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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced double-quantum nuclear magnetic resonance in spinning solids at rotational resonance (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5668-5677 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The excitation efficiency of double-quantum (2Q) coherences between pairs of spin-1/2 nuclei in rotating powdered solids is greatly enhanced at rotational resonance, where an integer multiple of the spinning speed matches the difference in isotropic chemical shifts. In powdered samples it is possible to transfer up to 50% of the single-quantum magnetization through the 2Q transitions, an order of magnitude more than is achievable in magic-angle-spinning experiments performed off rotational resonance. The effect is simulated numerically by integration of the homogeneous evolution propagator and described analytically using first-order average Hamiltonian theory. Rotational resonance enhanced 2Q filtering is demonstrated experimentally for doubly 13C-labeled samples of zinc acetate and diammonium oxalate monohydrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462666
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  • 2
    Electronic Resource
    Electronic Resource
    ARTIFICIAL INSEMINATION IN DENMARK BY FROZEN DONOR SEMEN SUPPLIED FROM A CENTRAL BANK (1979)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 86 (1979), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A central semen bank in Denmark supplied deep-frozen semen. Selection of donors, freezing technique, and practical details about transport of specimens are described. In one of the gynaecological departments supplied with frozen semen, 22 out of 30 patients who had artificial insemination became pregnant. The advantages and disadvantages of using frozen semen are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1979.tb10615.x
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  • 3
    Electronic Resource
    Electronic Resource
    Double-quantum homonuclear rotary resonance: Efficient dipolar recovery in magic-angle spinning nuclear magnetic resonance (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1805-1812 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe an efficient method for the recovery of homonuclear dipole–dipole interactions in magic-angle spinning NMR. Double-quantum homonuclear rotary resonance (2Q-HORROR) is established by fulfilling the condition ωr=2ω1, where ωr is the sample rotation frequency and ω1 is the nutation frequency around an applied resonant radio frequency (rf) field. This resonance can be used for double-quantum filtering and measurement of homonuclear dipolar interactions in the presence of magic-angle spinning. The spin dynamics depend only weakly on crystallite orientation allowing good performance for powder samples. Chemical shift effects are suppressed to zeroth order. The method is demonstrated for singly and doubly 13C labeled L-alanine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467759
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  • 4
    Electronic Resource
    Electronic Resource
    A systematic strategy for design of optimum coherent experiments applied to efficient interconversion of double- and single-quantum coherences in nuclear magnetic resonance (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3962-3968 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A systematic strategy for design of optimum experiments in multidimensional coherent spectroscopy is described and applied to nuclear magnetic resonance (NMR). First an appropriate bound on the quantum dynamics is employed to determine a theoretical upper limit on coherence transfer efficiency which translates into the sensitivity of the experiment. Next it is investigated whether the theoretical limit can be achieved by a series of selective rotations. Then the final step serves to convert the selective rotations found into a nonselective pulse experiment which has a more general applicability. The example chosen for illustration is double- to single-quantum coherence transfer in INADEQUATE which is one of the most popular NMR experiments. Using the design strategy presented we show how the sensitivity of INADEQUATE can be doubled. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472269
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  • 5
    Electronic Resource
    Electronic Resource
    Relative orientation of chemical shielding and dipolar coupling tensors: Mixed single- and double-quantum homonuclear rotary resonance nuclear magnetic resonance of rotating solids (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7587-7599 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A novel two-dimensional magic-angle spinning nuclear magnetic resonance (NMR) method for determination of relative orientation of dipolar and chemical shielding tensors for dipolar-coupled homonuclear spin-1/2-pairs of powder samples is described. Simultaneous recoupling of anisotropic chemical shielding and dipolar coupling interactions is accomplished using a homonuclear rotary resonance pulse sequence with the amplitude ωrf of a rf irradiation field matched to the spinning frequency ωr according to ωrf=ωr. Employing this technique in the first dimension of a two-dimensional experiment leads to powder spectra exhibiting strong dependence on the magnitudes and the relative orientation of the two shielding tensors and the dipolar coupling tensor correlated to a high-resolution spectrum in the sampling dimension. Various aspects of the recoupling experiment are described theoretically and the applicability of the method for determination of relative orientation of these three anisotropic tensors through numerical simulation is demonstrated on basis of experiments for a doubly 13C-labeled powder of L-alanine. With reference to this sample (and aminoacids in general), minor effects from simultaneous recoupling of the heteronuclear dipolar coupling between Cα and the amide 14N nucleus are evaluated. In the present case, the 13C–14N dipolar interaction is used in numerical simulations to refine our structural analysis and to obtain information about the absolute orientation of the 13C chemical shielding tensors relative to the molecular coordinate system. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473761
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  • 6
    Electronic Resource
    Electronic Resource
