Distribution by Scientific Domains
Distribution within Chemistry

Terms modified by Amino

  • amino acid
  • amino acid alteration
  • amino acid amide
  • amino acid analysis
  • amino acid availability
  • amino acid biosynthesis
  • amino acid biosynthetic pathway
  • amino acid building block
  • amino acid catabolism
  • amino acid change
  • amino acid composition
  • amino acid concentration
  • amino acid content
  • amino acid decarboxylase
  • amino acid degradation
  • amino acid deletion
  • amino acid derivative
  • amino acid difference
  • amino acid drink
  • amino acid ester
  • amino acid exchange
  • amino acid exchanges
  • amino acid extension
  • amino acid fragment
  • amino acid identity
  • amino acid l
  • amino acid level
  • amino acid ligand
  • amino acid metabolism
  • amino acid methyl ester
  • amino acid mixture
  • amino acid moiety
  • amino acid molecule
  • amino acid motif
  • amino acid mutation
  • amino acid neurotransmitter
  • amino acid nitrogen
  • amino acid number
  • amino acid oxidase
  • amino acid peptide
  • amino acid polypeptide
  • amino acid position
  • amino acid profile
  • amino acid protein
  • amino acid racemization
  • amino acid repeat
  • amino acid replacement
  • amino acid requirement
  • amino acid residue
  • amino acid sequence
  • amino acid sequence analysis
  • amino acid sequence comparison
  • amino acid sequence homology
  • amino acid sequence identity
  • amino acid sequence similarity
  • amino acid sequencing
  • amino acid side chain
  • amino acid similarity
  • amino acid site
  • amino acid starvation
  • amino acid substitution
  • amino acid supplementation
  • amino acid synthesis
  • amino acid transport
  • amino acid transporter
  • amino acid type
  • amino acid uptake
  • amino acid used
  • amino acid variation
  • amino acids
  • amino acids content
  • amino acids l
  • amino acids present
  • amino alcohol
  • amino alcohol ligand
  • amino aldehyde
  • amino butyric acid
  • amino carbonyl compound
  • amino compound
  • amino derivative
  • amino ester
  • amino function
  • amino functionality
  • amino group
  • amino groups
  • amino ketone
  • amino moiety
  • amino n
  • amino nitrile
  • amino nitrogen
  • amino side chain
  • amino substituent
  • amino sugar
  • amino terminus
  • amino transferase

  • Selected Abstracts

    Monocyclopentadienyl Phenoxido,Amino and Phenoxido,Amido Titanium Complexes: Synthesis, Characterisation, and Reactivity of Asymmetric Metal Centre Derivatives

    Giuseppe Alesso
    Abstract Reduction of phenol,imine derivatives R,N=CH(3,5-R2C6H2 -2-OH) (R = tBu; R, = C6H51a, p -MeC6H41b, Cy 1c, tBu 1d, 2,6-Me2C6H31e; R = H; R, = p -MeC6H41f; Cy = cyclohexyl) with MBH4 (M = Li, Na) or AlLiH4 in ethyl ether or thf at room temperature affords the phenol,amine compounds R,NHCH2(3,5-R2C6H2 -2-OH) 2a,c and 2e,f. The N -R-[2,4-di- tert -butyl]benzo-1-oxa-3-azine species (R = tBu 2d1, 2,6-Me2C6H32e1) are obtained by Mannich reaction of 2,4-di- tert -butylphenol with RNH2 in refluxing methanol. Intermediate 2d1 is converted in ethanol at room temperature into N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylamine (2d), whereas 2e is not obtained from 2e1 by using this procedure.N -alkyl,N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylaminecompounds tBuN(R)CH2(3,5- tBu2C6H2 -2-OH) (R = Me 2g, Et 2h, nPr 2i, CH2Ph 2j) are also prepared by the appropriate synthetic method. Treatment of 2a,c with 1 equiv. of TiCpCl3 in the presence of 2.5 equiv. of NEt3 in hexane at room temperature gives the monocyclopentadienyl phenoxido,amido monochloride complexes TiCp[R,NCH2(3,5- tBu2C6H2 -2-O)]Cl (R, = C6H53a, R, = p -MeC6H43b, R, = Cy 3c). The analogous complex Ti(,5 -C5H4SiMe2Cl)[C6H5NCH2(3,5- tBu2C6H2 -2-O)]Cl (4a) results from the reaction of 2a with Ti(,5 -C5H4SiMe2Cl)Cl3. Nevertheless, 2d reacts with TiCpCl3 in hexane in the presence of NEt3 at room temperature yielding the monocyclopentadienyl phenoxido dichloride compound TiCp[tBuNHCH2(3,5- tBu2C6H2 -2-O)]Cl2 (5), whereas in ethyl ether and in the absence of NEt3 adduct 5·HCl is obtained, which is further converted into TiCp[tBuNCH2(3,5- tBu2C6H2 -2-O)]Cl (3d) by addition of a NEt3/ethyl ether solution. The reaction of TiCpCl3 with 2a in the presence of 2.5 equiv. of NEt3 in a polar solvent (thf, CH2Cl2 or toluene) at room temperature affords TiCp[Ph(H)NCH2(3,5- tBu2C6H2 -2-O)]Cl (6a) as a mixture of two stereoisomers. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2a, 2d, 2e and 3d were determined by X-ray diffraction analysis from suitable single crystals. Preliminary studies of catalytic activity for ethylene polymerisation by using solid methylaluminoxane as cocatalyst were performed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Preparation of Optically Active ,-Amino[3]ferrocenophanes , Building Blocks for Chelate Ligands in Asymmetric Catalysis

