Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Flavin-photosensitized reactions of retinol and stilbene.

ABSTRACT: 1. Retinol and stilbene are both isomerized when they are illuminated anaerobically in the presence of flavins. 2. Triplet quenchers (e.g. oxygen, potassium iodide and paramagnetic ions) inhibit the reaction more efficiently than they quench flavin fluorescence. At 77 degrees C in a diethyl ether-isopentane-ethanol (5:5:2) glass retinol quenches flavin phosphorescence, but not its fluorescence. 3. For the stilbene reaction cis/trans photostationary-state mixtures are obtained with different flavins and these are linearly related to the phosphorescence transition energies of the flavins used. 4. The reaction involves the triplet state of flavin and a scheme for the reaction is suggested. 5. The dependence of the rate of reaction on substrate concentration is explicable in terms of this scheme. 6. The photobleaching of rhodopsin sensitized by flavin is also demonstrated.

SUBMITTER: Gordon-Walker A

PROVIDER: S-EPMC1179659 | biostudies-other | 1970 Dec

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Photosensitized [4+2]- and [2+2]-Cycloaddition Reactions of N-Sulfonylimines.

Project description:The synthesis of polycyclic compounds is of high interest due to the prevalence of these motifs in drugs and natural products. Herein, we report on the stereoselective construction of 3D bicyclic scaffolds and azetidine derivatives by modulation of N-sulfonylimines to achieve either [4+2]- or [2+2]-cycloaddition reactions. The utility of the method was established by further modulation of the product. Mechanistic studies are also included, which support reaction via Dexter energy transfer.

| S-EPMC10528476 | biostudies-literature

Triple-channel microreactor for biphasic gas-liquid reactions: Photosensitized oxygenations.

Project description:A triple-channel microreactor fabricated by means of a soft-lithography technique was devised for efficient biphasic gas-liquid reactions. The excellent performance of the microreactor was demonstrated by carrying out photosensitized oxygenations of ?-terpinene, citronellol, and allyl alcohols.

| S-EPMC3170200 | biostudies-other

Flavin-enabled reductive and oxidative epoxide ring opening reactions.

Project description:Epoxide ring opening reactions are common and important in both biological processes and synthetic applications and can be catalyzed in a non-redox manner by epoxide hydrolases or reductively by oxidoreductases. Here we report that fluostatins (FSTs), a family of atypical angucyclines with a benzofluorene core, can undergo nonenzyme-catalyzed epoxide ring opening reactions in the presence of flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NADH). The 2,3-epoxide ring in FST C is shown to open reductively via a putative enol intermediate, or oxidatively via a peroxylated intermediate with molecular oxygen as the oxidant. These reactions lead to multiple products with different redox states that possess a single hydroxyl group at C-2, a 2,3-vicinal diol, a contracted five-membered A-ring, or an expanded seven-membered A-ring. Similar reactions also take place in both natural products and other organic compounds harboring an epoxide adjacent to a carbonyl group that is conjugated to an aromatic moiety. Our findings extend the repertoire of known flavin chemistry that may provide new and useful tools for organic synthesis.

| S-EPMC9391479 | biostudies-literature

Identification of amino acid residues important in the cyclization reactions of chalcone and stilbene synthases.

Project description:Chalcone synthase (CHS) and stilbene synthase (STS) catalyse condensation reactions of p-coumaroyl-CoA and three C(2) units from malonyl-CoA up to a common tetraketide intermediate but then catalyse different cyclization reactions to produce naringenin chalcone and resveratrol respectively. On the basis of sequence alignment with other condensing enzymes including 3-ketoacyl-(acyl carrier protein) synthases of polyketide and fatty-acid synthases, site-directed mutagenesis was performed on the active-site G(372)FGPG loops in CHS and STS. The CHS-P375G mutant showed a 6-fold decrease in overall condensing activity with selectively increased production of p-coumaroyltriacetic acid lactone (CTAL, the derailment product of the tetraketide intermediate). Meanwhile, resveratrol production by STS-P(375)G strongly decreased to give various products in the order CTAL> resveratrol approximately bisnoryangonin>naringenin. As a result, naringenin production (cross-reaction) by STS-P(375)G was close to 30% of resveratrol production. Both G(374)L mutants of CHS and STS showed no condensing activity with residual malonyl-CoA decarboxylase activity. These results suggested that the G(372)FGPG loop in CHS and STS contribute to a determination of the outcome during cyclization reactions by serving as a part of the active-site scaffold on which the stereochemistry of cyclization is performed. These observations provide the first biochemical indication that cyclization reactions are modulated by active-site geometry. The implications for the evolutionary relationship of these enzymes are also discussed.

