ChemInform Abstract: MO CALCULATION OF THE OPTICAL ACTIVITY OF OLIGOPEPTIDES. II. OPEN CHAIN CONFORMATIONS. COMPARISON WITH SOME CYCLIC SYSTEMS

1978 ◽  
Vol 9 (17) ◽  
Author(s):  
M. ISELI ◽  
R. GEIGER ◽  
G. WAGNIERE
Keyword(s):  
Optical Activity ◽  
Open Chain ◽  
Mo Calculation ◽  
Cyclic Systems ◽  
Chain Conformations

Über Phosphazene XXXV, 31P-NMR-Untersuchungen VIII

1970 ◽  
Vol 25 (12) ◽  
pp. 1364-1370 ◽  
Author(s):  
Alfred Schmidpeter ◽  
Klaus Schumann
Keyword(s):  
Linear Function ◽  
31P Nmr ◽  
Degree Of Substitution ◽  
Amino Groups ◽  
Open Chain ◽  
Wide Range ◽  
Cyclic Systems

All accessible NMR shifts δ31P of phosphorus surrounded by four nitrogen atoms are compiled systematically. They cover the relatively wide range from -40 to +50 ppm. All shift differences observed correlate well with changes in nitrogen hybridization: in the order p3 → sp3 → sp2 → sp for nitrogen δ31P (N4) is shifted to a higher field. In particular, δ31P (N4) is a linear function of the degree of substitution, when phosphazeno groups are substituted by amino groups in open chain or cyclic systems. This is also true of δ31P (04) in alkoxy or phenoxy/phosphoroxy substitution series

scholarly journals Molecular structures of viruses from Raman optical activity

2002 ◽  
Vol 83 (10) ◽  
pp. 2593-2600 ◽  
Author(s):  
Ewan W. Blanch ◽  
Lutz Hecht ◽  
Christopher D. Syme ◽  
Vito Volpetti ◽  
George P. Lomonossoff ◽  
...  
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Optical Activity ◽  
Molecular Structures ◽  
Helical Conformation ◽  
Amino Acid Side Chain ◽  
Cowpea Mosaic Virus ◽  
Raman Optical Activity ◽  
Satellite Tobacco Mosaic Virus ◽  
Chain Conformations

A vibrational Raman optical activity (ROA) study of a range of different structural types of virus exemplified by filamentous bacteriophage fd, tobacco mosaic virus, satellite tobacco mosaic virus, bacteriophage MS2 and cowpea mosaic virus has revealed that, on account of its sensitivity to chirality, ROA is an incisive probe of their aqueous solution structures at the molecular level. Protein ROA bands are especially prominent from which, as we have shown by comparison with the ROA spectra of proteins with known structures and by using a pattern recognition program, the folds of the major coat protein subunits may be deduced. Information about amino acid side-chain conformations, exemplified here by the determination of the sign and magnitude of the torsion angle χ2,1 for tryptophan in fd, may also sometimes be obtained. By subtracting the ROA spectrum of the empty protein capsid (top component) of cowpea mosaic virus from those of the intact middle and bottom-upper components separated by means of a caesium chloride density gradient, the ROA spectrum of the viral RNA was obtained, which revealed that the RNA takes up an A-type single-stranded helical conformation and that the RNA conformations in the middle and bottom-upper components are very similar. This information is not available from the X-ray crystal structure of cowpea mosaic virus since no nucleic acid is visible.

MO-Calculation of the Optical Activity of Oligopeptides. I. Computational Procedure and Application to Small Helices

1977 ◽  
Vol 60 (6) ◽  
pp. 1831-1844 ◽  
Author(s):  
Georges Wagnière ◽  
Max Iseli ◽  
Rudolf Geiger ◽  
Werner Gans
Keyword(s):  
Optical Activity ◽  
Computational Procedure ◽  
Mo Calculation

scholarly journals Optical activity in ketones. The rotatory dispersion and circular dichroism of m-methyl cyclohexanone and of pulegone in their ketonic absorption bands

1937 ◽  
Vol 163 (915) ◽  
pp. 483-498 ◽  
Keyword(s):  
Optical Activity ◽  
Wave Length ◽  
Small Contribution ◽  
Asymmetric Carbon Atom ◽  
Absorption Bands ◽  
Open Chain ◽  
Aldehydes And Ketones ◽  
Sugar Derivatives ◽  
Absorption Frequencies ◽  
Asymmetric Carbon

Recent investigations of the rotatory dispersions of aldehydes and ketones led to the conclusion that the optical activity of these compounds is due almost entirely to the electrons of the carbonyl group and not directly to the asymmetric carbon atoms. A particularly striking example of this was found in the aldehydic sugar derivative, μ-arabinose pentaacetate, by Hudson, Wolfrom and Lowry (1933), who showed that when the calculated partial rotation contributed by the absorption band between 3000 and 2600 A was subtracted from the observed rotations for the whole molecule, a negligible residual rotation was left at every wave-length at which measurements were made between 6700 and 2300 A. In general, however, absorption frequencies lying in the Schumann region appear to make a small contribution; but the analysis has always been complicated in the cases so far examined by the fact that the molecules contain either two asymmetric carbon atoms, e. g. in camphor (Kuhn and Gore 1931), menthone and carvomenthone (Lowry and Lishmund 1935a), or as many as four in the open-chain sugar derivatives (Hudson and others 1933; Baldwin, Wolfrom and Lowry 1935). The absence of any large direct contribution from the asymmetric atoms might therefore be explained in two ways, namely, either that their partial rotations are actually very small, or, as may well be the case in the sugars (cf. Lowry 1935, p. 274), that, though large, they are of opposing signs and tend to annul one another at wavelengths remote from the region of absorption. It was thus desirable to examine an optically active ketone whose molecule contains only a single asymmetric carbon atom, with no other disturbing factor, and m-methyl cyclohexanone (I) was selected for this purpose.

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