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  • Organic Chemistry  (6)
  • Polymer and Materials Science  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Sequence dependence of secondary-structure formation part IVPart III: [1]. Helix-forming potential of amphiphilic oligopeptides containing aib residues (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 786-792 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of Aib-containing oligopeptides having the propensity to adopt amphiphilic helical conformations were investigated by CD spectroscopy in solution. The peptides CF3COOH.H-Pro-Glu-[Ala-Aib-Glu-Aib-]4Gly-OH (I), HCl.H-Pro-Ala-Aib-[Gul-Ala-Ala-Aib-]2Glu-Ala-Aib-Gly-PEGM (II), and CF3COOH.H-Ala-Aib-[Glu-Glu-Ala-Aib-]3PEGM (III) were synthesized according to the general principles of the liquid-phase method for peptide synthesis. Peptides I-III exhibit helical conformations in CF3CH2OH, MeOH, and in H2O at acidic pH; however, at pH 7, only II forms a stable helix, whereas I and III are predominantly in an unordered conformation. Some general features for the construction of amphiphilic helices are discussed in the light of the experimental data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690405
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  • 2
    Electronic Resource
    Electronic Resource
    Aza-Claisen Rearrangement: Synthesis of 5′-branched 5′-aminothymidinesDedicated with best personal wishes of D. B. to Professor Oskar Jeger on the occasion of his 80th birthday (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 1589-1606 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of both diastereoisomers of 5′-ethyl-substituted thymidine dimers, the (5′R)- and (5′S)-configurated 33a and 33b respectively, in which the natural phosphodiester linkage is replaced by an amide group (C(3′)-CH2CONH-CH(5′)(Et)), arc described. Their fully protected derivatives 35a and 35b, respectively, are suitable for incorporation into antisense oligonucleotides. Unexpectedly, an attempted PdII-catalysed aza-Claisen rearrangement of trichloroacetimidate 7 provided the diastereoisomerically pure cyclopropane derivative 17, whose structure was confirmed by X-ray analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800517
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Single-Centre Model for the Active Site of α-Chymotrypsin (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 410-414 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymer-bound heptapeptide H-Glu-His-Pro-Gly-Ser-Gly-PEGM was designed as a ‘single-centre model’ for the active site of α-chymotrypsin. The peptide was synthesized according to the general principles of the liquid-phase method for peptide synthesis, and its conformational properties were investigated by CD and IR spectroscopy in solution and in the solid state. In harmony with empirical prediction codes, experimental and theoretical conformational considerations, the peptide adopts a β-turn conformation stabilized by H-bonds involving the side chains of Glu, His, and Ser. The development of a H-bonded system similar to the active site of α-chymotrypsin leads to implications with respect to a possible catalytic activity of the model peptide.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690221
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  • 4
    Electronic Resource
    Electronic Resource
    Approaches to Synthetic Vaccines Design of Epitope-Containing Amphiphilic Peptides Matching the Antigenic Structure in the Native Protein (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 985-995 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general procedure for the design of synthetic vaccines with the retained conformational features of protein antigenic determinants is described. This new concept emerges from detailed studies on the relationship between primary sequence and secondary structure formation of synthetic peptides and takes advantage of the amphiphilic nature of epitope-containing peptide segments in the native protein to accomplish structural modifications. These segments, for example amphiphilic helices or β-sheets, are stabilized by the insertion of secondary structure-inducing amino-acid residues on the hydrophobic part of the peptide without affecting the spatial arrangement of functional residues on the hydrophilic side. The availability of amphiphilic peptides with tailor-made conformational properties, e.g. helices, β-sheets, and, moreover, assemblies of these blocks to structures of higher order (‘folding units’), allows the presentation and stabilization of continuous as well as discontinuous epitopes by this approach. This strategy is exemplified for the case of two discontinuous epitopes taken from lysozyme, which are matched to host molecules with adequate conformational features by the help of computer-assisted molecular modelling. The implications of this new concept for the design of synthetic vaccines are discussed with special emphasis to the important role of peptide synthesis and chemical structure modification.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690505
