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  • 1
    Electronic Resource
    Electronic Resource
    Biuret and its sulfur analogs: Structures and energies (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 301-313 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The calculations for biuret (B) and its two sulfur analogs, thiobiuret (TB) and dithiobiuret (DTB), were carried out using the ab initio LCAO-MO method at the Hartree-Fock level. The molecular structure of B was fully optimized using standard 3-21G and 6-31G* basis sets, while geometry optimizations of the TB's and DTB's were performed at the 3-21G* and 6-31G* levels. Only trans-isomers were found to be minimum structures on the HF/3-21G* potential-energy surfaces, whereas cis-forms are the first-order transition structures. The relative energies of the cis-conformers at MP 2/6-31G**//HF/6-31G* + 0.9 zero point energy (ZPE) level are equal to 47.4, 51.7, and 59.7 kJ mol-1 for TB, B, and DTB, respectively. Because of relatively large dipole moments, cis-conformers are predicted to be stabilized in polar solvents.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440216
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  • 2
    Electronic Resource
    Electronic Resource
    13C NMR studies of conformational isomerism in thioureas: Signal assignments via chemical shift and population trends (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 293-300 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 22.63 MHz 13C NMR spectra of a series of alkylated thioureas are reported. Characteristic Z and E spectral regions were found for the 13C = S resonances. The two regions were generally found to be non-overlapping for the series, with the region of the Z, Z resonances occurring more downfield than those of either the Z, E or E, Z conformers in the cases of 1,3-disubstitution. The Z, Z configuration became favored and the relative chemical shift difference (Rδ) increased linearly with increasing substituent size. At 217 K, hindered internal rotation caused a multiplicity of resonances which were normally single peaks in the broad band 1H decoupled 62.86 MHz 13C spectrum of CH3NHCSNH(CH2)2NHCSNHCH3 (2MTE) at room temperature. The trends in chemical shifts and populations were employed to assign tentatively the resonances of five of the six possible configurational isomers contributing to the 2MTE spectra at 217 K. The isomer populations are given. The 13C NMR spectra reported here led to signal assignments of Z and E isomers which supported prior 1H NMR results and contradicted more recent results of another 13C NMR study of N-methylthiourea. The major peak of the exchange doublet occurs at relatively high field strengths in both methanol-d5.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210502
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  • 3
    Electronic Resource
    Electronic Resource
    Hindered rotation in thioureas: Steric effects and conformationsThis research has been submitted by one of the authors (R. H. S.) as partial fulfillment of the requirements for the PhD degree in chemistry at Howard University, August 1972.Presented in part at the American Chemical Society South-eastern Regional Meeting, Charleston, South Carolina November 1973. (1975)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 143-150 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature dependent spectra of several mono-, di- and trialkylthioureas have been recorded. Free energy barriers to internal rotation about the C—N bonds have been calculated. In thioureas that were unsymmetrically substituted, free energy barriers were found to be different for each C—N bond with the more substituted amino group exhibiting the higher barrier. The monosubstituted thioureas showed different rotational barriers for the NH2 groups of the cis and trans isomers, respectively. The free energy barriers for the trans isomers were found to be substituent dependent and substantiate the reassignment of the high and low field substituent signals to the trans and cis isomers, respectively. The spectrum of 1-methyl-3-t-butylthiourea indicates restricted rotation of the t-butyl group at temperatures below 200 K.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270070307
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSFrh) on transmembrane electrical potentials in granulocytes: Relationship between enhancement of ligand-mediated depolarization and augmentation of superoxide anion (O-2) production (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 139 (1989), S. 361-369 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When human granulocytes that have been primed with recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSFrh) are activated by ligands that stimulate the respiratory burst, the amount of superoxide anion (O-2) they generate is significantly increased. We have found that the accelerated rate of O-2 release occurring under these conditions is accompanied by an antecedent increase in membrane depolarization. We examined the nature of the enhancement of membrane depolarization in GM-CSFrh-primed granulocytes and investigated its relationship to the increase in O-2 generation by N-formyl methionylleucylphenylalanine (fMLP)-activated granulocytes. We found that augmented depolarization could not be accounted for by a change in the resting membrane potential induced by the growth factor and was still present after either blocking passive transmembrane Na+ movement with dimethylamiloride or by increasing the membrane's permeability to K+ with valinornycin. When their ability to depolarize was virtually eliminated by dissipating the transmembrane K+ gradient, GM-CSFrh-pretreated cells continued to generate more O-2 after fMLP than did control cells. These results indicate that augmentation of the granulocyte's ability to generate O-2 anions, which is induced by priming with GM-CSFrh, is independent both of the resting transmembrane potential and of alterations in the extent of membrane potential change induced by stimuli such as fMLP.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041390219
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