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  • 1
    Electronic Resource
    Electronic Resource
    Conformational and biological properties of the Ala10-analog of human Des-Trp1, Nle12-minigastrin (1989)
    s.l. : American Chemical Society
    Biochemistry 28 (1989), S. 7182-7188 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00444a008
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of a Monte Carlo Strategy with a Combined DG/MDSA Method for Structure Determination of Bicyclic Peptides (1999)
    Springer
    Journal of molecular modeling 5 (1999), S. 287-295 
    Details
    ISSN: 0948-5023
    Keywords: Keywords Apamin, Distance Geometry, MOCCA, Monte Carlo Simulation, Molecular Dynamics ; Abbreviations DG, Distance Geometry; MDSA, Molecular Dynamic and Simulated Annealing; MC, Monte Carlo; NOE, Nuclear Overhauser Effect; CVFF, Consistent Valence Forcefield; Sec, selenocysteine; RMSD, Root Mean Square Deviation;
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The MC simulation program MOCCA and the combined methods of Distance Geometry and Molecular Dynamics are utilised for structural studies of four isomers of the bee venom toxin apamin. For the MC strategy the conformational space is reduced to torsional degrees of freedom. The study compares the efficiency of both simulation strategies for structure determination of bicyclic peptides and examines the limits of the Monte Carlo method. MOCCA shows a lower efficiency as compared to the combined methods of Distance Geometry and Molecular Dynamics for the structure determination of the bicyclic isomers of apamin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0089490050287
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  • 3
    Electronic Resource
    Electronic Resource
    Exogenous CCK and gastrin stimulate pancreatic exocrine secretion via CCK-A but also via CCK-B/gastrin receptors in the calf (1999)
    Springer
    Pflügers Archiv 438 (1999), S. 86-93 
    Details
    ISSN: 1432-2013
    Keywords: Key words CCK-A and CCK-B/G receptors ; Exocrine pancreatic secretion ; Gut regulatory peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A predominance of the pancreatic cholecystokinin (CCK) receptor of the B/gastrin subtype (CCK-B/G) was reported in calves older than 1 month. Specific CCK-A and CCK-B/G receptor antagonists (SR 27897 and PD 135158, respectively) were used to identify the CCK receptor subtype involved in exogenous CCK- and gastrin-induced exocrine pancreatic responses. Conscious calves (2 months old) with catheterized pancreas, jugular vein and duodenum were used; the pancreatic juice was continuously reinfused. CCK (30 pmol kg–1 min–1, 40 min) evoked an increase in pancreatic juice flow and enzyme secretion, while the same dose of gastrin increased enzyme secretion alone. CCK-induced pancreatic secretion was abolished by SR 27897 (15 nmol kg–1 min–1, 55 min) and reduced by PD 135158 (0.15 nmol kg–1 min–1, 55 min). Gastrin-induced enzyme secretion was reduced by PD 135158 (50% to 90%) and to a lesser extent by SR 27897 (50% to 60%). These results demonstrate that CCK and gastrin in the physiological range stimulate pancreatic exocrine secretion in calves and that these effects are partly mediated by CCK-B/G receptors. Although CCK-A receptors are not predominantly expressed, they seem to play a major role in the response of pancreatic exocrine secretion to CCK.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050883
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of selenocysteine peptides and their oxidation to diselenide-bridged compounds (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 3 (1997), S. 442-453 
    Details
    ISSN: 1075-2617
    Keywords: selenocysteine ; diselenide bridge ; selenide/sulphide bridge ; conformation ; redox potential ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the Fmoc/tBu protection scheme and the p-methoxybenzyl derivative of selenocysteine, the synthesis of related peptides in the selenol-protected form could be optimized by operating the coupling steps in the absence of auxiliary bases and by reducing the piperidine treatment to the minimum time required for quantitative Fmoc cleavage. Under these conditions, β-elimination of the p-methoxybenzylselenol as the main side reaction of these syntheses, as well as epimerization of the protected selenocysteine, was largely suppressed. Conversion of the selenol- and thiol-protected bis-selenocysteine and selenocysteine, cysteine peptides into the related cyclic monomeric forms by iodine-mediated oxidation failed since a complex mixture of compounds was produced. Cleavage of the selenoether bond with mercuric acetate was found to proceed smoothly, but displacement of the heavy metal ions by treatment with excesses of thiols or hydrogen sulphide was unsuccessful since a stable Hg2+ diselenide complex was obtained. However, oxidation was achieved in good yields by the dimethylsulphoxide/trifluoroacetic acid procedure and the peptides were then used for determining the redox potential of the diselenide and selenide/sulphide bridge, respectively. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    On the Mechanism of Hormone Recognition and Binding by the CCK-B/Gastrin Receptor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 3 (1997), S. 1-14 
