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  • Articles  (22)
  • X-ray diffraction  (22)
  • Springer  (22)
  • Nature Publishing Group
  • 1995-1999  (22)
  • 1960-1964
  • 1945-1949
  • 1997  (22)
  • Chemistry and Pharmacology  (22)
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  • Articles  (22)
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  • 1995-1999  (22)
  • 1960-1964
  • 1945-1949
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  • 1
    Electronic Resource
    Electronic Resource
    In situ tempering of melt spun AlGeSi-foils (1997)
    Springer
    Microchimica acta 125 (1997), S. 25-31 
    Details
    ISSN: 1436-5073
    Keywords: AlGeSi-alloys ; X-ray diffraction ; analytical transmission electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract AlGeSi-alloys of different composition were cast by a melt spin device to ribbons of 40 μm thickness. The ribbons melt near 500 °C and should be well suited for brazing of high strength Al-alloys. Because of the existence of metastable phases, these ribbons are brittle in the rapidly solidified state, but increasingly ductile and cuttable after an appropriate annealing between 200 and 400 °C. The thermally induced phase transformations are revealed by the hightemperature X-ray diffractograph as well as, with help of a heating sample holder, by the analytical transmission electron microscope (TEM). The identification of elements and phases is performed by X-ray Bragg reflexes and of electron diffraction (ED) patterns, whereby the latter can be associated to single microstructure details in the sub-μm range. Moreover, the distribution of the elements can be seen on distribution maps “din the light” of characteristic X-ray spectral lines. The observed microstructure of as-quenched AlGe45 with 2 or 4 mass-% Si was of similar appearence but more refined as in the AlGe45 alloy. It consists of α-Al primary crystals surrounded by an eutectic mixture of α-Al and two metastable intermetallic AlGe(Si) phases. Si was observed exclusively within these metastable phases. During an appropriate tempering the metastable phases transform into the equilibrium phases α-Al and β-Ge(Si). For this decomposition the temperature is decreased by alloying with Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246158
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  • 2
    Electronic Resource
    Electronic Resource
    Stresses in alumina scales on NiCrAlY-alloys determined by XSE and LRS (1997)
    Springer
    Microchimica acta 125 (1997), S. 275-278 
    Details
    ISSN: 1436-5073
    Keywords: alumina scales ; spallation ; stress measurement ; X-ray diffraction ; Raman spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of silicon and titanium on the spallation resistance of alumina scales grown on NiCrAlY-type alloys has been investigated. For this purpose cyclic oxidation experiments on model alloys with different additions of silicon or titanium were carried out at temperatures between 950 and 1100 °C. Selected samples were analysed by X-ray stress evaluation (XSE) after various times of oxidation. It was found that the compressive stresses measured at ambient temperature increase with increasing time and are affected by the presence of silicon. The XSE results were used to calibrate laser Raman spectroscopy (LRS) for strain measurement. Then, the suitability of Raman spectroscopy for stress measurement at higher temperatures was evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246196
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  • 3
    Electronic Resource
    Electronic Resource
    Structure investigations of thin MoSx films (1997)
    Springer
    Microchimica acta 125 (1997), S. 349-353 
    Details
    ISSN: 1436-5073
    Keywords: microstructure ; MoSx films ; X-ray diffraction ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of process parameters on the formation of microstructure of magnetron-sputtered MoSx-films on silicon wafers was investigated. The MoSx-films were analyzed by means of X-ray diffraction and TEM. The prepared MoSx-films show a microstructure in dimension of some nm without any prefered orientation or texture. The X-ray diffraction measurements indicate clearly differences in the structure for various preparation conditions. Simulations provided a first structural model for the description of the MoSx-films. The MoSx-films consist of two-dimensional nanocrystals and noncrystallographic randomly packed (001) planes. Transitions between these structural states and intermediate states determine the microstructure depending on the preparation conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246210
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular and electronic structure of halogen-substituted phosphaalkenes (1997)
    Springer
    Structural chemistry 8 (1997), S. 343-352 
    Details
    ISSN: 1572-9001
