Search Results
Results 301 - 350 of 1654
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Wu Guanghua - - 2008
Parkinson's disease (PD) is a progressive neurodegenerative disease that affects aged people. Although a number of genes have been linked to familial PD, the genetic causes of sporadic PD that accounts for 90% of all PD cases remain unclear. Accumulating evidence has demonstrated that alpha-synuclein aggregation is essential to the ...
Hybelbauerová Simona - - 2008
Metabolites of the wood-rotting fungus Stereum subtomentosum Pouzar (Basidiomycetes, order Russulales, family Stereaceae) occurring on birch (Betula pendula Roth) trees were phytochemically investigated for the first time. Three main metabolite chemotypes present in MeOH extracts of the fruit bodies, viz. steroids, fatty acids, and water-soluble sugars, were fractionated, isolated, and ...
Maina Ndegwa Henry - - 2008
Dextrans are the main exopolysaccharides produced by Leuconostoc species. Other dextran-producing lactic acid bacteria include Streptococci, Lactobacilli, and Weissella species. Commercial production and structural analysis has focused mainly on dextrans from Leuconostoc species, particularly on Leuconostoc mesenteroides strains. In this study, we used NMR spectroscopy techniques to analyze the structures ...
Dickstein Joshua S - - 2008
Alpha-iminoesters are useful precursors to substituted alpha-amino acid derivatives and are utilized in a number of organic transformations. As a consequence of the adjacent ester functionality, these imines are more reactive relative to other types of imines. While a significant body of work has focused on nucleophilic additions to the ...
Borah Jayanta M - - 2008
Adsorption kinetics, adsorption isotherms and surface complexation of trimesic acid onto alpha-alumina surfaces were investigated. Adsorption kinetics of trimesic acid with an initial concentration of 0.5 mM onto alpha-alumina surfaces were carried out in batch method in presence of 0.05 mM NaCl (aq) at pH 6 and 298.15, 303.15 and ...
Huguenot Florent - - 2008
Difluoroenol silyl ethers, produced in situ from acylsilanes and CF3TMS, react as electrophiles with amines to give difluoroimines, via the corresponding hemiaminal adduct, as evidenced by 19F NMR spectroscopy. Reaction with (R)-phenylglycinol led to 2-difluoromethyloxazolidines. After separation of the diastereomers, reduction with LAH and Strecker-type synthesis gave enantiopure alpha-difluoromethylamines and ...
Matteson Donald S - - 2008
This review includes a personal account of the history of the development of the alpha-amido boronic acid synthesis and related chemistry in the author's laboratory, as well as a review of some of the more significant developments that have occurred elsewhere more recently. The simple initial target, suggested by biochemist ...
Ahmed Safwat A - - 2008
Eleven new cannabinoid esters, together with three known cannabinoid acids and Delta9-tetrahydrocannabinol ( Delta9-THC ), were isolated from a high-potency variety of Cannabis sativa. The structures were determined by extensive spectroscopic analyses to be beta-fenchyl Delta9-tetrahydrocannabinolate ( 1), epi-bornyl Delta9-tetrahydrocannabinolate ( 2), alpha-terpenyl Delta9-tetrahydrocannabinolate ( 3), 4-terpenyl Delta 9-tetrahydrocannabinolate ( ...
Joseph A - - 2008
Clinical investigations of recombinant human acid alpha-glucosidase for the treatment of Pompe disease often reveal the appearance of therapy-specific antibodies. These antibodies could potentially interfere with recombinant human acid alpha-glucosidase efficacy and induce immunological consequences. Several immunosuppressive agents, including methotrexate, mycophenolate mofetil and cyclosporin A with azathioprine, were evaluated for ...
Weerakody Rangika - - 2008
Encapsulation of alpha-lipoic acid (LA) was carried out using chitosan as an encapsulant matrix. Placebo and LA-loaded chitosan microspheres were prepared by a spray-drying process. Scanning electron microscopy (SEM) studies confirmed the spherical particle geometry and the smooth surface morphology of LA-loaded particles. The particle size distribution (PSD) analysis of ...