    Patrick Liptau
    Treatment of 1,1,-diacetylferrocene (4) with dimethylamine and TiCl4 yielded the unsaturated dimethylamino-substituted [3]ferrocenophane product 5. Its catalytic hydrogenation gave the corresponding saturated [3]ferrocenophane system 6 (trans/cis , 7:1). The rac -[3]ferrocenophane amine 6 was partially resolved (to ca. 80% ee) by means of L - or D - O,O, -dibenzoyltartrate salt formation. Treatment of 4 with the pure (R)- or (S)-methyl(1-phenylethyl)amine (8)/TiCl4 gave the corresponding optically active unsaturated [3]ferrocenophane amines (R)-(+)- 9 and (S)-(,)- 9, respectively. Their catalytic hydrogenation again proceeded trans -selectively, giving the corresponding saturated diastereomeric [3]ferrocenophane amines (1R,3R,5R)- 10a and (1S,3S,5R)- 10b [starting from (R)- 9], their enantiomers ent - 10a and ent - 10b were obtained from (S)- 9, but with a poor asymmetric induction (10a/10b < 2:1). Quaternization of 6 (CH3I) followed by amine exchange using (R)- or (S)-methyl(1-phenylethyl)amine (8), respectively, proceeded with overall retention. Subsequent chromatographic separation gave the pure diastereoisomers (1R,3R,5R)- 10a and (1S,3S,5R)- 10b [from (R)- 8, ent - 10a and ent - 10b from (S)- 8] in > 60% yield. Subsequently, the benzylic (1-phenylethyl) auxiliary was removed from the nitrogen atom by catalytic hydrogenolysis to yield the enantiomerically pure (> 98%) ([3]ferrocenophanyl)methylamines (1R,3R)- 11 and (1S,3S)- 11, respectively, which were converted into the corresponding dimethylamino-substituted [3]ferrocenophanes (1R,3R)- 6 and (1S,3S)- 6. Each enantiomer from the following enantiomeric pairs was isolated in its pure form and characterized by X-ray diffraction: (R)- 9/(S)- 9; (1R,3R,5R)- 10a/(1S,3S,5S)- 10a; (1R,3R,5S)- 10b/(1S,3S,5R)- 10b; (1R,3R)- 11/(1S,3S)- 11. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Mild Synthesis of ,-Amino-,,,-difluoro Ketones from Acylsilanes and Trifluoromethyltrimethylsilane in a One-Pot Imino Aldol Reaction,

