Zhanlan Yang

Cesium cholate: determination of X-ray crystal structure indicates participation of the ring hydroxyl groups in metal binding.

The crystal structure of cesium cholate, C(24)H(36)(OH)(3) COOCs has been determined with three-dimensional X-ray diffractometer data. It crystallized in the monoclinic space group P2(1) with unit-cell dimensions a = 11.543(5) A, b = 8.614(3) A, and c = 12.662(5) A, beta(deg) = 107.95(2), V = 1197.7 A(3) and Z = 2. The atomic parameters were refined to a final r = 0.0269 and R(omega) = 0.0280 for 2342 observed reflections. Each Cs(+) is coordinated to 7 oxygen atoms from 5 different cholate anions with Cs-O distances ranging from 2.957(4) A to 3.678(5) A. In this crystal, 5 cholates are coordinated with 1 Cs(+), and 5 Cs(+) are coordinated with 1 cholate anion. Carboxyl and all the 3 ring hydroxyl groups of cholate anion participate in binding to Cs(+) simultaneously, and there is no water molecule coordinated with the Cs(+). The pattern of successive rows arranged with polar (p) and non-polar (n) faces in apposition leads to the formation of a sandwich sheet structure with polar and non-polar channels. The Cs ions lie within the polar interior of the sandwich. The H-bond network is reorganized in forming cesium cholate from cholic acid. All the oxygen atoms in cholate anion are involved in H-bonding reciprocally or with water molecules to form an extensive 3-dimensional network of H-bonds. Compared with cholic acid and other similar type of steroids, the coordination structure and H-bonding of Cs cholate crystal are distinct.

The interaction of Co2+ ions and sodium deoxycholate micelles

Abstract To mimic the interaction between divalent metal ions and bile slats in vivo, two groups of coordination complex compounds, crystalline and gel-like, were synthesized in vitro by mixing the aqueous solutions of CoCl 2 with sodium deoxycholate (NaDC) at various concentrations. Structures and compositions of the compounds were investigated using FT-IR, EXAFS, XRD as well as elemental and ICP analysis, respectively. Then the interaction of Co 2+ with deoxycholate in solution was observed by laser light scattering (LLS), Transmission electronic microscope techniques and ICP analysis. Conclusions are (1) the crystalline complexes, Co (DC) 2 ·3H 2 O were obtained by reaction of Co 2+ with mono-molecules of NaDC, and the gel-like complexes, Na n Co m (DC) n +2 m formed by reaction of Co 2+ with NaDC micelles. The gel-like complexes exhibit the non-stoichiometric character; (2) the coordination structures of carboxyl groups with Co 2+ were different between the crystalline and gel-like complexes. In Co(DC) 2 ·3H 2 O complex, the carboxyl groups of deoxycholate coordinated with Co 2+ in chelating and pseudo-chelating modes, but that in bridge mode in the case of Na n Co m (DC) n +2 m complexes. The non-stoichiometric complexes of Na n Co m (DC) n +2 m are formed with a macromolecular structure through the Co 2+ bridges; (3) NaDC can increase the solubility of Co(DC) 2 ·3H 2 O in aqueous solution, and larger micelles (30–80 nm diameter) formed in the supernate. It is a mixed micelle formed by Co 2+ ions bridges connecting with NaDC simple micelles. So these micelles are a new kind of micelle containing two kinds of metal ions; (4) these results are in agreement with those formed under physiological conditions in that the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. An ideal model of the interaction between Co 2+ and bile salts in vivo has been proposed.

The interaction of Cu2 + ions and NaDC micelles.

