共查询到20条相似文献,搜索用时 343 毫秒
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L Henry IK Leung TD Claridge CJ Schofield 《Bioorganic & medicinal chemistry letters》2012,22(15):4975-4978
γ-Butyrobetaine hydroxylase (BBOX) is a 2-oxoglutarate and Fe(II)-dependent oxygenase that catalyses the final step of L-carnitine biosynthesis in animals. BBOX catalyses the oxidation of 3-(2,2,2-trimethylhydrazinium)propionate (THP), a clinically used BBOX inhibitor, to form multiple products including 3-amino-4-(methyamino)butanoic acid (AMBA), which is proposed to be formed via a Stevens type rearrangement mechanism. We report the synthesis of AMBA and confirm that it is a product of the BBOX catalysed oxidation of THP. AMBA reacts with formaldehyde, which is produced enzymatically by BBOX, to give a cyclic adduct. 相似文献
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Raúl Pérez-Ruiz Olga Hinze J?rg-M Neud?rfl Dirk Blunk Helmut G?rner Axel G Griesbeck 《Photochemical & photobiological sciences》2008,7(7):782-788
The solution photochemistry of the ortho allyloxy-substituted benzophenone has been investigated in detail. Product analysis revealed formation of a diastereomeric mixture of dihydrobenzofuran derivatives by cyclization via a short-lived intermediate 1,5-biradical and an unusual acetal by a pseudo-Paternò-Büchi rearrangement. The latter reaction pathway was supported by means of laser flash photolysis, where a long-lived intermediate with a maximum absorption band at 380 nm was observed. Besides, theoretical calculations (TD-DFT) of this UV-transient resulted in a band with maximum intensity at 390 nm showing a good correlation between experimental results and theoretical calculations. For comparison, the meta-substituent substrate was also investigated showing preferred triplet-triplet energy transfer. 相似文献
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Shirshev SV Kuklina EM Maksimov AY Krapivina OA Parshakova NS 《Biochemistry. Biokhimii?a》2007,72(9):983-988
The existence of alphabetaT-lymphocyte differentiation processes have been demonstrated in mouse peripheral lymphoid organs during pregnancy. Study of pregnant Swiss mice has shown that the development of the second half of gestation is accompanied by expression of RAG-1 recombinase mRNA and unrearranged TCR alpha-chain (pre-TCRalpha) preferentially in T-lymphocytes of lymph nodes involved in uterine drainage (para-aortal lymph nodes), and to a lesser extent in other lymph nodes (mainly from axillary lymph nodes). The data suggest that during pregnancy the differentiation of alphabetaT lymphocytes may occur not only in central (thymus) but also in peripheral lymphoid organs. 相似文献
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A novel olefinic rearrangement. The enzymic conversion of cholesta-7,9-dien-3β-ol into cholesta-8,14-dien-3β-ol 总被引:1,自引:1,他引:0 下载免费PDF全文
1. [3alpha-(3)H]Cholesta-7,9-dien-3beta-ol is converted in high yield into cholesterol by a 10000g(av.) supernatant fraction of rat liver homogenate. 2. Incubation of cholesta-7,9-dien-3beta-ol with [4-(3)H]NADPH and rat liver microsomal fractions under anaerobic conditions resulted in (3)H being incorporated into the 14alpha-position of cholest-7-en-3beta-ol. 3. Under anaerobic conditions in the absence of NADPH cholesta-7,9-dien-3beta-ol was isomerized into cholesta-8,14-dien-3beta-ol by rat liver microsomal fractions. 相似文献
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In man, the gene for hydroxyacyl glutathione hydrolase (HAGH; glyoxalase II) is closely linked to the α-globin locus (HBα) on Chromosome 16. HAGH polymorphism in the mouse has now enabled the mapping of the murine homologue. Deletion mapping, congenic strain studies, and characterization of 41 recombinant inbred strains establish that the mouseHagh locus lies very close to the α-globin pseudogene (Hba-ps4) in the vicinity of the major histocompatibility locus (H-2) on chromosome 17. Several other loci have been identified previously that are also closely linked to the human α-globin locus but near the α-globin pseudogeneHba-ps4 in the mouse. These linkage relationships suggest that during the evolution of mice a translocation occurred that subdivided the α-globin locus, leaving one inactive α-globin gene still associated with theHagh locus and linked sequences, while moving and inserting the active α-globin locus and all distal sequences into an internal location on another autosome, the predecessor to mouse chromosome 11. 相似文献