    Sylvain Jonet
    Abstract ,-Amino-,,,-difluoro ketones have been very conveniently prepared in a one-pot procedure from acylsilanes, trifluoromethyltrimethylsilane and imines. The key intermediate in this reaction is a difluoroenoxysilane. The Lewis acid promoted imino aldol reaction was performed with BF3·OEt2 or under very mild conditions using a catalytic amount of Yb(OTf)3. The reaction with chiral benzylimines occurred in good yield with 52,78,% de. Palladium-catalyzed hydrogenolysis furnished an unprotected ,-amino-,,,-difluoro ketone or a ,-amino-,,,-difluoro alcohol. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Val-Ala Dipeptide Isosteres by Hydrocyanation of ,,-Amino ,,,-Unsaturated Ketones , Control of Stereoselectivity by the N -Protecting Group

    Fabio Benedetti
    Abstract Three diastereoisomeric hydroxyethylene isosters of the Val-Ala dipeptide were synthesized from ,,,-unsaturated ketones 1 derived from N -Boc- and N,N -dibenzyl- L -valine. The enones were hydrocyanated with diethylaluminum cyanide to give the corresponding ,-cyano ketones with the stereoselectivity depending on the protecting group. N -Boc protected enone 1a gave a 1:1 mixture of anti and syn adducts 4a, 5a while the corresponding N,N -dibenzyl compound 1c gave a 6:1 mixture of anti, syn adducts 4c, 5c. Borohydride reduction of the resulting cyano ketones is also controlled by the protecting group, resulting in opposite stereoselectivities for N -Boc and N,N -dibenzyl compounds. The cyano alcohols thus obtained were converted, in several steps, into two series of enantiomerically pure hydroxyethylene isosters of the Val-Ala dipeptide. In the first series the hydroxy group and the N -terminal of the isoster are internally protected through the formation of an oxazolidine; in the second series the hydroxy group and the C-terminal are protected as lactone. Two oxazolidines (28, 29), corresponding to syn,syn and syn,anti 4-hydroxy-5-amino acid isosters, and three lactones (23,25), corresponding to syn,syn, syn,anti, and anti,anti isosters were obtained by this approach. (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003) [source]

    Ring-opening metathesis polymerization of amino acid-functionalized norbornene derivatives

    Sutthira Sutthasupa
    Abstract Amino acid-derived novel norbornene derivatives, N,N,-(endo -bicyclo[2.2.1] hept-5-en-2,3-diyldicarbonyl) bis- L -alanine methyl ester (NBA), N,N,-(endo -bicyclo[2.2.1]hept-5-en-2,3-diyldicarbonyl) bis- L -leucine methyl ester (NBL), N,N,-(endo -bicyclo[2.2.1]hept-5-en-2,3-diyldicarbonyl) bis- L -phenylalanine methyl ester (NBF) were synthesized and polymerized using the Grubbs 2nd generation ruthenium (Ru) catalyst. Although NBA, NBL, and NBF did not undergo homopolymerization, they underwent copolymerization with norbornene (NB) to give the copolymers with Mn ranging from 5200 to 38,100. The maximum incorporation ratio of the amino acid-based unit was 9%, and the cis contents of the main chain were 54,66%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5337,5343, 2006 [source]

    Amino and cyano N atoms in competitive situations: which is the best hydrogen-bond acceptor?

    A crystallographic database investigation
    The relative hydrogen-bond acceptor abilities of amino and cyano N atoms have been investigated using data retrieved from the Cambridge Structural Database and via ab initio molecular orbital calculations. Surveys of the CSD for hydrogen bonds between HX (X = N, O) donors, N,T,C,N (push,pull nitriles) and N,(Csp3)n,C,N molecular fragments show that the hydrogen bonds are more abundant on the nitrile than on the amino nitrogen. In the push,pull family, in which T is a transmitter of resonance effects, the hydrogen-bonding ability of the cyano nitrogen is increased by conjugative interactions between the lone pair of the amino substituent and the C,N group: a clear example of resonance-assisted hydrogen bonding. The strength of the hydrogen-bonds on the cyano nitrogen in this family follows the experimental order of hydrogen-bond basicity, as observed in solution through the pKHB scale. The number of hydrogen bonds established on the amino nitrogen is greater for aliphatic aminonitriles N,(Csp3)n,C,N, but remains low. This behaviour reflects the greater sensitivity of the amino nitrogen to steric hindrance and the electron-withdrawing inductive effect compared with the cyano nitrogen. Ab initio molecular orbital calculations (B3LYP/6-31+G** level) of electrostatic potentials on the molecular surface around each nitrogen confirm the experimental observations. [source]

    anti -Selective Asymmetric Michael Reactions of Aldehydes and Nitroolefins Catalyzed by a Primary Amine/Thiourea,