By mixing an aqueous solution of CuCl2 with an NaDC aqueous solution of various concentration and initial molar ratio, seven coordinated samples with distinct appearances and characters were obtained. Their structures and components were investigated by FT-IR spectroscopy, EXAFS (the extended X-ray absorption fine structure), thermal analysis, X-ray diffraction, laser light scattering, TEM (transmission electron micrograph), element analysis and ICP (inductively coupled plasma) analysis. The following conclusions were given: (1) The complexes of Cu2+-NaDC with distinct appearances and properties were synthesized. (2) After Cu(DC)2 dissolved in NaDC aqueous solution, larger micelles (30-90 nm diameter) formed in the supernate, it is a mixed micelle with Cu(DC)2 and NaDC. So these micelles are a new kind of micelle containing two kinds of metal ions. This is a new result using metal ions as bridges to form micelle. (3) According to the different concentration of Cu2+ to NaDC, the complexes formed as gel or poly-crystals. Both the composition of gel complexes and the coordination structure of carboxyl groups with metal ions varied with the initial molar ratio of Cu2+ to Na+. The gel complexes exhibits the non-stoichiometric character. (4) These results are in agreement with physiological condition. All the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. We can suggest an ideal model of the interaction between Cu2+ and bile salts in vivo.

Progress in the study on the composition and formation mechanism of gallstone

Our serial studies from {dy1970}s on chemical composition, structure determination and formation mechanism of gallstones were reviewed. The chemical component investigation of brown-pigment gallstone demonstrated that it consists of macromolecules such as proteins, glycoproteins, polysaccharides, bilirubin polymers and pigment polymers, and biomolecules such as cholesterol, bile salts, calcium salts of carbonate, phosphate, fatty acids and bilirubinate as well as various metal ions. The binding of metal ions with bile salts and bilirubin plays important roles in gallstone formation, i.e., calcium bilirubinate complex is the major constitute of brown-pigment gallstones, and copper bilirubinate complex is critical in the black color appearance of black-pigment gallstone. The cross section of many gallstones exhibits a concentric ring structure composed of various small particles with a fractal character. This is nonlinear phenomenon in gallstone formation. Atypical model system of metal ions-deoxycholate (or cholate)-gel was chosen to mimic an in vitro pattern formation system. The experimental results suggested that a nonlinear scientific concept should be considered in understanding gallstone formation. Minor changes in the chemical composition and/or the microenvironment may lead to very different precipitate patterns with a variety of shapes, colors, appearances, and structures. A new model was suggested that periodical templets of periodical and fractal patterns were formed in the initial stage, then the spatio-temporal patterns grew gradually on it. Furthermore, the interaction between divalent metal ions and bile saltsin vitro was investigated, and the results indicated that non-stoichiometric M(DC)2-NaDC mixed complexes with mixed micelles structure can be formed in physiological condition.

Preparation and Characterization of Lanthanum Carbonate Octahydrate for the Treatment of Hyperphosphatemia

We proposed a new approach to prepare lanthanum carbonate via reactions between lanthanum chloride and NaHCO3. In the reaction, small amount of NaHCO3 solution was firstly added to the acidic lanthanum chloride solution to generate lanthanum carbonate nuclei and then NaHCO3 is added to the lanthanum chloride at a constant speed. This approach makes both precipitation reaction and neutralization reaction take place simultaneously. Consequently, lanthanum carbonate is produced at low pH environment (pH below 4.0) so that the risk of generating lanthanum carbonate hydroxide is reduced. The product of the above reaction is validated by EDTA titration, elemental analysis, and XRD characterization. In addition, we established a FTIR spectroscopic method to identify La(OH)CO3 from La2(CO3)2·8H2O. Lanthanum carbonate exhibits considerable ability to bind phosphate.

Development of narrow-band TLC plates for TLC/FTIR analysis

The present paper focuses on the development of narrow-band thin-layer chromatography (TLC) coupled with Fourier transform Infrared spectroscopy (FTIR) technique. We adopted a new method to prepare a narrow-band TLC plate by using silver iodide as stationary phase. The narrow-band TLC plate exhibits a variety of advantages: the preparation time is about 20 minutes, while 3–7 days are needed to prepare a common TLC plate suitable for TLC/FTIR analysis by using “settlement volatilization method”. Furthermore, the usage of stationary phase in narrow-band TLC plates decreases by about one order of magnitude in comparison with that of common TLC plates. This is very important for an expensive stationary phase such as silver iodide. In addition, experimental results of TLC/FTIR analysis on mixed samples containing rhodamine B and bromocresol green demonstrate the detection limit significantly improves by using the narrow-band TLC technique.

