Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Conformational energy studies on N-methylated analogs of thyrotropin releasing hormone, enkephalin, and luteinizing hormone-releasing hormone (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1943-1973 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Empirical conformational energy calculations have been carried out for N-methyl derivatives of alanine and phenylalanine dipeptide models and N-methyl-substituted active analogs of three biologically active peptides, namely thyrotropin-releasing hormone (TRH), enkephalin (ENK), and luteinizing hormone-releasing hormone (LHRH). The isoenergetic contour maps and the local dipeptide minima obtained, when the peptide bond (ω) preceding the N-methylated residue is in the trans configuration show that (1) N-methylation constricts the conformational freedom of both the ith and (i + 1)th residues; (2), the lowest energy position for both residues occurs around φ = -135° ± 5° and ψ = 75° ± 5°, and (3) the αL conformational state is the second lowest energy state for the (i + 1)th residue, whereas for the ith residue the C5 (extended) conformation is second lowest in energy. When the peptide bond (ωi) is in the cis configuration the ith residue is energetically forbidden in the range φ = 0° to 180° and ψ = -180° to +180°. Conformations of low energy for ωi = 0° are found to be similar to those obtained for the trans peptide bond. In all the model systems (irrespective of cis or trans), the αR conformational state is energetically very high. Significant deviations from planarity are found for the peptide bond when the amide hydrogen is replaced by a methyl group. Two low-energy conformers are found for [(N-Me)His2]TRH. These conformers differ only in the φ and ψ values at the (N-Me)His2 residue. Among the different low-energy conformers found for each of the ENK analogs [D-Ala2,(N-Me)Phe4, Met5]ENK amide and [D-Ala2,(N-Me)Met5]ENK amide, one low-energy conformer was found to be common for both analogs with respect to the side-chain orientations. The stability of the low-energy structures is discussed in the light of the activity of other analogs. Two low-energy conformers were found for [(N-Me)Leu7]LHRH. These conformations differ in the types of bend around the positions 6 and 7 of LHRH. One bend type is eliminated when the active analog [D-Ala6,(M-Me)Leu7]LHRH is considered.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Conformational transitions and geometry differences between low-energy conformers of N-acetyl-N′-methyl alanineamide: An ab initio study at the 4-21G level with gradient relaxed geometriesPaper 34 in the series “Ab Initio Studies of Structural Features Not Easily Amenable to Experiment.” (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2335-2347 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Energy pathways between the αR, β′, C7eq, and β-regions of the conformational energy surface of N-acetyl-N′-methylalanyl amide were obtained by SCF ab initio calculations on the 4-21G level, with gradient geometry optimization at each point. The calculations indicate that no barrier exists at this computational level between αR and β′. The variation of geometry (bond distances and bond angles) with conformation is analyzed in detail, and the most important geometrical parameters that should be treated as variables in both empirical energy calculations and in the fitting of polypeptide chains in proteins by x-ray methods are identified. In addition to the φ,ψ correlation discussed previously for the helical state, a correlation of these dihedral angles in the β-region is described.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360231115
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The nature of the branches in poly(vinyl chloride)Dedicated to Prof. Dr. H. Mark on his 80th birthday (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 1 (1975), S. 227-234 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: IR-spektroskopische Untersuchungen von Polyäthylen-Proben, dargestellt durch Reduktion von Polyvinylchlorid mit Lithiumaluminiumhydrid, ließen darauf schließen, daß Polyvinylchlorid Seitenketten enthält, die seine Morphologie und Festkörpereigenschaften wesentlich beeinflussen. Die Natur dieser Seitenketten war bisher unbekannt. Es wird anhand von 13C-NMR Spektren gezeigt, daß die Verzweigungen in reduziertem Polyvinylchlorid aus Methylgruppen bestehen, die vermutlich aus Chlormethylgruppen des ursprünglichen Polymeren entstanden sind. Die untersuchte Probe enthielt ca. 3 CH3-Gruppen pro 1000 CH2-Gruppen, jedoch is dieses Verhältnis vermutlich von der Polymerisationstemperatur abhängig. Zusätzlich wurden Anzeichen für längere Seitenketten gefunden, die allerdings nur in einem Ausmaß von weniger als 1 pro 1000 CH2-Gruppen vorhanden sein dürften.