    ANGEWANDTE CHEMIE, Issue 52 2009
    Hisatoshi Uehara Dr.
    "anti" geht auch: Hoch anti -selektive Michael-Reaktionen eines funktionalisierten Aldehyds mit Nitroolefinen gelangen in Gegenwart eines Katalysators mit primärer Amino- und Thioharnstoff-Funktion (siehe Schema; TBS=tert -Butyldimethylsilyl). Die Reaktion beruht auf der Bildung eines Z -konfigurierten Enamin-Intermediats. [source]

    2,- N -(Pyren-1-yl)acetyl-2,-Amino-,-L-LNA: Synthesis and Detection of Single Nucleotide Mismatches in DNA and RNA Targets

    CHEMBIOCHEM, Issue 10 2007
    T. Santhosh Kumar
    Precise positioning of intercalators furnishes a SNP-detection tool. The conformationally locked 2-oxo-5-azabicyclo-[2.2.1]heptane skeleton of 2,-amino-,-L-LNA monomer X directs the N2,-linked pyrene moiety into nucleic acid duplex cores to give highly stabilized duplexes. We have used this precise positioning of pyrene moieties to develop probes that signal the presence of single-nucleotide mismatches in DNA/RNA targets by excimer signal formation. [source]

    ChemInform Abstract: Syntheses of Chiral ,-Amino ,-Perfluoroalkylpropanol Derivatives.

    CHEMINFORM, Issue 18 2008
    Masaaki Omote
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    A Stable (Amino)(phosphino)carbene as Bidentate Ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

    CHEMINFORM, Issue 29 2006
    Emmanuelle Teuma
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    Synthesis of ,-Diazo-,-hydroxyesters Through a One-Pot Protocol by Phase-Transfer Catalysis: Application to Enantioselective Aldol-Type Reaction and Diastereoselective Synthesis of ,-Amino-,-hydroxyester Derivatives.

    CHEMINFORM, Issue 23 2006
    Kazuya Hasegawa
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    Intramolecular Nucleophilic Epoxidation of ,-Amino-,,,-unsaturated Esters with an N-Hydroperoxymethyl Group.

    CHEMINFORM, Issue 48 2005
    Dongwon Yoo
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Synthesis of Novel Amino- and Acetylamino-4-methylcoumarins and Evaluation of Their Antioxidant Activity.

    CHEMINFORM, Issue 36 2005
    Yogesh K. Tyagi
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Synthesis of Substituted 3-(5-Amino-[1,3,4]thiadiazol-2-yl)-2H-pyrano[2,3-c]pyridin-2-ones.

    CHEMINFORM, Issue 51 2004
    Irina O. Zhuravel
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Synthesis of trans-(3S)-Amino-(4R)-alkyl- and -(4S)-aryl-piperidines via Ring-Closing Metathesis Reaction.

    CHEMINFORM, Issue 16 2003
    X. Eric Hu
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Synthesis of New Optically Active Amino- and Alkoxy-Tertiary Monophosphines.

    CHEMINFORM, Issue 50 2002
    Eugenia Fagadar-Cosma
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    ChemInform Abstract: Stereoselective Cyanation of Chiral ,-Amino Aldehydes by Reaction with Nagata,s Reagent: A Route to Enantiopure ,-Amino-,-hydroxy Acids.

    CHEMINFORM, Issue 31 2001
    Jose M. Andres
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Synthesis and Anticonvulsant Activity of Some Novel 3-Aryl Amino/Amino-4-aryl-5-imino-,2 -1,2,4-thiadiazoline.

