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  • 1
    ISSN: 1075-2617
    Keywords: α-chymotrypsin ; enzymatic peptide synthesis ; frozen system ; Nα-unprotected substrates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability of the endopeptidase α-chymotrypsin (EC 3.4.21.1) to catalyse the reaction of various Nα- unprotected di- and tripeptide ester derivatives with H-Leu-NH2, and with a series of C-terminal free di- and tripeptides at -15° C in frozen aqueous solution was investigated. The enzyme is able to synthesize N- and C-terminal unprotected penta- and hexapeptides in up to 92% yield, depending on the amino component used, in a single-step segment-condensation reaction. Freezing the reaction mixture resulted in significantly increased peptide yields compared with the reaction at room temperature. The enzyme shows a modified nucleophilic specificity in frozen solution compared with room temperature. Nucleophilic amino components with positively charged amino acids in P2′ -position are accepted. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 2
    ISSN: 1075-2617
    Keywords: α-trifluoromethyl substituted amino acids ; α-chymotrypsin ; proteolytic stability ; Cα,α-disubstituted glycines ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of model peptides containing α-trifluoromethyl-substituted amino acids in five different positions relative to the predominant cleavage site of the serine protease α-chymotrypsin was synthesized by solution methods to investigate the influence of α-Tfm substitution on the proteolytic stability of peptides. Proteolysis studies demonstrated absolute stability of peptides substituted in the P1 position and still considerable proteolytic stability for peptides substituted at the P2 and P′2 positions compared with the corresponding unsubstituted model peptide. Comparison with peptides containing the fluorine-free disubstituted amino acid α-aminoisobutyric acid allowed to separate electronic from steric effects. Furthermore, the absolute configuration of the α-Tfm-substituted amino acid was found to exert considerable effects on the proteolytic stability, especially in P′1 substituted peptides. Investigations of this phenomenon using empirical force field calculations revealed that in the (S,R,S)-diasteromer the steric constraints exhibited by the α-Tfm group can be outweighed by an advantageous interaction of the fluorine atoms with the serine side chain of the enzyme. In contrast, a favourable interaction between substrate and enzyme is impossible for the (S,S,S)-diastereomer. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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  • 3
    ISSN: 1075-2617
    Keywords: conformational analysis ; NMR spectroscopy ; X-ray diffraction ; peptide-based taste ligands ; artificial sweeteners ; computer simulations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dipeptide taste ligand L-aspartyl-D-2-aminobutyric acid-(S)-α-ethylbenzylamide was found to be about 2000 times more potent than sucrose. To investigate the molecular basis of its potent sweet taste, we carried out conformational analysis of this molecule and several related analogues by NMR spectroscopy, computer simulations and X-ray crystallographic studies. The results of the studies support our earlier model that an ‘L’-shape molecular array is essential for eliciting sweet taste. In addition, we have identified an aromatic group located between the stem and the base of the ‘L-shape’, which is responsible for enhancement of sweetness potency. In this study, we also assessed the optimal size of the essential hydrophobic group (X) and the effects of the chirality of the second residue toward taste. ©1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
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  • 4
    ISSN: 1075-2617
    Keywords: melittin immunogenicity ; T-cell epitopes ; human T-cell clone ; truncated melittin ; substituents on melittin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on immunogenicity studies, two T-cell epitopes in melittin were found to be functional in guinea pigs, one being centrally located, the other one residing in the C-terminal chain. In Balb/c mice only the central epitope was found to be active. A human T-cell clone was found by T-cell proliferation studies to employ strictly the C-terminal chain. Truncation of melittin peptides at the N-terminus did not markedly affect the capacity of guinea pigs to develop anti-IgG responses towards peptidic epitopes and towards a C-terminally attached haptenic group. Attachment of various substituents inside and outside the T-cell epitopic areas had no marked effect on antibody responses. In contrast, the substituents positioned within a T-cell epitope abolished T-cell proliferation. This difference between whole animal data and cellular in vitro responses is presently not understood. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 1075-2617