Lin Wei-Yu - - 2008
To determine the efficacy of coenzyme Q10 (CoQ10) and alpha-lipoic acid (alpha-LA), either alone or in combination, to protect the contractile responses of the rabbit urinary bladder from damage caused by repetitive stimulation in the presence or absence of in vitro ischemia. Four groups of New Zealand white rabbits (4 ...
Fuchs M - - 2009
Procedures for the analysis of free alpha-keto acids in human fluids (i.e. plasma, cerebrospinal fluid, urine, etc.) as well as for studying the dynamic free alpha-keto acid pools in differentiated tissues and organ cells have been the subject of growing clinical interest in the study of metabolic regulatory and pathophysiological ...
Gao Hong - - 2008
Chebulagic acid, isolated form Terminalia chebula Retz, proved to be a reversible and non-competitive inhibitor of maltase with a K(i) value of 6.6 muM. The inhibitory influence of chebulagic acid on the maltase-glucoamylase complex was more potent than on the sucrase-isomaltase complex. The magnitude of alpha-glucosidase inhibition by chebulagic acid ...
Maity Prantik - - 2008
C(alpha)-tetrasubstituted alpha-amino acids are widely used to design and prepare peptides and peptide mimics with constrained conformations. Subcategories of these compounds are cyclic C(alpha)-tetrasubstituted alpha-amino acids, in which both alpha-substituents are covalently connected. This survey presents recent advances in the synthesis and application of cyclic C(alpha)-tetrasubstituted alpha-amino acids in a ...
Makeeva A V - - 2008
The effects of lipoic acid on intensity of free radical reactions, citrate content, and aconitate hydratase during myocardial ischemia have been investigated. Treatment with lipoic acid normalized biochemiluminescence parameters and citrate level, which were increased in the myocardial pathology. Treatment with lipoic acid also increased specific activity of aconitate hydratase, ...
Alemán José - - 2008
An easy and simple synthetic approach to optically active alpha,alpha-quaternary alpha-amino acids using asymmetric organocatalysis is presented. The addition of oxazolones to nitroalkenes catalyzed by thiourea cinchona derivatives provides the corresponding alpha,alpha-quaternary alpha-amino acid derivatives with good yields, excellent diastereoselectivities (up to 98 % dr), and from moderate to good ...
Wada Naoki - - 2008
alpha-Lipoic acid (LA) and its reduced form dihydrolipoic acid (DHLA) are well known as strong antioxidants. LA has the characteristic distorted five membered 1,2-dithiolane ring, which is quite vulnerable to UV irradiation. The UV induced decomposition of LA and the effect of the following addition of biothiols to the photoirradiated ...
Dolashka-Angelova Pavlina - - 2008
A new hemocyanin was isolated from the hemolymph of garden snails Helix vulgaris, composed of two isoforms, HvH1 and HvH2 separated on an ion exchange column DEAE-Sepharose 6CL. Structural and immunological properties of Helix vulgaris hemocyanin were studied in comparison with molluscan Hcs Rapana venosa and Megathura crenulata. The possibility ...
Soto-Cairoli Buddy - - 2008
The disilylation of alpha-amino acids 1 to provide 2 (72-87%) was achieved without racemization. An unprecedented borane-mediated semi-reduction strategy was devised to convert 2 to stable, isolable oxazaborolidines 3 (100%) which were hydrolyzed to provide 5 (49-60%) as pure, stable compounds. Analysis of the Mosher amides (8) of the gamma-amino ...
Werther Tobias - - 2008
The gene rv0853c from Mycobacterium tuberculosis strain H37Rv codes for a thiamine diphosphate-dependent alpha-keto acid decarboxylase (MtKDC), an enzyme involved in the amino acid degradation via the Ehrlich pathway. Steady state kinetic experiments were performed to determine the substrate specificity of MtKDC. The mycobacterial enzyme was found to convert a ...
Norén Katarina - - 2008
The adsorption of amino acids onto mineral surfaces plays an important role in a wide range of areas, e.g., low-temperature aqueous geochemistry, bone formation and protein-bone interactions. In this work, the adsorption of three alpha aminoacids (sarcosine, MIDA and EDDA) onto goethite (alpha-FeOOH) was studied as a function of pH ...
