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Results 401 - 450 of 753
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Bao X - - 2000
The principal supply of carbon precursors for fatty acid synthesis in leaf tissue has been a much debated topic, with some experiments suggesting a direct supply from the C3 products of photosynthetic carbon fixation and colleagues suggesting the utilization of free acetate (for which concentrations in leaves in the range ...
Harada N - - 2000
We have developed an automated synthesis apparatus for L-[3-11C]-labeled aromatic amino acids by improved multi-enzymatic reactions. Use of a specially designed reaction vessel and of CH2Cl2 as a solvent has greatly simplified the overall operation, proving to be suitable for automated synthesis, and also has given better yields and higher ...
Shapiro R - - 2000
Many scientific theories of the origin of life suggest that life began with the spontaneous formation of a replicator (a self-copying organic polymer) within an unorganized chemical mixture, or "soup." A profound difficulty exists, however, with the idea of RNA, or any other replicator, at the start of life. Existing ...
Eastmond P J - - 2000
Measurements of metabolic fluxes in whole embryos and isolated plastids have revealed major changes in the pathways of carbon utilization during cotyledon filling by oilseed rape (Brassica napus L.) embryos. In the early cotyledon stage (stage A), embryos used sucrose (Suc) predominantly for starch synthesis. Plastids isolated from these embryos ...
Miwa M - - 2000
In a previous study, we have demonstrated that sodium arsenite (arsenite) as chemical stress stimulates heat shock protein 27 (HSP27) induction and arachidonic acid release in osteoblast-like MC3T3-E1 cells, and that the response of HSP27 induction is coupled with metabolic activity of the arachidonic acid cascade. In the present study, ...
Delle Monache G - - 2000
A convenient synthesis of (S)- and (R)-4-vinyl oxazolidin-2-one 1 and 2 from the same inexpensive starting material, D-isoascorbic acid, is described. The title compounds were obtained in 44% and 38% yield, respectively, by operationally simple steps. This approach is a suitable alternative to the literature methods and enhances the synthetic ...
Jackowski S - - 2000
PtdCho accumulation is a periodic, S phase-specific event that is modulated in part by cell cycle-dependent fluctuations in CTP:phosphocholine cytidylyltransferase (CCT) activity. A supply of fatty acids is essential to generate the diacylglycerol (DG) precursors for phosphatidylcholine (PtdCho) biosynthesis but it is not known whether the DG supply is also ...
DePietro F R - - 1999
The relative contributions of tyrosine (TYR) and phenylalanine (PHE) to the synthesis of dihydroxyphenylalanine (DOPA) were studied in PC12 cells following inhibition of aromatic L-amino acid decarboxylase with m-hydroxybenzylhydrazine (NSD-1015). Cells were incubated with varying concentrations of unlabeled L-TYR and L-PHE, and either L-(3)H-TYR or L-(3)H-PHE. Following incubation, labeled and ...
Phetsuksiri B - - 1999
Isoxyl (ISO), a thiourea (thiocarlide; 4, 4'-diisoamyloxythiocarbanilide), demonstrated potent activity against Mycobacterium tuberculosis H37Rv (MIC, 2.5 micrograms/ml), Mycobacterium bovis BCG (MIC, 0.5 microgram/ml), Mycobacterium avium (MIC, 2.0 microgram/ml), and Mycobacterium aurum A+ (MIC, 2.0 microgram/ml), resulting in complete inhibition of mycobacteria grown on solid media. Importantly, a panel of clinical ...
Imai E - - 1999
A flow reactor simulating a submarine hydrothermal system was constructed for examining the likelihood of oligopeptide synthesis from amino acids alone without recourse to any of condensing agents, templates or metallic ions. We demonstrated that when the initial reactant is glycine, the flow reactor can synthesize both di- and tri-glycine. ...
Chênevert Robert - - 1999
Both enantiomers of cis-6-(hydroxymethyl)- and cis,cis-4-hydroxy-6-(hydroxymethyl)pipecolic acids, piperidine-based nonproteinogenic amino acids, have been synthesized from starting materials obtained from enzymatic desymmetrizations.
Chiarugi A - - 1999
The use of o-methoxybenzoylalanine, a selective kynureninase inhibitor, has been proposed with the aim of reducing brain synthesis of quinolinic acid, an excitotoxic tryptophan metabolite. In liver homogenates, however, this compound caused unexpected accumulation of 3-hydroxyanthranilic acid, the product of kynureninase activity and the precursor of quinolinic acid. To explain ...
McCollom T M - - 1999
Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and ...
Downing Susan V. - - 1999
The total synthesis of the macrocyclic hexapeptide bistratamide D is reported. The synthetic strategy involved assembly of enantiomerically pure oxazole, thiazole, and oxazoline segments derived from amino acids. Macrocyclization of the hexapeptidic aminooxazoline-oxazole-thiazole carboxylic acid fragment was accomplished by activation with O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU).
