Factors involved in the formation of amorphous and crystalline calcium carbonate: a study of an ascidian skeleton.

The majority of invertebrate skeletal tissues are composed of the most stable crystalline polymorphs of CaCO(3), calcite, and/or aragonite. Here we describe a composite skeletal tissue from an ascidian in which amorphous and crystalline calcium carbonate coexist in well-defined domains separated by an organic sheath. Each biogenic mineral phase has a characteristic Mg content (5.9 and 1.7 mol %, respectively) and concentration of intramineral proteins (0.05 and 0.01 wt %, respectively). Macromolecular extracts from various biogenic amorphous calcium carbonate (ACC) skeletons are typically glycoproteins, rich in glutamic acid and hydroxyamino acids. The proteins from the crystalline calcitic phases are aspartate-rich. Macromolecules extracted from biogenic ACC induced the formation of stabilized ACC and/or inhibited crystallization of calcite in vitro. The yield of the synthetic ACC was 15-20%. The presence of Mg facilitated the stabilization of ACC: the protein content in synthetic ACC was 0.12 wt % in the absence of Mg and 0.07 wt % in the presence of Mg (the Mg content in the precipitate was 8.5 mol %). In contrast, the macromolecules extracted from the calcitic layer induced the formation of calcite crystals with modified morphology similar to that expressed by the original biogenic calcite. We suggest that specialized macromolecules and magnesium ions may cooperate in the stabilization of intrinsically unstable amorphous calcium carbonate and in the formation of complex ACC/calcite tissues in vivo.     

Triacontyl modified silica gel as a sorbent for the preconcentration of polycyclic aromatic hydrocarbons in aqueous samples prior to gas chromatographic-mass spectrometry determination

<正>Triacontyl modified silica gel as a sorbent coupled with gas chromatography-mass spectrometry(GC-MS) was developed to determine EPA prior 16 polycyclic aromatic hydrocarbons(PAHs) in water samples.Various parameters of solid-phase extraction such as organic modifier solvent,eluent,sample flow rate and volume were optimized.The developed method was found to yield a linear calibration curve in the concentration range of 0.05-8μg/L with respect to naphthalene,acenaphthylene,acenaphthene and 0.01-8μg/L for dibenz[a,h]anthracene and 0.05-14μg/L for fluorene,phenanthrene,anthracene and 0.01-14μg/L for the rest of analytes.Furthermore,the good accuracy and repeatability of the method made sure the requirements for achieving reliable analysis of PAHs in the environmental water samples,and the recoveries of optimal method were in the range of 80-120%except to higher volatility PAHs.C_(30)-bonded silica was proved to be an efficient sorbent for extraction of high molecular weight PAHs.     

Temperature-sensitive micrometer-thick layers of hyaluronan grafted on microspheres

The giant polyelectrolyte glycosaminoglycan hyaluronan (1-10 MDa) is a major component of the pericellular coat on a variety of cells, where it is an important modulator and mediator of early cell adhesion events. This pericellular layer can reach 5 mum thickness on cells that produce cartilage (chondrocytes), and up to 2 mum on Xenopus laevis kidney epithelial cells (A6). We are interested in generating model systems for the pericellular coat in order to learn more about the structure and function of hyaluronan on biological or artificial surfaces. We report here the synthesis of model systems where a coat of coordinatively cross-linked hyaluronan of up to 2 mum thickness was covalently photografted onto polystyrene microspheres. The hydrated coat was imaged directly by environmental scanning electron microscopy (ESEM) at close to 100% relative humidity. The key feature of the procedure is the reversible reverse-temperature phase transition of hyaluronan induced by trivalent lanthanide cations, which is exploited to achieve sufficient density for grafting of thick layers. The microsphere-grafted coat shows a temperature-dependent swelling when labeled with lanthanide ions (Gd(3+) or Tb(3+)). We directly observed a volume contraction of 20% with increasing temperature between 1 and 11 degrees C by wet-mode ESEM.     

Iridoid glucosides from Allamanda neriifolia

<正>A new iridoid glucoside,allamanoid(1),was isolated from the aerial parts of Allamanda neriifolia,together with three known glucosides,plumieride,protoplumericin,and nicotiflorin.Their structures were elucidated by 1D and 2D spectroscopic analyses, hydrolysis,and comparison with literature data.     