Jung Young Chun - - 2007
Reported herein is a novel approach to the total syntheses of (-)-alpha-kainic acid and (+)-alpha-allokainic acid, where the stereochemistries on C(2), C(3), and C(4) of the pyrrolidine core were introduced efficiently and selectively. A regio- and stereoselective C-H insertion reaction was utilized to prepare the gamma-lactam as an intermediate. A ...
Millefiori Salvatore - - 2008
The geometries, relative energies, gas-phase static and dynamic dipole polarizabilities of the two most stable neutral forms and of the zwitterionic form of the twenty naturally occurring amino acids have been obtained by Density Functional and conventional ab initio Hatree-Fock theories using correlation consistent basis sets. Mean electronic polarizabilities (<alpha(e)>s) ...
Young Aidan G - - 2007
The adsorption of the ligands alpha-lipoic acid, dihydrolipoic acid, and dithiothreitol to films of deposited CdS nanoparticles was studied in situ by ATR-IR spectroscopy. For alpha-lipoic acid and dihydrolipoic acid, the spectra of the adsorbed species closely resemble those of the respective solution species. However, for dithiothreitol, the spectrum of ...
Kawamoto Haruo - - 2008
Boric acid inhibited the acid-catalyzed depolymerization of cellulose in sulfolane, a non-aqueous medium, at high temperature. Formation of the dehydration products such as levoglucosenone, furfural, and 5-hydroxymethyl furfural were also effectively inhibited. Similar inhibition was observed for cellooligosaccharides and starch, although the glucosidic bonds in methyl glucopyranosides and methyl cellobioside ...
Bertelsen Kresten - - 2007
We present the use of 2H magic-angle spinning (MAS) NMR on methyl-deuterated alpha-amino isobutyric acid (Aib) as a new method to obtain fast and accurate structural constraints on peptaibols in membrane-bound environments. Using nonoriented vesicle-reconstituted samples we avoid the delicate preparation of oriented samples, and the use of MAS ensures ...
Balakrishnan Shalini - - 2007
To introduce chirality and functional groups adjacent to guanidiniums to modulate specificity and affinity in recognition, N,N'-bis(Boc)-alpha-guanidino acids were synthesized from alpha-amino acid methyl esters. Protected alpha-guanidino acids coupled to cyclohexylamine and trans-1,4-diaminocyclohexane in good yield and with retention of stereochemistry. Boc deprotection was conducted under mild acidic conditions (0.5 ...
Hampel Daniela - - 2007
The biosynthesis of the monoterpenes (-)-alpha-pinene, linalool, and the norisoprenoids alpha- and beta-ionone in raspberry fruits (rubus idaeus L.) was investigated by in vivo feeding experiments with [5,5-(2)H2]-mevalonic acid lactone and [5,5-(2)H2]-1-deoxy-D-xylulose. The volatile compounds were extracted by stirbar sorptive extraction and analyzed using thermal desorption-multidimensional gas chromatography-mass spectrometry (TD-enantio-MDGC-MS). ...
Xu G - - 2007
The intermittency characteristics of the longitudinal (u) and transverse (v) velocity and temperature (theta) at similar Taylor microscale Reynolds numbers have been compared in a turbulent round jet. We examine the scaling exponents zeta_{alpha}(n) ( alpha=u , v , and theta ) of structure functions (deltaalpha);{n} , the intermittency exponents ...
Linares Denis - - 2008
The feasibility of trans-2-methyl-5-isopropylhexa-2,5-dienoic acid (novalic acid) accumulation using the alpha-pinene degradation pathway of Pseudomonas rhodesiae CIP 107491 was studied. This appeared possible by using concentrated living bacterial cells produced under oxygen limitation with alpha-pinene as sole carbon source. The second step of the process, the bioconversion itself, had to ...
Isobe Kimiyasu - - 2007
An oxidase catalyzing conversion of N(alpha)-benzyloxycarbonyl-L-lysine (N(alpha)-Z-L-lysine) to N(alpha)-benzyloxycarbonyl-L-aminoadipate-delta-semialdehyde (N(alpha)-Z-L-AASA) was purified from Rhodococcus sp. AIU Z-35-1, and its properties were revealed. This enzyme catalyzed an oxidative deamination of the epsilon-amino group of N(alpha)-acyl-L-lysine and the alpha-amino group of N(epsilon)-acyl-L-lysine. The apparent K(m) value for N(alpha)-acetyl-L-lysine was much larger than ...
