Apolipoproteins A-1 and A-2 were purified from human plasma. At concentrations present in human bile these proteins prolonged the nucleation time of cholesterol monohydrate crystals when added to model systems of supersaturated bile. In contrast, apolipoprotein C-3 and other serum proteins did not have this effect. Also, when human gallbladder bile was fractionated by gel filtration chromatography, apolipoproteins A-1 and A-2 were among the proteins present in a fraction of bile enriched in potent inhibitors of cholesterol crystal nucleation. These findings suggest that apolipoproteins A-1 and A-2 in supersaturated human gallbladder bile could inhibit the rate of formation of solid cholesterol crystals and thus help to prevent spontaneous cholesterol gallstone formation in humans.
Resolution of mandelic acid (MA), a racemic compound, is presented in this article using direct crystallization from enantiomeric enriched water solutions. Final crystals with enantiomeric excess (ee) of (R)-MA higher than 96.4% were obtained. Because of the presence of the opposite enantiomer ((S)-MA), it was reported that nucleation and growth of (R)-MA was inhibited at the initial stage of the experiment (Perlberg, et al. Ind. Eng. Chem. Res. 2005, 44, 1012-1020. In order to understand the nucleation and growth kinetics of (R)-MA in the presence of (S)-MA, batch crystallization experiments were performed for controlled linear cooling mode with various operating conditions. Nucleation and growth parameters were then estimated by nonlinear fitting the measured liquid concentrations obtained from the signals of in situ attenuated total reflectance infrared (ATR-IR) spectroscopy and online polarimetry with model predictions. The effects of supersaturation, seed amount, cooling rate, and the presence of opposite enantiomer on the growth and nucleation rate of (R)-MA were discussed.
In
this work the solubility of two polymorphic forms A and B of
erlotinib hydrochloride in isopropanol (IPA) and acetone were determined
by means of high-performance liquid chromatography (HPLC) in the temperature
range from (273.15 to 303.15) K. The experimental data were correlated
with the modified Apelblat equation. In particular, the effect of
the surfactant Tween 80 on the solubility of both polymorphs was studied
as well. The results show that the solubility of both polymorphs generally
increases with the temperature, and polymorph A has a higher solubility
than polymorph B which indicates that polymorph A is the metastable
form. The modified Apelblat equation shows a good agreement with the
experimental data with a percent error less than 3 %. Furthermore,
the solubility of both polymorphs increases in a linear fashion with
increasing the content of Tween 80 in organic solvents, wherein Tween
80 presents a same solubilization capacity to both polymorphs and
a higher solubilization capacity in acetone than in IPA.
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