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1.
Electron spin resonance of eumelanin from hair: photoinduced radicals in solid matrix 总被引:1,自引:0,他引:1
R Bibang R Arnaud J Lemaire A Deflandre G Lang 《Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society》1989,2(5):387-394
KBr matrices appear to be convenient media to reveal the radicals formed on light exposure of eumelanin dispersions. The ESR signal of eumelanin dispersed at low concentration in KBr pellets is analyzed during and after irradiation at various wavelengths. Different types of radicals are observed. R'1- and R1-types of radicals are assigned, respectively, to neutral and deprotonated intrinsic phenoxy radicals of eumelanin. R'1 can be oxidized by oxygen as opposite to R1. R2- and R'2-types are formed in the indolic site. Water favours the conversion of R2, unreactive with oxygen, into R'2 which can be oxidized. R'1 and R2 result of an electron photoejection, respectively, from the phenolic and the indolic site. The R3-type radicals are associated with the band-to-band excitation of eumelanin considered as a semiorganized solid. 相似文献
2.
Marie Arnaud Stefan Krause Richard J. Norby Thuong Huyen Dang Nezha Acil Nicholas Kettridge Vincent Gauci Sami Ullah 《Global Change Biology》2023,29(12):3256-3270
Mangroves are among the most carbon-dense ecosystems worldwide. Most of the carbon in mangroves is found belowground, and root production might be an important control of carbon accumulation, but has been rarely quantified and understood at the global scale. Here, we determined the global mangrove root production rate and its controls using a systematic review and a recently formalised, spatially explicit mangrove typology framework based on geomorphological settings. We found that global mangrove root production averaged ~770 ± 202 g of dry biomass m−2 year−1 globally, which is much higher than previously reported and close to the root production of the most productive tropical forests. Geomorphological settings exerted marked control over root production together with air temperature and precipitation (r2 ≈ 30%, p < .001). Our review shows that individual global changes (e.g. warming, eutrophication, drought) have antagonist effects on root production, but they have rarely been studied in combination. Based on this newly established root production rate, root-derived carbon might account for most of the total carbon buried in mangroves, and 19 Tg C lost in mangroves each year (e.g. as CO2). Inclusion of root production measurements in understudied geomorphological settings (i.e. deltas), regions (Indonesia, South America and Africa) and soil depth (>40 cm), as well as the creation of a mangrove root trait database will push forward our understanding of the global mangrove carbon cycle for now and the future. Overall, this review presents a comprehensive analysis of root production in mangroves, and highlights the central role of root production in the global mangrove carbon budget. 相似文献
3.
Brice Maxime Nkouayeb Nangmou Hermine Laure Maza Djomkam Georges Bellier Tabekoueng Willifred Dongmo Tékapi Tsopgni Gabin Thierry Mbahbou Bitchagno Michel Arnaud Mbock Raceline Gounoue Kamkumo Marcel Frese Bruno Ndjakou Lenta Silvère Augustin Ngouela Nobert Sewald Anatole Guy Blaise Azebaze 《化学与生物多样性》2023,20(4):e202200271
The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC50s) of 0.57 and 1.26 μg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio-guided fractionation led to an ethyl acetate fraction with IC50s of 2.68 and 1.85 μg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside ( 1 ) with IC50s of 0.33 and 1.30 μM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid ( 2 ), ursolic acid ( 3 ), quafrinoic acid ( 4 ), quinovic acid ( 5 ), quinovic acid 3-O-β-D-fucopyranoside ( 6 ), oleanolic acid ( 7 ), oleanolic acid 3-acetate ( 8 ), friedelin ( 9 ), β-sitosterol ( 10a ), stigmasterol ( 10b ) and stigmasterol 3-O-β-D-glucopyranoside ( 11 ). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio-assays were performed using nucleic acid gel stain (SYBR green I)-based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside ( 1 ) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria. 相似文献
4.
