Relationship between proton-proton nmr coupling constants and substituent electronegativities. III. Conformational analysis of proline rings in solution using a generalized Karplus equation

Biopolymers ◽  
1981 ◽  
Vol 20 (6) ◽  
pp. 1211-1245 ◽  
Author(s):  
C. A. G. Haasnoot ◽  
F. A. A. M. De Leeuw ◽  
H. P. M. De Leeuw ◽  
C. Altona
Keyword(s):  
Conformational Analysis ◽  
Proton Nmr ◽  
Coupling Constants ◽  
Proton Proton ◽  
Karplus Equation

Conformational analysis of key disaccharide components of Brucella A and M antigens

1990 ◽  
Vol 68 (7) ◽  
pp. 979-988 ◽  
Author(s):  
Thomas Peters ◽  
Jean-Robert Brisson ◽  
David R. Bundle
Keyword(s):  
Conformational Analysis ◽  
Boltzmann Distribution ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Structural Elements ◽  
Torsion Angles ◽  
Proton Proton ◽  
Vicinal Proton ◽  
Polysaccharide Antigens ◽  
Nuclear Overhauser

The synthetic α 1,2 and α 1,3 disaccharide methyl glycosides of 4-amino-4,6-dideoxy-D-mannose 1–6 that constitute key structural elements of Brucella A and M antigens were analyzed by 1H and 13C nuclear magnetic resonance spectroscopy. A detailed conformational analysis was performed for the N-acetylated derivatives 1 and 4 as well as for the amino derivatives 2 and 5. Potential energy calculations using the GESA program established the global minima for the disaccharides 1, 2, 4, and 5, and mapped the energy surface as a function of the glycosidic torsion angles [Formula: see text] and ψ. Ensemble averaged nuclear Overhauser enhancements, weighted according to the Boltzmann distribution function, were derived for each of the four disaccharides. This procedure improved the fit between experimentally and theoretically derived nOe values, when compared to interpretations based on a single conformer model. The Brucella A and M antigens are homopolymers of 4-formamido-4,6-dideoxy-D-mannose and, as.N-formyl groups (saccharides 3, 6, and 8) are essential for the binding of these antigens to their respective antibodies, amide conformation was analyzed by examination of the vicinal proton–proton and proton–carbon coupling constants of the model monosaccharide 8. The conformational properties of the model compounds 1–8 were used to model the Brucella A and M polysaccharide antigens. Keywords: conformational analysis, disaccharide conformation, nuclear Overhauser measurements, molecular modeling, Brucella antigen.

Relationship between protonproton NMR coupling constants and substituent electronegativities. V—Empirical substituent constants deduced from ethanes and propanes

1989 ◽  
Vol 27 (6) ◽  
pp. 564-576 ◽  
Author(s):  
Cornelis Altona ◽  
Johannes H. Ippel ◽  
Aldert J. A. Westra Hoekzema ◽  
Cornelis Erkelens ◽  
Michel Groesbeek ◽  
...  
Keyword(s):  
Proton Nmr ◽  
Coupling Constants ◽  
Proton Proton ◽  
Substituent Constants
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