    Keywords: Phosphaalkanes ; molecular structure ; electronic structure ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Peculiarities of the molecular and electronic structure of P- and C-halogen-substituted phosphaalkenes have been considered on the basis of results of X-ray diffraction studies and quantumchemical calculations. Introduction of an electronegative halogen atom is shown to have an insignificant effect on the intramolecular bond angle distribution, whereas the influence on the P=C bond length is noticeable. Thus, in P-substituted phosphaalkenes it substantially increases the polarization of the P=C bond (which causes its noticeable shortening). In C-substituted phosphaalkenes the effect of halogen atoms is less pronounced: decreasing the P=C bond polarization leads only to its slight elongation. In addition, a considerable elongation of the phosphorus-halogen bond in comparison with three-coordination phosphorus compounds is a peculiarity of the molecular structure of P-halogen-substituted phosphaalkenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02281247
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  • 5
    Electronic Resource
    Electronic Resource
    Comprehensive studies of Tolperisone·HCl-cyclodextrin complexes (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 503-514 
    Details
    ISSN: 1572-8943
    Keywords: cyclodextrins ; IR spectroscopy ; thermal analysis ; Tolperisone-HCl ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid inclusion complexes of TolperisoneHCl with five various cyclodextrins were prepared by kneading and spray drying. The complex formation between the drug and the cyclodextrins were proven using thermoanalytical methods, X-ray diffraction, IR spectroscopy. The results of the solid state investigations were supported by the liquid phase investigations, such solubility and parition constant measurements and stability constant determination. Among all cyclodextrins used the β- and γ-CD-s were found to be the best complexing agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979497
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  • 6
    Electronic Resource
    Electronic Resource
    DSC and X-ray studies on side-chain crystallization of comb-like polymers (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 115-121 
    Details
    ISSN: 1572-8943
    Keywords: comb-like polymer ; DSC ; fluorocarbon chain ; side-chain crystallization ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF2)nCH2OCOCH=CH2, (FnA) and H(CF2)nCH2OCOC(CH3)=CH2, (FnMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF10A and PF10MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF10A in 1st heating, enthalpy change δH f was 18 kJ mol−1 and entropy change δS f was 45 J K−1 mol−1, while for PF10MA the values δH f and δSf were 5.3 kJ mol−1 and 14 J K−1 mol−1, respectively. Melted PF8A crystallized slowly, whereas PF8MA with same fluorocarbon chain and also both of PF6A and PF6MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987428
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature resolved X-ray diffraction as a tool of thermal analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1025-1037 
    Details
    ISSN: 1572-8943
    Keywords: crystallographic evaluation ; evaluation with difference procedure ; kinetics ; Rietveld refinement ; X-ray diffraction ; temperature resolved
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Time and temperature resolved X-ray diffraction was used for thermal analysis. Series of diffraction patterns were measured, while the samples are heated/cooled stepwise or isothermally with freely selectable temperature programs. The method was applied for the investigation of the phase transitions of ammonium nitrate and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraaza-cyclooctane), when the identification of phases was required. Its capability in the field of kinetics is demonstrated with the isothermal investigation of the solid state reaction of ammonium nitrate with copper oxide and the non-isothermal investigation of the high temperature corrosion of nickel, which was performed by means of a difference procedure. For obtaining structural details peak fitting and Rietveld refinement were applied for the investigation of ammonium nitrate and HMX.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01996790
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  • 8
    Electronic Resource
    Electronic Resource
    Phase formation and thermal stability of the compounds in the Bi2O3-PbO system (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1197-1205 
    Details
    ISSN: 1572-8943
    Keywords: Bi2O3-PbO system ; DTA-TG ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The scientific interest for the Bi2O3-PbO system has increased due to the importance of the PbO in the high-T c superconducting phase formation in the Bi2O3-SrO-CaO-CuO system. Also Bi2O3-PbO system contains compounds with some specific semiconductor and dielectric properties and Bi2O3-based solid solutions are well known as high oxygen ion conductors. Previously, several low melting defined compounds have been identified in the system: 6Bi2O3·PbO; 3Bi2O3·2PbO; 4Bi2O3·5PbO; 4Bi2O3·6PbO and Bi2O3·3PbO. This work deals with the phase formation and thermal stability of these compounds. Under non-isothermal conditions, in all mixtures regardless of the Bi2O3/PbO ratio, the compound 6Bi2O3·PbO is preferentially formed, followed by the compound 4Bi2O3·5PbO. The formation of the compound 4Bi2O3·6PbO was not confirmed while the formation of the compound Bi2O3 3PbO occurs through a complex mechanism which includes an intermediate step in which a solid solution with the litharge structure was identified. Under isothermal conditions in the same temperature range the tendency to form the stoichiometric compounds increases. All compounds form, decompose and melt at temperatures between 530–780°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01983675
