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M Adamich

Publications and source records attributed to M Adamich.

9 recordsLinked to original sources
PubMed1984

Highly sensitive immunoassays based on use of liposomes without complement.

We describe a novel liposome-based immunoassay in which covalently linked hapten-cytolysin conjugates are used instead of complement and surface-immobilized immunoreagents. Stable, unilamellar liposomes containing entrapped alkaline phosphatase as a marker enzyme were prepared by dialysis of octyl glucoside from suspensions of cholesterol and egg yolk lecithin. The resulting vesicles could be immediately lysed by addition of either bee venom melittin or hapten-melittin conjugates. Using ouabain, an analog of digoxin, we synthesized conjugates that were more lytic than mellitin alone but that were inhibited in the presence of antibody. This inhibition was affected by adding competing free digoxin at various concentrations to obtain standard curves. The same liposome preparations could be lysed with a biotin-melittin conjugate, which was inhibited by avidin. The latter system was affected by free biotin and might be used to couple this approach to various heterogeneous immunoassays.

Alkaline Phosphatase↗
PubMed1979

Action of cobra venom phospholipase A2 toward lipids of erythrocyte membranes.

The activity of cobra venom phospholipase A2 toward phospholipids in erythrocyte membranes is enhanced significantly following ghosting of the membrane. The specificity observed is phosphatidylethanolamine greater than phosphatidylcholine and is the reverse of that expected from model studies with individual phospholipids. It is shown, utilizing phospholipid mixtures, that the activity and specificity of cobra venom phospholipase A2 is dependent on the presence of other lipids and their organization.

Elapid Venoms↗
PubMed1978

Exploring the action and specificity of cobra venom phospholipase A2 toward human erythrocytes, ghost membranes, and lipid mixtures.

We have investigated the action and substrate specificity of phospholipase A2 (EC 3.1.1.4) purified from cobra venom (Naja naja naja) toward intact and Triton-solubilized human erythrocytes, toward ghost membranes, and toward extracted ghost lipids in mixed micelles with Triton X-100. We have found that: (i) phospholipids in the outer surface of intact erythrocytes are extremely poor substrates for the phospholipase, (ii) phospholipids in ghost erythrocyte membranes and in Triton-solubilized erythrocytes are suitable substrates for the enzyme, (iii) in these latter systems which contain a mixture of lipids, phosphatidylethanolamine is preferentially hydrolyzed, whereas in model studies on individual phospholipid species in mixed micelles with Triton, phosphatidylcholine is the preferred substrate of the enzyme, and (iv) the preferential hydrolysis of phosphatidylethanolamine is also observed for extracted ghost lipid mixtures in mixed micelles. These results demonstrate a dependence of phospholipase A2 activity on the ghosting procedure and a dependence of substrate specificity on the presence of other lipids. The relevance of these findings to the interpretation of membrane lipid asymmetry studies utilizing phospholipases is considered in detail.

Colloids↗