Andrea Robitzki Alexandra Mack Arnaud Chatonnet Paul G. Layer 《Journal of neurochemistry》1997,69(2):823-833
Abstract: The function of the enzyme butyrylcholinesterase (BChE) in the developing and mature brain is still unclear. We have inserted 577 bp of the 5' upstream region plus 106 bp of the exon 1 of the rabbit BChE gene in reverse orientation under control of an SV40 early promoter derivative in an expression vector. This vector was introduced by calcium phosphate-mediated transfection into embryonic chicken retina cells during the first days of reaggregation culture. Depending on the retinal origin, the transfected cell population forms histotypic retina-like spheres, so-called rosetted or stratified retinospheroids. We show that antisense 5'-BChE gene expression decreased the steady-state mRNA level of BChE and the translation of the BChE protein, inhibited proliferation, and accelerated histogenesis in both cellular systems. The pronounced effects of antisense 5'-BChE transfection of spheroids document a key role of BChE during the early reaggregation process of retinal cells, most likely by regulating their growth and differentiation. 相似文献
5.
The Dekkera intermedia strain studied has the ability to ferment cellobiose. The ethanol concentration obtained was 75 g/L from 180 g/L cellobiose (80% of theoretical yield). The fermentation of more concentrated solutions of cellobiose did not proceed well. 相似文献
6.
7.
Does the neurotropic action of adrenocorticotrophic hormone involve a lipolytic step? 总被引:1,自引:0,他引:1
The stimulatory effect of adrenocorticotrophic hormone (ACTH)-related synthetic peptides on the hydrolysis of emulsified trioleoylglycerol by a rat brain lipase was studied. The ACTH effect was related to the net positive charge associated with the basic amino acid residues at position 15-18 in the ACTH sequence, as well as to the presence of the NH2-terminal amino acid residues at position 1-2. The ACTH effect on lipolysis was markedly reduced when lipids were partially removed from the enzyme preparation by extraction with chloroform/acetone. Full restoration of the stimulatory effect was obtained upon addition of phosphatidylcholine (2 mg/ml) to the lipolytic medium. Striking similarities between the structure-activity pattern for the stimulatory effect of ACTH on brain lipase and that described for the receptor-mediated actions of ACTH on adrenal and fat cells suggest that the ACTH effect might involve recognition of a binding site associated with the brain enzyme. Complete log concentration response curves obtained with four ACTH analogs may also be regarded as simulating hormone-receptor interaction. These findings are discussed in relation to the possibility that ACTH may have a neurohormonal role via lipase-catalyzed changes in the lipid matrix of membranes. 相似文献
8.
In vitro translation of messenger ribonucleic acid from sporulating and nonsporulating strains of Bacillus subtilis. 总被引:1,自引:1,他引:0 下载免费PDF全文
An Escherichia coli translation system supplemented with ribonucleic acid from sporulating Bacillus subtilis produces unique polypeptides which are missing among translation products of ribonucleic acid from six early sporulation mutants. 相似文献
9.
Gruber Véronique Berna Patrick P. Arnaud Thierry Bournat Philippe Clément Christèle Mison Dominique Olagnier Béatrice Philippe Laurence Theisen Manfred Baudino Sylvie Bénicourt Claude Cudrey Claire Bloës Carole Duchateau Nathalie Dufour Sylvie Gueguen Catherine Jacquet Séverine Ollivo Catherine Poncetta Christine Zorn Nathalie Ludevid Dolores Van Dorsselaer Alain Verger Robert Doherty Annette Mérot Bertrand Danzin Charles 《Molecular breeding : new strategies in plant improvement》2001,7(4):329-340
A recombinant dog gastric lipase with therapeutic potential for the treatment of exocrine pancreatic insufficiency was expressed in transgenic tobacco plants. We targeted the protein using two different signal sequences for either vacuolar retention or secretion. In both cases, an active glycosylated recombinant protein was obtained. The recombinant enzymes and the native enzyme displayed similar properties including acid resistance and acidic optimum pH. The proteolytic maturation and the specific activity of the recombinant proteins, however, were found to be dependent on subcellular compartmentalization. Expression levels of recombinant dog gastric lipase were about 5% and 7% of acid extractable plant proteins for vacuolar retention and secretion respectively. This expression system already has allowed the production of tens of grams of purified lipase through open-field culture of transgenic tobacco plants. 相似文献
10.