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  • 9
    Electronic Resource
    Electronic Resource
    Oxygen exchange study in phase transformations of superconducting bismuth cuprates (Pb2212 and Pb2223) (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 401-407 
    Details
    ISSN: 1572-8943
    Keywords: bismuth cuprates ; DTA-DTG ; oxygen partial pressure ; X-ray diffraction ; zirconia sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxygen exchange between the condensed phase(s) and the gas phase was studied as a function of temperature for superconducting phases of the system (Bi,Pb)-Sr-Ca-Cu-O. An oxygen probe apparatus allowed confirmation that the variation in oxygen composition in the Pb2212 and Pb2223 superconducting phases is a reversible phenomenon on heating and cooling. It was demonstrated that the mass loss of both phases, for the 905 and 980°C isotherms, was due to the oxygen composition variation and to PbO loss (this latter phenomenon begin irreversible).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01980500
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal Stability of Sol-Gel Hydrotalcites (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 437-442 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel hydrotalcites ; X-ray diffraction ; aluminum precursors ; hydrotalcites Mg/Al ratio ; mixed metal hydroxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-Gel Hydrotalcites were synthesized using magnesium ethoxide and variable aluminum sources: aluminum acetilacetonate, aluminum chloride, aluminum nitrate and aluminum sulfate; in all cases, the gelation was done at pH 10. X-ray diffraction studies show that the crystallinity depends on the aluminum precursor used. The crystallinity was found in the order aluminum acetylcetonate 〉 aluminum chloride 〉 aluminum nitrate 〉 aluminum sulfate. The precursor determines the sintering behavior as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018309420745
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  • 11
    Electronic Resource
    Electronic Resource
    Thermal stability of sol-gel hydrotalcites (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 437-442 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel hydrotalcites ; X-ray diffraction ; aluminum precursors ; hydrotalcites Mg/Al ratio ; mixed metal hydroxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-Gel Hydrotalcites were synthesized using magnesium ethoxide and variable aluminum sources: aluminum acetilacetonate, aluminum chloride, aluminum nitrate and aluminum sulfate; in all cases, the gelation was done at pH 10. X-ray diffraction studies show that the crystallinity depends on the aluminum precursor used. The crystallinity was found in the order aluminum acetylcetonate〉aluminum chloride〉aluminum nitrate〉aluminum sulfate. The precursor determines the sintering behavior as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436879
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  • 12
    Electronic Resource
    Electronic Resource
    Study of the Complex Between the Contrast Agent lobitridol (Xenetix®) and Elastase (PPE): A Model for Hydrophobic Site Protection in Drug-Protein Interactions (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 1713-1717 
    Details
    ISSN: 1573-904X
    Keywords: iobitridol ; proteinase ; hydrophobic shielding ; contrast agent ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The concept of Hydrophilic Sphere Stabilization, or Hydrophobic Shielding, has been postulated in the synthesis of biocompatible contrast agents in vascular imaging. To improve the safety of these polyiodinated agents, interactions with protein hydrophobic sites in biomacromolecules should be kept as low as possible. In order to evaluate the level of interactions with proteins, we have selected the serine proteinase Elastase, in presence of Iobitridol (Xenetix®), as a model. Methods. The complex between Iobitridol and Pancreatic Porcine Elastase was investigated by X-ray diffraction techniques, on saturated monocrystals, using the synchrotron radiation at 0.98Å. Results. In contrast to Iohexol, which displays several interactions including one in the active site, Iobitridol is unable to interact directly with elastase. Only one partially occupied site is found in between two molecules of the crystal packing. Conclusions. The validation of the 'hydrophobic shielding' concept, which was at the origin of the design of the Iobitridol molecule, has been proven to be an essential feature in minimizing in vivo protein interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012123628123
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  • 13
    Electronic Resource
    Electronic Resource
    Tensile properties and structure of polypropylene fibres spun from a blend of different polymer grades (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 617-626 
    Details
    ISSN: 1435-1536