Zakharova E A - - 1999
Quantum chemical methods AM1 and PM3 and chromatographic methods were used to qualitatively characterize pathways of bacterial production of indole-3-acetic acid (IAA). The standard free energy changes (delta G(o)'sum) for the synthesis of tryptophan (Trp) from chorismic acid via anthranilic acid and indole were calculated, as were those for several ...
Chiarugi A - - 1999
o-Methoxybenzoylalanine, a selective kynureninase inhibitor, caused unexpected accumulation of 3-hydroxyanthranilic acid (3OH-ANA), the product of kynureninase activity and the precursor of quinolinic acid (QUIN) in liver homogenates incubated with 3OH-kynurenine (3OH-KYN). In order to explain this observation, we investigated the interaction(s) of o-methoxybenzoylalanine with 3-hydroxyanthranilic acid dioxygenase, the enzyme responsible ...
Carballeira N M - - 1998
The total synthesis of the naturally occurring (Z)-2-methoxy-5-hexadecenoic acid and (Z)-2-methoxy-6-hexadecenoic acid was accomplished using as a key step Mukaiyama's trimethylsilyl cyanide addition to 4- and 5-pentadecenal, respectively. These syntheses further confirm the structures of the natural marine fatty acids and corroborate their cis double-bond stereochemistry. The title compounds were ...
Jossek R - - 1998
Purified recombinant poly(hydroxyalkanoic acid), PHA, synthase from Chromatium vinosum was used to examine in vitro poly(3-hydroxybutyric acid) (P(3HB)) formation. In combination with purified propionyl-coenzyme A transferase of Clostridium propionicum a two-enzyme in vitro P(3HB) biosynthesis system was established which allowed the synthesis of P(3HB) from free D-(-)-3-hydroxybutyric acid as substrate. ...
Manthey M K - - 1998
The design, synthesis, and enzymic evaluation of cis- and trans-4-mercapto-6-oxo-1,4-azaphosphinane-2-carboxylic acid 4-oxide 5 against mammalian dihydroorotase is presented. The design strategy for 5 was based on the strong affinity of phosphinothioic acids for zinc and that 5 also resembles the postulated tetrahedral transition state for the enzyme-catalyzed reaction. The synthesis ...
Pizer E S - - 1998
Pharmacological inhibitors of the anabolic enzyme, fatty acid synthase (FAS), including the natural product cerulenin and the novel compound c75, are selectively cytotoxic to cancer cells via induction of apoptosis, apparently related to the tumor cell phenotype of abnormally elevated fatty acid synthetic metabolism. As part of a larger effort ...
Arcos JA - - 1998
The enzymatic synthesis of several sorbitol diesters whose HLB values are similar to those of monoglycerides (the largest single type of food-grade emulsifiers) has been studied. The procedure is carried out by the simple addition of the polyol to a solution of the fatty acid and is based on continuous ...
Amend J P - - 1998
Thermodynamic calculations showed that the autotrophic synthesis of all 20 protein-forming amino acids was energetically favored in hot (100 degrees C), moderately reduced, submarine hydrothermal solutions relative to the synthesis in cold (18 degrees C), oxidized, surface seawater. The net synthesis reactions of 11 amino acids were exergonic in the ...
Schujman G E - - 1998
A hallmark of sporulation of Bacillus subtilis is the formation of two distinct cells by an asymmetric septum. The developmental programme of these two cells involves the compartmentalized activities of sigmaE in the larger mother cell and of sigmaF in the smaller prespore. A potential role of de novo lipid ...
Weber A L - - 1998
Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine ...
Saran T - - 1998
The synthesis of kynurenic acid (KYNA) from kynurenine was measured in the cerebral cortical slices. In vitro, ammonium acetate at the subtoxic to toxic concentration range from 1 mM to 10 mM dose-dependently inhibited KYNA synthesis (IC50=2.99 mM). Ammonia treatment in vivo decreased KYNA synthesis by 30%. These results suggest ...
Vasudevan S - - 1998
Administration of either ammonia or glycine to both rats and mice results in an increased synthesis in the liver and urinary excretion of orotic acid. The two most relevant observations obtained are that carbamoyl phosphate synthesized inside the mitochondria is involved in the increased synthesis of orotic acid and that ...
Pan Bing-Feng - - 1998
Lactones derived from hydroxy fatty acids have many applications. Compared to conventional chemical synthesis, lipases catalyzed synthesis of lactones is simple, mild and highly productive. The effects of hydroxy fatty acid chain length, solvents, lipase type and steric factor on the yield and on the distribution of the produced lactones ...