Xian Mo - - 2007
A new route to alpha-keto acids is described, based on the ozonolysis of enol acetates obtained from alpha-substituted beta-keto esters. Escherichia coli branched chain aminotransferase (BCAT) activity toward a variety of substituted 2-oxoglutaric acids was demonstrated analytically. BCAT was shown to have a broad substrate spectrum, complementary to that of ...
Bew Sean P - - 2007
We report the application of "click" chemistry for the synthesis of hybrid calixarenes appended on the upper rim with carbohydrate and N,C-protected alpha-amino acids. The chemoselective N- or C-deprotection of the alpha-amino acids and their subsequent transformation into dipeptides is described. The first example of a chemo-enzymatic synthesis on upper ...
Durrani Arjumand I - - 2007
Alpha-lipoic acid is an antioxidant used both in the prevention and treatment of various oxidative stress related diseases. It is an important constituent of some dietary supplements and can also be found in plant and animal sources. A rapid method for the determination of alpha-lipoic acid in dietary supplements based ...
Harel Tal - - 2007
Alpha-alkyl amino acids can be efficiently prepared in high yields from the respective amino acids themselves. The key step is the oxidation of the amine function to create the corresponding alpha-nitro acid in a fast and very high yield reaction followed by phase-transfer alkylation and finally reduction to the desired ...
Borissow Charles N - - 2007
The jadomycins are a series of natural products produced by Streptomyces venzuelae ISP5230 in response to ethanol shock. A unique structural feature of these angucyclines is the oxazolone ring, the formation of which is catalyzed by condensation of a biosynthetic aldehyde intermediate and an amino acid. The feeding of enantiomeric ...
May James M - - 2007
The reducing capacity of erythrocytes has been used clinically as to estimate resistance to oxidant stress. In this work we targeted the antioxidant capacity of pyridine nucleotide disulfide reductases of these cells by measuring their ability to reduce the disulfide alpha-lipoic acid. Erythrocyte reduction of alpha-lipoic acid and related disulfides ...
Krause Jean-Michel - - 2007
The dynamics of glycoprotein hormone alpha-subunit (GPHalpha) maturation and GPHalpha alpha homodimer formation were studied in presence (JEG-3 choriocarcinoma cells) and absence (HeLa cells) of hCGbeta. In both cases, the major initially occurring GPHalpha variant in [35S]Met/Cys-labeled cells carried two N-glycans (M(r app) = 22 kDa). Moreover, a mono-N-glycosylated in ...
Chen Yen-Hsu - - 2007
Sepsis causes intrahepatic cholestasis and leads to hepatic failure. However, the pathophysiology of hepatic events is unclear. Expression of rat hepatic bile acid coenzyme A-amino acid N-acyltransferase (rBAT), a major enzyme for the conjugation of bile acids, is significantly decreased during sepsis. rBAT transcriptional regulation is mainly by a heterodimer ...
Carballeira Néstor M - - 2007
4-thiatetradecanoic acid exhibited weak antifungal activities against Candida albicans (ATCC 60193), Cryptococcus neoformans (ATCC 66031), and Aspergillus niger (ATCC 16404) (MIC=4.8-12.7 mM). It has been demonstrated that alpha-methoxylation efficiently blocks beta-oxidation and significantly improve the antifungal activities of fatty acids. We examined whether antifungal activity of 4-thiatetradecanoic acid can be ...
da Silva Ferreira António César - - 2007
The aim of this work was the simultaneous determination of both ketoacids and dicarbonyl compounds in wine. To detect ketoacid compounds in wine, a method based on the quinoxaline derivatives by the reaction with diaminobenzene, currently employed to detect alpha-dicarbonyl compounds, was developed. The quinoxaline derivatives were detected by RP-HPLC ...
Posa Mihalj - - 2007
The critical micellar concentration (CMC) values of keto derivatives of cholic acid (3alpha,12alpha-dihydroxy-7-oxo-5beta-cholanoic acid, 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanoic acid, 12alpha-hydroxy-3,7-dioxo-5beta-cholanoic acid, 3alpha-hydroxy-7,12-dioxo-5beta-cholanoic acid, 3,7,12-triketo-5beta-cholanoic acid) and cholic acid itself, were determined. Replacement of hydroxyl groups in cholic acid molecule with keto groups yields the derivatives whose CMC values increase with increase in the ...
