The role of zinc in the stabilization of the dimeric form of bacterial alpha-amylase.

Bacterial alpha-amylase was shown by equilibrium and velocity-sedimentation studies to be a monomer-dimer equilibrium system in 0.10M-NaCl/0.015M-calcium acetate/0.

Self-association of troponin.

Ox muscle troponin was shown by equilibrium- and velocity-sedimentation studies to undergo concentration-dependent dissociation into its constituent subunits as well as self-association in imidazole buffers, pH 6.9. The extent of troponin association was found to be strongly dependent on ionic strength and also to exhibit a dependence on pH and temperature; under conditions physiological in regard to pH, temperature and ionic strength the extent of polymerization of troponin is considerable in 2 mg/ml solutions.

Self-association of alpha-chymotrypsin at low ionic strength in the vicinity of its pH optimum.

The self-association of alpha-chymotrypsin and its di-isopropyl phosphoryl derivative in in I0.03 sodium phophate buffer, pH7,9, was investigated by velocity sedimentation, equilibrium sedimentation and difference gel chromatography. No differences between the native and chemically modified enzyme were observed in the ultracentrifuge studies, and only a marginal (0.

An electrophoretic study of the reversible binding of phosphate to ovalbumin.

An electrophoretic method is described for the measurement of relatively weak interaction of ions with proteins, and illustrated with the ovalbumin-phosphate system in 0.1I buffers, pH6.1.

Rabbit muscle myogen. Interactions with phosphate as the source of non-enantiography in moving-boundary electrophoresis.

Rabbit muscle myogen has been subjected to moving-boundary electrophoresis and velocity sedimentation in 0.0187 M-potassium phosphate buffer, pH7.7, I = 0.

Ligand-induced polymerization.

Three models of ligand-induced polymerization are considered, encompassing dimerization of acceptor-ligand complex and cross-linking of monomer units via a ligand bridge to form either dimer or linear chains. For each model a binding equation is developed and examined in terms of limits, form, and intersection within a family of curves, each member constructed with fixed but different total acceptor concentration. The characteristics of the binding curves that emerge are correlated with those found by examining the dependence on ligand concentration of either the weight-average molecular weight of the acceptor constituent or a function of it.

A mammalian nicking endonuclease.

Purification and properties are described for an endonuclease isolated from calf thymus which attacks double-stranded, unmodified DNA, primarily by making single-strand breaks. No detectable acid-soluble products arise from the reaction. Double-strand breaks may occasionally be produced by the introduction of single-strand breaks on opposite strands in close proximity.

Beef muscle troponin: evidence for multiple forms of troponin-T.

A method is described for the purification of troponin from beef skeletal muscle. The resultant preparation differs from the troponin of rabbit skeletal muscle in that it contains at least two forms of the tropomyosin-binding component, Troponin-T: these are designated as the 37 000 and 40 000 dalton forms of Troponin-T on the basis of sodium dodecyl sulphate gel electrophoresis. Either of these Troponin-T forms may be used to reconstitute troponin by mixing with the appropriate amounts of the calcium-binding (Troponin-C) and and actomyosin ATPase-inhibitory (Troponin-I) components.

Evaluation of equilibrium constants for the interaction of lactate dehydrogenase isoenzymes with reduced nicotinamide-adenine dinucleotide by affinity chromatography.

Rabbit muscle lactate dehydrogenase was subjected to frontal affinity chromatography on Sepharose-oxamate in the presence of various concentrations of NADH and sodium phosphate buffer (0.05 M, pH 6.8) containing 0.

Further evidence for the concept of bovine plasma arylesterase as a lipoprotein.

Purified preparations of bovine plasma arylesterase were obtained by isoelectric focusing of enzyme prepared by (NH4)2SO4 fractionation of plasma and chromatography on DEAE-cellulose and Sephadex G-200. Although the high-density-lipoprotein fraction (HDL2) of serum provides an alternative source of enzyme, the enzymic activity of preparations made from it is much less stable. The purified arylesterase preparation has a molecular weight of 440000 and a partial specific volume of 0.

Quantitative interpretation of concentration-dependent migration in gel chromatography of reversibly polymerizing solutes.

A theoretical expression is derived for concentration dependence of elution volume in the gel chromatography of a non-interacting solute. Experimental results for bovine serum albumin on Sephadex G-100 are shown to be in good agreement with the predicted gel-chromatographic behaviour. The theoretical treatment of concentration dependence is extended to include a solute undergoing rapid reversible polymerization (nA in equilibrium C).

Co-operative binding of oxytocin to bovine neurophysin II.

The interaction of oxytocin with bovine neurophysin II in 0.1 M-sodium phosphate, pH 5.8, was investigated by equilibrium-dialysis and sedimentation studies.

Carboxylesterases (EC 3.1.1). The molecular sizes of chicken and pig liver carboxylesterases.

The molecular size of pig liver carboxylesterase has been investigated under a variety of conditions of pH and ionic strength. From equilibrium and velocity sedimentation at pH 4.0 and pH 7.

Interaction of aldolase with the troponin-tropomyosin complex of bovine muscle.

Ultracentrifugal studies of mixtures of aldolase and the troponin-tropomyosin complex from bovine muscle showed the existence of a labile interaction between these two myofibrillar constituents in imidazole buffers, pH6.8, I 0.02-0.

Use of affinity chromatography for the quantitative study of acceptor-ligand interactions: The lactose synthetase system.

From the effects of N-acetyl-d-glucosamine and d-glucose on the elution of the A protein of human lactose synthetase from a column of Sepharose-alpha-lactalbumin, values of 200m(-1) and 0.57m(-1) are deduced for the association constants describing the interaction between the enzyme and the respective monosaccharides.

Effects of lipid removal on the molecular size and kinetic properties of bovine plasma arylesterase.

A purified arylesterase preparation from bovine plasma was characterized to the extent that it has a partial specific volume of 0.91ml/g and an apparent z-average molecular weight of 440000. The relatively large magnitude of the former reflects the presence of phospholipids, cholesterol, triglycerides and beta-carotene, the last-named being responsible for the pronounced yellow colour of the preparation.