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Flavin spectra

Shinkai and Kunitake (1977b) prepared a hydrophobic flavin analogue, 3-hexadecyl-10-butylisoalloxazine [56]. Its absorption spectrum in CTAB micelles showed distinct shoulders at 420 nm and 460-470 nm, as in the flavin spectrum in organic solvents. This indicates that [56] is located in the hydrophobic region of the micelle. Isoalloxazine [56] bound to a cationic micelle readily oxidizes 2-mercaptoethanol, 1,4-butanedithiol, and thiophenol (Shinkai and Kunitake, 1977b Shinkai et al., 1977a). In non-micellar... [Pg.468]

Abeles and co-workers have studied the inactivation reaction of 3-dimethyl-amino-1-propyne with bovine liver MAO-A (93). Again, the inactivation reaction was found to be stoichiometric and irreversible, with covalent modification of the flavin cofactor suggested by irreversible bleaching of the flavin spectrum. Based on the chemical and spectral properties and pK of the enzymically de-... [Pg.340]

Monoamine oxidase is also susceptible to inactivation by olefins such as ally-lamine. An isotope effect of 2.3S on inactivation by [l- Halallylamine and formation of a reduced flavin spectrum are consistent with monoamine oxidase-catalyzed oxidation of the compound (Rando and Eigner, 1977). Because the... [Pg.235]

Xanthine Oxidase. One of the most thoroughly studied flavoproteins is xanthine oxidase. This enzyme has been purified from milk and from liver. Recently the milk enzyme, for many years known as the Schardin-ger enzyme, has been crystallized in a highly purified state. For many years the absorption spectrum of the purified enzyme was a source of concern, because instead of the two distinct characteristic flavin peaks, an end absorption was always found to obscure the flavin spectrum. This has now been found to be the true spectrum of the enzyme. In addition to FAD, the enzyme contains iron and molybdenum in the ratio, 8 iron 2 FAD 2 Mo per mole of enzyme. Molybdenum does not affect... [Pg.176]

Latia luciferase is colorless and normally nonfluorescent. However, the luciferase fluoresces visibly in alkaline solutions. The fluorescence is most prominent in a KCN solution, showing an emission spectrum that is very close to the bioluminescence spectrum and also to the fluorescence emission of a flavin (FAD) except for the 370 nm... [Pg.191]

The addition of sulfite to APS reductase results in changes of the flavin visible spectrum that are explained by the formation of an adduct between the sulfite and the FAD group (135). Addition of AMP to the as-isolated enzyme causes no change in the spectroscopic properties. Addition of AMP to the sulfite-reacted enzyme causes the reduction of center I. However, the formation of a semiquinone signal has never been observed either by EPR or visible spectroscopies. Also, Mossbauer and EPR data indicate that AMP closely interacts with center I (139). [Pg.384]

D. gigas AOR was the first Mo-pterin-containing protein whose 3D structure was solved. From D. desulfuricans, a homologous AOR (MOD) was purified, characterized, and crystallized. Both proteins are homodimers with-100 kDa subunits and contain one Mo-pterin site (MCD-cofactor) and two [2Fe-2S] clusters. Flavin moieties are not found. The visible absorption spectrum of the proteins (absorption wavelengths, extinction coefficients, and optical ratios at characteristic wavelengths) are similar to those observed for the deflavo-forms of... [Pg.397]

B. Nicotinamide and Flavin Coenzymes.—High-frequency (220 MHz) H n.m.r. spectroscopy shows that there are differences in conformation between oxidized and reduced pyridine coenzymes. A preliminary report on the P n.m.r. spectra of NAD+ and NADH confirms these observations, as the spectrum of NAD+ consists of an AB quartet while there is only a single resonance discernible in the spectrum of NADH. [Pg.135]

FIGURE 13.6 Whole bacterial-cell EPR. A frozen concentrated suspension of cells from the sulfate-reducing bacterium Desulfovibrio vulgaris gives an EPR spectrum with only a [2Fe-2S]1+ signal and a flavin radical signal, both from adenosine phosphosulfate reductase. [Pg.224]

The defenders of the carotenoid-photoreceptor-hypothesis have always understood the shape of these action spectra in the blue to mean that the bluelight receptor is a carotenoid. Indeed, in Fig. 6 3 it can be observed, that the three-peak absorption spectrum of trans-0-carotenoid (in hexene) agrees well with the observed action spectrum of the avena coleoptile (Fig. 3 5). However, there remains one loose end which has been the crucial point of controversy in this field, ever since Galston and Baker66 suggested in 1949 that the photoreceptor for phototropism might be a flavin Flavin absorbs in the near UV, /3-carotenoid does not. [Pg.10]

