Brewster Angle Microscopy of Calcium Oxalate Monohydrate Precipitation at Phospholipid Monolayer Phase Boundaries

Abstract

The precipitation of calcium oxalate monohydrate (COM) at phospholipid monolayers confined to the air/water interface is observed in situ with the aid of Brewster angle microscopy. COM crystals appear as bright objects that are easily identified and quantified to assess the effects of different conditions on crystallization. Crystal precipitation was monitored at monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in liquid condensed (LC) and liquid expanded (LE) phases. Within the LC phase, higher pressures reduce the incidence of crystallization at the interface, implying that within this phase precipitation is enhanced by higher compressibility or fluidity of the monolayer. Precipitation at biphasic LC/LE and LE/gas (G) monolayers was also studied. COM appears preferentially at phase boundaries of the DPPC LC/LE and LE/G monolayers. However, when an LC/LE phase boundary is created by two different phospholipids that are phase segregated, such as DPPC and 1,2-dimyristoyl-sn-glycero-3-phosphocholine, crystal formation occurs away from the interface within the DPPC LC phase. It is suggested that COM growth at phase boundaries is preferred only when there is molecular exchange between the phases.

Induction of Ring‐Shaped Calcium Oxalate Patterns by Boundaries between Liquid Expanded Phase and Liquid Condensed Phase in Langmuir‐Blodgett Film

“…The LC phase boundary has a high density of lipid molecules with partial order, and its enough fluidity can allow reorganization of the lipids to effectively stabilize the nucleating crystal phase. 7,13 The studies of COM precipitation by Talham et al 7 at DPPC monolayers with two phases in equilibrium also revealed that crystal formation occurred preferentially at the phase boundary, either LC/LE or LE/G (gas). The preferential precipitation at the LC/LE boundaries has also been observed by BAM for CaCO 3 under fatty acids 14 and by light scattering microscopy combined with fluorescence microscopy for COM.…”

“…As shown in Figure 2, the LC and LE phases coexisted at the surface pressure of 10 mN/m. 7 The onset of the sur- face pressure for the DPPC/NBD-PC monolayer was detected at an area of 0.83 nm 2 /molecule, indicating the emergence of a uniform LE phase from the LE/gaseous (G) coexistence. And the LE/LC coexistence plateau of DPPC/NBD-PC monolayer was typically observed in the isotherm at molecular areas between 0.65 and 0.50 nm 2 /molecule.…”

“…Especially, the phospholipid monolayers were used as models for domains of like lipids found at the outer surface of a membrane bilayer. 1,2,[6][7][8][9] Although the Langmuir-Blodgett (LB) technique has been used for decades, the applications of this method have been frustrated by the defects of LB films ranging from pinholes to larger scale reorganization of the layers. These defects can be induced by various factors.…”

“…10 Talham et al 7 showed that phospholipid phase boundaries played an important role in CaOxa precipitation when biphasic lipid monolayers were held at the air-water interface over a metastable CaOxa subphase. COM crystals were shown to preferentially form at phase boundaries between liquid condensed (LC) and liquid-expanded (LE) phases.…”

Influence of Bacillus subtilis on the growth of calcium oxalate

“…To better understand the role of organic matrices in urinary stone formation, Langmuir monolayers [3][4], vesicles [5], biomoleculars [6], etc., were used to induce the nucleation and growth of CaOx crystals. Our groups recently studied crystal growth of CaOx in reverse microemulsion of p-octyl polyethylene glycol phenylether (OP)/iso-octyl alcohol (IOA)/cydohexane/water containing different kinds of amino acids, and found that amino acids, pH values and surfactants can influence the formation of CaOx crystal [7].…”