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L D Barron

Publications and source records attributed to L D Barron.

26 records · Page 2Linked to original sources
PubMed1994

Beta-sheet and associated turn signatures in vibrational Raman optical activity spectra of proteins.

We have measured the aqueous solution vibrational Raman optical activity (ROA) spectra of concanavalin A, alpha-chymotrypsin, and beta-lactoglobulin, all of which are rich in beta-sheet, together with that of the model beta-turn peptide L-pro-L-leu-gly-NH2. Possible ROA signatures of antiparallel beta-sheet include a strong sharp positive band at approximately 1,313 cm-1 associated with backbone amide III C alpha H and NH deformations, and an amide I couplet, negative at low wavenumber and positive at high, centered at approximately 1,658 cm-1. Negative ROA bands in the range approximately 1,340-1,380 cm-1, which might originate in glycine CH2 deformations, appear to be characteristic of beta-turns. Our results provide further evidence that ROA is a more incisive probe of protein conformation than conventional vibrational spectroscopy, infrared, or Raman, because only those few vibrational coordinates within a given normal mode that sample the skeletal chirality directly contribute to the corresponding ROA band intensity.

Amino Acid Sequence↗
PubMed1994

Vibrational Raman optical activity of glycoproteins.

This paper reports the first vibrational Raman optical activity (ROA) spectrum of a glycoprotein. The sample, orosomucoid (alpha 1-acid glycoprotein), shows ROA bands characteristic of a high beta-sheet content together with new bands which could be specific for the carbohydrate and its association with the protein. Our results suggest that ROA spectra of intact glycoproteins may contain information about both protein and carbohydrate conformation and the mutual influence on each other's stability and conformation.

Carbohydrate Conformation↗
PubMed1992

Vibrational Raman optical activity of enzymes.

Advances in Raman optical activity (ROA) instrumentation, based on the employment of a backscattering geometry together with a back-thinned CCD detector and a single-grating spectrograph with a holographic edge filter, have now enhanced the sensitivity to the level necessary to provide vibrational ROA spectra of proteins in aqueous solution. Early results show at least four separate regions in protein ROA spectra associated with vibrations of the backbone which appear to characterize the alpha-helix, beta-sheet, reverse turn and random-coil secondary conformation content. Side-group ROA features also appear, with tryptophan particularly prominent in lysozyme and alpha-lactalbumin. ROA should become a sensitive new probe of protein folding and ligand-induced conformational change in aqueous solution.

Enzymes↗
PubMed1991

Vibrational Raman optical activity of carbohydrates.

Vibrational Raman optical activity (R.o.a.) spectra of a range of carbohydrates in aqueous solution, measured in back-scattering between 700 and 1500 cm-1, are presented. Features were revealed that appear to be characteristic of details of the stereochemistry. Effects associated with the glycosidic linkage in di- and oligo-saccharides are prominent.

Arabinose↗
PubMed1987

Fundamental symmetry aspects of chirality.

Physical systems which exhibit distinguishable enantiomers under space inversion are not necessarily chiral. A new definition of chirality is proposed that enables true and false chirality to be distinguished. Although spatial enantiomorphism is sufficient to guarantee chirality in a stationary object, enantiomorphous systems are not necessarily chiral when motion is involved. Only a truly chiral influence can induce absolute asymmetric synthesis in a reaction mixture at thermodynamic equilibrium, but false chirality might suffice if equilibrium is not attained. Parity violation lifts only the degeneracy of enantiomers of truly chiral systems, the true enantiomers (i.e. strictly degenerate) being interconverted by space inversion together with charge conjugation. The time-independence of optical activity arising from parity violation is contrasted with the time-dependence of that arising from spontaneous parity breaking.

Electromagnetic Fields↗
PubMed1972

Parity and optical activity.

Simple pictorial arguments can demonstrate that the natural and Faraday rotation experiments conserve parity and time-reversal invariance. The method can be used to predict possible new effects without recourse to mathematical theories.

Journal Article↗