Determination of the preferred tautomeric form of histamine by 13C nmr spectroscopy

1977 ◽  
Vol 55 (5) ◽  
pp. 576-578 ◽  
Author(s):  
William F. Reynolds ◽  
Chau W. Tzeng
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
13C Nmr ◽  
Tautomeric Form ◽  
Chemical Shifts ◽  
13C Nmr Spectroscopy ◽  
Imidazole Ring ◽  
Shift Method ◽  
Ph Dependent

The pH-dependent 13C chemical shifts for histamine indicate an approximate 4:1 preference for the Nτ-H tautomer of the imidazole ring, similar to that previously deduced for L-histidine. It is concluded that the 13C chemical shift method is a complimentary technique to the method of determining tautomer preference from pK values. Factors determining the tautomer preference in histamine and L-histidine are discussed.

scholarly journals DETERMINATION OF CHEMICAL STRUCTURE OF METHYL HYDROXYETHYLCELLULOSE BY 13C NMR SPECTROSCOPY

2019 ◽  
Vol 62 (8) ◽  
pp. 102-112
Author(s):  
Sergey G. Kostryukov ◽  
Sergey V. Araslankin ◽  
Pavel S. Petrov ◽  
Valentin A. Kalyazin ◽  
Angam Adil Ismail Al-Rubaye
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Program Analysis ◽  
Chemical Structure ◽  
Chemical Shifts ◽  
Structural Parameters ◽  
13C Nmr Spectroscopy ◽  
Degree Of Substitution ◽  
Integrated Intensities

This paper discusses the determination of the structural parameters of methyl hydroxyethylcellulose (MHEC) by 13C NMR spectroscopy. Four samples of methyl hydroxyethylcellulose (MHEC, DS ~ 1.7) of different viscosity aqueous solutions were analyzed to determine the distribution of methyl and hydroxyethyl groups in different positions of the anhydroglucose unit of the polymer chain. For this purpose, MHEC samples were subjected to acid-catalyzed hydrolysis in the presence of sulfuric acid. Optimal conditions for complete hydrolysis leading to methyl and hydroxyethyl substituted D-glucose derivatives were determined. The structure of the hydrolysis products was studied by 13С NMR spectroscopy. The assignment of carbon atom signals in the 13С NMR spectra was made based on chemical shifts calculated using BIOPSEL program. Analysis of the integrated intensities of the C-atom groups of the products of hydrolysis allowed us to determine the distribution of substituents in the anhydroglucose unit. The values of the degree of substitution in 2, 3 and 6 positions (DSC-2, DSC-3 и DSC-6) are calculated, the number of methoxyl (DSMe) and hydroxyethoxyl (DSHE) groups is determined, the total degree of substitution (DStotal) is calculated. The distribution of substituents in different positions of the glucopyranose unit indicates the highest reactivity of 2 and 6 positions, as well as hydroxyl in the hydroxyethyl group. In this paper, the degree of substitution in four different MHEC samples with known DS values is determined. Comparative analysis of the results obtained with the data specified by the manufacturer confirms the high accuracy of the considered method. The proposed method for determining the chemical structure of MHEC is informative since the method allows determining the distribution of substituents for different positions of the anhydroglucose unit and the degree of substitution of each substituent.

Natural abundance 13C-NMR spectroscopy for the quantitative determination of fecal fat

2003 ◽  
Vol 36 (7) ◽  
pp. 505-510 ◽  
Author(s):  
P Kunz ◽  
B Künnecke ◽  
I Kunz ◽  
H Lengsfeld ◽  
M von Kienlin
Keyword(s):  
Nmr Spectroscopy ◽  
Quantitative Determination ◽  
13C Nmr ◽  
13C Nmr Spectroscopy ◽  
Natural Abundance ◽  
Fecal Fat

Determination of the structural configuration of cresol–novolak resins by 13C NMR spectroscopy

1982 ◽  
Vol 27 (9) ◽  
pp. 3449-3454 ◽  
Author(s):  
J. A. Carothers ◽  
E. Gipstein ◽  
W. W. Fleming ◽  
T. Tompkins
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
13C Nmr Spectroscopy ◽  
Structural Configuration

Intracellular pH determination by 13C-NMR spectroscopy

1993 ◽  
Vol 264 (3) ◽  
pp. C755-C760 ◽  
Author(s):  
V. P. Chacko ◽  
R. G. Weiss
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Intracellular Ph ◽  
13C Nmr ◽  
Nonlinear Least Squares ◽  
13C Nmr Spectroscopy ◽  
31P Nmr Spectroscopy ◽  
Rat Hearts ◽  
13C Nuclear Magnetic Resonance ◽  
Wide Range

A noninvasive method for the determination of pH by the 13C-nuclear magnetic resonance (NMR) chemical shift of the C-3 carbon of sn-glycerol 3-phosphate is described. Nonlinear least-squares analysis of the chemical shift variation of the C-3 resonance of sn-glycerol 3-phosphate with pH at 37 degrees C in solutions and in perchloric acid extracts of tissue yielded a pKa of 6.2, making it a very sensitive indicator of pH in the approximate range of 5-7. Intracellular pH determined by the present 13C-NMR method correlated well with simultaneous measurements of pH by 31P-NMR spectroscopy over a wide range during normal perfusion and ischemic conditions in intact rat hearts. These findings indicate that this approach is particularly suited for quantification of intracellular pH over the physiological range in intact tissues and that observed in ischemic myocardium.

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