Nevertheless, the avena coleoptile exhibits a curvature to unilateral UV-illumina-tion with a satisfactory log-linear response/time relationship38) (the bending mode is similar to that observed for the second positive curvature which develops from the coleoptile base cf. 2.2). Fig. 5 338) shows that the double-peaked action spectrum does not match neither flavin (Fig. 5 5,16S)) nor carotenoid absorption (Fig. 5 4,183)), most likely excluding both as photoreceptors. The growth hormone auxin (cf. 2.4 and Scheme 1) has been discussed to be a possible photoreceptor. However, in this case, this is not supported by the action spectrum either. [Pg.11]

Composite action spectra characteristics of carotenoid (Fig. 8 2,169)) and flavin (Fig. 8 1,49)), imitated by the low temperature absorption spectra, are compared with the avena action spectrum (Fig. 8 3). Song and Moore pointed out on this basis, that the carotenoid is a rather unlikely photoreceptor, whereas the flavin is169). [Pg.14]

Another role of bluelight is exhibited by the moth Pectinophora gossypiella. A circadian rhythm of egg hatching can be initiated with a brief light pulse. The action spectrum (similar to Fig. 16 2,27)) again suggests a flavin photoreceptor. [Pg.25]

Fig. 22. (A) Comparison of flavin triplet -> triplet absorption spectra (downwards drawn) with bluelight-induced (440 nm) phototropic curvature of aVena coleoptiles as inhibited by strong monochromatic light in the long wave visible region 154). (B) Comparison of the growth response of Phycomyces induced by strong laser light of wavelength longer than 590nm46, with the flavin phosphorescence spectrum los)... Fig. 22. (A) Comparison of flavin triplet -> triplet absorption spectra (downwards drawn) with bluelight-induced (440 nm) phototropic curvature of aVena coleoptiles as inhibited by strong monochromatic light in the long wave visible region 154). (B) Comparison of the growth response of Phycomyces induced by strong laser light of wavelength longer than 590nm46, with the flavin phosphorescence spectrum los)...
Fig. 22k. The reasonably good fit between the measured points and the triplet-triplet (T i -> Tn) absorption spectrum of flavin (dotted lines, 174>117)) again suggests a flavin photoreceptor. These authorsIS4) assume an effective decrease of the lifetime of the lowest triplet state by quick triplet-triplet (Tj Tn) turnovers, thereby inhibiting photochemistry (i.e. initiation of phototropism). Fig. 22k. The reasonably good fit between the measured points and the triplet-triplet (T i -> Tn) absorption spectrum of flavin (dotted lines, 174>117)) again suggests a flavin photoreceptor. These authorsIS4) assume an effective decrease of the lifetime of the lowest triplet state by quick triplet-triplet (Tj Tn) turnovers, thereby inhibiting photochemistry (i.e. initiation of phototropism).
The low temperature absorption spectrum of isotropically dissolved flavin resembles blue-light action spectra, that of carotene does not (Fig. 8,49,169)). [Pg.41]

A sensitivity to the blue portion of the visible spectrum is a characteristic of many cells. With some of these cells, both in vivo and in vitro spectral evidence argues against the involvement of flavins. Amongst the protozoa, these cells include Chlamydomonas sp.56-74) ... [Pg.50]

Upon purification of the XDH from C. purinolyticum, a separate Se-labeled peak appeared eluting from a DEAE sepharose column. This second peak also appeared to contain a flavin based on UV-visible spectrum. This peak did not use xanthine as a substrate for the reduction of artificial electron acceptors (2,6 dichlor-oindophenol, DCIP), and based on this altered specificity this fraction was further studied. Subsequent purification and analysis showed the enzyme complex consisted of four subunits, and contained molybdenum, iron selenium, and FAD. The most unique property of this enzyme lies in its substrate specificity. Purine, hypoxanthine (6-OH purine), and 2-OH purine were all found to serve as reductants in the presence of DCIP, yet xanthine was not a substrate at any concentration tested. The enzyme was named purine hydroxylase to differentiate it from similar enzymes that use xanthine as a substrate. To date, this is the only enzyme in the molybdenum hydroxylase family (including aldehyde oxidoreductases) that does not hydroxylate the 8-position of the purine ring. This unique substrate specificity, coupled with the studies of Andreesen on purine fermentation pathways, suggests that xanthine is the key intermediate that is broken down in a selenium-dependent purine fermentation pathway. ... [Pg.141]

Vitamin B2, or riboflavin, is the metabolic precursor to two flavin coenzymes essential for the integrity of a spectrum of redox reactions. [Pg.205]

Foster Tony Cashmore has consistently argued that we simply can t know what the absorption spectra of the cryptochromes will be. Others have argued differently. The empirical evidence of a comparison between a flavin absorption spectrum and that of the new CRYl over-expression by Ahmad and colleagues suggests that there is a close correlation. [Pg.25]

Dunlap One of the experiments done in a microbial system to prove the involvement of flavins is to feed the experimental organism flavin analogues and thereby move the peak of the action spectrum in a predictable way. Is this feasible in mice ... [Pg.50]


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See also in sourсe #XX -- [ Pg.402 ]




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