Home About us Contact
|
Home About us Contact | ||
|
|
||
Aspartic Acid (aspartic + acid)
Terms modified by Aspartic Acid Selected AbstractsFerrocene Conjugates Containing Diarginine and Aspartic Acid: Salt Bridge Interactions in WaterEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29-30 2009Anas Lataifeh Abstract The ferrocene peptide conjugates of diarginine (MeO-Fc-Arg-Arg-NH2) (1) and aspartic acid [Boc-Fca-Asp(OH)-OH] (2) were found to form a stable 1:1 associate in aqueous solution. The molecular recognition was achieved through a combination of multipoint hydrogen bonding (H-bonding) sites and a guanidinium-carboxylate ion pair. The associate stoichiometry was confirmed by using ESI-MS and NMR experiments; the NMR titration curve shows multiple equilibria with stepwise interconversion from 1:2,,,1:1 binding ratios, and the electrochemical behaviour of the ferrocenyl groups (Fc, Fca) confirm the formation of an ion pair. The CD spectra in the peptide region exhibit a characteristic absorption of a more ordered structure, while the ferrocene helical chirality remains intact. The solid-state IR measurements exclude the involvement of the amide backbone in the interaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Easy Access to Orthogonally Protected ,-Alkyl Aspartic Acid and ,-Alkyl Asparagine Derivatives by Controlled Opening of ,-Lactams.CHEMINFORM, Issue 47 2003Guillermo Gerona-Navarro Abstract For Abstract see ChemInform Abstract in Full Text. [source] Enantioselective Recognition of Aspartic Acids by Chiral Ligand Exchange PotentiometryELECTROANALYSIS, Issue 11 2004Yanxiu Zhou Abstract Enantioselective resolution is realized by combining potentiometry with ligand exchange (CE) in a new method called chiral ligand exchange potentiometry (CLEP). A chiral selector, N -carbobenzoxy- L -aspartic acid (N-CBZ-L-Asp), preferentially recognizes D -aspartic acid (D-Asp) and undergoes ligand exchange with the enantiomeric labile coordination complexes of [Cu(II)(D-Asp)2] or [Cu(II)(L-Asp)2] to form a diastereoisomeric complex [(D-Asp)Cu(II)(N-CBZ-L-Asp)] (a) or [(L-Asp)Cu(II)(N-CBZ-L-Asp)] (b). Considerable stereoselectivity occurs in the formation of these diastereoisomeric complexes, and their net charges were ,2 (a) and 0 (b), respectively, resulting in different Nernst factor (electrode slope), thus enabling chiral D-Asp to be distinguished by potentiometry without any pre- or postseparation processes. [source] Identification of a novel mutation of SH3BP2 in cherubism and demonstration that SH3BP2 mutations lead to increased NFAT activation ,,HUMAN MUTATION, Issue 7 2006Steven A. Lietman Abstract We describe a novel missense mutation (Aspartic acid to Asparagine, p.D419N (g.1371G>A, c.1255G>A) within exon 9 of SH3BP2 in a patient with cherubism, an autosomal dominant syndrome characterized by excessive osteoclastic bone resorption of the jaw. Two siblings and the father were carriers but lacked phenotypic features. Transient expression of p.D419N (c.1255G>A), as well as three previously described exon 9 mutations from cherubism patients (p.R415Q (c.1244G>A), p.D420E (c.1259G>A), and p.P418R (c.1253C>G)) increased activity of NFAT (nuclear factor of activated T-cells), an osteoclastogenic mediator, indicating that cherubism results from gain of function mutations in SH3BP2. Published 2006 Wiley-Liss, Inc. [source] The equivalent potential of water for electronic structure of aspartic acidJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2008Tian Zhang Abstract The equivalent potential of water for the electronic structure of aspartic acid (Asp,) in solution is constructed by the first-principles, all-electrons, ab initio calculations. Aspartic acid is a hydrophilic amino acid which is negatively charged in neutral water solution. The main process of calculation consists of three steps. Firstly, the geometric structure of the cluster containing Asp, and water molecules is calculated by the free cluster calculation. Then, based on the obtained geometric structure, the electronic structure of Asp, with the potential of water molecules is calculated using the self-consistent cluster-embedding method. Finally, the electronic structure of Asp, with the potential of dipoles is calculated. The results show that the major effect of water on Asp,'s electronic structure is lowering the occupied molecular orbitals by about 0.02 Ry on average, and narrowing energy gap by 10.8%. The effect of water on the electronic structure of Asp, can be simulated by dipoles potential. © 2008 Wiley Periodicals, Inc.J Comput Chem, 2008. [source] Enantioselective Recognition of Aspartic Acids by Chiral Ligand Exchange PotentiometryELECTROANALYSIS, Issue 11 2004Yanxiu Zhou Abstract Enantioselective resolution is realized by combining potentiometry with ligand exchange (CE) in a new method called chiral ligand exchange potentiometry (CLEP). A chiral selector, N -carbobenzoxy- L -aspartic acid (N-CBZ-L-Asp), preferentially recognizes D -aspartic acid (D-Asp) and undergoes ligand exchange with the enantiomeric labile coordination complexes of [Cu(II)(D-Asp)2] or [Cu(II)(L-Asp)2] to form a diastereoisomeric complex [(D-Asp)Cu(II)(N-CBZ-L-Asp)] (a) or [(L-Asp)Cu(II)(N-CBZ-L-Asp)] (b). Considerable stereoselectivity occurs in the formation of these diastereoisomeric complexes, and their net charges were ,2 (a) and 0 (b), respectively, resulting in different