Effects of temperature and sodium carboxylate additives on mineralization of calcium oxalate in silica gel systems

Urolithiasis remains a major medical problem in China, especially in Guangdong Province in the southest of China[1]. A survey in Shenzhen city, the most southern city in China, showed the incidence of renal calculus was 4.87%, being 6.12% in the males and 4.07% in the females[2]. The prevalence of renal calculus has been more as the age advances and in the male population and so was in the less-educated population. The recurrence rate is more than 80%, with a moderate improvement by conventi…     

1, 8-Dihydroxyanthraquinone-Ca(II) Reaction. Spectrofluorimetric Determination of Traces of Ca(II)

Abstract

1, 8-Dihydroxyanthraquinone (1, 8-DHAn) shows a fluorescent reaction with Ca(II) ion in ethanol-water mixtures and ammoniacal medium.

In the present work the 1, 8-DHAn-Ca(II) complex has been studied spectrofluorimetrically. The complex shows two excitation maxima at 485 nm and 495 nm and its emission maximum is centered at 615 nm. A 2:1 (R:C) stoichiometry and a log K_est of 7.38±0.22 for the overall equilibrium have been found for the complex.

A new method for the spectrofluorimetric determination of Ca(II) between 50 and 550 ngml^?1 has been proposed. The interference level of foreign ions has been established.     

L—组氨酸和色氨酸三元体系中稀土（Ⅲ）,钙（Ⅱ）的化学形态

在模拟生理条件下（３７℃,Ｉ＝０．１５ｍｏｌ／ＬＮａＣｌ）,用ｐＨ电位滴定与计算机模拟计算相结合的方法研究了镨（Ⅲ）、钆（Ⅲ）、铽（Ⅲ）、镱（Ⅲ）４ｔｋｈ ｔｑｄ ｆｆｆｆｙｂ ｂｂ ｔ ｑｇｈ （Ⅱ）、锌（Ⅱ）离子在Ｌ－组氨酸、色氨酸三元体系中的化学形态。讨论了稀土（Ⅲ）、钙（Ⅱ）和锌（Ⅱ）的物种分布特点。     

凝胶体系中羧酸对草酸钙结晶的影响

羧酸是泌尿系结石形成的抑制剂。本文采用双扩散法考察凝胶体系中一元羧酸HAc、二元羧酸酒石酸、三元羧酸柠檬酸和四元羧酸EDTA对草酸钙(CaOx)结晶的影响。HAc没有抑制作用。酒石酸和柠檬酸能够改变一水草酸钙(COM)晶体的形貌，并抑制草酸钙晶体二维生长，这种抑制作用随时间的增加而增强。EDTA使COM晶体在长度方向生长更快，而在宽度和厚度上生长更慢。随着结晶温度的降低，形成草酸钙晶体的时间增加，且二水草酸钙(COD)的比例增加。在5℃的低温条件下，添加有二元、三元和四元羧酸的CaOx结晶中，COD成为主要的物相。     

Evaluation of the adsorption affinity of proteins to calcium hydroxyapatites by desorption and pre-adsorption methods

The adsorption affinity of bovine serum albumin (BSA) and lysozyme (LSZ) to calcium hydroxyapatite (CaHAP) was evaluated by desorption and two step adsorption methods. These experiments were carried out at 15°C in a 1×10⁻⁴ mol dm⁻³ KCl solution of pH 6.0. BSA molecules were scarcely desorbed, exhibiting an irreversible adsorption of BSA, though LSZ slightly desorbed. This result supports our previous findings that LSZ adsorbs weakly onto phosphate ions exposed on ac or bc faces of CaHAP while BSA adsorbs strongly onto positively charged sites on ac or bc faces of CaHAP. The amount of adsorbed LSZ was markedly increased by the pre-adsorption of BSA, where LSZ was adsorbed onto BSA-covered CaHAP. On the other hand, the amount of adsorbed BSA was not changed by the pre-adsorption of LSZ. In both pre-adsorption systems it was confirmed by an HPLC method that no protein molecule pre-adsorbed was desorbed after the post-adsorption procedure. Therefore, it was interpreted that the enhancement of adsorption of positively charged LSZ is induced by an electrostatic attractive force through pre-adsorption of negatively charged BSA molecules with a high coverage. However, since the coverage of LSZ onto CaHAP is considerably low, no stimulation of BSA adsorption occurred on the LSZ-covered surface. The formation of double protein adsorbed layers consisting of pre- and post-adsorbed proteins was proposed.     