    CHEMINFORM, Issue 34 2008
    Arun Gupta
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Molecular recognition of sugars by lanthanide (III) complexes of a conjugate of N, N -bis[2-[bis[2-(1, 1-dimethylethoxy)-2-oxoethyl]amino]ethyl]glycine and phenylboronic acid

    Elisa Battistini
    Abstract A novel conjugate of phenylboronic acid and an Ln(DTPA) derivative, in which the central acetate pendant arm was replaced by the methylamide of L -lysine, was synthesized and characterized. The results of a fit of variable 17O NMR data and a 1H NMRD profile show that the water residence lifetime of the Gd(III) complex (150,ns) is shorter than that of the parent compound Gd(DTPA)2, (303,ns). Furthermore, the data suggest that several water molecules in the second coordination sphere of Gd(III) contribute to the relaxivity of the conjugate. The Ln(III) complexes of this conjugate are highly suitable for molecular recognition of sugars. The interaction with various sugars was investigated by 11B NMR spectroscopy. Thanks to the thiourea function that links the phenylboronic acid targeting vector with the DTPA derivative, the interactions are stronger than that of phenylboronic acid itself. In particular, the interaction with N -propylfructosamine, a model for the glucose residue in glycated human serum albumin (HSA), is very strong. Unfortunately, the complex also shows a rather strong interaction with hexose-free HSA (KA,=,705,±,300). Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Cell hydration and mTOR-dependent signalling

    ACTA PHYSIOLOGICA, Issue 1-2 2006
    F. Schliess
    Abstract Insulin- and amino acid-induced signalling by the mammalian target of rapamycin (mTOR) involves hyperphosphorylation of the p70 ribosomal S6 protein kinase (p70S6-kinase) and the eukaryotic initiation factor 4E (eIF4E) binding protein 4E-BP1 and contributes to regulation of protein metabolism. This review considers the impact of cell hydration on mTOR-dependent signalling. Although hypoosmotic hepatocyte swelling in some instances activates p70S6-kinase, the hypoosmolarity-induced proteolysis inhibition in perfused rat liver is insensitive to mTOR inhibition by rapamycin. Likewise, swelling-dependent proteolysis inhibition by insulin and swelling-independent proteolysis inhibition by leucine, a potent activator of p70S6-kinase and 4E-BP1 hyperphosphorylation, in perfused rat liver is insensitive to rapamycin, indicating that at least rapamycin-sensitive mTOR signalling is not involved. Hyperosmotic dehydration in different cell types produces inactivation of signalling components around mTOR, thereby attenuating insulin-induced glucose uptake, glycogen synthesis, and lipogenesis in adipocytes, and MAP-kinase phosphatase MKP-1 expression in hepatoma cells. Direct inactivation of mTOR, stimulation of the AMP-activated protein kinase, and the destabilization of individual proteins may impair mTOR signalling under dehydrating conditions. Further investigation of the crosstalk between the mTOR pathway(s) and hyperosmotic signalling will improve our understanding about the contribution of cell hydration changes in health and disease and will provide further rationale for fluid therapy of insulin-resistant states. [source]

    Novel interactors and a role for supervillin in early cytokinesis,

    CYTOSKELETON, Issue 6 2010
    Tara C. Smith
    Abstract Supervillin, the largest member of the villin/gelsolin/flightless family, is a peripheral membrane protein that regulates each step of cell motility, including cell spreading. Most known interactors bind within its amino (N)-terminus. We show here that the supervillin carboxy (C)-terminus can be modeled as supervillin-specific loops extending from gelsolin-like repeats plus a villin-like headpiece. We have identified 27 new candidate interactors from yeast two-hybrid screens. The interacting sequences from 12 of these proteins (BUB1, EPLIN/LIMA1, FLNA, HAX1, KIF14, KIFC3, MIF4GD/SLIP1, ODF2/Cenexin, RHAMM, STARD9/KIF16A, Tks5/SH3PXD2A, TNFAIP1) co-localize with and mis-localize EGFP-supervillin in mammalian cells, suggesting associations in vivo. Supervillin-interacting sequences within BUB1, FLNA, HAX1, and MIF4GD also mimic supervillin over-expression by inhibiting cell spreading. Most new interactors have known roles in supervillin-associated processes, e.g. cell motility, membrane trafficking, ERK signaling, and matrix invasion; three (KIF14, KIFC3, STARD9/KIF16A) have kinesin motor domains; and five (EPLIN, KIF14, BUB1, ODF2/cenexin, RHAMM) are important for cell division. GST fusions of the supervillin G2-G3 or G4-G6 repeats co-sediment KIF14 and EPLIN, respectively, consistent with a direct association. Supervillin depletion leads to increased numbers of bi- and multi-nucleated cells. Cytokinesis failure occurs predominately during early cytokinesis. Supervillin localizes with endogenous myosin II and EPLIN in the cleavage furrow, and overlaps with the oncogenic kinesin, KIF14, at the midbody. We conclude that supervillin, like its interactors, is important for efficient cytokinesis. Our results also suggest that supervillin and its interaction partners coordinate actin and microtubule motor functions throughout the cell cycle. © 2010 Wiley-Liss, Inc. [source]

