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  • 1
    Electronic Resource
    Electronic Resource
    Motions of an α-helical polypeptide: Comparison of molecular and harmonic dynamics (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 645-677 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular and harmonic dynamics simulations have been performed for a decaglycine α-helix. The extent of anharmonicity for various observables is studied by a direct comparison of the two types of simulations, at temperatures ranging from 5 to 300 K. The fluctuations of the cartesian, internal and normal mode coordinates, and their time dependence, are analyzed. The heat capacity of the α-helix is evaluated both from the temperature response of the system to an energy perturbation and from the fluctuations in the temperature of the system. It is shown that the anharmonicity depends on the kind of observable. The root mean square atomic fluctuations have significant anharmonic components at temperatures above 100 K. In contrast, the dihedral angle fluctuations are much closer to being harmonic at all the temperatures considered. The analysis of potentials of mean force experienced by individual atoms shows that atomic displacements have approximately Gaussian distributions from 50 to 300 K, with different force constants at each temperature (quasi-harmonic model). At 300 K, the force constants obtained by molecular dynamics are significantly lower than in the harmonic case. The time dependence of the projection of the molecular dynamics displacements on the normal mode coordinates shows that mode mixing is important above 100 K. The motions of the helix associated with the low-frequency normal modes are described and illustrated.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290402
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  • 2
    Electronic Resource
    Electronic Resource
    Helix-coil transitions in a simple polypeptide model (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2033-2045 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simplified model of a polypeptide chain is described. Each residue is represented by a single interaction center. The energy of the chain and the force acting on each residue are given as a function of the residue coordinates. Terms to approximate the effect of solvent and the stabilization energy of helix formation are included. The model is used to study equilibrium and dynamical aspects of the helix-coil transition. The equilibrium properties examined include helix-coil equilibrium constants and their dependence on chain position. Dynamical properties are examined by a stochastic simulation of the Brownian motion of the chain in its solvent surroundings. Correlations in the motions of the residues are found to have an important influence on the helix-coil transition rates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191108
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  • 3
    Electronic Resource
    Electronic Resource
    Quasi-harmonic method for studying very low frequency modes in proteins (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1099-1112 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quasi-harmonic approximation is described for studying very low frequency vibrations and flexible paths in proteins. The force constants of the empirical potential function are quadratic approximations to the potentials of mean force; they are evaluated from a molecular dynamics simulation of a protein based on a detailed anharmonic potential. The method is used to identify very low frequency (∼1 cm-1) normal modes for the protein pancreatic trypsin inhibitor. A simplified model for the protein is used, for which each residue is represented by a single interaction center. The quasi-harmonic force constants of the virtual internal coordinates are evaluated and the normal-mode frequencies and eigenvectors are obtained. Conformations corresponding to distortions along selected low-frequency modes are analyzed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230610
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative metabolic profiling of valproic acid in humans using automated gas chromatographic/mass spectrometric techniques (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 192-199 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An automated gas chromatographic/mass spectrometric assay is described for the antiepileptic drug valproic acid (VPA) and 14 of its metabolites in plasma or urine. Quantitative analysis of the parent drug and its biotransformation products was carried out with the aid of trimethylsilyl derivatives, and was performed by selected ion monitoring gas chromatography/mass spectrometry (normally of [M - CH3]+ species) using an HP 5790 mass selective detector (MSD) quadrupole mass spectrometer. The analysis was fully automated, in that simple injection, data acquisition, integration, quantification and report functions were carried out during unattended operation by an HP 59970C ChemStation™ computer system. The method exhibits good accuracy and high precision, with correlation coefficients greater than 0.990 for all standard curves. Replicate analyses of pooled plasma samples over a 4 month period exhibited an inter-day variation of less than 15% for the parent drug and ten of its metabolites. Moreover, the high dynamic range of the MSD instrument permitted quantification of VPA and minor metabolites thereof (e.g. the hepatotoxic terminal olefin, Δ4-VPA) at levels as disparate as 260 μg ml-1 (VPA) and 14 ng ml-1 (Δ4-VPA) in a single analysis. The high stability and sensitivity of the assay, combined with the fully automated features of the instrumentation, make the method ideally suited to expanded clinical studies and for the routine monitoring of potentially high-risk patients on VPA therapy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180308
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  • 5
    Electronic Resource
    Electronic Resource
    Glanzrhodinieren in dicken SchichtenVorgetragen am 6. 6. 1958 auf dem II. Kongreß der Europäischen Föderation För Korrosion in Frankfurt/M (1958)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 9 (1958), S. 686-689 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Glossy and Thick Rhodium CoatingsRhodium has been used for twenty years to prevent the tarnishing of silver goods and silver jewellery. Today, Rhodium finds its applications in engineering too. The 'decorative' coatings are glossy but only 1 micron thick. The 'technological' coatings of thicknesses varying between 2 and 25 microns, are always dull.However, for certain purposes it is desirable to obtain both thick and glossy Rhodium coatings. The author, therefore, examines the effects of various additives: cetain metal salts delay the disappearance of the gloss with a coating thickness of up to 2 microns, but the true gloss-producing agents appear to be active only on the surface. A number of such surfaceactive materials (anion-active, cathion-active and non-ionising) were investigated. Some of these produce glossy coatings with a thickness of far more than 10 microns. In addition, the porosity of the coat and its surface tesion is greatly reduced, the porosity of the coat and its surface tension is greatly reduced and thereby the corrosion resistance of the Rhodium is significantly improved. However, results of these experiments are not entirely consistent and work in this field continues.