| S-EPMC1221246 | biostudies-other

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis.

Project description:New trans- and cis-o-stilbene-methylene-sydnones 3a,b were synthesized by transforming the trans- and cis-o-aminomethylstilbene derivative, obtained by reduction of corresponding o-cyano derivatives, into glycine ester derivatives (43 and 31% yield) followed by hydrolysis (90 and 96% yield), nitrosation and ring closure with acetic acid anhydride (30 and 40% yield). The products were submitted to photochemical and thermal intramolecular [3 + 2] cycloadditions to afford diverse heteropolycyclic compounds. Photochemical reactions afforded cis-3-(4-methylphenyl)-3a,8-dihydro-3H-pyrazolo[5,1-a]isoindole (11, 12.5% yield) and trans-3-(4-methylphenyl)-3a,8-dihydro-3H-pyrazolo[5,1-a]isoindole (12, 5% yield). Thermal reactions afforded 3-(4-methylphenyl)-3,3a,8,8a-tetrahydroindeno[2,1-c]pyrazole (14, 50% yield) and 11-(4-methylphenyl)-9,10-diazatricyclo[7.2.1.0(2,7)]dodeca-2,4,6,10-tetraene (15, 22% yield).

| S-EPMC3252871 | biostudies-literature

Bronsted acid catalysis of photosensitized cycloadditions.

Project description:Catalysis is central to contemporary synthetic chemistry. There has been a recent recognition that the rates of photochemical reactions can be profoundly impacted by the use of Lewis acid catalysts and co-catalysts. Herein, we show that Brønsted acids can also modulate the reactivity of excited-state organic reactions. Brønsted acids dramatically increase the rate of Ru(bpy)3 2+-sensitized [2 + 2] photocycloadditions between C-cinnamoyl imidazoles and a range of electron-rich alkene reaction partners. A combination of experimental and computational studies supports a mechanism in which the Brønsted acid co-catalyst accelerates triplet energy transfer from the excited-state [Ru*(bpy)3]2+ chromophore to the Brønsted acid activated C-cinnamoyl imidazole. Computational evidence further suggests the importance of driving force as well as geometrical reorganization, in which the protonation of the imidazole decreases the reorganization penalty during the energy transfer event.

| S-EPMC8145945 | biostudies-literature

Small molecule macroarray construction via palladium-mediated carbon-carbon bond-forming reactions: highly efficient synthesis and screening of stilbene arrays.

Project description: Not available

| S-EPMC3181100 | biostudies-literature

Homeostasis of retinol in lecithin: retinol acyltransferase gene knockout mice fed a high retinol diet.