    Synthesis and screening of substituted 1,4-naphthoquinones (NPQs) as antifilarial agents

    Nisha Mathew
    Abstract Eleven amino-substituted 1,4-naphthoquinones were synthesized via the reaction of 1,4-naphthoquinone with different primary and secondary mono- and diamines in the presence of dichloromethane ethanol (1:2) solvent at room temperature. All compounds were purified by flash column chromatography, characterized by TLC, HPLC, 13C-NMR, 1H-NMR, and FT-IR spectral analysis and were evaluated in vitro for antifilarial activity using adult bovine filarial worm Setaria digitata by assessing worm motility and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction. Seven of the 11 compounds had macrofilaricidal activity with compounds 9 (2-[(1,3-dimethylbutyl) amino] naphthalene-1,4-dione) and 11 (2-(4-methylpiperazin-1-yl) naphthalene-1,4-dione) having maximum activity (ED50 values of 0.91 and 1.2,µM, respectively, at 48,h). The effect of different substitutions on antifilarial activity is discussed. Drug Dev Res 2009. © 2009 Wiley-Liss, Inc. [source]

    Voltammetric Study of Nitro Radical Anion Generated from Some Nitrofuran Compounds of Pharmacological Significance

    ELECTROANALYSIS, Issue 1 2003
    S. Bollo
    Abstract The electrochemical behavior of 2-(5-amino- 1,3,4-oxadiazolyl)-5-nitrofuran (NF359) and its comparison with well-known drugs such as nifurtimox (NFX) and nitrofurazone (NFZ) in protic, mixed and aprotic media by cyclic voltammetry, tast and differential pulse polarography was studied. All the compounds were electrochemically reducible in all media being the reduction of the nitrofuran group the main voltammetric signal. The one-electron reduction couple due to the nitro radical anion formation was visualized in mixed (for NF359 and NFZ) and aprotic media (for all compounds). By applying a cyclic voltammetric methodology we have calculated the decay constants (k2) of the corresponding nitro radical anions in mixed and aprotic media. In mixed medium data fit well with a disproportionation reaction of the nitro radical anion but in aprotic medium fit better with a dimerization reaction. Also, considering cyclic voltammetric measurements in aprotic media we have estimated the reduction potential of the RNO2/RNO2., couple in aqueous medium, pH 7 (E17 values) finding very good correlation with E17 values obtained by pulse radiolysis. Furthermore we have calculated the equilibrium constants from the electron transfer from nitro radical anion to oxygen (kO2) finding that nitro radical anion from NF359 is thermodynamically favored to react with oxygen in respect to both NFZ and NFX. [source]

    Design, characterization, and utilization of a fast fluorescence derivatization reaction utilizing o -phthaldialdehyde coupled with fluorescent thiols

    ELECTROPHORESIS, Issue 7 2007
    Suminda Hapuarachchi
    Abstract We have developed a chemical derivatization scheme for primary amines that couples the fast kinetic properties of o -phthaldialdehyde (OPA) with the photophysical properties of visible, high quantum yield, fluorescent dyes. In this reaction, OPA is used as a cross-linking reagent in the labeling reaction of primary amines in the presence of a fluorescent thiol, 5-((2-(and-3)- S -(acetylmercapto)succinoyl)amino)fluorescein (SAMSA fluorescein), thereby incorporating fluorescein (,,=,78,000,M,1, quantum yield of 0.98) into the isoindole product. Detection is based on excitation and emission of the incorporated fluorescein using the 488,nm laser line of an Ar+ laser rather than the UV-excited isoindole, thereby eliminating the UV light sources for detection. Using this method, we have quantitatively labeled biologically important primary amines in less than 10,s. Detection limits for analysis of glutamate, glycine, GABA, and taurine were less than 2,nM. We present the characterization of OPA/SAMSA-F reaction and the potential utility of the derivatization reaction for dynamic chemical monitoring of biologically relevant analytes using CE. [source]