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This study focused on metabolic changes in the neuronal human cell line AGE1.HN upon increased ammonia stress. Batch cultivations of α(1)-antitrypsin (A1AT) producing AGE1.HN cells were carried out in media with initial ammonia concentrations ranging from 0mM to 5mM. Growth, A1AT production, metabolite dynamics and finally metabolic fluxes calculated by metabolite balancing were compared. Growth and A1AT production decreased with increasing ammonia concentration. The maximum A1AT concentration decreased from 0.63g/l to 0.51g/l. Central energy metabolism remained relatively unaffected exhibiting only slightly increased glycolytic flux at high initial ammonia concentration in the medium. However, the amino acid metabolism was significantly changed. Fluxes through transaminases involved in amino acid degradation were reduced concurrently with a reduced uptake of amino acids. On the other hand fluxes through transaminases working in the direction of amino acid synthesis, i.e., alanine and phosphoserine, were increased leading to increased storage of excess nitrogen in extracellular alanine and serine. Glutamate dehydrogenase flux was reversed increasingly fixing free ammonia with increasing ammonia concentration. Urea production additionally observed was associated with arginine uptake by the cells and did not increase at high ammonia stress. It was therefore not used as nitrogen sink to remove excess ammonia. The results indicate that the AGE1.HN cell line can adapt to ammonia concentrations usually present during the cultivation process to a large extent by changing metabolism but with slightly reduced A1AT production and growth. 相似文献
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Summary Using ultrarapid-freezing techniques and freezefracture electron microscopy, we report here a close association between cardiac gap junctions and specialized membrane domains containing regularly-spaced furrows. These specialized furrowed domains are observed only during periods of gap junction re-organisation (i.e., connexon redistribution) and may reflect the presence of underlying cytoskeletal elements controlling the position of connexons in the membrane. 相似文献
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A C-glycoside analogue of N-Fmoc-serine beta-N-acetylglucosaminide 1 was synthesized stereoselectively from a sulfone derivative of serinol thio-N-acetylglucosamide 8 using a Ramberg-B?cklund rearrangement as a key step. 相似文献
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Both anomers of 1-O-[N-(tert-butoxycarbonyl)-L-α-glutamyl]-d-glucopyranose (2) were converted into the unprotected 1-esters, characterised as the trifluoroacetate salts 3α and 3β. On esterification with diazomethane and acetylation, the N-acetylated derivative of 3β and 2β gave the peracetylated 1-O-[5-methyl N-acetyl- and -tert-butoxycarbonyl-L-glutam-1-oyl]-β-d-glucopyranoses (4β and 6β), respectively. Similar treatment of 2α and 3β led to acyl migration, to yield 1,3,4,6-tetra-O-acetyl-2-O-[5-methyl N-(tert-butoxycarbonyl)-L-glutam-1-oyl]-α-d-glucopyranose (7α,64%) with traces of 7β, and a mixture (≈2:1:0.2) of the N-acetyl analogue of 7α (8α), 4α, and 8β, respectively. Treatment of 1-O-[5-methyl N-(tert-butoxycarbonyl)-L-glutam-1-oyl]-α-d-glucopyranose (10) and the corresponding glutam-5-oyl isomer 12 in N,N-dimethylformamide with diazomethane for 1 h resulted in 1 → 2 O-acyl transfer to give, upon acetylation, 7α and the fully acetylated 2-O-[1-methyl N-(tert-butoxy- carbonyl)-L-glutam-5-oyl]-α-d>-glucopyranose in yields of 70 and 90 %, respectively; in the absence of diazomethane, 10 and 12 remained unchanged. Similar experiments with α-d-glucopyranosyl esters of N-acetylglycine, N-acetylalanine, and N-(tert-butoxycarbonyl)phenylalanine yielded the 2-O-acyl derivatives in high yields and with high retention of anomeric configuration. The structures of the rearrangement products were proved both spectroscopically and chemically. The results imply that diazomethane functions as a base in the migration process. 相似文献
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Timothy P. Shiau Ashley Houchin Satheesh Nair Ping Xu Eddy Low Ramin Najafi Rakesh Jain 《Bioorganic & medicinal chemistry letters》2009,19(4):1110-1114
New topical anti-infectives comprised of N,N-dichloro-β,β-disubstituted taurines [Tetrahedron Lett. 2008, 49, 2193; Biorg. Med. Chem. Lett. 2009, 19, 196] have been examined for structure–stability relationships (SSR) based upon various alkyl, heteroalkyl and cycloalkyl β-substitutions. These substitutions affect order-of-magnitude changes in the aqueous stability of these N,N-dichloroamines which can undergo Stieglitz rearrangement of alkyl groups under extremely mild conditions (H2O, pH 4–7, 0–20 mM acetate or phosphate buffer, 20–40 °C). This process produces β-ketosulfonic acids which function as substrates for chlorination by the N-chlorotaurines which leads to their further degradation. 相似文献
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