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Biomedical subjects

W L Peticolas

Publications and source records attributed to W L Peticolas.

At least 73 records · Page 4Linked to original sources
PubMed1975

Application of Raman spectroscopy to biological macromolecules.

The Raman spectra of biological macromolecules arise from molecular vibrations of either the backbone chains or the side chains. The frequencies of the Raman bands lie in a region between 200 cm-1 and 3000 cm-1. From certain frequencies of the vibrations of the backbone chains one can determine the conformation or secondary structure of a macromolecule. Thus for polypeptides and proteins the frequencies of the Amide I and Amide III vibrations allow one to determine the averge conformation of their backbone chain. In polynucleotides and nucleic acids, the frequency of the phosphate diester stretch of the phosphate furanose chain varies between 814 cm-1 for A conformation and 790 cm-1 for B conformation. Raman spectra of the bases in nucleic acids can be used to determine base stacking and hydrogen bonding interactions. Thus Raman spectroscopy is an important tool for determining the conformation structure of proteins and nucleic acids.

Animals↗
PubMed1975

Frequency-dependent diffraction from enzymatic breathing modes.

The intensity of the time-dependent Fourier transform of any macro-molecule which contains a cleft of the sort that exists in the protein lysozyme is derived. It is shown that there is a region of this transform in which this intensity varies nearly sinusoidally with time with a frequency equal to that of the macromolecule's breathing mode of vibration, and where, therefore, the diffracted power will be primarily at this single frequency. Observation of this power will allow the experimental determination of the frequency of this mode, which is expected to be much lower than those observable by Raman spectroscopy.

Chemical Phenomena↗
PubMed1972

Determination of the backbone structure of nucleic acids and nucleic acid oligomers by laser Raman scattering.

Raman spectra of fibers of DNA that have been prepared in the A, B, and C forms are presented and compared with Raman spectra of DNA and RNA in dilute solution. It is shown that the phosphate vibrations in the region 750-850 cm(-1) are very sensitive to the specific conformation of the phosphate group in the backbone chain and are virtually independent of all ohter factors. Thus, a very simple method for the determination of the specific conformation of the backbone chain of nucleic acids, at least so far as the sugar-phosphate chain is concerned, appears available. The method is applied to short oligomers and dimers of ribonucleosides. It is found that at low temperatures, at pH 7, the phosphate group goes into the geometry of the A conformation when the stacking forces between the bases are sufficiently strong.

Animals↗
PubMed1972

Conformationally dependent low-frequency motions of proteins by laser Raman spectroscopy.

Low-frequency Raman bands (lower than 50 cm(-1)) exist in certain proteins. They are dependent upon the conformation of the protein molecule, but are relatively independent of the form of the sample, i.e., whether it is a film or a crystal.Low-frequency Raman spectra were obtained from samples of alpha-chymotrypsin that had been prepared in several ways. A peak at about 29 cm(-1) was found for all samples except the one that had been denatured with sodium dodecyl sulfate. Such low frequency motions must arise from vibrations that involve all, or very large portions, of the protein molecule.

Acylation↗
PubMed1971

Laser Raman investigation of the effect of cholesterol on conformational changes in dipalmitoyl lecithin multilayers.

Large and abrupt changes are observed at 38 degrees C in the 1100 cm(-1) region of the Raman spectrum of aqueous dipalmitoyl lecithin multilayers. They correspond to conformational changes due to the melting of the paraffin side chains. The addition of cholesterol to the multilayers broadens but does not abolish these changes. It is suggested that the addition of cholesterol decreases the interactions between adjacent paraffin side chains of lecithin, causing a change from a cooperative to a noncooperative gel-liquid crystal transition. Removal of water from dipalmitoyl lecithin also results in a noncooperative transition strikingly similar to that caused by addition of cholesterol. Raman spectroscopy thus provides a new and sensitive probe for analyzing the structures of membranes and their constituents.

Chemical Phenomena↗