Nernst factor (electrode slope), thus enabling chiral D-Asp to be distinguished by potentiometry without any pre- or postseparation processes. [source] Characterizing the regulation of the Pu promoter in Acinetobacter baylyi ADP1ENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Wei E. Huang Summary Effective gene trapping and screening requires sensory and regulatory compatibility of both host and exogenous systems. The naturally competent bacterium Acinetobacter baylyi ADP1 is able to efficiently take up and integrate exogenous DNA into the chromosome, making it an attractive host system for a wide range of metagenomic applications. To test the ability of A. baylyi ADP1 to express the XylR-regulated Pu promoter from Pseudomonas putida mt-2, we have constructed and examined an A. baylyi ADP1 strain, ADPWH- Pu-lux-xylR. The Pu promoter in ADPWH- Pu-lux-xylR was specifically induced by toluene, m -, p - and o- xylene. The substrate-induced Pu promoter was highly dependent on the growth medium: it was repressed in rich media until stationary phase, but was immediately induced in minimal medium with glucose as the sole carbon source (MMG). However, the Pu promoter was repressed in MMG when it was supplemented with 5 g l,1 yeast extract. Further investigation showed that the Pu promoter in MMG was repressed by 0.5 g l,1 aspartic acid or asparagine, but not repressed by glutamine. Changing the carbon/nitrogen ratios by addition of ammonia did not significantly affect the Pu promoter activity but addition of nitrate did. These results show that A. baylyi ADP1 reproduced characteristics of the XylR-regulated Pu promoter observed in its original host. It demonstrates that A. baylyi could provide an excellent genetic host for a wide range of functional metagenomic applications. [source] Ferrocene Conjugates Containing Diarginine and Aspartic Acid: Salt Bridge Interactions in WaterEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29-30 2009Anas Lataifeh Abstract The ferrocene peptide conjugates of diarginine (MeO-Fc-Arg-Arg-NH2) (1) and aspartic acid [Boc-Fca-Asp(OH)-OH] (2) were found to form a stable 1:1 associate in aqueous solution. The molecular recognition was achieved through a combination of multipoint hydrogen bonding (H-bonding) sites and a guanidinium-carboxylate ion pair. The associate stoichiometry was confirmed by using ESI-MS and NMR experiments; the NMR titration curve shows multiple equilibria with stepwise interconversion from 1:2,,,1:1 binding ratios, and the electrochemical behaviour of the ferrocenyl groups (Fc, Fca) confirm the formation of an ion pair. The CD spectra in the peptide region exhibit a characteristic absorption of a more ordered structure, while the ferrocene helical chirality remains intact. The solid-state IR measurements exclude the involvement of the amide backbone in the interaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Oxidative stress on EAAC1 is involved in MPTP-induced glutathione depletion and motor dysfunctionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2008Koji Aoyama Abstract Excitatory amino acid carrier 1 (EAAC1) is a glutamate transporter expressed on mature neurons in the CNS, and is the primary route for uptake of the neuronal cysteine needed to produce glutathione (GSH). Parkinson's disease (PD) is a neurodegenerative disorder pathogenically related to oxidative stress and shows GSH depletion in the substantia nigra (SN). Herein, we report that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice, an experimental model of PD, showed reduced motor activity, reduced GSH contents, EAAC1 translocation to the membrane and increased levels of nitrated EAAC1. These changes were reversed by pre-administration of n-acetylcysteine (NAC), a membrane-permeable cysteine precursor. Pretreatment with 7-nitroindazole, a specific neuronal nitric oxide synthase inhibitor, also prevented both GSH depletion and nitrotyrosine formation induced by MPTP. Pretreatment with hydrogen peroxide, l -aspartic acid ,-hydroxamate or 1-methyl-4-phenylpyridinium reduced the subsequent cysteine increase in midbrain slice cultures. Studies with chloromethylfluorescein diacetate, a GSH marker, demonstrated dopaminergic neurons in the SN to have increased GSH levels after NAC treatment. These findings suggest that oxidative stress induced by MPTP may reduce neuronal cysteine uptake, via EAAC1 dysfunction, leading to impaired GSH synthesis, and that NAC would exert a protective effect against MPTP neurotoxicity by maintaining GSH levels in dopaminergic neurons. [source] Respiratory responses evoked by blockades of ionotropic glutamate receptors within the Bötzinger complex and the pre-Bötzinger complex of the rabbitEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2005Donatella Mutolo Abstract The respiratory role of excitatory amino acid (EAA) receptors within the Bötzinger complex (BötC) and the pre-Bötzinger complex (pre-BötC) was investigated in ,-chloralose,urethane anaesthetized, vagotomized, paralysed and artificially ventilated rabbits by using bilateral microinjections (30,50 nL) of EAA receptor antagonists. Blockade of both N -methyl- d -aspartic acid (NMDA) and non-NMDA receptors by 50 mm kynurenic acid (KYN) within the BötC induced a pattern of breathing characterized by low-amplitude, high-frequency irregular oscillations superimposed on tonic phrenic activity and successively the