    Details
    ISSN: 1075-2617
    Keywords: peptide lipidation ; vesicles ; lipid interaction ; conformation ; receptor binding ; ligand receptor docking ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipidation with long-chain di-fattyacyl-glycerol moieties was used to anchor gastrin and CCK peptides irreversibly to lipid bilayers. Intervesicular lipopeptide transfer to model phospholipid bilayers is fast and quantitative, leading to a different mode of insertion of lipo-gastrin and lipo-CCK in lipid bilayers. Lipo-gastrin remains exposed to the bulk solvent in a predominantly random coil structure as a consequence of electrostatic repulsion, whereas lipo-CCK exhibits a pronounced tendency to form peptide domains with insertion of its C-terminus into more hydrophobic compartments of the bilayer. Thereby Ca2+ at physiological concentrations favours this aggregational phenomenon. Since both lipo-peptides were found to retain almost full receptor affinity despite their irreversible anchorage to the bilayer, a membrane-bound pathway in the receptor recognition and binding process is indeed possible. According to the data collected in this study, CCK might possibly use this pathway, whereas accumulation of gastrin on the cell membrane with prefolding of the ligand at the water/lipid interface is hardly conceivable. Nevertheless the observed receptor interaction of the deliberately membrane-anchored gastrin offers interesting constraints for computational docking experiments on a modelled CCK-B/gastrin receptor by additionally taking into account information derived from mutagenesis studies. Despite the limitations of such modelling experiments, the resulting picture of the gastrin/receptor complex allowed the visualization and rationalization of the experimental results of the extensive structure-function studies performed previously on this family of gastrointestinal hormones. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Cysteine Racemization in Peptide Synthesis: A New and Easy Detection Method (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 2 (1996), S. 271-275 
    Details
    ISSN: 1075-2617
    Keywords: peptide synthesis ; cysteine ; racemization ; enantiomeric resolution ; capillary electrophoresis ; gas chromatography ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method has been developed for the rapid determination of D-cysteine contents in synthetic peptides. It is based on the reduction of cystine residues, when present, with tris- alkylphosphines, selective derivatization of the cysteine residues with 4-vinylpyridine, followed by acid hydrolysis of the (4-pyridylethyl)cysteine -peptides. Baseline enantiomeric resolution of theD,L-S-β-(4-pyridylethyl)cysteine, and thus quantification ofD- enantiomer contents at levels ≤1%, is easily achieved by capillary zone electrophoresis exploiting the host-guest complexation principle with crown ethers or by gas chromatography on chiral glass capillary columns upon conventional derivatization of the hydrolysate. The acid-stability of the (4-pyridylethyl)cysteine derivative prevents racemization via thiazoline intermediates and allows for standardization of the acid hydrolysis-dependent racemization.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.83
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  • 7
    Electronic Resource
    Electronic Resource
    Metal ion binding affinities of gastrin and CCK in membrane mimetic environments (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 360-370 
    Details
    ISSN: 1075-2617
    Keywords: Gastrin ; CCK ; lipo-derivatization ; calcium ; terbium ; circular dichroism ; phosphorescence ; conformational ; lipid bilayers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fully active gastrin and CCK analogues [Nle15]-gastrin- 17 and [Nle, Thr]-CCK-9 were analysed for their Ca2+ and Tb3+ affinities in various membrane mimetic conditions. In TFE both gastrin and CCK exhibited high affinities for calcium and terbium. At saturation level identical metal ion/peptide ratios were determined with Ca2+ and Tb3+, i.e. R = 3 for gastrin and R = 1 for CCK, confirming the very similar coordination properties of the two metal ions. The conformational effects of both metal ions were found to be very similar with a disordering effect in the case of gastrin and a conformational transition to β-turn type structure in the case of CCK. In order to mimic more properly physiological conditions, similar experiments were performed in the prsence of phospholipid bilayers. No interaction of