    Keywords: cyclic opioid peptide analogue ; side-chain to side-chain cyclized peptides ; solid-phase peptide synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel type of cyclic opiod peptide analogue, cyclo(N∊,N∊′-carbonyl- D-Lys2,Lys5)enkephalinamide, was prepared from a linear precursor peptide. The peptide was synthesized on the Merrifield resin and also by a combination of the solid-phase technique and the classical method in solution. In both cases the cyclization was performed by reaction of bis(4-nitrophenyl)carbonate with the free side-chain amino groups of the two lysine residues. The described method permits the convenient preparation of novel peptide analogues cyclized via a ureido group incorporating the side-chain amino groups of two α,ω-diamino acid residues. The cyclic enkephalin analogue containing a 21-membered ring structure showed preference for μ over δ opioid receptors in opioid bioassays in vitro. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
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  • 6
    ISSN: 1075-2617
    Keywords: β-thymosins ; LDMS ; phylogenetic distribution ; primary structure ; thymosin β14 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The study of the phylogenetic distribution of the β-thymosin family is important to elucidate its biological function further. A new thymosin, designated as thymosin β14, consisting of 40 amino acid residues and with a molecular weight of 4537 Da as determined by ion spray mass spectrometry, was isolated from the sea urchin. The N-terminus of this polypeptide is blocked by an acetyl group as found by matrix-assisted laser desorption mass spectrometric and amino acid analysis. The primary structure was elucidatd by Edman degradation of the HPLC-purified thymosin β14 fragments produced by digestion with endoproteinase Asp-N and trypsin. Sequence comparison reveals that thymosin β14 is 73% homologous to thymosin β4, obtained from calf thymus. By isolating and characterising the structure of thymosin β14 from the sea urchin, an invertebrate, substantial knowledge about the phylogenetic distribution and evolution of β-thymosins is gained. © 1997 European Peptide Society and John Wiley & Sons Ltd.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 1075-2617
    Keywords: lipopeptides ; lipid mimetics ; synthesis ; phospholipase A2 ; inhibition ; monolayer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipid mimetics, synthetic molecules that resemble natural lipids either structurally or functionally, have been developed as potential medicinal substances. They have been successfully applied in the development of drug and peptide delivery systems and for the development of inhibitors or lipid metabolizing enzymes. Phospholipase A2 is considered to be involved as the rate-limiting step in the production of lipid mediators of inflammatory responses and, as such, it has been a target for drug design. A series of lipid mimetics including lipopeptides, amides and alcohols of lipidic α-amino acids, have been tested by bulk and monolayer assay techniques. The findings suggested the direct interaction of the tested compounds with porcine pancreatic phospholipase A2. The inactivation of the enzyme occurred in a competitive manner. The most active compound 1 (2-amino-N-hexadecyl-L-hexanamide) showed an apparent IC50 of 12 μ M and inhibitory power Z=13 in the monolayer assay. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 2 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    ISSN: 1075-2617
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 9
    ISSN: 1075-2617
    Keywords: 2-Hydroxy-4-methoxybenzyl-amino acids ; Hmb-derivatives ; peptide synthesis ; solid phase synthesis ; difficult sequences ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Hydroxy-4-methoxybenzyl-amino acid residues inhibit interchain association in solid phase peptide synthesis. They are easily introduced through their N,O-bisFmoc derivatives. Preparation of a range of these derivatives is described.
    Additional Material: 7 Tab.
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  • 10
    ISSN: 1075-2617
    Keywords: Binary peptide libraries ; identification of peptide components ; non-coupling operation ; omission library ; portioning-mixing synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By introducing a new operation (non-coupling), our portioning-mixing method has become suitable for preparing binary peptide libraries. We demonstrate that all the expected components of a simple library are present in the mixture. The number of components in such libraries, the molar ratio of peptides as well as the possibilities of screening are discussed.
    Additional Material: 2 Ill.
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