    Keywords: Key words High-modulus polypropylene fibre ; polymer blend ; manufacturing process ; X-ray diffraction ; tensile properties ; fibre structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The tensile behavior of fibres, spun from a blend of small percentage of plastic grade poly-propylene with fibre grade poly-propylene, was studied in relation to their structure. The spinning and drawing process was optimized in order to increase the elastic moduli of produced filament yarns. By such optimization of the process a tenacity of 0.7 GPa, an elastic modulus of 14.8 GPa and a dynamic modulus of 19 GPa were attained. From diffuse small-angle X-ray scattering the presence of voids, up to 11.5%, was established. Voidness of the fibrillar structure was confirmed with electron micrographs. In spite of the rather drastic changes in morphology the mechanical properties of high void fibrillar structures are good, indicating that the load bearing units of the filament have maintained their integrity. The improved mechanical behavior of highly drawn fibres spun from 10/90 plastic/fibre grade polymer blend is related to higher crystalline and above all to higher amorphous orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050127
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  • 14
    Electronic Resource
    Electronic Resource
    On the plastic deformation of bulk syndiotactic polypropylene (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 1088-1092 
    Details
    ISSN: 1435-1536
    Keywords: Key words Semi-crystalline polymers ; X-ray diffraction ; necking ; phase transformation ; molecular mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The plastic deformation of syndiotactic polypropylene (sPP) bulk samples has been investigated. A structural comparison of the initial states before and after plastic deformation by necking is carried out by X-ray diffraction observations. Independent of the initial states (amorphous, semi-crystalline with different crystal phases), only the planar all-trans crystal form of sPP is present in the deformed samples after necking. Form these results, molecular mechanisms of the plastic deformation in the neck zone of semi-crystalline polymers will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050188
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  • 15
    Electronic Resource
    Electronic Resource
    Spontaneous formation of zwitterionic vesicles: chemical structure-vesicle formation relationships (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 224-227 
    Details
    ISSN: 1435-1536
    Keywords: Zwitterionic surfactants ; vesicles ; lamellar phase ; X-ray diffraction ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract New double-chain zwitterionic surfactants were shown to undergo spontaneous dispersion as vesicles in water by means of simple dilution of the lamellar phase. The molecular parameters of relevance were investigated in a systematic study of the structure of the lamellar phase and of the ability of spontaneous formation of vesicles in a series of homologous zwitterionic surfactants. Thus, the double-chain zwitterionic surfactants which occupies a small interfacial area per molecule in spite of the large size of their hydrophilic headgroup can form spontaneous vesicles. In this case, the bending modulus ¯k of the surfactant film is strongly negative and the short-range repulsive interactions between hydrophilic groups protruding from the surfactant films into water allow a large swelling of the lamellar phase, and are the origin of the colloidal stability of the vesicles dispersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188955
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  • 16
    Electronic Resource
    Electronic Resource
    Hydrogen bonding incis-2,3-epoxycyclooctanol (1997)
    Springer
    Structural chemistry 8 (1997), S. 149-154 
    Details
    ISSN: 1572-9001
    Keywords: Epoxide group ; hydrogen bonding ; hydrogen bonding to epoxide groups ; cyclooctane conformation ; X-ray diffraction ; cis-2,3-epoxycyclooctanol ; crystal structure determination ; cis-2,3-epoxycy-clooctanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrogen bonding and the electron-withdrawing or electron-donating characteristics of substituent groups that are neighboring to epoxide groups can affect the reactivity of the epoxide ring. The crystal structure ofcis-2,3-epoxycyclooctanol has been determined as a saturated eight-membered ring compound in which a hydroxyl group is attached to the C(1) atom that is adjacent to a 2,3-fused epoxy ring. The findings are that the longer epoxide C-O bond (and hence the one expected to be more readily broken) is the one farther from the hydroxyl group [1.462(1) å versus 1.447(1) å] and that the optimal hydrogen bonding is to an adjacent molecule radier than within the molecule. The shortest C-C bond is that of the epoxide group; the bond adjacent to it (on the side farther from the hydroxyl group) is the next shortest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262850
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  • 17
    Electronic Resource
    Electronic Resource
    β-Amino acid residues: Conformational characterization of an N- and C-protected homo-β-(S)-leucine (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 129-134 
    Details
    ISSN: 1573-3904
    Keywords: homo-β-Amino acids ; β-Amino acid residue ; X-ray diffraction ; Crystal structure ; Solid-state conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An N- and C-protected derivative of homo-β-leucine, Fmoc-homo-β-(S)-leucine methyl ester, synthesized from the corresponding proteinogenic parent α-amino acid in enantiopure form has been fully characterized in the solid state by X-ray diffraction analysis. The crystal conformation of this new residue indicates an extended conformation for this homo-β-residue, with the ϕ torsion angle being more constrained than the µ and ψ angles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008895310236