disappearance of respiratory rhythmicity in the presence of intense tonic inspiratory discharges (tonic apnea). KYN microinjections into the pre-BötC caused similar respiratory responses that, however, never led to tonic apnea. Blockade of NMDA receptors by D(,)-2-amino-5-phosphonopentanoic acid (D-AP5; 1, 10 and 20 mm) within the BötC induced increases in respiratory frequency and decreases in peak phrenic amplitude; the highest concentrations caused tonic apnea insensitive to chemical stimuli. Blockade of non-NMDA receptors by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 1, 10 and 20 mm) within the BötC produced only less pronounced increases in respiratory frequency. Responses to D-AP5 in the pre-BötC were similar, although less pronounced than those elicited in the BötC and never characterized by tonic apnea. In the same region, CNQX provoked increases in respiratory frequency similar to those elicited in the BötC, associated with slight reductions in peak phrenic activity. The results show that EAA receptors within the investigated medullary subregions mediate a potent control on both the intensity and frequency of inspiratory activity, with a major role played by NMDA receptors. [source] Synthesis and Glycosidase Inhibitory Study of New Polyhydroxylated IndolizidinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2008Delphine Baumann Abstract The synthesis of two polyhydroxylated indolizidines as potenticial glycosidase inhibitors is reported. The piperidine ring was formed by an intramolecular Mannich-type reaction between ethyl trans -4-oxo-2-butenoate and the two ,-amino ketones (,)-1-(2-methyl-1,3-dioxan-2-yl)propan-2-amine and(+)-1-(benzyloxymethyl)-2-(2-methyl-1,3-dioxan-2-yl)ethylamine. The synthesis of this amine was performed in eight steps from L -aspartic acid. The key steps of the formation of the framework involved dihydroxylation, nucleophilic substitution, and reduction. The last hydroxy group was introduced by hydrolysis of the acetal moiety followed by reduction of the resulting ketone. The inhibitory properties of the two synthesized indolizidines were evaluated against a variety of commercial glycosidases. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis of Novel Nucleo-,-Amino Acids and Nucleobase-Functionalized ,-PeptidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2003Arndt M. Brückner Abstract Four novel ,-amino acids bearing the canonical nucleobases guanine, cytosine, adenine, and thymine in the side chain, are synthesized starting from Boc- L -aspartic acid 4-benzyl ester. The syntheses are accomplished in six steps by the nucleophilic substitution of (S)-,-(tert -butoxycarbonylamino)-,-bromopentanoic acid benzyl ester with the corresponding nucleobase derivative as the key step. The guaninyl and cytosinyl ,-amino acids were built into ,-peptides that were studied by temperature-dependent CD and UV spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Structural and functional insights into Erwinia carotovora l -asparaginaseFEBS JOURNAL, Issue 17 2008Anastassios C. Papageorgiou Bacterial l -asparaginases are enzymes that catalyze the hydrolysis of l -asparagine to aspartic acid. For the past 30 years, these enzymes have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukemia. Their intrinsic low-rate glutaminase activity, however, causes serious side-effects, including neurotoxicity, hepatitis, coagulopathy, and other dysfunctions. Erwinia carotovora asparaginase shows decreased glutaminase activity, so it is believed to have fewer side-effects in leukemia therapy. To gain detailed insights into the properties of E. carotovora asparaginase, combined crystallographic, thermal stability and cytotoxic experiments were performed. The crystal structure of E. carotovoral -asparaginase in the presence of l -Asp was determined at 2.5 Å resolution and refined to an Rcryst of 19.2 (Rfree = 26.6%) with good stereochemistry. Cytotoxicity measurements revealed that E. carotovora asparaginase is 30 times less toxic than the Escherichia coli enzyme against human leukemia cell lines. Moreover, denaturing experiments showed that E. carotovora asparaginase has decreased thermodynamic stability as compared to the E. coli enzyme and is rapidly inactivated in the presence of urea. On the basis of these results, we propose that E. carotovora asparaginase has limited potential as an antileukemic drug, despite its promising low glutaminase activity. Our analysis may be applicable to the therapeutic evaluation of other asparaginases as well. [source] The most C-terminal tri-glycine segment within the polyglycine stretch of the pea Toc75 transit peptide plays a critical role for targeting the protein to the chloroplast outer envelope membraneFEBS JOURNAL, Issue 7 2006Amy J. Baldwin The protein translocation channel at the outer envelope membrane of chloroplasts (Toc75) is synthesized as a larger precursor with an N-terminal transit peptide. Within the transit peptide of the pea Toc75, a major portion of the 10 amino acid long stretch that contains nine glycine residues was shown to be necessary for directing the protein to the chloroplast outer membrane in vitro[Inoue K & Keegstra K (2003) Plant J34, 661,669]. In order to get insights into the mechanism by which the polyglycine stretch mediates correct targeting, we divided it into three tri-glycine segments and examined the importance of each domain in