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Amino acid, carbon atoms, chemical shifts

Chemical-shift Differences of the Amino Acid Carbon Atoms of a-Glycosylated and Nonglycosylated Di- and Tri-peptides... [Pg.33]

After the introduction of C-labels into the protein or glycoprotein molecule, the ability to assign the resonances to specific carbon atoms is essential. In the case of glycophorin (see Fig. 1), it may readily be seen that 5 lysine residues and 1 N-terminal amino acid (per species) can be reduc-tively di[ C]methylated. This could theoretically lead to 6 resonances (or possibly more, if chemical-shift nonequivalence is observed for the dimethyl species) in the C spectrum of methylated glycophorin A. However, in most cases, the N, N -di[ C]methyllysine resonances all occur near, or at, the same frequency. It is then necessary to be able at least to assign, or... [Pg.177]

Table XVIII contains the 13C-n.m.r.-spectral data for the model compounds a,/ -Araf — Hyp and a,/ -Ara/— Hyp. The assignments of Qfi and Cs of Hyp were readily obtained19 by comparison with 13C data for L-Hyp in the free amino acid form and for L-Hyp residues of peptides.109 The chemical shift of C 5 was, as expected, 7-8 p.p.m. downfield from the values reported for nonglycosylated L-Hyp. The chemical shifts of C and Cy appeared in the same region as carbohydrate resonances and were therefore identified through their chemical shift-pH dependence.19 The chemical shift of the / -anomeric carbon atom in compound 60 is rather up-field, in agreement with a syn orientation for the C-1 - O-1 and... Table XVIII contains the 13C-n.m.r.-spectral data for the model compounds a,/ -Araf — Hyp and a,/ -Ara/— Hyp. The assignments of Qfi and Cs of Hyp were readily obtained19 by comparison with 13C data for L-Hyp in the free amino acid form and for L-Hyp residues of peptides.109 The chemical shift of C 5 was, as expected, 7-8 p.p.m. downfield from the values reported for nonglycosylated L-Hyp. The chemical shifts of C and Cy appeared in the same region as carbohydrate resonances and were therefore identified through their chemical shift-pH dependence.19 The chemical shift of the / -anomeric carbon atom in compound 60 is rather up-field, in agreement with a syn orientation for the C-1 - O-1 and...
A semi-empirical molecular orbital method for the correlation of charge distributions with 13C shifts in amino acids was described [95]. Plotting of chemical shift parameters versus charge density changes of a-carbon atoms relative to the corresponding atoms in the parent hydrocarbons permits prediction of the chemical shifts of the a-carbons with an accuracy of about 10%. However, the slope (280 ppm per electron) in Fig. 5.12 is... [Pg.421]

In 1974, Deber and Blout [59,60] reported for the first time that they could discriminate between ions of D- and L-amino acids with the help of macrocyclic peptides. In 13C-NMR spectra cyclopeptides c(L-Pro-L-Gly)3 or c(L-Pro-L-Gly)4 showed different chemical shifts for the carbon atoms of D- and L-amino acids salts. [Pg.339]


See other pages where Amino acid, carbon atoms, chemical shifts is mentioned: [Pg.25]    [Pg.27]    [Pg.34]    [Pg.25]    [Pg.27]    [Pg.34]    [Pg.26]    [Pg.26]    [Pg.8]    [Pg.11]    [Pg.24]    [Pg.30]    [Pg.31]    [Pg.31]    [Pg.134]    [Pg.208]    [Pg.508]    [Pg.125]    [Pg.76]    [Pg.140]    [Pg.421]    [Pg.421]    [Pg.33]    [Pg.33]    [Pg.209]    [Pg.373]    [Pg.162]    [Pg.644]    [Pg.140]    [Pg.297]    [Pg.83]    [Pg.42]    [Pg.44]    [Pg.105]    [Pg.257]    [Pg.17]    [Pg.594]    [Pg.699]    [Pg.319]    [Pg.8]    [Pg.11]    [Pg.24]    [Pg.31]   


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Acidizing chemicals

Amino acid carbon atoms

Amino acids Chemical

Carbon atoms chemical shifts

Carbonate, chemical

Chemic acid

Chemical atom

Chemical shift atoms

Chemical shift, carbon

Shift atomic

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