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  • 18
    Electronic Resource
    Electronic Resource
    Crystallographic structure of a helical lipopeptaibol antibiotic analogue (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 213-218 
    Details
    ISSN: 1573-3904
    Keywords: α/310-Helix〉 ; Nitroxide amino acid ; Peptide conformation ; X-ray diffraction ; α-Tetrasubstituted amino acids ; Trichogin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An X-ray diffraction analysis of the [Fmoc0,TOAC4,8, Leu-OMe11] analogue of thelipopeptaibol antibiotic trichogin A IV shows that the undecapeptide isfolded in a right-handed, mixed α/310-helix. The helicalmolecules are connected in a head-to-tail arrangement along the b-axisthrough C=O···H-N intermolecular H-bonding. Thispacking mode generates a hydrophobic cavity where the FmocNα-protecting groups are accommodated. The distances andangles between the nitroxide groups of the two TOAC residues, separated byone turn of the α-helix, have been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008874816982
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  • 19
    Electronic Resource
    Electronic Resource
    Synthesis and structural analysis of vinylogous peptides (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 415-422 
    Details
    ISSN: 1573-3904
    Keywords: Pseudopeptide ; Turn mimic ; Vinylogous peptides ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A Z- or E-ethenyl group has been inserted between the α-carbon andthe carboxyl group of the proline residue by stereoselective Hornersynthesis. The resulting vinylogous amino acid has been coupled with aminocompounds by classical methods, and model amino acid derivatives anddipeptides containing a Z- or E-CH=CMe group have been investigated insolution by 1H-NMR and IR spectroscopy, and in the solid stateby X-ray diffraction. The E-ethenyl group gives rise to an openconformation and the Z-conformer to a folded structure with anintramolecular hydrogen bond closing a nine-membered pseudocycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008846232043
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  • 20
    Electronic Resource
    Electronic Resource
    β-amino acid residues: Conformational characterization of an N- and C-protectedhomo-β-(S)-leucine (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 129-134 
    Details
    ISSN: 1573-3904
    Keywords: homo-β-Amino acids ; β-Amino acid residue ; X-ray diffraction ; Crystal structure ; Solid-state conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An N- and C-protected derivative ofhomo-β-leucine, Fmoc-homo-β-(S)-leucine methyl ester, synthesized from the corresponding proteinogenic parent α-amino acid in enantiopure form has been fully characterized in the solid state by X-ray diffraction analysis. The crystal conformation of this new residue indicates and extended conformation for thishomo-β-residue, with the ϕ torsion angle being more constrained than the μ and ψ angles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443524
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  • 21
    Electronic Resource
    Electronic Resource
    Crystallographic structure of a helical lipopeptaibol antibiotic analogue (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 213-218 
    Details
    ISSN: 1573-3904
    Keywords: α/310-Helix ; Nitroxide amino acid ; Peptide conformation ; X-ray diffraction ; α-Tetrasubstituted amino acids ; Trichogin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An X-ray diffraction analysis of the [Fmoc0, TOAC4,8, Leu-OMe11]analogue of the lipopeptaibol antibiotic trichogin A Iv shows that the undecapeptide is folded in a right-handed, mixed α/310-helix. The helical molecules are connected in a head-to-tail arrangement along the b-axis through C=O...H-N intermolecular H-bonding. This packing mode generates a hydrophobic cavity where the Fmoc Nα-protecting groups are accommodated. The distances and angles between the nitroxide groups of the two TOAC residues, separated by one turn of the α-helix, have been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02442878
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  • 22
    Electronic Resource
    Electronic Resource
    Synthesis and structural analysis of vinylogous peptides (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 415-422 
    Details
    ISSN: 1573-3904
    Keywords: Pseudopeptide ; Turn mimic ; Vinylogous peptides ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A Z-orE-ethenyl group has been inserted between the α-carbon and the carboxyl group of the proline residue by stereoselective Horner synthesis. The resulting vinylogous amino acid has been coupled with amino compounds by classical methods, and model amino acid derivatives and dipeptides containing a Z-orE-CH=CMe group have been investigated in solution by1H-NMR and IR spectroscopy, and in the solid state by X-ray diffraction. TheE-ethenyl group gives rise to an open conformation and the Z-conformer to a folded structure with an intramolecular hydrogen bond closing a ninemembered pseudocycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02442910
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