GROWTH OF CALCIUM-OXALATE MONOHYDRATE AT PHOSPHOLIPID LANGMUIR MONOLAYERS

Calcium oxalate monohydrate crystals have been nucleated from metastab le solutions at Langmuir monolayers of the phospholipids dipalmitoylph osphatidylglycerol (DPPG), dipalmiteylphosphatidylserine and dipalmito ylphosphatidylcholine and the fatty acid arachidic acid. The phospholi pid monolayers were used as model systems for domains of pure lipid in cellular media as part of investigations of their potential role in t he nucleation of calcium oxalate in the urinary tract. Crystal formati on was monitored at the air/water interface using Brewster angle micro scopy and in transferred films using SEM and TEM. For each Langmuir mo nolayer, it was observed that nucleation is heterogeneous and is selec tive with respect to the orientation and morphology of the precipitate d crystals with up to 90% of crystals growing with the (1 0 (1) over b ar) face oriented towards the monolayer interface. The selectivity is attributed to calcium binding at the lipid monolayer favoring formatio n of the calcium-rich (1 0 (1) over bar) face. The behavior at each mo nolayer was similar, although a higher rate of crystal formation was o bserved at the anionic DPPG interface. (C) 1998 Elsevier Science B.V. All rights reserved.