    A high-throughput on-line microdialysis-capillary assay for D -serine

    ELECTROPHORESIS, Issue 7-8 2003
    Kylie B. O'Brien
    Abstract A high-throughput method is described for the analysis of D -serine and other neurotransmitters in tissue homogenates. Analysis is performed by microdialysis-capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection in a sheath flow detection cell. Sample pretreatment is not required as microdialysis sampling excludes proteins and cell fragments. Primary amines are derivatized on-line with o -phthaldialdehyde (OPA) in the presence of ,-mercaptoethanol followed by on-line CE-LIF analysis. Under the separation conditions described here, D -serine is resolved from L -serine and other primary amines commonly found in biological samples. Each separation requires less than 22 s. Eliminating the need for sample pretreatment and performing the high-speed CE analysis on-line significantly reduces the time required for D -serine analysis when compared with traditional methods. This method has been used to quantify D -serine levels in larval tiger salamander retinal homogenates, as well as dopamine, ,-amino- n -butyric acid (GABA), glutamate and L -aspartate. D -serine release from an intact retina was also detected. [source]

    Structure,activity analysis of the potentiation by aminothiols of the chromosome-damaging effect of bleomycin in G0 human lymphocytes

    George R. Hoffmann
    Abstract The radioprotective aminothiols 2-[(aminopropyl)amino] ethanethiol (WR-1065) and cysteamine (CSM) potentiate the induction of chromosomal damage by the radiomimetic compound bleomycin (BLM) in G0 human lymphocytes. To investigate the mechanism of potentiation, we measured the clastogenic activity of BLM in the cytokinesis-block micronucleus assay in the presence and absence of amines, thiols, and aminothiols. The hydroxy analog of WR-1065, 2-(3-aminopropylamino) ethanol (WR-OH), potentiates BLM only slightly, indicating the critical nature of the thiol group. As thiols, WR-1065 and CSM may donate electrons for the activation of Fe+2 -BLM or for the regeneration of Fe+2 -BLM from inactive Fe+3 -BLM. The amines putrescine, spermidine, and spermine all potentiate BLM, but they are weaker potentiators than the aminothiols, and they are effective only at high concentrations. Their activity, like that of WR-OH, is probably a consequence of conformational alteration of DNA. Dithioerythritol (DTE) and 2-mercaptoethanol (2-ME), thiols lacking an amino group, are less effective potentiators of BLM than are the aminothiols. The thiol group of WR-1065 and CSM is therefore essential, but insufficient, for explaining the strong enhancement of BLM activity. The cationic nature of CSM and WR-1065, conferred by the amino groups, evidently concentrates the active thiol function at the site of BLM action on DNA. As expected on this basis, the diamine WR-1065 is a more effective potentiator of BLM than is the monoamine CSM, whereas cysteine and N -acetylcysteine (NAC), which lack a net positive charge, potentiate BLM only weakly. These studies suggest that potentiation of the clastogenic action of BLM by aminothiols can be explained by the combination of a thiol-mediated redox mechanism and an amine-mediated targeting of the thiol function to DNA. Environ. Mol. Mutagen. 37:117,127, 2001 © 2001 Wiley-Liss, Inc. [source]

    Effect of drug-induced cytotoxicity on glucose uptake in Hodgkin's lymphoma cells