Project description:We analyzed the retinoid levels and gene expression in various tissues after wild-type (Wt) and lecithin:retinol acyltransferase (LRAT-/-) knockout mice were fed a high retinol diet (250 IU/g). As compared to Wt, LRAT-/- mice exhibited a greater and faster increase in serum retinol concentration (mean+/-S.D., Wt, 1.3 +/- 0.2 microM to 1.5 +/- 0.3 microM in 48 h, p > 0.05; LRAT-/-, 1.3 +/- 0.2 microM to 2.2+/-0.3 microM in 48 h, p < 0.01) and a higher level of retinol in adipose tissue (17.2 +/- 2.4 pmol/mg in Wt vs. 34.6 +/- 8.0 pmol/mg in LRAT-/-). In the small intestines of Wt mice higher levels of retinol (96.4 +/- 13.0 pmol/mg in Wt vs. 13.7 +/- 7.6 pmol/mg in LRAT-/- and retinyl esters (2493.4 +/- 544.8 pmol/mg in Wt vs. 8.2 +/- 2.6 pmol/mg in LRAT-/- were detected. More retinol was detected in the feces of LRAT-/- mice (69.3 +/- 32.6 pmol/mg in LRAT-/- vs. 24.1 +/- 8.6 pmol/mg in Wt). LRAT mRNA levels increased in the lungs, small intestines, and livers of Wt mice on the high retinol diet, while CYP26A1 mRNA levels increased greatly only in the LRAT-/- mice. After 4 weeks, no significant differences between Wt mice and LRAT-/- mice were observed in either the serum retinol level or in the prevalence of Goblet cells in jejunal crypts. Our data indicate that the LRAT-/- mice maintain the homeostasis of retinol as the dietary retinol increases by increasing the excretion of retinol from the gastrointestinal tract, increasing the distribution of retinol to adipose tissue, and enhancing the catabolism by CYP26A1. We show that LRAT plays a role in maintaining a stable serum retinol concentration when dietary retinol concentration fluctuates.

| S-EPMC2486431 | biostudies-literature

Retinol Dehydrogenase 10 Reduction Mediated Retinol Metabolism Disorder Promotes Diabetic Cardiomyopathy

Project description:Diabetic cardiomyopathy (DCM) is a primary myocardial injury induced by diabetes mellitus (DM) with a complex pathogenesis. In this study, we identified disordered cardiac retinol metabolism in T2DM mice and patients characterized by retinol (vitamin A, Rol) overload, all-trans retinoic acid (atRA) deficiency and retinoic acid receptors (RARs) reduction, and demonstrated that both cardiac Rol overload and atRA deficiency promote DCM by supplementing T2DM mice with Rol or atRA. Mechanically, by constructing cardiomyocyte-specific conditional RDH10-knockout mice and overexpressing RDH10 in T2DM mice via adeno-associated virus, we verified that the reduction in cardiac retinol dehydrogenase 10 (RDH10) is the initiating factor for cardiac retinol metabolism disorder and its resulting DCM. Additionally, lipotoxicity and ferroptosis contribute to the effect of retinol metabolism disorder on DCM. Based on these results, we suggest that the reduction of cardiac RDH10 and its mediated disorder of cardiac retinol metabolism is a new mechanism underlying DCM.

2023-01-15 | GSE202418 | GEO

Flavin oxidation in flavin-dependent N-monooxygenases.

Project description:Siderophore A (SidA) from Aspergillus fumigatus is a flavin-containing monooxygenase that hydroxylates ornithine (Orn) at the amino group of the side chain. Lysine (Lys) also binds to the active site of SidA; however, hydroxylation is not efficient and H2 O2 is the main product. The effect of pH on steady-state kinetic parameters was measured and the results were consistent with Orn binding with the side chain amino group in the neutral form. From the pH dependence on flavin oxidation in the absence of Orn, a pKa value >9 was determined and assigned to the FAD-N5 atom. In the presence of Orn, the pH dependence displayed a pKa value of 6.7 ±0.1 and of 7.70 ±0.10 in the presence of Lys. Q102 interacts with NADPH and, upon mutation to alanine, leads to destabilization of the C4a-hydroperoxyflavin (FADOOH ). Flavin oxidation with Q102A showed a pKa value of ~8.0. The data are consistent with the pKa of the FAD N5-atom being modulated to a value >9 in the absence of Orn, which aids in the stabilization of FADOOH . Changes in the FAD-N5 environment lead to a decrease in the pKa value, which facilitates elimination of H2 O2 or H2 O. These findings are supported by solvent kinetic isotope effect experiments, which show that proton transfer from the FAD N5-atom is rate limiting in the absence of a substrate, however, is significantly less rate limiting in the presence of Orn and or Lys.

| S-EPMC6295899 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data