Effect of phospholipase A2 hydrolysis products on calcium oxalate precipitation at lipid interfaces.

Urinary stones are commonly composed of an inorganic component, calcium oxalate, or calcium phosphate and an organic matrix of lipids, carbohydrates, and proteinaceous matter. Of interest is the role that the organic matrix elements may play as catalysts for the heterogeneous nucleation of the calcium salts, and a number of studies have examined the role of lipids in calcium oxalate monohydrate (COM) formation. In this study, products of lipid hydrolysis from phospholipase A(2) (PLA(2)) are examined for their effect on COM formation using Langmuir monolayers as model lipid membrane assemblies.

Formation of single-crystalline aragonite tablets/films via an amorphous precursor.

Thin tablets and films of calcium carbonate have been grown at the air-water interface via an amorphous precursor route using soluble process-directing agents and a Langmuir monolayer based on resorcarene. By using appropriate concentrations of poly(acrylic acid-sodium salt) in combination with Mg2+ ion, an initially amorphous film is deposited on the monolayer template, which subsequently crystallizes into a mosaic film composed of a mixture of single-crystalline and spherulitic patches of calcite and aragonite. Of particular importance is the synthesis of single-crystalline "tablets" of aragonite (approximately 600 nm thick), because this phase generally forms needle-like polycrystalline aggregates when grown in vitro.

Role of lipids in urinary stones: studies of calcium oxalate precipitation at phospholipid langmuir monolayers.

This article reviews the authors' experiments on calcium oxalate growth at lipid monolayers. Calcium oxalate is the principal mineral component of most urinary stones. Membrane constituents associate either actively or passively with calcific minerals during stone formation, and it has been proposed that lipid assemblies play a significant role, possibly providing sites for the initial nucleation event.