Bui C T - - 1998
The 5-(4-formyl-3,5-dimethoxyphenoxy)valeric acid (Barany) linker and its monomethoxy analog were applied to the Multipin method of solid phase synthesis. A comparative assessment of reductive amination and cleavage of these linkers under conditions of multiple synthesis indicated that both were applicable to a broad range of primary amines including aniline and ...
Dong-Ryul L - - 1997
Effects of various amino acids and tryptophan metabolites on the synthesis of nerve growth factor (NGF) in cultured mouse astroglial cells were evaluated. L-Tryptophan stimulated NGF production in a dose-dependent manner. Serotonin and quinolinic acid slightly increased NGF synthesis. L-Kynurenine had a marked stimulatory effect on NGF production at a ...
Salagnad C - - 1997
The enzymatic synthesis of 2-keto-3-deoxy-D-glycero-D-galacto-nonopyranulosonic acid (KDN) starting from D-mannose and pyruvic acid using Neu5Ac-aldolase has been scaled up. A repetitive batch ultrafiltration bioreactor was used for the KDN synthesis on 100 g scale with a conversion of up to 85%. Furthermore, a 440 mL pilot-scale enzyme membrane reactor (EMR) ...
Pon R T - - 1997
When hydroquinone-O,Ooffiacetic acid is used as a linker arm in solid phase oligonucleotide synthesis, the time for NH4OH cleavage of oligodeoxy- or oligoribonucleotides is reduced to only 2 min. This allows increased productivity on automated DNA synthesizers without requiring any other modifications to existing reagents or synthesis and deprotection methods. ...
Boger D L - - 1997
The synthesis of N-[7-(2-amino-3,4-dihydro-4-oxo-quinazolin-6-yl) -6-formyl-1-oxo-heptyl]-L-glutamic acid (2, abenzyl 10-formyl-5,8,10-trideazafolic acid) as a potential enzyme-assembled tight binding inhibitor of glycinamide ribonucleotide transformylase (GAR Tfase) or aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) is reported. The inhibitor was prepared by a convergent synthesis utilizing the sequential alkylations of acetaldehyde dimethylhydrazone with 6 and ...
Srivastava Rajiv R. - - 1997
The synthesis of an unnatural amino acid, 1-amino-3-[2-(1,7-dicarba-closo-dodecaboran(12)-1-yl)ethyl]cyclobutanecarboxylic acid, was achieved. This new potential BNCT agent was prepared via the monoalkylation of m-carborane with 4-bromobutene to produce 4-m-carboranyl-1-butene, which was then subjected to a 2 + 2 cycloaddition using dichloroketene. The resultant boronated cyclobutanone was reductively dechlorinated prior to the ...
Lee R E - - 1997
Through the use of 2,2-[2H]palmitic acid pulse labeling of the whole cells of C. matruchotti and analysis by gas chromatography-mass spectrometry of the non-labeled and [2H]-labeled corynomycolates, we established a new mechanism for palmitate condensation devoid of the postulated carboxylation step. This evidence allowed the design and synthesis of several ...
Matarrese M - - 1997
5-Methoxy-1-[4-(trifluoromethyl)-phenyl]-1-pentanone-O-(2-aminoethyl)oxi me (fluvoxamine), a potent clinically used antidepressant, was labelled with carbon-11 (t1/2 = 20.4 min) as a potential radioligand for the non-invasive assessment of serotonin uptake sites in the human brain with positron emission tomography (PET). The two-step radiochemical synthesis consisted of O-methylation of an amino-protected desmethyl precursor with ...
Ibrom W G - - 1997
The syntheses of mono-; di-, tri- and tetranitroxanthones via intramolecular Friedel-Crafts acylation of nitrated 2-phenoxybenzoic acids as well as via selective stepwise nitration of xanthone and the nitroxanthones gained from the first route are described. The synthesized nitroxanthones investigated by DSC (differential scanning calorimetry) analysis show a surprisingly high thermodynamic ...
McKay C P - - 1997
Laboratory simulations of shocks created with a high-energy laser demonstrate that the efficacy of organic production depends on the molecular, not just the elemental composition of the shocked gas. In a methane-rich mixture that simulates a low-temperature equilibrium mixture of cometary material, hydrogen cyanide and acetylene were produced with yields ...
Espey M G - - 1997
We aimed to determine the relative role of quinolinic acid synthesis in purified human microglia, monocyte-derived macrophages and astrocytes in the human brain following immune stimulation. Microglia and macrophages significantly increased quinolinic acid synthesis from tryptophan following activation by either lipopolysaccharide or interferon-gamma. Quinolinic acid synthesis by individual microglia was ...
Herman L W - - 1997
Conditions for the synthesis of synthetic peptide combinatorial libraries (SPCLs) from mixtures of amino acids were explored. In a one-pot synthesis, the effect of the starting concentrations of amino acids on the resulting library composition was studied, and the optimum balance of amino acids was determined. Protein sequencing, MALDI-TOF, and ...