    Two-dimensional pulse techniques for determination of radio-frequency field strengths and proton multiplicities in NMR spectroscopy (1987)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 109 (1987), S. 901-902 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00237a046
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  • 7
    Electronic Resource
    Electronic Resource
    Systematic design and evaluation of multiple-pulse experiments in nuclear magnetic resonance spectroscopy using a semi-continuous Baker–Campbell–Hausdorff expansion (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 3780-3791 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show that an explicit solution to a semi-continuous analog to the Baker–Campbell–Hausdorff (BCH) problem can be derived by an appropriate combination of the Magnus and BCH expansions. The resulting semi-continuous BCH (scBCH) expansion forms a valuable tool for solving the time-dependent Schrödinger equation for Hamiltonians with complicated, piecewise continuous time dependence. Such Hamiltonians are typical in multiple-pulse coherent spectroscopy. Using the scBCH expansion we derive a number of general formulas, including relations for permuted pulse sequences. These formulas simplify calculation of the effective Hamiltonian for advanced multiple-pulse experiments and allow for evaluation of this to considerably higher order than is possible using the Magnus expansion. This is important for the detailed analysis and systematic design of multiple-pulse experiments which emphasize some interactions while effectively suppressing others. The scBCH expansion is applied to problems of homonuclear dipolar decoupling in solid-state NMR and broadband heteronuclear decoupling in liquid-state NMR. Improved high-order pulse sequences for on- and off-resonance decoupling are introduced and existing recursive expansion strategies are evaluated within the presented theoretical framework. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476978
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  • 8
    Electronic Resource
    Electronic Resource
    Elimination of high order terms in multiple pulse nuclear magnetic resonance spectroscopy: Application to homonuclear decoupling in solids (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7571-7586 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A novel approach to the design of solid state nuclear magnetic resonance multiple pulse experiments is described. Based on time dependent perturbation theory the pulse cycle decoupling principle is extended to fifth order. Furthermore, by analyzing symmetry and commutator relations for high order terms in the average Hamiltonian expansion we introduce so-called z-rotational decoupling accomplished by concatenation of phase shifted pulse cycles. These fundamental tools prove extremely useful for the development of multiple pulse techniques capable of eliminating undesired interactions to high order in the average Hamiltonian expansion. The applicability of the methods is demonstrated by construction of homonuclear multiple-pulse decoupling methods which suppress pure dipolar terms up to fifth order and cross terms between rf inhomogeneity and dipolar coupling to second order in the Magnus expansion. For the dipolar terms this represents an improvement by two orders of magnitude compared to previous homonuclear decoupling sequences. High order truncation decoupling sequences based on the BLEW-12 and magic sandwich pulse cycles are compared to state-of-the-art methods numerically and by preliminary experiments. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473760
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  • 9
    Electronic Resource
    Electronic Resource
    A flat-coil NMR probe with hydration control of oriented phospholipid bilayer samples (1995)
    Springer
    Journal of biomolecular NMR 5 (1995), S. 311-314 
    Details
    ISSN: 1573-5001
    Keywords: Flat-coil probe ; Solid-state NMR ; Oriented lipid bilayer ; Hydration control ; 31P chemical shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A novel flat-coil solid-state NMR probe capable of controlling the hydration of oriented phospholipid bilayers in the course of long-term experiments, is described. Perfect hydration control for at least five days of intense radio-frequency pulsing is demonstrated using 31P NMR of oriented dimyristoylphospha-tidylcholine bilayers. The probe design will be of particular importance for studies of peptides and proteins oriented in lipid bilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211758
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and assembly of soybean β-conglycinin in vitro (1992)
    Springer
    Plant molecular biology 18 (1992), S. 259-274 
    Details
    ISSN: 1573-5028
    Keywords: β-conglycinin ; soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The construction of SP6-derived expression plasmids that encode normal and modified β-conglycinin subunits is described. With the exception of an additional methionine at their NH2-terminal ends and the lack of glycans, the normal subunits synthesized at the direction of these plasmids coresponded to mature α and β subunits isolated from soybean seeds. The subunits assembled into trimers in vitro that were equivalent in size to those formed in vivo. This result shows that the glycans are not required either for protein folding or oligomer assembly. Subunits produced from other plasmids, which had modifications in a highly conserved hydrophobic region in the COOH-terminal end of the subunits, either did not assemble or assembled at an extremely low rate compared to unmodified subunits. Structural changes at the more hydrophilic NH2-terminal end had mixed effects. Several subunits modified in this region assembled into trimers at rates that were either equal or greater than those for normal α subunits. Others assembled less completely than the normal subunits. Our results indicate that the in vitro synthesis and assembly assay will be useful in evaluating structure-function relationships in modified β-conglycinin subunits. The results also show that structural changes at the NH2-terminal end of the subunits are tolerated to a greater extent than modifications in the hydrophobic conserved region in the COOH-terminal half of the subunits, and this information will be useful in efforts to improve soybean quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034954
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