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  • 1
    Electronic Resource
    Electronic Resource
    Activation Energy for Permeation of Phosphonium Cations through Phospholipid Bilayer Membrane (1994)
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 4312-4318 
    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/bi00180a027
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  • 2
    Electronic Resource
    Electronic Resource
    Structural analysis of uniaxially aligned polymers using solid-state nitrogen-15 NMR (1993)
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 6660-6663 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00076a056
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  • 3
    Electronic Resource
    Electronic Resource
    NMR imaging of diffusion of small organic molecules in silk fibroin gel (1991)
    s.l. : American Chemical Society
    Macromolecules 24 (1991), S. 620-622 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00002a045
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  • 4
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectral assignment of five polyolefins determined from the chemical shift calculation and the polymerization mechanism (1991)
    s.l. : American Chemical Society
    Macromolecules 24 (1991), S. 2334-2340 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00009a033
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spectral assignments of regioirregular polypropylene determined from two-dimensional INADEQUATE spectra and chemical shift calculations (1992)
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 4876-4881 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00045a008
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  • 6
    Electronic Resource
    Electronic Resource
    The relationship between amide proton chemical shifts and secondary structure in proteins (1995)
    Springer
    Journal of biomolecular NMR 6 (1995), S. 227-236 
    Details
    ISSN: 1573-5001
    Keywords: Chemical shift ; Amide proton ; Magnetic anisotropy ; Secondary structure ; Ribonuclease H ; Leucine zipper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The parameters for HN chemical shift calculations of proteins have been determined using data from high-resolution crystal structures of 15 proteins. Employing these chemical shift calculations for HN protons, the observed secondary structure chemical shift trends of HN protons, i.e., upfield shifts on helix formation and downfield shifts on β-sheet formation, are discussed. Our calculations suggest that the main reason for the difference in NH chemical shifts in helices and sheets is not an effect from the directly hydrogen-bonded carbonyl, which gives rise to downfield shifts in both cases, but arises from an additional upfield shift predicted in helices and originating in residues i-2 and i-3. The calculations also explain the well-known relationship between amide proton shifts and hydrogen-bond lengths. In addition, the HN chemical shifts of the distorted amphipathic helices of the GCN4 leucine zipper are calculated and used to characterise the solution structure of the helices. By comparing the calculated and experimental shifts, it is shown that in general the agreement is good between residues 15 and 28. The most interesting observation is that in the N-terminal half of the zipper, although both calculated and experimental shifts show clear periodicity, they are no longer in phase. This suggests that for the N-terminal half, in the true average solution structure the period of the helix coil is longer by roughly one residue compared to the NMR structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197804
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  • 7
    Electronic Resource
    Electronic Resource
    A method for the calculation of protein α-CH chemical shifts (1992)
    Springer
    Journal of biomolecular NMR 2 (1992), S. 83-98 
    Details
    ISSN: 1573-5001
    Keywords: Protein ; NMR ; Chemical shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The chemical shifts of CαH protons have been calculated for 9 proteins, based on coordinates taken from high-resolution crystal structures. Chemical shifts were calculated using ring-current shifts, shifts arising from magnetic anisotropies of bonds, and shifts arising from the polarizing effect of polar atoms on the Cα-H bond. The parameters used were refined iteratively to give the best fit to (experimental — random coil) shifts over the set of 9 proteins. A further small correction was made to the averaged Gly CαH shift. The calculated shifts match observed shifts with correlation coefficients varying between 0.45 and 0.86, with a standard deviation of about 0.3 ppm. The differences between calculated and observed shifts have been studied in detail, including an analysis of different crystal structures of the same protein, and indicate that most of the differences can be accounted for by small differences between the structure in solution and in the crystal. Calculations using NMR-derived structures give a poor fit. The calculations reproduce the experimentally observed differences between chemical shifts for CαH in α-helix and β-sheet. Most of the differentiation in secondary structure-dependent shifts arises from electric field effects, although magnetic anisotropy also makes a large contribution to the net shift. Applications of the calculations to assignment (including stereospecific assignment) and structure determination are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02192802
