Abstract
Using complementary physical-chemical techniques we defined five different crystallization pathways as functions of time (30 days) and increasing lecithin (egg yolk) content in pathophysiologically relevant model biles super-saturated (cholesterol saturation indices, 1.2 - 2.7) by dilution of approximately equal to 29 g/dl bile salt-lecithin-cholesterol micellar solutions. As evidenced by quasi-elastic light-scattering spectroscopy, supersaturation was heralded by the appearance of unilamellar vesicles. With the lowest lecithin contents, arc-like crystals with habit and density (d 1.030 g/mL) consistent with anhydrous cholesterol appeared first and evolved via helical and tubular crystals to form plate-like cholesterol monohydrate crystals (d 1.045 g/mL). With higher lecithin fractions, cholesterol monohydrate crystals appeared earlier than arc and other transitional crystals. With typical physiological lecithin contents, early liquid crystals (d 1.020 g/mL) were followed by cholesterol monohydrate crystals and subsequent appearances of arc and other intermediate crystals. With higher lecithin contents, liquid crystals were followed by cholesterol monohydrate crystals only, and at the highest lecithin mole fractions, liquid crystals appeared that did not generate solid crystals. Added calcium increased solid crystal number in proportion to its concentration (5 - 20 mM) but did not influence appearance times, crystallization pathways, or micellar cholesterol solubilities. Decreases in temperature (37 degrees --> 4 degrees C), total lipid concentration (7.3 --> 2.4 g/dL), and bile salt hydrophobicity (3 alpha, 12 alpha --> 3 alpha, 7 alpha, 12 alpha --> 3 alpha, 7 beta hydroxylated taurine conjugates) progressively shifted all crystallization pathways to lower lecithin contents, retarded crystallization, and decreased micellar cholesterol solubilities. The lecithin content of mother biles decreased markedly during crystallization especially where liquid crystals were a coexisting phase at equilibrium. This systematic study provides a framework for understanding cholesterol crystallization in human and animal biles and for examining factors that influence the kinetics of phase separation.
Highlights
Using complementary physical-chemical techniques we defined five different crystallization pathways as functions of time (30 days) and increasing lecithin content in pathophysiologically relevant model biles supersaturated by dilution of =29 g/dl bile salt-lecithin-cholesterol micellar solutions
By 0.5 h of dilution, the micellar biles had produced unilamellar vesicles as evidenced by an order of magnitude increases in R h values (Fig. 1) and this was confirmed by vitreous ice electron microscopy
In systems that formed stable liquid crystals, (0.4 < L/TC, L/TCDC, and L/mixture of BS (MBS) < 1.0) Quasielastic light-scatteringspectroscopy (QLS) was terminated because of excess turbidity which was earliest at 4°C (Fig. 1)
Summary
Using complementary physical-chemical techniques we defined five different crystallization pathways as functions of time (30 days) and increasing lecithin (egg yolk) content in pathophysiologically relevant model biles supersaturated (cholesterol saturation indices, 1.2-2.7) by dilution of =29 g/dl bile salt-lecithin-cholesterol micellar solutions. 4"C),total lipid concentration (7.3 + 2.4 g/dL), and bile salt hydrophobicity (3a,12a -+ 3a,7a + 3a,7a,12a + 3a,7P hydroxylated taurine conjugates) progressively shifted all crystallization pathways to lower lecithin contents, retarded crystallization, and decreased micellar cholesterol solubilities. Complete mapping of crystallization pathways during cholesterol precipitation from model bile: influence of physical-chemical variables of pathophysiologic relevance and identification of a stable liquid crystallinestate in cold, dilute and hydrophilic bile saltcontaining systems.J. Supplementary key words gallstones phospholipid lecithin liquid crystals crystal habits crystal density phase diagrams microscopy quasi-elasticlight-scattering calcium. Microscopic detection of ChM crystals in human bile was proposed as the ratelimiting step in gallstone formation [2, 3] and is commonlybut erroneouslycalled"nucleation"(2).the overall processes can be subdivided into true
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