The interaction between amino acids and metal ions (I). The FT-IR spectroscopic study of the binding between d,l-homocysteic acid and alkali metal ions

D,L-Homocysteic acid (DLH), an amino acid in the mammalian central nervous system, can excite the cerebral activities and has been proposed as an agonist of endogenous glutamate receptor. It contains -NH(3)(+), -COOH and -SO(3)(-) groups, therefore, the interactions between DLH and metal ions may be expected. In the present investigation, the complexes of DLH with NH4(+), Li+, Na+ and K+ at different pH conditions were synthesized and characterized by Fourier transform infrared (FT-IR) spectroscopy. It was concluded that the structures of the complexes prepared at pH 2.6 and 4.0 are similar to each other and the C=O groups are mono-dentate coordination for these complexes. However, the structures of the complexes synthesized at pH 13.0 change considerably from the complexes at pH 2.6 and 4.0, which show that dissociation has occurred in aqueous solution. The four cations coordinate to DLH, which result in the rearrangement of the hydrogen bond network and the skeletal structure change of the ligand.

Using Lanthanum Fluoride Fine Particles as Stationary Phase for Thin-Layer Chromatography/Fourier Transform Infrared Spectroscopy Analysis

While in situ TLC/FTIR technique has tremendous potential in the analysis of complex mixtures, the conventional stationary phase, such as silica gel, used for TLC/FTIR analysis, has strong absorption in IR region and thus brings about severe interference in the obtained FTIR spectra of the separated samples. In this work, we propose to use lanthanum fluoride fine particles as a new stationary phase of a TLC plate. The average size of LaF3 particles is around 100 nm. FTIR spectrum of the LaF3 particles has no interfering absorption. Preliminary TLC experiments show that mixtures of rhodamine B and methylene blue mixture can be successfully separated by this new TLC plate using LaF3 fine particles as a stationary phase. Methylene blue and rhodamine B from separated spot can be clearly detected by using in situ FTIR spectra.

Influence of La3+ ions on the egg-yolk phosphatidylcholine and sodium taurocholate self-assemblies in aqueous suspension

In this study, the influence of La3+ on the mixed egg-yolk phosphatidylcholine (EYPC)-sodium taurocholate (TC) aggregates was investigated by using turbidity, quasi-elastic light-scattering (QELS) technique, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). La3+ ions exert different effects on different EYPC-TC aggregates. The EYPC-TC mixed spheroidal micelles are stable in the presence of La3+ ions. The EYPC-TC vesicles are aggregated by the interaction of La3+ with the EYPC phosphate group. Particularly, La3+ causes structural transition of the EYPC-TC mixed disk micelles by changing the colloidal properties of TC. This process includes two steps, destruction of mixed disk micelles and formation of mixed spheroidal micelle. Several intermediate structures such as multi-lamellar vesicles and cylindrical micelles were observed during the transition. The experimental data and analysis in the current study suggest that metal ion is one of the important factors to control the structure of the EYPC-TC self-assemblies. And the possible influence of metal ions on the properties of bile biocolloid has been discussed.

The pressure tunning Raman spectral studies of the bilirubinIXα and neutral calcium bilirubinate at high external pressure

The bilirubinIXalpha and its neutral calcium bilirubinate were studied using Raman spectroscopy at high external pressure. The results showed that the bilirubinIXalpha has two pressure-induced phase transitions (15-18 and 30-36 kbar) and three pressure phase areas. Its pressure sensitivities in the low-pressure phase are very low. It is believed that the four internally hydrogen bonds in bilirubinIXalpha molecule cause the atoms to attract each other tightly in the bilirubinIXalpha molecule. Therefore, the low pressure is not strong enough to shorten the bonds significantly. The pressure sensitivities in the middle-pressure phase are much higher than those in the low-pressure phase, but those in the high-pressure phase are slightly lower than in the middle-pressure phase. There is only one pressure-induced phase transition (25-34 kbar) in the neutral calcium bilirubinate. The pressure sensitivities in the low-pressure phase are higher than those in the high-pressure phase as usually.