyme

Cited by 69 publications

References 79 publications

DETERMINATION OF THE pk VALUES OF THE LUMIFLAVIN TRIPLET STATE BY FLASH PHOTOLYSIS

DETERMINATION OF THE pk VALUES OF THE LUMIFLAVIN TRIPLET STATE BY FLASH PHOTOLYSIS

Redox Properties of LOV Domains: Chemical versus Photochemical Reduction, and Influence on the Photocycle

5‐(2‐Thiolyl)‐1,5‐dihydro‐flavin: A model of group transfer in flavin dependent substrate dehydrogenation

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