A new dammarane-type triterpene saponin from Gynostemma pentaphyllum

<正>One new dammarane-type triterpene saponin,named(20S)-3β,20,21-trihydroxydammar-24-ene 3-O-[α-L-rhamnopyranosyl- (1→2)][β-D-xylopyranosyl(1→3)]-β-D-glucopyranoside(1),was isolated from the aerial parts of Gynostemma pentaphyllum (Thunb.) Makino.Its structural elucidation was accomplished mainly on the basis of the interrelation of spectroscopic methods, such as IR,HR-TOF-MS,NMR.     

Synthesis,liquid crystalline and luminescent properties of trimeric phenylenevinylene with end-groups of(R)-(+)-2-methylbutyric acid ester

The trimeric phenylenevinylene with the symmetrical chiral end-groups(ChTPV) was synthesized.The liquid crystalline and luminescent properties of the ChTPV have been studied by differential scanning calorimetry(DSC),polarized optical microscopy (POM),absorption and photoluminescence spectra.The results indicated that the ChTPV exhibits mesophase over a wide temperature range and a typical optical texture of smectic phase.In contrast with the spectra of the solution,that of the film showed blue-shift in m...     

An improved synthesis of bis(cyclopentadienone)

<正>An improved strategy for the synthesis of 3,3'-(oxy-p-phenylene)bis(2,4,5-triphenylcyclopentadienone) was developed,which includes three steps:Friedel-Crafts reaction,oxidation and condensation.Importantly,the use of KMnO_4 made the second step simple and efficient,which has potential application to synthesis of bis(cyclopentadienone)s.The course of oxidation has been confirmed by isolated intermediates.     

An organic hydrogel as a matrix for the growth of calcite crystals

The growth of calcite in an aqueous gel of was studied and the appearance of the crystals was found to change over time. Crystals removed from the gel at progressively longer times showed severely affected surfaces resulting from dissolution. If crystals were removed from the gel after 3.5 hours, at which point there were no etch pits, and then placed in either buffer or pure water, etch pits, similar to those observed on crystals that are left in the gel, were observed. Control calcite crystals exposed to similar conditions (water or buffer) show no significant dissolution after equivalent times. A probable cause of the altered dissolution is the non-specific occlusion of gelator aggregates at sites of imperfection. The gel appears to provide a microenvironment in which the molecules that form the matrix also participate in the crystallization. This system allows the study of the unique properties of a gel for influencing the nucleation and growth of inorganic crystals, some of which may be important for better understanding biomineralization.     

N,N,N'''',N''''-四[2-(1-乙基苯并咪唑)甲基]乙二胺及其高氯酸盐的晶体结构

本文通过单晶X-射线衍射法测定了EtEDTB1.4C2H5OH5H2O 1和H4EtEDTB(ClO4)4 C2H5OH 2的晶体结构。晶体学数据如下:1的分子式为C44.8H66.4N10O6.4, Mr = 847.48, 属三斜晶系, 空间群P, a = 11.489 (2), b = 11.866(3), c = 12.002(3) , = 97.47(2), ?= 114.564(13), ?= 114.11(2)? V = 1266.6(5) 3, Z = 1, Dc = 1.111 g/cm3, F(000) = 456, m(MoK? = 0.076 mm-1。共收集衍射数据5207条, 其中独立衍射数据4323条(Rint = 0.0257), 1318条可观测衍射数据(I > 2(I))用于结构计算。结构由直接法解出, 并用全矩阵最小二乘法修正, 最终偏离因子R = 0.0706, wR = 0.1802。分子具有对称中心, 4个苯并咪唑基团围绕中心呈螺旋桨状均匀排布。在1的晶体中, EtEDTB分子通过水和乙醇的氢键相连形成二维网状结构。2的分子式为C44H58Cl4N10O17, Mr = 1140.80, 属单斜晶系, 空间群C2/c, a = 24.260(5), b = 13.040(3), c = 17.680(4) , ?= 97.50(3)? V = 5545.2(2) 3, Z = 4, Dc = 1.366 g/cm3, F(000) = 2384, m(MoK? = 0.289 mm-1。共收集衍射数据12055条, 其中独立衍射数据6360条(Rint = 0.0408), 2875条可观测衍射数据(I > 2(I))用于结构计算。结构由直接法解出, 并用全矩阵最小二乘法修正, 最终偏离因子R = 0.0692