targeting specificity in vitro. Replacement of the most C-terminal segment with alanine residues resulted in mistargeting the protein to the stroma, while exchange of either of the other two tri-glycine regions had no effect on correct targeting. Furthermore, simultaneous replacement of the N-terminal and middle tri-glycine segments with alanine repeats did not cause mistargeting of the protein as much as those of the N- and C-terminal, or the middle and C-terminal segments. These results indicate that the most C-terminal tri-glycine segment is important for correct targeting. Exchanging this portion with a repeat of leucine or glutamic acid also caused missorting of Toc75 to the stroma. By contrast, its replacement with repeats of asparagine, aspartic acid, serine, and proline did not largely affect correct targeting. These data suggest that relatively compact and nonhydrophobic side chains in this particular region play a crucial role in correct sorting of Toc75. [source] Biosynthesis of the cyanobacterial reserve polymer multi-L-arginyl-poly-L-aspartic acid (cyanophycin)FEBS JOURNAL, Issue 17 2000Mechanism of the cyanophycin synthetase reaction studied with synthetic primers Biosynthesis of the cyanobacterial nitrogen reserve cyanophycin (multi- l -arginyl-poly- l -aspartic acid) is catalysed by cyanophycin synthetase, an enzyme that consists of a single kind of polypeptide. Efficient synthesis of the polymer requires ATP, the constituent amino acids aspartic acid and arginine, and a primer like cyanophycin. Using synthetic peptide primers, the course of the biosynthetic reaction was studied. The following results were obtained: (a) sequence analysis suggests that cyanophycin synthetase has two ATP-binding sites and hence probably two active sites; (b) the enzyme catalyses the formation of cyanophycin-like polymers of 25,30 kDa apparent molecular mass in vitro; (c) primers are elongated at their C-terminus; (d) the constituent amino acids are incorporated stepwise, in the order aspartic acid followed by arginine, into the growing polymer. A mechanism for the cyanophycin synthetase reaction is proposed; (e) the specificity of the enzyme for its amino-acid substrates was also studied. Glutamic acid cannot replace aspartic acid as the acidic amino acid, whereas lysine can replace arginine but is incorporated into cyanophycin at a much lower rate. [source] Involvement of Gln937 of Streptococcus downei GTF-I glucansucrase in transition-state stabilizationFEBS JOURNAL, Issue 13 2000Vincent Monchois Multiple alignment of deduced amino-acid sequences of glucansucrases (glucosyltransferases and dextransucrases) from oral streptococci and Leuconostoc mesenteroides has shown them to share a well-conserved catalytic domain. A portion of this domain displays homology to members of the ,-amylase family (glycoside hydrolase family 13), which all have a (,/,)8 barrel structure. In the glucansucrases, however, the ,-helix and ,-strand elements are circularly permuted with respect to the order in family 13. Previous work has shown that amino-acid residues contributing to the active site of glucansucrases are situated in structural elements that align with those of family 13. In ,-amylase and cyclodextrin glucanotransferase, a histidine residue has been identified that acts to stabilize the transition state, and a histidine is conserved at the corresponding position in all other members of family 13. In all the glucansucrases, however, the aligned position is occupied by glutamine. Mutants of glucosyltransferase I were constructed in which this glutamine, Gln937, was changed to histidine, glutamic acid, aspartic acid, asparagine or alanine. The effects on specific activity, ability to form glucan and ability to transfer glucose to a maltose acceptor were examined. Only histidine could substitute for glutamine and maintain Michaelis,Menten kinetics, albeit at a greatly reduced kcat, showing that Gln937 plays a functionally equivalent role to the histidine in family 13. This provides additional evidence in support of the proposed alignment of the (,/,)8 barrel structures. Mutation at position 937 altered the acceptor reaction with maltose, and resulted in the synthesis of novel gluco-oligosaccharides in which ,1,3-linked glucosyl units are joined sequentially to maltose. [source] Stimuli-Responsive Thin Coatings Using Elastin-Like Polymers for Biomedical ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Rui R. Costa Abstract Smart thin coatings using a recombinant elastin-like polymer (ELP) containing the cell attachment sequence arginine,glycine,(aspartic acid) (RGD) are fabricated for the first time through simple deposition of the ELP dissolved in aqueous-based solutions. The biopolymer is produced and characterized using electrophoresis and mass spectroscopy. The temperature and pH responsiveness are assessed by aggregate size measurements and differential scanning calorimetry. The deposition of the studied ELP onto chitosan is followed in situ with a quartz-crystal microbalance with dissipation monitoring (QCM-D). Contact angle measurements are performed at room temperature and at 50,°C, showing reversible changes from a moderate hydrophobic behavior to an extremely wettable surface. AFM analysis performed at room temperature reveals a smooth surface and no organized structure. At 50,°C, the surface presents spherical nanometer-sized structures of