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Biomedical subjects

D Rickwood

Publications and source records attributed to D Rickwood.

At least 73 records · Page 4Linked to original sources
PubMed1978

Studies of Epstein-Barr virus (EBV)-associated nuclear antigen: solubilization from Raji cell chromatin with 5 M-urea-2 M-nacl and fractionation on hydroxyapatite.

EBNA-containing chromatin from Raji cells was solubilized by treatment with high concentrations of urea and salt and fractionated by hydroxyapatite chromatography. Fractions eluting at different phosphate concentrations were analysed for the presence of EBNA by means of an anti-EBNA-specific 125I-labelled IgG absorption assay. The antigen was found in fractions containing non-histone chromatin proteins.

Antigens, Viral↗
PubMed1977

The modification of nuclear proteins by ADP-ribosylation.

When incubated in vitro purified mouse nuclei incorporate NAD into poly(ADP-Rib). Analysis of the product on CsDl/urea gradients showed that a large proportion of the poly(ADP-Rib) was not attached to protein. The free poly(ADP-Rib) did not appear to arise through degradation and its chain length was significantly longer than the poly(ADP-Rib) attached to proteins. Fractionation of the proteins on hydroxyapatite revealed that tissue-specific modification of both the histones and non-histone proteins, had occurred. In the case of one protein species there was evidence for the existence of several forms with different numbers of ADP-Rib residues.

Animals↗
PubMed1977

Solubilisation of Epstein-Barr virus (EBV)-associated nuclear antigen from Raji cells and chromatin by treatment with various molarities of NaCl.

The solubilisation of Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA) by treatment with various molarities of NaCl was investigated using the 125I--IgG absorption assay. Ninety percent of the antigenic activity detected using the 125I--IgG absorption assay was insoluble at 0.15 M NaCl. It could be rendered soluble by treatment with 2.0 M NaCl, but reprecipitated upon return to 0.15 M NaCl. EBNA was partially extracted from Raji chromatin by treatment with 0.35 M NaCl. The efficiency of extraction was increased by homogenisation in 2.0 M NaCl followed by dialysis to 0.35 M NaCl. The data demonstrate the close association of EBNA with Raji chromatin and suggest that it may be a chromatin-associated non-histone protein.

Antigens, Viral↗
PubMed1975

Improved techniques for the fractionation of non-histone proteins of chromatin on hydroxyapatite.

The effect of the dissociation medium on the fractionation of chromatin on hydroxyapatite has been studied. Optimal separations of the histones and non-histone protein are only achieved when columns are run in buffers containing high concentrations of sodium ions. We have modified our previously published method such that the chromosomal proteins can be recovered in virtually quantitative yields. Each of the hydroxyapatite fractions has been analysed with respect to nucleic acid content and the proteins have been analysed by two-dimensional gel electrophoresis.

Animals↗
PubMed1975

A study of the interaction of histones with DNA using isopycnic centrifugation in metrizamide gradients.

Isopycnic sedimentation in metrizamide gradients has shown that mouse-liver histones bind co-operatively to both homologous and bacterial DNA's. However, at low input ratios of histone to DNA, two types of stable complex are formed, depending on the histone concentration. One complex contains half as much histone as DNA while the other contains approximately equal amounts of histone and DNA. At high input ratios of histone to DNA extra histone is bound giving complexes containing up to twice as much histone as DNA. Poly-L-lysine and protamine were also found to bind co-operatively to DNA.

Animals↗
PubMed1974

Isopycnic sedimentation of DNA in metrizamide: the effect of low concentrations of ions on buoyant density and hydration.

Metrizamide, an inert, non-ionic organic compound, dissolves in water to give a dense solution in which DNA bands isopycnically at a density corresponding to that of fully hydrated DNA. Density-gradient centrifugation in solutions of metrizamide has been used to determine the effects of very dilute solutions of salts on the buoyant density of native and denatured DNA. It has been shown that the buoyant density of DNA is dependent on both the counter-cation and the anion present. Interpretation of the data in terms of the degree of hydration of the macromolecule indicates that (i), NaDNA is more highly hydrated than CsDNA; and (ii), the hydration of NaDNA varies with anion in the order sulphate< fluoride< chloride< bromide< iodide. It is suggested that isopycnic centrifugation in metrizamide is a simple method for determining the effects of salts (and other small molecules) on the hydration of nucleic acids under conditions of high ratios of salt to DNA (> 5 x 10(3) moles/mole) while high (0.999) water activity is maintained.

Animals↗