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Biomedical subjects

I O Walker

Publications and source records attributed to I O Walker.

At least 37 records · Page 2Linked to original sources
PubMed1975

A model for chromatin sub-structure incorporating symmetry considerations of histone oligomers.

Symmetry considerations of the kind of structures which can be generated when dimers of histones f2al-f3 and f2a2-f2b interact lead to the following conclusions: chromatin subunits based on closed-shell structures give rise to discrete, non-interacting nucleoprotein subunits with the histones arranged at random along the DNA chain; open structures based on infinite helices give rise to highly ordered, regular arrangements of dimers. A model is proposed in which helical polymers of f2al-f3 and f2b-f2a2 form a central core with the DNA helically arranged around it. The helical repeat contains 9.6 turns of B-form DNA and one molecule each of f2al, f2a2, f2b, f3 and f1. The pitch of the helix is 53Angstrom and the other diameter 130Angstrom. The protein molecular repeat is 106Angstrom.

Amino Acid Sequence↗
PubMed1974

The solubility of calf thymus chromatin in sodium chloride.

The solubility of calf thymus chromatin and chromatin depleted of F1-histone has been examined under various conditions in sodium chloride. F1-depleted DNH was more soluble than native DNH at low concentrations but this difference became small at high concentrations (1mg/ml). Both exhibited minimum solubility in 0.15M -NaCl. The effect of pH and of maleylation of the mino acid side chains on the solubility implied that electrostatic interactions dominated the precipitation reaction. Urea had no effect on the solubility of either complex. N.m.r. studies showed that the chromatin behaved as a rigid complex at all salt concentrations less than 0.6 molar.

Animals↗
PubMed1974

The reactivity of the thiol groups of calf thymus deoxyribonucleohistone.

The reactivities of the two cysteine thiol groups of calf thymus F3 histone were investigated using 5,5'-dithiobis-[2- nitrobenzoic acid], (DTNB). In isolated histone, both thiol groups were available for reaction. However, analysis of reaction profiles of native deoxyribonucleohistone, (DNH), in various solvent conditions, together with gel electrophoresis studies of DNH modified with DTNB, showed that only one of the thiol groups is normally modified by the reagent. If NaCl is present (above 1.OM) the other thiol group can also be modified. The reactivities of both groups were largely independent of the degree of DNH supercoiling and of the binding of F3 to the DNA.

Animals↗