    Notes: The presence of branches in poly(vinyl chloride) as indicated by previous IR measurements on the polymer reduced to polyethylene by means of lithium aluminum hydride is believed to affect materially the morphology and solid state properties of poly(vinyl chloride); however, up to the present, the nature of these branches has not been known. By use of 13C-NMR on reduced poly(vinyl chloride) it is demonstrated that the brances are methyl groups, presumably corresponding to chloromethyl groups in the original polymer. In the sample studied, the frequency is ca. 3 methyl groups per 1000 CH2 groups, but this is expected to depend on the temperature of polymerization. There is also some evidence for long branches, probably not exceeding 1 per 1000 CH2 groups.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.020011975115
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray diffraction studies of human salivary α-amylase (1991)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 11 (1991), S. 230-232 
    Details
    ISSN: 0887-3585
    Keywords: parotid saliva ; enzyme ; crystals ; X-ray analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Nonglycosylated α-amylase, a major component of human parotid saliva, has been crystallized by the vapor diffusion technique using 2-methyl-2,4-pentanediol as the precipitant in the presence of CaCl2 at pH 9.0. The crystals are orthorhombic, space group P212121 with unit cell dimensions of a = 53.3, b = 75.8, and c = 138.1 Å. The asymmetric unit contains one amylase molecule. The solvent content is 54%. The crystals are stable to X-rays and diffract up to 2.8 Å and appear to be suitable for X-ray diffraction studies.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340110308
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    High resolution NMR spectroscopy of synthetic polymers in bulk, by Richard A. Komoroski, Ed., VCH, Deerfield Beach, FL, 1986, 379 pp. Price: $49.50 (1987)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 25 (1987), S. 426-427 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1987.140251009
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Transport of toluene through fully swollen polyethylene (1969)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 15 (1969), S. 208-214 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments have been carried out to measure the permeation of tritium-labeled toluene through polyethylene films fully swollen with chlorobenzene, mesitylene, cumene, toluene, ethylbenzene, cyclohexane, tetrahydronaphthalene, and decahydronaphthalene. The results show characteristic Arrhenius temperature dependence over the range 25 to 40°C. The permeation of toluene through the films appears to be enhanced by increased solubility of the swelling agent (estimated from the work of others) in the film and there also appears to be a rough correlation between permeability of toluene and the boiling points and vapor pressures of the swelling agents. The range of permeabilities measured at 25°C. is 2.09 × 10-7 to 0.51 × 10-7 sq.cm./sec., the extremes of measured permeation activation energy, Ep, are 11.41 to 16.68 kcal./mole, and the pre-exponential factor, Po, falls within the interval 36.59 to 1.29 × 105 sq.cm./sec. A very definite linear relationship or compensation effect is evident between Po and Ep. Except as mentioned above, none of these quantities appears to correlate uniformly with the following properties of swelling solvent: molecular weight, dipole moment, specific gravity, vapor pressure, boiling point, heat of vaporization, critical temperature, viscosity, surface tension, molar volume, molecular area or other molecular dimensions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690150216
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Spectroscopic Study of the Hydration Equilibria and Water Exchange Dynamics of Lanthanide(III) Complexes of 1,7-Bis(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DO2A) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 1001-1006 
    Details
    ISSN: 1434-1948