Fathi R - - 1997
Phosphorus has been used as a scaffold to prepare combinatorial libraries of phosphoramidates in which one of the diversity elements resulted from derivatives of amino acids. A small library was prepared for analytical and characterization purposes, followed by a larger library of approximately 8800 compounds. Libraries were assembled on solid ...
Choi Seok-Ki - - 1996
This paper presents a short synthesis of new analogs of N-acetylneuraminic acid (Neu5Ac) varied structurally at C-5. The synthetic strategy includes indium-mediated coupling reactions between ethyl 2-(bromomethyl)acrylate and N-derivatized mannosamines, and the ozonolysis of the resulting enoates. The main advantage of this indium-mediated allylation for the synthesis of neuraminic acids ...
Slayden R A - - 1996
Thiolactomycin (TLM) possesses in vivo antimycobacterial activity against the saprophytic strain Mycobacterium smegmatis mc2155 and the virulent strain M. tuberculosis Erdman, resulting in complete inhibition of growth on solid media at 75 and 25 micrograms/ml, respectively. Use of an in vitro murine macrophage model also demonstrated the killing of viable ...
Septak M - - 1996
Fully protected CPG-immobilized monomer, dimer and trimer oligonucleotides were used to study depurination during the chemical synthesis of oligonucleotides. Disappearance of the oligonucleotide during acid exposure time relative to an internal thymidine standard not subject to depurination was monitored by reverse phase HPLC analysis. Depurination half-times obtained for dichloroacetic acid ...
Braghiroli D - - 1996
Taurine has been shown to exert many biological effects. Among them, the ability of this amino acid to induce a reduction of arterial blood pressure, when administered intracerebroventricularly (i.c.v.) to mammals, has been established since a long time ago. To gain further information on the structure-activity requirements for taurine's hypotensive ...
Wolf G - - 1996
Fasting causes a decrease in the rate of synthesis of fatty acid synthase, the central enzyme in fatty acid synthesis, while refeeding carbohydrate increases synthesis. Insulin also increases the synthesis of fatty acid synthase, while glucagon causes a decline. The mechanism was shown to be transcriptional activation-mediated through a 2.1-kb ...
Sledjeski D D - - 1996
The genes (cps) involved in the synthesis of the colanic acid capsular polysaccharide in Escherichia coli K-12 are transcriptionally regulated by numerous proteins. Two of these, RcsB and RcsC, share homology with two-component regulatory elements that respond to environmental stimuli. Osmotic shock by sucrose or NaCl transiently increased transcription of ...
Scott B O - - 1996
The solid phase synthesis of libraries containing a 1,3,4,6-tetrasubstituted-2,5-diketo-1,4-piperazine scaffold (DKP) or a 3,4,6-trisubstituted-2,5-diketo-1,4-morpholine scaffold (DKM) from alpha-bromocarboxylic acids and amines is described. Using a design strategy which we refer to as divergent library design, both templates were prepared from a common intermediate. The general utility of this synthetic route ...
Mulzer Johann - - 1996
The unnatural enantiomer of the amino acid detoxinine and both diastereomeric 3-hydroxy-D-prolines have been prepared from D-mannitol via the O-silylated hydroxyproline 12 as a common key intermediate.
Farrer R G - - 1995
Brefeldin A (BFA) has been used extensively to study the intracellular transport and processing of proteins and sphingolipids because of its dramatic alteration of the structural and functional organization of the Golgi. We have examined the effect of BFA on the synthesis of galactosylceramide sulfate (SGalCer) and its immediate precursor ...
Priebe H - - 1995
The origin of 4-acetyl-2-[N-acetyl-3,5-bis(2,3-dihydroxypropylcarbamoyl)- 2,4,6-triiodoanilinomethyl]-5,7-diiodo-3,4-dihydro-2H-benzo[1,4]ox azine- 6,8-dicarboxylic acid bis(2,3-dihydroxypropylamide) = N-acetyl cyclized iodixanol, 2-[N-acetyl-3,5-bis-(2,3-dihydroxypropylcarbamoyl)-2,4,6- triiodoanilinomethyl]-5,7-diiodo-3,4-dihydro-2H-benzo[1,4]oxazine- 6,8-dicarboxylic acid bis(2,3-dihydroxypropylamide) = cyclized iodixanol and 5,5'-(N-acetyl-2-hydroxypropane-1,3-diyldiamino)bis[N,N'-bis(2,3- dihydroxypropyl)-2,4,6-triiodoisophthalamide] = deacetyl iodixanol in the manufacturing process of the X-ray contrast agent 3,3',5,5'-tetrakis(2,3-dihydroxypropylcarbamoyl)-2,2',4,4',6,6'-++ +hexaiodo- N,N'-(2-hydroxypropane-1,3-diyl)diacetanilide = iodixanol is discussed and their synthesis and purification are described. ...
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