    Ursula Banning
    Abstract:,Background:,In Hodgkin's lymphoma, F-18-fluoro-deoxy- d -glucose positron emission tomography (FDG-PET) is used for staging and response evaluation after chemotherapy. However, drug-mediated downregulation of glucose uptake in viable Hodgkin's lymphoma cells might limit the use of FDG-PET. Methods:,We analyzed the effect of etoposide on cell viability and uptake of F-18-fluoro-deoxy- d -glucose or the glucose analog 2-[N -(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) in vitro. Results:,Etoposide induced a dose-dependent cytotoxicity in HDLM-2 cells which was significantly correlated with reduced FDG uptake. However, it also significantly increased the portion of viable cells which did not take up 2-NBDG. Interestingly, etoposide-induced cytotoxicity was mainly mediated via caspase-dependent mechanisms, whereas the cell death induced by deprivation of glucose was mediated via caspase-independent mechanisms. Conclusion:,Etoposide-mediated reduction of glucose uptake by Hodgkin's lymphoma cells is mainly caused by cell death. In a small fraction of viable cells, etoposide might downregulate glucose transporters and/or hexokinase activity and by that inhibit glucose uptake. This, however, might not lead to false-negative results of response evaluation in Hodgkin's lymphoma patients after chemotherapy, because inhibition of glucose uptake itself seems to be a strong inducer of cell death. Altogether, this study provides important in vitro evidence to clarify the mechanisms by which FDG-PET monitors the effect of anti-cancer treatment in Hodgkin's lymphoma patients. [source]

    hypercloso -Hexa(amino)hexaboranes: Structurally Related to Known hypercloso -Dodecaboranes, Metastable with Regard to Their Classical Cycloisomers

    Wahid Mesbah
    Abstract B6(NMe2)6 (2a) is the first neutral hypercloso -hexaborane to be characterized by X-ray structural analysis. The geometry of 2a is in nice agreement with that of the Ci symmetric molecule computed at the B3LYP/6-311+G** level of theory. Two B3 triangles with long B···B distances in 2a are reminiscent of those in Hawthorne's benzyloxy-substituted hypercloso -dodecaboranes 6a,b. Upon heating to 200 °C, 2a transforms into Nöth's classical cyclohexaborane 1a. Computations at the B3LYP/6-311+G** + ZPE level of theory show 1a to be 21.6 kcal,mol,1lower in energy than 2a, that is, the latter is metastable. hypercloso -Hexaborane B6(NEt2)6 (2b), which was reported to be thermodynamically more stable than 1b, is computed to be 22.4 kcal,mol,1less stable than 1b. Pure 1b is shown here not to transform into 2b upon standing in solution, which is in contrast to reports in the literature for a mixture containing 1b. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    One-Dimensional Coordination Polymers of MnII, CuII, and ZnII Supported by Carboxylate-Appended (2-Pyridyl)alkylamine Ligands , Structure and Magnetism

    Himanshu Arora
    Abstract Four new complexes [MnII(L1OO)(H2O)][ClO4]·2H2O (1), [ZnII(L1OO)][ClO4]·2H2O (2), [CuII(L3OO)][CF3SO3]·H2O (3), and [ZnII(L3OO)][ClO4] (4) (L1OO, = 3-[(2-(pyridine-2-yl)ethyl){2-(pyridine-2-yl)methyl}amino]propionate; L3OO, = 3-[(2-(pyridine-2-yl)ethyl){(dimethylamino)ethyl}amino]propionate) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1, 3, and 4 are one-dimensional chain-like coordination polymers. In 1 distorted octahedral MnN3O3 and in 3 square-pyramidal CuN3O2 coordination is satisfied by three nitrogen atoms and an appended carboxylate oxygen atom of the ligand, and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 4 trigonal bipyramidal ZnN3O2 coordination environment is provided by two nitrogen atoms and an appended carboxylate oxygen atom of the ligand in the equatorial plane, and the two axial positions are satisfied by a tertiary amine nitrogen and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 1 the MnII center is coordinated by an additional water molecule. In these complexes each monomeric unit is sequentially connected by syn - anti carboxylate bridges. Temperature-dependent magnetic susceptibilities for 1 and 3 are measured, revealing antiferromagnetic interactions through syn - anti carboxylate bridges between the MII centers. Analysis of the crystal packing diagram reveals that in 1 extensive ,,, stacking involving alternate pyridine rings of adjacent 1D chain exists, which eventually lead to the formation of a 2D network structure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Growth of Metal Nanoparticles in a Sol-Gel Silica Thin Film

    Miroslava Malenovska
    Abstract Silica films on glass substrates with homogeneously dispersed platinum, gold or silver nanoparticles were prepared by sol-gel processing mixtures of tetraethoxysilane and {3-[(2-aminoethyl)amino]propyl}triethoxysilane complexes of the corresponding metal ions, followed by dip-coating and hydrogen treatment of the films at elevated temperatures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]