collapsed biopolymer chains. Such results suggest that the ELP chains, when collapsed, aggregate into micelle-like structures at the surface of the substrate, increasing its water affinity. Cell adhesion tests on the developed coatings are conducted using a SaOS-2 cell line. Enhanced cell adhesion could be observed in the H-RGD6-coated surfaces, as compared with the original chitosan monolayer. An intermediate behavior is found in chitosan coated with the corresponding ELP without the RGD sequence. Therefore, the developed films have great potential as biomimetic coatings of biomaterials for different biomedical applications, including tissue engineering and controlled delivery of bioactive agents. Their thermo-responsive behavior can also be exploited for tunable cell adhesion and controlled protein adsorption. [source] Roles of mammalian sterile 20-like kinase 2-dependent phosphorylations of Mps one binder 1B in the activation of nuclear Dbf2-related kinasesGENES TO CELLS, Issue 12 2009Yijun Bao Mammalian nuclear Dbf2-related (NDR) kinases (LATS1, LATS2, NDR1 and NDR2) play a role in cell proliferation, apoptosis and morphological changes. Mammalian sterile 20-like (MST) kinases and Mps one binder (MOB) proteins are important in the activation of NDR kinases. MOB1 is phosphorylated by MST1 and MST2 and this phosphorylation enhances the ability of MOB1 to activate NDR kinases. The phosphorylated MOB1 can be more effective as a scaffold protein to facilitate the MST-dependent phosphorylation of NDR kinases and/or as a direct activator of NDR kinases. We previously reported that Thr74 of MOB1B is phosphorylated by MST2. Thr12 and Thr35 have also been identified as phosphorylation sites. In this study, we quantified the phosphorylation of Thr74 using the phosphorylated Thr74-specific antibody. Thr74 is indeed phosphorylated by MST2, but the efficiency is low, suggesting that MOB1B can activate NDR kinases without the phosphorylation of Thr74. We also showed that the phosphorylated MOB1B activates NDR1 T444D and LATS2 T1041D, in which threonine residues phosphorylated by MST kinases are replaced with phosphorylation-mimicking aspartic acid, more efficiently than the unphosphorylated MOB1B does. This finding supports that the phosphorylation of MOB1B enhances its ability as a direct activator of NDR kinases. [source] Primary Cell Adhesion on RGD-Functionalized and Covalently Crosslinked Thin Polyelectrolyte Multilayer Films,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005C. Picart Abstract Polyelectrolyte multilayers (PEMs) are now widely used for biomedical applications. In this work, we investigated the primary osteoblast adhesion properties of PEMs of poly(L -lysine) (PLL), poly(L -glutamic acid) (PGA), poly(alginic acid) (Palg), and poly(galacturonic acid) (Pgal). In order to compensate for the poor adhesion of the as-synthesized films, two kinds of film modifications were achieved: a purely physical modification by film crosslinking, and a chemical modification by grafting a arginine,glycine,aspartic acid (RGD) peptide to PGA. Crosslinking was performed using a water-soluble carbodiimide in combination with N -hydroxysulfosuccinimide (sulfo-NHS) to induce amide formation. This reaction was followed by Fourier-transform IR spectroscopy. For film functionalization, a 15-amino-acid peptide was grafted to PGA and deposited as the top layer of the film. PLL/PGA, PLL/Palg, and PLL/Pgal films were crosslinked or functionalized. The films were tested for both short-term adhesion properties and long-term proliferation of primary osteoblasts. Whereas the effect of film crosslinking on short-term adhesion was moderate, it was much more important for the RGD-functionalized films. On the other hand, the long-term proliferation was the same or even higher for the crosslinked films as compared with the functionalized films. This effect was particularly enhanced for the PLL/Palg and PLL/Pgal films. Finally, we functionalized PLL/PGA that had been crosslinked prior to PGA-RGD deposition. These architectures exhibited even higher short-term adhesion and proliferation. These results clearly show the important role of the physical properties of the films, besides their chemical properties, for the modulation of primary cell-adhesion behavior. [source] Helicobacter pylori CagA: Analysis of Sequence Diversity in Relation to Phosphorylation Motifs and Implications for the Role of CagA as a Virulence FactorHELICOBACTER, Issue 3 2001Doyle J. Evans Jr Abstract CagA is transported into host target cells and subsequently phosphorylated. Clearly this is a mechanism by which Helicobacter pylori could take control of one or more host cell signal transduction pathways. Presumably the end result of this interaction favors survival of H. pylori, irrespective of eventual damage to the host cell. CagA is noted for its amino acid (AA) sequence diversity, both within and outside the variable region of the molecule. The primary purpose of this review is to examine how variation in the type and number of CagA phosphorylation sites might determine the outcome of infection by different strains of H. pylori. The answer to this question could help to explain the widely disparate results obtained when H. pylori CagA status has been compared to type and severity of disease outcome in different populations, that is in different countries. Analysis of all available CagA sequences