the peptides with the bilayers was observed even in the presence of phospholipid bilayers. No interaction of the peptides with the bilayers was observed even in the presence of mmolar Ca2+ concentrations. Induced lipid interaction via N-terminal lipodervatization of gastrin and CCK allowed to translocate quantitatively the two hormones into phospholipid bilayers and to examine the effect of extravesicular Ca2+ on the conformation of the peptide headgroups and on their display at the water/lipid interphase. The CCK moiety of the lipo-CCK inserted into phospholipid bilayers interacts with the lipid phase and addition of Ca2+ enhances the clustering of the peptide headgroups in a more β-sheet type conformation. Conversely, insertion of lipo-gastrin into the bilayers leads to full exposure of the gastrin headgroup to the bulk water in predominantly random coil structure. Again Ca2+ provokes aggregation. As the lipo-peptide/phospholipid system still represents only an artificial model, it remains hazardous to derive a biological relevance from these data. The significantly higher affinity of lanthanide ions than Ca2+ for the peptides could well play a role in the inhibibitory activity of lanthanum on the signal transduction of the CCK family of hormones.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.310010603
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Conformational analysis of bioactive peptides in reverse micelles as mimics of cell membrane environments (1995)
    Springer
    International journal of peptide research and therapeutics 1 (1995), S. 171-177 
    Details
    ISSN: 1573-3904
    Keywords: Bioactive peptides ; Conformation ; Reverse micelles ; Circular dichroism ; Infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Conformational preferences of secretin as a model peptide have been analyzed by CD and IR spectroscopy in reverse micelles of AOT/isooctane/water and compared to those in aqueous TFE, in SDS micelles and in DMPG vesicles. Among the systems examined, reverse micelles and phospholipid vesicles displayed almost identical conformational equilibria. Very high lipid-to-peptide ratios can be obtained in reverse micelles with full retention of optical transparency, even at millimolar peptide concentrations, thus indicating this system to be an interesting mimic of cell membrane environments for spectroscopic analysis of bioactive peptide conformations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00117953
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  • 9
    Electronic Resource
    Electronic Resource
    Conformational preferences of Leu-enkephalin in reverse micelles as membrane-mimicking environment (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 591-606 
    Details
    ISSN: 0006-3525
    Keywords: Leu-enkephalin ; [13C, 15N]-backbone-labeled ; reverse micelles ; conformation ; CD ; FTIR ; nmr ; distance geometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enkephalin represents one of the bioactive peptide molecules most extensively investigated both in solution and in the crystal state. Depending upon the environment chosen for such studies, three main conformational states were identified for this flexible, linear pentapeptide - i.e., an extended conformation, a single-bend, and a double-bend structure. Since CD and Fourier transform ir (FTIR) spectra of Leu-enkephalin solubilized in negatively charged reverse micelles of bis (2-ethylhexyl)sulfosuccinate sodium salt/isooctane/water were supportive of a restricted conformational space of the aromatic side chains and of a bended type fold, we have analyzed by nmr the conformational preferences of Leu-enkephalin in reverse micelles using a synthetic [13C, 15N]-backbone-labeled sample. The overall conformation derived from nuclear Overhauser effect spectroscopy (NOESY) and 15N-filtered rotating frame NOESY (ROESY) spectra and by distance geometry calculations is a double-bend fold of the backbone that is comparable to one of the known x-ray structures. Thereby the tyrosine side chain is inserted into the hydrophobic core of the reverse micelles in a restrained conformational space as well evidenced by NOEs between the aromatic ring protons and the surfactant. The proximity of the aromatic rings of tyrosine and phenylalanine indicate a preferred structure consistent with the postulated conformation of the opioid peptide in the δ-receptor-bound state. These results confirm the interesting and promising properties of reverse micelles as membrane mimetica. © 1997 John Wiley & Sons, Inc. Biopoly 41: 591-606, 1997
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 10
    Electronic Resource
    Electronic Resource
    A new efficient method for the synthesis of 1,4-benzodiazepine-2,5-dione diversomers (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 295-300 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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