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  • 5
    Electronic Resource
    Electronic Resource
    Confromational Studies on Peptides Containing Enantiometric α-Methyl α-Amino Acids. Part I. Differential conformational properties of (R)- and (S)-2-methylaspartic acid (1992)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 75 (1992), S. 1198-1210 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of four model peptides of the general formula Ac-Tyr-Xaa-Yaa-Zaa-Ala-Lys-Glu-ala-Ala-Glu-Lys-Ala-Zaa-Yaa-Xaa-Lys-NH2 (Xaa-Yaa-Zaa = Ala-Ala-(R)-Asp(2-Me), 1; Ala-Ala-(S)-Asp(2-Me), 2; Ala-Aib-Asp, 3; Ala-Ala-Asp, 4; Asp(2-Me) = 2-methylaspartic acid; Aib = 2-aminoisobutyric acid) were studied by CD spectroscopy in solution, to evaluate the helix-inducing potential of enantiomerically pure 2-methylaspartic acid as a function of its chirality at C(2). At neutral pH and 1°, all peptides exhibit significant helix formation in aqueous solution, the degree of helicity increasing in the order 4 3 ≈ 1. Lowering the pH to 2 results in a dramatic increase in helicity for peptide 1, while the diastereoisomeric peptide 2 now exists in a predominantly unordered conformation. Helix induction by protonated (R)-Asp(2-Me) exceeds Aib-induced helix formation in peptide 3, and the helix content of 1 in aqueous solution at pH 2 is comparable to the degree of helicity in the strongly helix-inducing solvent 2,2,2-trifluoroethanol.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19920750420
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  • 6
    Electronic Resource
    Electronic Resource
    The Construction of New Proteins. Part IIIPart 11: [4]. Artificial folding units by assembly of amphiphilic secondary structures on a template (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 835-847 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new general strategy for the construction of artificial proteins with predetermined tertiary structure is presented. Amphiphilic α-helix and β-sheet-forming oligopeptides are assembled on a multifunctional ttemplate molecule which directs the peptide blocks to adopt characteristic folding topologies. The design, synthesis, and conformational properties of these template-assembled synthetic proteins (TASP) are exemplified for βαβ-, α-helix-bundle- and β-barrel-like tertiary structures using specially designed oligopeptides as template molecules. In contrast to linear polypeptide chains of comparable molecular weights, these conceptually novel marcromolecules are readily accessible to chemical synthesis and exhibit excellent solubility in a number of solvents. Experimental evidence is provided for a template-induced intramolecular folding to secondary and tertiary structures in aqueous solutions. This approach opens new prospects for the chemical construction of biomacromolecules with tailormade structural and functional properties.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710419
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  • 7
    Electronic Resource
    Electronic Resource
    The construction of new proteinsPaper presented at the meeting of the GDCh-Fachgruppe “Makromolekulare Chemie” on “New Polymers-special properties-new technologies” in Bad Nauheim (W.-Germany) on April 14/15, 1986. (1986)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 145 (1986), S. 211-229 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent progresses in the elucidation of the folding mechanism and topology of proteins revealed that the formation of folding units with specific topological features is not restricted to a unique primary sequence. This finding presents the basis for the design of polypeptides having the propensity to fold into a tertiary structure that can be achieved by the assembly of peptide blocks exhibiting stable secondary structures. Conformational studies on model peptides show that Aib containing peptides with chain-lengths of 12-15 residues are able to form stable amphiphilic helices in solution. On the other hand, oligopeptides with alternating hydrophilic and hydrophobic residues are capable for β-structure formation for chain-lengths of 6-8 residues. Those amphiphilic secondary structures have been used as building-blocks for the design and synthesis of artificial folding units, their amphiphilic nature acting as major driving force for intramolecular folding. Spectroscopic data obtained for two polypeptides designed as βαβ-models actually suggest a folded conformation of these molecules in aqueous solution. The implications of these findings for the design of biologically active folded polypeptides are discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1986.051450112
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  • 8
    Electronic Resource
    Electronic Resource
    Poly(ethylene glycol)-bound peptides as single centre models for enzyme-like catalysis (1985)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 6 (1985), S. 785-789 
    Details
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1985.030061113
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