Hydrogen Bonding to Active-Site Histidine in Peptidyl Boronic Acid Inhibitor Complexes of Chymotrypsin and Subtilisin:  Proton Magnetic Resonance Assignments and H/D Fractionation

1999 ◽  
Vol 121 (19) ◽  
pp. 4684-4689 ◽  
Author(s):  
Donghui Bao ◽  
W. Phillip Huskey ◽  
Charles A. Kettner ◽  
Frank Jordan
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Active Site ◽  
Boronic Acid ◽  
Proton Magnetic Resonance ◽  
Resonance Assignments ◽  
Acid Inhibitor ◽  
Active Site Histidine

Solvent effects in ultraviolet spectral studies of hydrogen bonding between phenol and N,N-dimethylacetamide

1967 ◽  
Vol 45 (18) ◽  
pp. 2033-2038 ◽  
Author(s):  
F. Takahashi ◽  
W. J. Karoly ◽  
J. B. Greenshields ◽  
N. C. Li
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Complex Formation ◽  
Equilibrium Constant ◽  
Proton Magnetic Resonance ◽  
Mixed Solvent ◽  
Resonance Method ◽  
Spectral Studies ◽  
Magnetic Resonance Method ◽  
Hydrogen Bonded

Ultraviolet spectral studies of hydrogen bonding between phenol and N,N-dimethylacetamide (DMA) in several media are reported. The equilibrium constant for the formation of the phenol–DMA complex is strongly solvent dependent, varying from 295 1/mole in cyclohexane to 130 in CCl4 and 16 in CHCl3, all at 28°. The greatly reduced value in CHCl3 indicates that the measured equilibrium constant is only an apparent one which does not take into account the decrease in free DMA concentration resulting from hydrogen-bonded complex formation with the solvent acting as hydrogen donor. In CCl4/CHCl3 mixed solvent, in the range of [chloroform] = 0 to 1.227 M, the measured equilibrium constant, K′, varies linearly with K′ [chloroform]. The slope of the line corresponds to the equilibrium constant for the formation of the hydrogen-bonded complex between CHCl3 and DMA in CCl4. The value, 0.9 1/mole, agrees with that obtained from a proton magnetic resonance method. The agreement is particularly noteworthy when we consider that the concentrations of phenol used in the proton magnetic resonance and ultraviolet spectral methods differ by a factor of 200, which leads definitely to the conclusion that the hydrogen-bonded CHCl3–DMA complex formed is 1:1. In cyclohexane/CHCl3 mixed solvent, similar results are obtained.

Selective deshielding of aromatic protons in some ortho-substituted acetanilides

1968 ◽  
Vol 46 (15) ◽  
pp. 2593-2600 ◽  
Author(s):  
James R. Bartels-Keith ◽  
Ronald F. W. Cieciuch
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Solvent Effects ◽  
Proton Magnetic Resonance ◽  
Aromatic Proton ◽  
Intramolecular Hydrogen Bonding ◽  
Low Field ◽  
Intramolecular Hydrogen

Certain ortho-substituted acetanilides exhibit proton magnetic resonance signals at unusually low field for the amido proton and the aromatic proton adjacent to the acetamido group. This effect, explicable in terms of intramolecular hydrogen-bonding, has been observed for nitro, carbonyl, sulfamoyl, and sulfonyl substituents. Solvent effects are discussed.

Aromatic amides. VII. Steric hindrance to hydrogen bonding in ortho-substituted acetanilides

1972 ◽  
Vol 25 (3) ◽  
pp. 639 ◽  
Author(s):  
BD Andrews ◽  
AJ Poynton ◽  
ID Rae
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Steric Hindrance ◽  
Proton Magnetic Resonance ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen ◽  
Magnetic Resonance Spectra

A series of 2-substituted 3,5-dimethylanilines and their N-acetyl derivatives have been synthesized, and their proton magnetic resonance spectra recorded. Intramolecular hydrogen bonding between the amide N-H and the 2-substituent is disturbed by steric hindrance of the 2-substituent only in the case of the 2-nitro, 2-acetyl, and 2-methoxycarbonyl substituents.

THE INTERACTION OF SILICON TETRAFLUORIDE WITH METHANOL

1963 ◽  
Vol 41 (6) ◽  
pp. 1477-1484 ◽  
Author(s):  
J. P. Guertin ◽  
M. Onyszchuk
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Absorption Band ◽  
Hydrogen Bonds ◽  
Infrared Spectrum ◽  
Proton Magnetic Resonance ◽  
Methanol Solution ◽  
Silicon Tetrafluoride ◽  
Conductivity Measurements ◽  
Bond Stretching

Silicon tetrafluoride reacts with methanol in a 1:4 mole ratio, forming the complex SiF4.4CH3OH, which freezes to a glass at about −20° and is completely dissociated in the gaseous phase at 25°. Conductivity measurements show clearly that it is a very weak electrolyte in methanol solution. Its infrared spectrum does not contain an Si—O bond stretching absorption band. Proton magnetic resonance measurements provide strong evidence of hydrogen bonding between silicon tetrafluoride and methanol. These results indicate that the structure of the complex requires tetracovalent rather than hexacovalent silicon and strong hydrogen bonds between methanol and each of the four fluorine atoms.

Hydrogen Bonding Study of Quinoline and Coal-Derived Asphaltene Components with o-Phenylphenol by Proton Magnetic Resonance

1976 ◽  
Vol 9 (11) ◽  
pp. 733-741 ◽  
Author(s):  
Scott R. Taylor ◽  
Laurine G. Galya ◽  
Barbara J. Brown ◽  
Norman C. Li
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance
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