Conversion of the fourth complement component studied by crossed immunoelectrophoresis

C4 in EDTA plasma and partially purified C4 give a β₂ peak on crossed immunoelectrophoresis. During electrophoresis C4 in serum is converted to a product of fast β₁ mobility, usually accompanied by a slow β₂ peak. Conversion in serum is inhibited by EDTA. Storage of serum at room temperature results in a gradual increase of the slow β₂ peak. Storage of EDTA plasma changes the configuration of the native β₂ peak. C[unk]s, trypsin, chymotrypsin, plasmin or thrombin added to partially purified C4 is capable of producing a fast β₁ C4 protein peak. C[unk]s, trypsin and chymotrypsin give this conversion product also when added to EDTA serum. C[unk]s, trypsin and chymotrypsin also give rise to a show β₂ and an inter α C4 conversion product in serum, probably consisting of complex formations between C4 and other serum proteins. Enzyme inhibitors known to interfere with C[unk] inhibit the conversion of C4 in serum on agarose electrophoresis. The results suggest that such conversion is caused by an activation of C1 during electrophoresis.

Factor VIII recombination after dissociation by CaCl12

Factor VIII is a large protein molecule of molecular weight 2,000,000 or larger that elutes in the void volume on agarose gel chromatography. It has been shown previously that high concentrations of alkali halides and, more specifically, 0.25 M Ca(2+) dissociate the molecule into a large carrier protein and a small fragment that retains the factor VIII activity. Factor VIII was prepared from normal canine plasma collected in sodium oxalate and heparin and adsorbed with BaSO(4). Results with Ca(2+) dissociation were the same as those obtained with fraction prepared from canine plasma collected in sodium citrate. The addition of 0.1 M epsilon-aminocaproic acid in the dissociation step had no effect. Fractionation of canine hemophilic plasma produced preparations without activity, and no activity was found when these inert preparations were dissociated with Ca(2+). These results indicate that the Ca(2+) dissociation is a true dissociation and not caused by enzymatic degradation by plasmin, thrombin, or activated factors VII, IX, or X. The apparent molecular weight of the small active fragment of factor VIII determined by gel chromatography was about 100,000. Finally, when the large carrier protein and the small active fragment of factor VIII were separated by gel chromatography, mixed, and dialyzed free of Ca(2+), they recombined to form a large active molecule that appeared in the void volume on agarose gel chromatography.

The purification of nicotinamide nucleotide-dependent dehydrogenases on immobilized cofactors

1. The general applicability of affinity chromatography to the purification of nicotinamide nucleotide-dependent dehydrogenases on immobilized cofactors is illustrated with several examples taken from crude systems. 2. Methods for overcoming the inevitable loss of selectivity experienced with these polymers are suggested. Effective use of the appropriate nucleotide, the second substrate and other interacting ligands can be made to selectively alter the chromatographic behaviour of the desired enzyme.

Affinity chromatography of lactate dehydrogenase on immobilized nucleotides

The interaction of two isoenzymes of lactate dehydrogenase from pig heart muscle (H(4)) and rabbit skeletal muscle (M(4)), with immobilized nucleotides was examined: the effects of pH and temperature on the binding of lactate dehydrogenase were studied with immobilized NAD(+) matrices. The influence of substrate, product and sulphite on the binding of heart muscle lactate dehydrogenase to immobilized NAD(+) was investigated. The interaction of both lactate dehydrogenase isoenzymes with immobilized pyridine and adenine nucleotides and their derivatives were measured. The effects of these parameters on the interaction of lactate dehydrogenase with immobilized nucleotides were correlated with the known kinetic and molecular properties of the enzymes in free solution.

Purification by affinity chromatography of the molecular forms of acetylcholinesterase present in fresh electric-organ tissue of electric eel

An acetylcholinesterase inhibitor-Sepharose conjugate was prepared by coupling a derivative of the powerful acetylcholinesterase inhibitor, N-methylacridinium, to CNBr-activated Sepharose. Use of this conjugate permitted direct purification, by affinity chromatography, of the two molecular forms of acetylcholinesterase, 14 and 18 S, present in fresh electric organ tissue. The purified 14S and 18S acetylcholinesterases retained the capacity to aggregate at low ionic strength displayed by crude extracts of the enzyme. The major polypeptide components of the 14S and 18S enzymes, as revealed by acrylamide gel electrophoresis, closely resemble those observed in the 11S form of acetylcholinesterase, previously purified after tryptic digestion of electric-organ tissue.