Calorimetric studies of refractory corundum

Calorimetry has been used in the investigations of calcium aluminate materials produced as a binder for aluminate-corundum composites of high refractoriness. The kinetics and of hydration process was thus characterized and the optimum compositions of initial binders and cement-corundum refractory filler blends could be selected for further tests. The acceleration of heat evolution - the shortening of so-called induction period and relatively high heat output in the presence of corundum was observed. It means the acceleration of hydration process, that is early crystallisation of hydration products and subsequent further dissolution of initial anhydrous aluminate phases. In the presence of fine grained corundum particles these phenomena should be attributed to the nucleating effect of fine corundum particles. This revised version was published online in July 2006 with corrections to the Cover Date.     

Discrimination between Olfactory Receptor Agonists and Non‐agonists

A joint approach combining free‐energy calculations and calcium‐imaging assays on the broadly tuned human 1G1 olfactory receptor is reported. The free energy of binding of ten odorants was computed by means of molecular‐dynamics simulations. This state function allows separating the experimentally determined eight agonists from the two non‐agonists. This study constitutes a proof‐of‐principle for the computational deorphanization of olfactory receptors.     

Calcite Microneedle Arrays Produced by Inorganic Ion‐Assisted Anisotropic Dissolution of Bulk Calcite Crystal

Besides studies on the mineralization process, research on the demineralization of minerals provides another way to understand the crystallization mechanism of biominerals and fabricate crystals with complicated morphologies. The formation of ordered arrays of c‐axis‐oriented calcite microneedles with a tri‐symmetric structure and lengths of more than 20 μm was realized on a large scale for the first time through anisotropic dissolution of calcite substrates in undersaturated aqueous solution in the presence of ammonium salts. The lengths and the aspect ratios of the calcite microneedles can be tuned by simply changing the concentrations of the ammonium salts and the dissolution time. The shape of the transverse cross sections of the calcite microneedles obtained in the presence of NH₄Cl and NH₄Ac is almost regularly triangular. The tri‐symmetric transverse cross‐section geometry of the calcite microneedles could be attributed to the tri‐symmetric feature of rhombohedral calcite atomic structures, the synergetic interactions between electrostatic interaction of ammonium ions and dangling surface carbonate groups, and the ion incorporation of halide ions.     

Halide‐Free Diarylcalcium Complexes—Syntheses,Structures, and Stability

A general procedure was developed for the synthesis of diarylcalcium complexes by addition of KOtBu to arylcalcium iodides in THF. Intermediate arylcalcium tert‐butanolate dismutates immediately leading to insoluble tert‐butanolate precipitates of calcium. Depending on the steric demand and denticity of additional neutral aliphatic azabases, mononuclear or dinuclear complexes trans‐[Ca(α‐Naph)₂(thf)₄] ( 1 ), [Ca(β‐Naph)₂(thf)₄] ( 2 ), [Ca(Tol)₂(tmeda)]₂ ( 3 ), [Ca(Ph)₂(tmeda)]₂ ( 4 ), [Ca(Ph)₂(pmdta)(thf)] ( 5 ), [Ca(hmteta)(Ph)₂] ( 6 ), and [Ca([18]C‐6)(Ph)₂] ( 7 ) were isolated (Naph=naphthyl; meda=N,N,N′,N′‐tetramethylethylenediamine; pmdta= N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine; hmteta=N,N,N′,N′′,N′′′,N′′′‐hexamethyltriethylenetetramine). The Ca?C bond lengths vary between 250.8 and 263.5 pm, the ipso‐carbon atoms show low‐field‐shifted resonances in the ¹³C NMR spectra.     

Macromolecule Loading into Spherical,Elliptical, Star‐Like and Cubic Calcium Carbonate Carriers

We fabricated calcium carbonate particles with spherical, elliptical, star‐like and cubical morphologies by varying relative salt concentrations and adding ethylene glycol as a solvent to slow down the rate of particle formation. The loading capacity of particles of different isotropic (spherical and cubical) and anisotropic (elliptical and star‐like) geometries is investigated, and the surface area of such carriers is analysed. Potential applications of such drug delivery carriers are highlighted.