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  • 8
    Electronic Resource
    Electronic Resource
    A method for studying the structure of uniaxially aligned biopolymers using solid state 15N-nmr: Application to Bombyx mori silk fibroin fibers (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 847-861 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent advances in the application of solid state nmr spectroscopy to uniformly aligned biopolymers have opened a window through which to view the detailed structure of biological macromolecules that are unable to be seen with standard techniques for structure determination such as x-ray diffraction. Atomic resolution structural details are obtained from solid state nmr data in the form of bond orientations, which yield the relative positions of specific atoms within the molecule. For static aligned systems such as fibers, in which rapid reorientation about the axis of alignment does not occur, it has generally been necessary to perform trial and error line-shape simulations to extract structural details from nmr spectra arising from a single type of nuclear spin interaction. In the present work, a new method is developed in which solid state 15N-nmr spectra obtained from uniaxially aligned molecules placed with the axis of alignment both parallel and perpendicular to the magnetic field are analyzed to yield the orientations of specific molecular bonds. Analytical expressions are derived that utilize spectral features read from 15N chemical shift anisotropy line shapes to calculate a discrete number of possible orientations for a specific site. The 15N-1H dipolar interaction is employed to further narrow the number of unique orientations possible for a given site. With this method, a neighborhood of possible orientations is quickly determined, and full line-shape simulations within this region of allowed space can be performed to refine the limits of orientation. This technique demonstrates the use of a single type of isotopic label to determine the orientation of a specific molecular group such as a peptide plane within a protein. Results from the application of this method to the Bombyx mori silk fibroin protein provide structural detail that is consistent with currently accepted structural models based on fiber diffraction studies. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330513
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  • 9
    Electronic Resource
    Electronic Resource
    13C NMR studies of the polymerization mechanism and the dynamics of poly(alkyl methacrylate) grafted onto silk fibers (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1321-1327 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR was extensively used to determine the tacticity of poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA) grafted onto silk fibers using radiation-induced graft copolymerization. All polymers are predominantly syndiotactic and the tacticity is virtually independent of the degree of grafting. The value of PΣ (= Pm/r + Pr/m) was calculated from the triad distribution and was found to be approximately one. This indicates that all the above polymer chains grafted onto silk fibers are syndiotactic and obey Bernoullian statistics. The number-average sequence length of either meso or racemic additions was determined using the triad distribution. The 13C NMR relaxation parameters, spin-lattice relaxation time, T1, and nuclear Overhauser effect, NOE, were observed and then the value of the correlation time for average segmental motion, τc, and the width parameter, p, were determined by assuming a log χ2 distribution for the correlation time. A relatively small value of p was obtained, indicating that the distribution of the correlation time is large. Taking into account the τc values of different poly(alkyl methacrylate) chains grafted onto silk fibers, the following order of segmental motion was furnished: PMMA 〉 PEMA 〉 PBMA.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910611
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  • 10
    Electronic Resource
    Electronic Resource
    Water sorption, membrane potentials, and ion permeability of styrene-grafted Bombyx mori silk fibroin membrane (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 535-543 
    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: Characterization of styrene-grafted Bombyx mori silk fibroin membrance was investigated. It was revealed from the water sorption and 1H nuclear magnetic resonance (NMR) measurements that the amounts of water adsorbed on the silk fibroin membranes decreased by the styrene grafting and the states of water adsorbed on the styrene-grafted silk fibroin membranes were not homogeneous; the presence of two components of water adsorbed on the membranes at 60% relative humidity was observed. In addition, the fraction of the fast component decreased with increasing styrene grafting. The membrane potentials increased with increasing of the grafting. The KCl permeability of the membrane strongly depends on the degree of styrene grafting.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360307
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