revealed that CagA contains both tyrosine phosphorylation motifs (TPMs) and cyclic-AMP-dependent phosphorylation motifs (CPMs). There are two potential CPMs near the N-terminus of CagA and at least two in the repeat region; these are not all equally well conserved. We also defined a 48-residue AA sequence, which includes the N-terminal TPM at tyrosine (Y)-122, which distinguishes between Eastern (Hong Kong-Taiwan-Japan-Thailand) H. pylori isolates and those from the West (Europe-Africa-the Americas-Australia). All 28 of the Eastern type CagA proteins have a functional N-terminal TPM whereas 11 of 47 (23.4%) of the Western type contain an inactive motif, with threonine (T) replacing the critical aspartic acid (D) residue. Only 13 of 24 (54%) known CagA sequences have an active TPM in the repeat region and only one has two TPMs in this region. The potential TPM near the C-terminus of CagA is not likely to be important since only 3 of 24 (12.5%) sequences were found to be intact. Protein database searches revealed that the AA sequence immediately following the TPM at Y-122 in CagA is homologous with a pair of PDZ domains which are common in signal transducing proteins, particularly tyrosine phosphatases. This provides a theoretical link between CagA and many of the observed responses of host cells to H. pylori. In summary, not all CagA proteins are equal in their potential for initiating host cell responses via signal transduction pathways. The degree of functional diversity of this protein depends upon which phosphorylation motifs are critical to the biological activity of CagA. [source] Functional characterization of the NF-,B transcription factor gene REL2 from Anopheles gambiaeINSECT SCIENCE, Issue 3 2007NGO T. HOA Abstract The REL2 gene plays an important role in innate immunity against both Gram (+) and Gram (-) bacteria and malaria parasites in Anopheles gambiae, the main vector of malaria in Africa. Through alternative splicing, REL2 produces two protein products, REL2F (with a Rel-homology domain as well as an inhibitory ankyrin repeat region) and REL2S (without the ankyrin repeats). In the immune-competent cell line Sua1B from An. gambiae, REL2 has been shown to be a key regulator for cecropin A (or CEC1). The high level expression of CEC1 in Sua1B was postulated to be the result of constitutive activation of REL2F. Here we showed that REL2F is indeed processed, albeit at a low level, in the Sua1B cell line. The primary cleavage requires residue 678 (an aspartic acid). Proteolytic cleavage of REL2F can be enhanced by challenge with bacteria Escherichia coli and Bacillus subtilis, but not with fungus Beauveria bassiana. The inducible cleavage can be substantially reduced by RNA interference against PGRP-LC and CASPL1. Over-expression of REL2S or a constitutively active form of REL2F (REL2F380C or REL2F678) in An. gambiae cell line can further increase expression of CEC1 and other antimicrobial peptide genes. Over-expression of these constitutive active proteins in an immune naive cell line, MSQ43, from Anopheles stephensi, results in even more dramatic increased expression of antimicrobial peptides. [source] Kinetics and mechanism of oxidation of a ternary complex involving dipicolinatochromium(III) and DL -aspartic acid by N -bromosuccinimideINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2004Hassan A. Ewais The kinetics of oxidation of [CrIII(Dpc)(Asp)(H2O)2] (Dpc = dipicolinic acid and Asp = DL -aspartic acid) by N -bromosuccinimide (NBS) in aqueous solution have been found to obey the equation: where k2 is the rate constant for the electron transfer process, K1 is the equilibrium constant for deprotonation of [CrIII(Dpc)(Asp)(H2O)2], K2 and K3 are the pre-equilibrium formation constants of precursor complexes [CrIII(Dpc)(Asp)(H2O)(NBS)] and [CrIII(Dpc)(Asp)(H2O)(OH)(NBS)],. Values of k2 = 4.85 × 10,2 s,1, K1 = 1.85 × 10,7 mol dm,3, and K2 = 78.2 mol,1 dm3 have been obtained at 30°C and I = 0.1 mol dm,3. The experimental rate law is consistent with a mechanism in which the deprotonated [CrIII(Dpc)(Asp)(H2O)(OH)], is considered to be the most reactive species compared to its conjugate acid. It is assumed that electron transfer takes place via an inner-sphere mechanism. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 394,400, 2004 [source] Production of Garcinia wine: changes in biochemical parameters, organic acids and free sugars during fermentation of Garcinia mustINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2010Amit Kumar Rai Summary Garcinia wine was prepared by fermentation of ameliorated must of Garcinia xanthochymus using Saccharomyces cerevisiae. The present studies focused on changes in biochemical parameters (brix, pH, aldehydes, esters and alcohols), organic acids (reduction of oxalic acid), free sugars and antioxidant activities on fermentation of Garcinia must. The wine had higher amount of residual sugars contributing to the calorific value. The aldehydes and esters content in the final wine were 0.034% and 0.26%, respectively. There was reduction of citric acid and oxalic acid (antinutritional factor) and synthesis of aspartic acid and glutamic acid. Garcinia beverage was accepted on sensory analysis with high score for desirable attributes and overall quality with alcohol content of 6.1%. There was increase in total phenolics (0.039% gallic acid equivalent) and reducing power on fermentation