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Biomedical subjects

S Beychok

Publications and source records attributed to S Beychok.

At least 55 records · Page 3Linked to original sources
PubMed1971

Optical activity of human lysozyme.

The ultraviolet circular dichroism spectra of human lysozyme are presented. Effects of pH and added inhibitor (N-acetyl-D-glucosamine) were examined and the results were compared with similar measurements of hen egg-white lysozyme. The near-ultraviolet CD spectral bands are substantially different in the human and hen egg-white enzymes. In addition to marked dissimilarities in the spectral interval 260-300 nm, an unusual CD band occurs at an anomalous wavelength (313 nm) in human lysozyme. The pH dependence of the latter suggests a possible interaction, absent in hen egg-white lysozyme, between a tryptophan and a tyrosine residue. Analysis of the spectra furthermore suggests lesser net rotational strengths of tryptophan bands in hen egg-white lysozyme than in human lysozyme, although the latter has one less tryptophan residue. The relationship between the CD spectra and the sequence differences of the proteins is discussed, as well as the CD spectra (published by others) of a closely related protein, bovine alpha-lactalbumin. Contributions of cystine residues to the spectra are examined in the light of possible differences in chirality of one of the four disulfide bridges.The far-ultraviolet CD spectra of human and egg-white lysozyme are quite similar, though not identical. In view of the pronounced differences in side-chain optical activity, and of the effect of pH variation on the far-ultraviolet CD spectrum of human lysozyme, it is likely that at least part of the observed difference in spectra is due to nonpeptide optical activity, and that the proteins have a secondary structure in common.

Amino Acid Sequence↗
PubMed1966

Circular dichroism of biological macromolecules.

Circular dichroism, the unequal absorption of right and left circularly polarized light, is a manifestation of optical activity in the vicinity of absorption bands. To the experimental scientist interested in the conformation of macromolecules and in the sensitive response of optical activity to conformational alteration, it offers a relatively new and powerful means of understanding the environment of chromophoric residues. As a tool in the elucidation of electronic spectra, it should be useful to the theoretical scientist in identifying weakly allowed absorption bands as well as in providing rotational parameters which can be compared with the developing theory of optical activity. I have stressed application of circular dichroism, to experimental aspects of protein and nucleic acid conformation in solution. Much is still uncertain in particular quantitative details. However, even these early results shed new light and yield new information on the conformation of these molecules.

Chemical Phenomena↗