    Notes: Rhodium wird seit über zwei Jahrzehnten angewandt, um das Anlaufen von Silberwaren und Silberschmuck zu verhüten. Heute hat Rhodium auch in der Technik Eingang gefunden. Die „dekorativen“ Schichten sind glänzend, jedoch nicht stärker als 1 Mikron; die „technischen“ Schichten, deren Dicke zwischen 2 und 25 Mikron schwankt, sind stets matt.Für gewisse Zwecke ist es jedoch erwünscht, dicke und glänzende Rhodiumüberzüge zu erhalten. Der Verfasser hat daher die Wirkung verschiedener Zusätze geprüft: Gewisse Metallsalze verzögern das Schwinden des Glanzes bei einer Schichtdicke bis zu zwei Mikron, jedoch scheinen die ausgesprochenen glanzgebenden Produkte oberflächenaktive Stoffe zu sein. Eine Reihe synthetischer oberflächenaktiver Produkte  -  anionaktive, kationaktive und nichtionogene  -  wurde untersucht. Einige davon ergeben glänzende Überzüge bei Schichtdicken, die weit über 10 Mikron liegen. Die Porosität der Schicht und ihre Oberflächenspannung werden außerdem stark herabgesetzt und dadurch wird die Korrosionsbeständigkeit des Rhodiums deutlich verbessert. Die erhaltenen Ergebnisse sind jedoch noch nicht durchweg konstant und die Arbeiten auf diesem Gebiet werden fortgesetzt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19580091103
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  • 6
    Electronic Resource
    Electronic Resource
    Spectroscopic evidence for mechanochemical effects of moisture in epoxy resinsThe authors are grateful to Dr. I. J. Goldfarb and Dr. C. E. Browning of the Air Force Materials Laboratory for their valuable suggestions. This research was performed under Air Force Materials Laboratory contract F33615-76-C-5071. (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 1643-1664 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Internal reflectance Fourier transform infrared (FT-IR) spectra of tetraglycidyl diaminodiphenylmethane (TGDDM) cured with diaminodiphenyl sulfone (DDS) obtained before and after exposure to the combined effect of stress, elevated temperature, and moisture (STM), elevated temperature and moisture (TM), or stress and elevated temperature (ST) environments were used to search for evidence of irreversible chemical changes in epoxy resins. These changes were compared with the infrared changes observed during the late stages of curing. The infrared intensities of the bands attributed to the sulfone group are sensitive to chemical changes and moisture content, which suggests their potential use as molecular monitors within the epoxy network. The results of eight experimental series provide spectroscopic evidence indicating that exposure of epoxy specimens to STM and TM environments that greatly exceed anticipated service conditions results in detectable rupture of chemical bonds in the polymer network. The extent of bond rupture is independent of the applied stress in the 0-90 kg/cm2 range. Internal swelling stresses are therefore believed responsible for the observed bond cleavages. Spectral evidence indicates that postcure reactions are the most prominent chemical changes induced by exposure of epoxy specimens to the ST, SM, M, and T environments.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070240707
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  • 7
    Electronic Resource
    Electronic Resource
    Amphiphilic networks. X. Diffusion of glucose and insulin (and nondiffusion of albumin) through amphiphilic membranes (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 35 (1997), S. 157-163 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Select semipermeable amphiphilic membranes have been prepared and their diffusional characteristics for glucose, insulin, and albumin investigated. The membranes were prepared by cast copolymerization of a hydrophilic monomer (i.e., N,N-dimethyl acrylamide, or N,N-dimethylaminoethyl methacrylate) with the hydrophobic crosslinker methacrylate-ditelechelic polyisobutylene. The products have sufficient mechanical properties for the fabrication of swollen membranes, sheets, tubes, etc. Membranes have been identified which allowed the rapid simultaneous countercurrent diffusion of glucose (Mn = 180 Da) and insulin (Mn = 5733 Da) but did not allow albumin (Mn ∼ 60,000 Da) to pass. Evidently, the effective molecular weight cutoff point of these membranes is in the 6-60-KDa range. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Monitoring the composite curing process with a fluorescence-based fiber-optic sensorPart of this research was conducted under the McDonnell Douglas Independent Research and Development program, and part by U.S. Air Force Contract F33615-85-C-5024. (1991)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 12 (1991), S. 96-101 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A novel cure sensor, based on the combination of fiber-optic fluorometry and the viscosity/degree-of-cure dependence of the epoxy resin fluorescence, was developed to provide a reliable low-cost cure-monitoring sensor for control of composite manufacturing. The capability of the first-generation sensor to monitor chemorheological changes that occur during the autoclave cure of carbon-epoxy laminates was successfully demonstrated. An improved second-generation sensor, which simultaneously monitors the changes in the epoxy fluorescence intensity and the wavelength of maximum emission, was also developed. The changes in the sensor intensity and wavelength signals, as a function of cure time, provide characteristic profiles that reveal the main chemorheological events of the cure cycle; these signals follow the changes in the degree-of-cure to completion. The configuration of the optrode-laminate interface strongly affects the signal profiles and their reproducibility. A “resin cavity” optrode-laminate interface, which improves reproducibility, was developed and tested.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750120205
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