but decrease in 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity. [source] Sensory aroma from Maillard reaction of individual and combinations of amino acids with glucose in acidic conditionsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2008Kam Huey Wong Summary The aroma produced in glucose,amino acids (individual and in combination) Maillard reaction, under acidic conditions at 100 °C were determined and compared by trained panellist. Proline produced pleasant, flowery and fragrant aroma. Phenylalanine and tyrosine produced dried roses aroma. Alanine produced fruity and flowery odour, while aspartic acid and serine both produced pleasant, fruity aroma. Arginine, produced a pleasant, fruity and sour aroma at pH 5.2, but not at its natural pH. Glycine, lysine, threonine and valine produced a pleasant caramel-like odour. Isoleucine and leucine gave off a burnt caramel aroma. Methionine developed a fried potato odour. Cysteine and methionine produced savoury, meaty and soy sauce-like flavours. A combination of these amino acids produced different types of aroma, with the stronger note dominating the odour of the mixture. This study will help the prediction of flavour characteristics of hydrolysates from different protein sources. [source] Identification of novel single nucleotide polymorphisms within the NOTCH4 gene and determination of association with MHC allelesINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 2 2003R. Tazi-Ahnini Summary Mapping of disease susceptibility loci within the MHC has been partly hampered by the high degree of polymorphism of the HLA genes and the high level of linkage disequilibrium (LD) between markers within the MHC region. It is therefore important to identify new markers and determine the level of LD between HLA alleles and non-HLA genes. The NOTCH4 gene lies at the centromeric end of the MHC class III region, approximately 335 kb telomeric of the DRB1 locus. The encoded protein is an oncogene that is important in regulating vascular development and remodelling. A recent report has linked polymorphisms within NOTCH4 with risk of developing schizophrenia. We have investigated if coding polymorphisms exist within this gene and have identified three single nucleotide polymorphisms; a synonomous T to C transition at +1297 (HGBASE accession number SNP000064386), a synonomous A to G transition at +3061 (SNP000064387) and an A to G transition at +3063 which results in a replacement of glycine with aspartic acid at amino acid 279 (SNP000064388). The allele frequencies of +1297T, +3061A and +3063G were 0.65, 0.66 and 0.66, respectively. Linkage disequilibrium was detected both between these markers and with MHC alleles. These findings can be used in the fine mapping of disease susceptibility alleles within the MHC. [source] Stabilized and Immobilized Bacillus subtilis Arginase for the Biobased Production of Nitrogen-Containing ChemicalsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Abstract L -Ornithine could serve as an intermediate in the biobased production of 1,4-diaminobutane from L -arginine. Using the concept of biorefinery, L -arginine could become widely available from biomass waste streams via the nitrogen storage polypeptide cyanophycin. Selective hydrolysis of L -arginine to L -ornithine is difficult to perform chemically, therefore the stabilization and immobilization of Bacillus subtilis arginase (EC,3.5.3.1) was studied in a continuously stirred membrane reactor system. Initial pH of the substrate solution, addition of L -aspartic acid and reducing agents all appeared to have an effect on the operational stability of B. subtilis arginase. A remarkably good operational stability (total turnover number, TTN=1.13,108) at the pH of arginine free base (pH,11.0) was observed, which was further improved with the addition of sodium dithionite to the substrate solution (TTN>1,109). B. subtilis arginase was successfully immobilized on three commercially available epoxy-activated supports. Immobilization on Sepabeads EC-EP was most promising, resulting in a recovered activity of 75% and enhanced thermostability. In conclusion, the stabilization and immobilization of B. subtilis arginase has opened up possibilities for its application in the biobased production of nitrogen-containing chemicals as an alternative to the petrochemical production. [source] ORIGINAL ARTICLE: Ileal endogenous amino acid flow of broiler chickens under high ambient temperatureJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 5 2010A. F. Soleimani Summary High environmental temperature has detrimental effects on the gastrointestinal tract of poultry. An experiment was conducted to determine the effect of acute heat stress on endogenous amino acid (EAA) flow in broiler chickens. A total of 90, day-old broiler chicks were housed in battery cages in an environmentally controlled chamber. Chicks were fed a nitrogen-free diet on day 42 following either no heat exposure (no-heat) or 2 weeks exposure to 35 ± 1 °C for 3 h from days 28 to 42 (2-week heat) or 1 week exposure to 35 ± 1 °C for 3 h from days 35 to 42 (1 week heat). The most abundant amino acid in the ileal flow was glutamic acid, followed by aspartic acid, serine and threonine in non-heat stressed group. The EAA flow in 1-week heat and 2-week heat birds were significantly (p < 0.05) higher than those under no heat exposure (14682, 11161 and 9597 