Funchal Cláudia - - 2007
Accumulation of the branched-chain alpha-keto acids (BCKA), alpha-ketoisocaproic acid (KIC), alpha-keto-beta-methylvaleric acid (KMV) and alpha-ketoisovaleric acid (KIV) and their respective branched-chain alpha-amino acids (BCAA) occurs in tissues and biological fluids of patients affected by the neurometabolic disorder maple syrup urine disease (MSUD). The objective of this study was to verify ...
Okada Yasuyo - - 2007
A unique multibranched cyclomaltooligosaccharide (cyclodextrin, CD) of 6(1),6(3),6(5)-tri-O-alpha-maltosyl-cyclomaltoheptaose [6(1),6(3),6(5)-tri-O-alpha-maltosyl-beta-cyclodextrin, (G(2))(3)-betaCD] was prepared. The physicochemical and biological properties of (G(2))(3)-betaCD were determined together with those of monobranched CDs (6-O-alpha-D-glucopyranosyl-alpha-cyclodextrin (G(1)-alphaCD), 6-O-alpha-D-glucopyranosyl-beta-cyclodextrin (G(1)-betaCD), and 6-O-alpha-maltosyl-beta-cyclodextrin (G(2)-betaCD)). NMR spectra of (G(2))(3)-betaCD were measured using various 2D NMR techniques. The solubility of (G(2))(3)-betaCD in ...
Undheim K - - 2008
The focus has been on the development of methodology for stereoselective preparation of spiroannulated intermediates of the Schöllkopf chiron and further transformations to cyclic alpha-amino acids. The spiroannulations are effected by Ru(II)-catalysed ring-closing metathesis reactions, by Ru(II)- and Pd(0)-catalysed cycloisomerisations, by Rh(II)-carbenoid cyclisation reactions and by intramolecular aldol condensations. Hydrolytic ...
Zhang Li - - 2007
An aerobic bacterium, designated strain E5HC-32(T), was isolated from soil underlying the decaying leaf litter of a slash pine forest located in south east Queensland, Australia. The strictly aerobic, motile rod-shaped cells (0.8-1.6 x 2.6-4.8 microm) produced subterminal spherical spores which distended the cells. Strain E5HC-32(T) grew optimally in 1 ...
Di Gioia Maria Luisa - - 2007
We report here a convenient and simple solid-phase synthesis of N-nosyl-N-methyl-alpha-amino acids and N-Fmoc-N-methyl-alpha-amino acids, important building blocks for the synthesis of conformationally restricted and protease-resistant natural peptides and peptide analogues. The methodology involves the use of 2-chlorotrityl chloride resin to temporarily protect the carboxylic group of alpha-amino acids and ...
Iida Akira - - 2007
A pentafluorophenylammonium triflate (PFPAT) catalyst (5 mol %) successfully promoted C-acylation of enol silyl ethers with acid chloride to produce various beta-diketones (12 examples; 62-92% yield). Similarly, C-acylation of ketene silyl acetals or ketene silyl thioacetals (i.e., crossed Claisen condensation) proceeded smoothly to provide not only alpha-monoalkylated beta-keto (thio)esters but ...
Pazos Manuel - - 2007
Benzoic acid-derived phenolics (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, vanillic acid, syringic acid, and gallic acid) and the polyphenols epicatechin and epigallocatechin gallate (EGCG) were evaluated for their efficiency in regenerating alpha-tocopherol from alpha-tocopheroxyl radical in comparison with ascorbyl palmitate, which is known to regenerate alpha-tocopherol. Ethanolic solutions of phenolic compounds were ...
Sleebs Brad E - - 2007
1,3-oxazinan-6-ones have been utilized in a series of enolate reactions to produce 5-hydroxy and 5-alkyl-4-substituted-1,3-oxazinan-6-ones with excellent trans diastereoselectivity. Highlighting the versatility of the oxazinanone, a number of transformations were performed to produce a variety of protected N-H and N-methyl alpha-hydroxy- and alpha-methyl-beta-amino acids.
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