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Biomedical subjects

P F DAVISON

Publications and source records attributed to P F DAVISON.

At least 19 recordsLinked to original sources
PubMed1963

Tropocollagen: significance of protease-induced alterations.

Interaction properties of tropocollagen are markedly altered by treatment with pepsin. This treatment liberates terminal or near-terminal covalently bonded peptides whose amino acid composition is strikingly different from the composition of the pepsin-resistant triple-helix body of the macromolecule. Pepsin also converts most of the beta-chains to alpha-chains. This fact indicates that the interchain link is also external to the body of the macromolecule and probably involves peptides. The role of these properties in bioregulative mechanisms is briefly discussed.

Amino Acids↗
PubMed1963

Physicochemical studies on the reaction between formaldehyde and DNA.

The reaction between formaldehyde and phage T7 DNA has been studied by optical absorbance and sedimentation measurements. Through the course of denaturation, OD(200) and s(20, w) rise; after the attainment of full hyperchromicity the s(20, w) falls sharply, suggesting a decrease in molecular weight. Conditions in which formaldehyde causes cross-linking are defined. Some experimental applications of the denaturation technique are given. Evidence which suggests that preformed single-strand interruptions may exist in phage DNA is briefly discussed.

Coliphages↗
PubMed1962

Studies on the sonic degradation of deoxyribonucleic acid.

T7 DNA was partially degraded by x-rays, DNAase, and sonic irradiation. The molecular weight distributions were calculated from sedimentation velocity studies on the resulting preparations. Comparison with the theoretical curve derived by Montroll and Simha showed that the first two degradative methods act grossly at random, whereas sonication is a non-random process resulting in the preferential halving of the DNA molecules in solution.

DNA↗
PubMed1962

Hyperchromicity and strand separation in bacterial DNA.

Studies of the per cent of strand separation of N(14)-N(15) hybrid coli DNA heated to various temperatures in formaldehyde have shown that the process of strand separation is a function of temperature and formaldehyde concentration and is directly related to the measured hyperchromicity. No strands separate until about 75 per cent of full hyperchromicity is obtained, and even at apparently full hyperchromicity a large fraction of the strands may be held together, possibly by guanine-cytosine-rich regions.

Cytosine↗
PubMed1961

Damage by visible light to the acridine orange--DNA complex.

Salmon DNA has been irradiated with visible light in the presence of acridine orange. If the dye is bound to the DNA, there results: (a) a decrease in sedimentation coefficient, (b) a lowering of viscosity, and (c) a decrease in the thermal denaturation temperature. CsCl banding experiments show that the first two effects reflect depolymerization of the DNA. Depolymerization apparently occurs by single-strand scission although some double-strand scission is not excluded. The destabilization of secondary structure results probably from chemical attack on the components of the individual strands.

Acridine Orange↗
PubMed1960

Physical-chemical studies of proteins of squid nerve axoplasm, with special reference to the axon fibrous protein.

The proteins in the axoplasm of the squid, Dosidicus gigas, have been resolved electrophoretically into a major fraction including the fibrous protein, and possibly its structural subunits, and a minor fraction including at least two proteins with low sedimentation coefficients. A partially reversible change in the structure of the fibrous protein occurs under the action of 0.4 M salt or high pH. These experiments have been interpreted to indicate that in the intact fiber one, or a few, protofibrils are arranged helically or longitudinally along the fiber axis, and linked by electrostatic bonds. On the dissociation of these bonds the separated protofibrils assume a less extended form and sediment more rapidly than the intact fibers. Some material with a lower sedimentation rate is also released on the dissociation. This fraction may comprise smaller chain fragments. The volume fraction and the approximate refractive index of the fibers have been calculated.

Animals↗