mg/kg of dry matter intake respectively). Moreover, the EAA flow of 2-week heat group was less than 1-week heat group by approximately 36%. These observations suggest that the effect of heat stress on EAA flow is mostly quantitative; however, heat stress may also alter the content of EAA flow qualitatively. [source] Changes in amino acid composition in the tissues of African catfish (Clarias gariepinus) as a consequence of dietary L-carnitine supplementsJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2002R. O. A. Ozório A study was undertaken to examine the effect of different amounts of dietary lysine (13 and 21 g kg,1 diet), lipid (80 and 160 g kg,1 diet) and L -carnitine (0.2 and 1.0 g kg,1 diet) on growth performance, proximate composition and amino acid metabolism of the African catfish (Clarias gariepinus). Juvenile African catfish (23 ± 1.5 g/fish) were stocked into 70-L aquaria (16 aquaria, 28 fish/aquarium) connected to a recirculation system during a maximum period of 74 days. All groups were fed at a level of 24 g kg,0.8 day,1 in an experiment run at pair feeding. Animals receiving 1.0 g carnitine accumulated up to six times more carnitine in their tissues than animals receiving 0.2 g (P < 0.05). Acyl-carnitine and free L -carnitine levels increased in the whole body and in tissues. Dietary L -carnitine supplements increased protein-to-fat ratios in the body, but did not affect growth rate. Protein-to-fat ratios were only affected when the biosynthesis capacity of L -carnitine was restricted due to low lysine levels and when there was a shortage of dietary fat. When lysine was offered at 21 g kg,1 feed, dietary L -carnitine supplements did not affect the amino acid concentrations of body tissues. Dietary L -carnitine supplements raised the concentration of glutamic acid,>,aspartic acid,>,glycine > alanine > arginine > serine > threonine in skeletal muscle tissue (P < 0.05). Total amino acid concentration in muscle and liver tissues (dry-matter basis) increased from 506 to 564 and from 138 to 166 mg g,1, respectively, when diets were offered with high L -carnitine, low lysine and low fat levels. These data suggest that dietary L -carnitine supplementation may increase fatty acid oxidation and possibly decrease amino acid combustion for energy. [source] Extraction equilibria and separation of phenylalanine and aspartic acid from water with di(2-ethylhexyl)phosphoric acidJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2006Su-Hsia Lin Abstract The distribution equilibria of single and binary L -phenylalanine and L -aspartic acid between water and a kerosene solution of di(2-ethylhexyl)phosphoric acid (D2EHPA) were studied. It was shown that the distribution ratios of phenylalanine generally increased with increasing aqueous pH (2,5) in the D2EHPA concentration range 0.1,0.5 mol dm,3, but those of aspartic acid decreased with increasing solution pH. Different reaction stoichiometries were proposed for the extraction of phenylalanine and aspartic acid under the conditions studied. The extraction equilibrium constants were obtained. Competitive extraction in binary systems was more apparent in the pH range where the cationic form of amino acids was not predominant. The present results indicated that selective separation of phenylalanine to aspartic acid was possible with this cationic extractant when they were extracted at higher pH and stripped using higher acidity of HCl solution. Copyright © 2006 Society of Chemical Industry [source] Rationally designed mutations convert complexes of human recombinant T cell receptor ligands into monomers that retain biological activityJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2005Jianya Y Huan Abstract Single-chain human recombinant T cell receptor ligands derived from the peptide binding/TCR recognition domain of human HLA-DR2b (DRA*0101/DRB1*1501) produced in Escherichia coli with and without amino-terminal extensions containing antigenic peptides have been described previously. While molecules with the native sequence retained biological activity, they formed higher order aggregates in solution. In this study, we used site-directed mutagenesis to modify the ,-sheet platform of the DR2-derived RTLs, obtaining two variants that were monomeric in solution by replacing hydrophobic residues with polar (serine) or charged (aspartic acid) residues. Size exclusion chromatography and dynamic light scattering demonstrated that the modified RTLs were monomeric in solution, and structural characterization using circular dichroism demonstrated the highly ordered secondary structure of the RTLs. Peptide binding to the ,empty' RTLs was quantified using biotinylated peptides, and functional studies showed that the modified RTLs containing covalently tethered peptides were able to inhibit antigen-specific T cell proliferation in vitro, as well as suppress experimental autoimmune encephalomyelitis in vivo. These studies demonstrated that RTLs encoding the Ag-binding/TCR recognition domain of MHC class II molecules are innately very robust structures, capable of retaining potent biological activity separate from the Ig-fold domains of the progenitor class II structure, with prevention of aggregation accomplished by modification of an exposed surface that was buried in the progenitor structure. Copyright © 2004 Society of Chemical Industry [source] | |||||||||||||||||||||||||||||||||||||