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Flavins, substituted

Oxidative substitutions at ring junction positions in various tetrahydro-5-deaza-pterins (79JA6068) and -flavins (77JA6721) have been studied, e.g. to give (13), and the oxidation-reduction reactions of 5-deazaflavins (e.g. 78CL1177, 80CPB3514) across the 1,5-positions, e.g. (19) (20), are involved in their co-enzymic role in enzymic oxidations (see Section... [Pg.205]

Francisco, W. A., et al. (1996). Interaction of bacterial luciferase with 8-substituted flavin mononucleotide derivatives. /. Biol. Chem. 271 104-110. [Pg.396]

A class of enzymes capable of removing sulfur from alkane sulfonates exists, which may have relevance in microbial desulfurization of alkyl sulfides. A gene cluster ssuEADCB was identified in E. coli. The enzyme SsuD was capable of conversion of pentane sulfonic acid to pentaldehyde and sulfite. It was reported to be capable of conversion of alkyl sulfonates from C2 to CIO, as well as substituted ethanesulfonates and sulfonated buffers. The SsuE was a flavin-reducing enzyme that provided FMNH2 to the SsuD. [Pg.103]

Fig. 21. Top The general Jablonski diagram for the flavin chromophore. The given wavelengths for absorption and luminescence represent crude average values derived from the actual spectra shown below. Due to the Franck-Condon principle the maxima of the peak positions generally do not represent so-called 0 — 0 transitions, but transitions between vibrational sublevels of the different electronically excited states (drawn schematically). Bottom Synopsis of spectra representing the different electronic transitions of the flavin nucleus. Differently substituted flavins show slightly modified spectra. Absorption (So- - S2, 345 nm S0 -> Si,450nm 1561) fluorescence (Sj — S0) 530 nm 156)) phosphorescence (Ty Sq, 605 nm 1051) triplet absorption (Tj ->Tn,... Fig. 21. Top The general Jablonski diagram for the flavin chromophore. The given wavelengths for absorption and luminescence represent crude average values derived from the actual spectra shown below. Due to the Franck-Condon principle the maxima of the peak positions generally do not represent so-called 0 — 0 transitions, but transitions between vibrational sublevels of the different electronically excited states (drawn schematically). Bottom Synopsis of spectra representing the different electronic transitions of the flavin nucleus. Differently substituted flavins show slightly modified spectra. Absorption (So- - S2, 345 nm S0 -> Si,450nm 1561) fluorescence (Sj — S0) 530 nm 156)) phosphorescence (Ty Sq, 605 nm 1051) triplet absorption (Tj ->Tn,...
To reach the reductive step of the azo bond cleavage, due to the reaction between reduced electron carriers (flavins or hydroquinones) and azo dyes, either the reduced electron carrier or the azo compound should pass the cell plasma membrane barrier. Highly polar azo dyes, such as sulfonated compounds, cannot pass the plasma membrane barrier, as sulfonic acid substitution of the azo dye structure apparently blocks effective dye permeation [28], The removal of the block to the dye permeation by treatment with toluene of Bacillus cereus cells induced a significant increase of the uptake of sulfonated azo dyes and of their reduction rate [29]. Moreover, cell extracts usually show to be more active in anaerobic reduction of azo dyes than whole cells. Therefore, intracellular reductases activities are not the best way to reach sulfonated azo dyes reduction the biological systems in which the transport of redox mediators or of azo dye through the plasma membrane is not required are preferable to achieve their degradation [13]. [Pg.200]

Interestingly, the flavin molecule is significantly easier to excite than the other heterocycles investigated. The first singlet excitation energy is only 3.0 eV (413 nm), and the probability of transition is intermediate. The second band with possible singlet excitation lies at 3.8 eV. Hence, if one intends to construct systems that are more readily excited, substituted flavins seem to be a more appropriate route than the furocoumarins, whereas the latter are easier to ionize. [Pg.150]

The one-electron oxidation of iV-benzylphenothiazine by nitric acid occurs in the presence of /i-cyclodextrin, which stabilizes the radical cation by incorporation into its cavity. The reaction is inhibited by adamantane, which preferentially occupies the cavity. Novel Pummerer-type rearrangements of / -sulfinylphenyl derivatives, yielding /7-quinones and protected dihydroquinones, and highly enantioselective Pummerer-type rearrangements of chiral, non-racemic sulfoxides have been reviewed. A comprehensive study has demonstrated that the redox potential for 7- and 8-substituted flavins is linearly correlated with Hammett a values. DFT calculations in [3.3.n]pro-pellanes highlight low ionization potentials that favour SET oxidative cleavage of the strained central C-C bond rather than direct C-H or C-C bond attack. Oxidations and reductions in water have been reviewed. ... [Pg.245]

In flavin-dependent monooxygenases, a flavin-oxygen intermediate reacts with the substrate, also producing water in a second step, and requiring cofactors for regeneration of the flavin moiety. The unusual flavoprotein vanillyl-alcohol oxidase (EC 1.1.3.38), in which the flavin moiety is covalently bound, catalyzes the oxidation of p-substituted phenols as well as deamination, hydroxylation and dehydrogenation reactions [10]. [Pg.42]

Babior, who has studied this enzyme at several stages of its purification, found in lysates of PMNs which were activated with zymosan that of eight potential biological reductants only reduced pyridine nucleotides supported the formation of O ". The K , for NADPH was less than the K , for NADH and the activity was decreased in preparations from three patients with chronic granulomatous disease. In accord with predictions based on reaction 7, 0.55 molecule of O7 was measured per molecule of NADPH oxidized under conditions of saturating concentrations of cytochrome c The enzyme which was extracted with Triton X-100 from a granule-rich fraction from activated PMNs, required an external source of FAD for the formation of O from NADPH . Riboflavin and FMN would not substitute. Flavin adenine dinucleotide was proposed as a necessary cofactor, which was probably lost when the enzyme was treated with the detergent. [Pg.51]

Today, four kinds of 8a-substituted peptides are known (Scheme 2). The published data up to 1976 were summarized recently . The chemical synthesis of the various flavin peptides and their physical properties are described in the references given in Table 2 and were reviewed recently . ... [Pg.77]

The 8a-modified flavins show some remarkable physical properties which differ from those of common flavins. Since these properties are very helpful in the identification of modified 8a-substituted flavocoenzymes originating from biological materials the physical properties are presented briefly here. Compared to riboflavin (Scheme 2, (7), R = H) the visible light absorption properties of (2) to... [Pg.79]

Ackrell, B. A. C., McIntire, W., Edmondson, D. E., Kearney, E. B. The semiquinone form of succinate dehydrogenase and other Sa-substituted flavoenzymes. In Flavins and flavoproteins (Massey, V., Williams, C. H. eds.) pp. 488-491, New York, Amsterdam, Oxford, Elsevier/North Holland 1982... [Pg.137]


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See also in sourсe #XX -- [ Pg.320 ]




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