    Keywords: Imaging agents ; Lanthanides ; NMR spectroscopy ; DNA cleavage ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydration state of a series of [Ln(DO2A)(H2O)n]+ complexes in aqueous solution at pH = 6.4-7.0 was studied by measuring the lanthanide-induced 17O shifts (LIS) of water [Ln includes elements from Ce to Yb; DO2A = 1,7-bis(carboxymethyl)-1,4,7,10-tetraazacyclododecane]. Their contact contribution, obtained from Reilley plots, indicated a decrease in the inner-sphere water coordination number of the [Ln(DO2A)(H2O)n]+ complexes from n = 3 (Ce-Eu), to n = 2 (Tb-Yb). A temperature-dependent UV/Vis absorption study of the 578-582 nm 7F0 → 5D0 transition band of [Eu(DO2A)(H2O)n]+ in aqueous solution showed that this complex is present in an equilibrium between eight- and nine-coordinate species with n = 2 and n = 3, respectively. The hydration equilibrium parameters (2 ↔ 3), K2-3298 = 4.0 ± 0.2, ΔH2-30 = -12.1 ± 1 kJ mol-1 and ΔS2-30 = -28.9 ± 3 J mol-1 K-1,correspond to an average hydration number of 2.65-2.85 in the temperature range 273-363 K. A variable temperature, multiple field 17O NMR study combined with direct EPR measurements of the transverse electronic relaxation rates has been used to obtain the parameters characterizing water exchange, rotation and electronic relaxation, all influencing the proton relaxivity of [Gd(DO2A)(H2O)2-3]+. The small increase in the water exchange rate of [Gd(DO2A)(H2O)2-3]+ (kex298 = (10 ± 5) × 106s-1) relative to that of[Gd(DOTA)(H2O)]- (4.8 × 106 s-1) is a consequence of an unfavorable interplay of charge and hydration equilibria. The value of τR298 = 40 ± 1 ps is short, and the electronic relaxation rate (1/T2e ≍ 1.2 × 1010 s-1) is fast relative to [Gd(DOTA)(H2O)]- (1.3-2.4 × 109 s-1 for B = 0.34 T). These parameters negate to some extent the expected increase in proton relaxivity of the [Gd(DO2A)(H2O)2-3]+ complex.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99338_s.pdf or from the author.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    Kinetic energy effects in an ion ensemble subjected to mass-selective isolation and resonance excitation: A simulation study (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 499-509 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simulation study is described of the behaviour of ions confined in a quadrupole ion trap during each of two separate operations of a tandem mass spectrometric experiment. The two operations are those of mass-selective ion isolation and mass-selective resonance excitation to the point of ion ejection from the ion trap. The method of mass-selective ion isolation simulated is that of consecutive ion isolation. Simulation data indicate that the collisional history of the ions prior to the isolation process can greatly influence the degree to which ions survive this process. Simulation data for mass-selective resonance ejection are compared with experimental data obtained with a Finnigan-MAT ion trap mass spectrometer. In each operation, the facility with which ions absorb energy from the field within the ion trap, whether this field is derived from the R.F. drive potential or a supplementary potential, can determine the extent to which ions are retained within the ion trap during the two mass-selective operations described.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280506
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Die Versorgung der deutschen Gasanstalten mit Steinkohlen (1915)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 28 (1915), S. 213-214 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19150283403
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Assignment of the histidine 12-threonine 45 hydrogen-bonded proton in the nmr spectrum of ribonuclease A in H2O (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 959-974 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Described herein are proton nmr experiments on chemically modified derivatives of ribonuclease A designed to elucidate the origin of an exchangeable resonance, assigned previously to a histidine ring N proton that titrates between 11 to 13 ppm with a pKa of 6.1 in H2O solution. Histidines 48 and 105, which are distant from the active site, are eliminated as candidates for this resonance from inhibitor binding studies on the enzyme in acetate-water solutions. This exchangeable resonance titrates with modified pKa's and constant area over the above pH range in His-119-N1-carboxymethylated-RNase A and des-(121-124)-RNase A, thus eliminating the imidazole N3 proton in the His 119-Asp 121 hydrogen bond. In His-12-N1-carboxymethylated-RNase A, this resonance is also observable, but broadens on raising the pH above 7 and at elevated temperatures above neutrality. It exhibits a pH-independent chemical shift characteristic of the protonated state of histidine. On the basis of these findings, this exchangeable resonance, designated a, is assigned to the imidazole N1 proton of His 12, which is hydrogen-bonded to the carbonyl oxygen of Thr 45 in the crystal.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140506
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...