Heavy-metal remediation by a fungus as a means of production of lead and cadmium carbonate crystals

We show here that reaction of the fungus, Fusarium oxysporum, with the aqueous heavy-metal ions Pb2+ and Cd2+ results in the one-step formation of the corresponding metal carbonates. The metal carbonates are formed by reaction of the heavy-metal ions with CO2 produced by the fungus during metabolism and thus provide a completely biological method for production of crystals of metal carbonates. The PbCO3 and CdCO3 crystals thus produced have interesting morphologies that are shown to arise because of interaction of the growing crystals with specific proteins secreted by the fungus during reaction. An additional advantage of this approach is that the reaction leads to detoxification of the aqueous solution and could have immense potential for bioremediation of heavy metals. Under conditions of this study, the metal ions are not toxic to the fungus, which readily grows after exposure to the metal ions.     

Biosynthesis of CaCO3 crystals of complex morphology using a fungus and an actinomycete

The biosynthesis of CaCO3 by reaction of aqueous Ca2+ ions with a fungus, Fusarium sp., and an actinomycete, Rhodococcus sp. (both plant organisms), is described. In the case of the fungus, cruciform-shaped calcite crystals are obtained (SEM picture A) while the actinomycete yielded the unstable polymorph of CaCO3, vaterite (SEM picture B). Specific proteins secreted by the microorganisms are responsible for the morphology and crystallography control observed. A highlight of this approach is that the microorganisms also provide CO2 for reaction with the Ca2+ ions, making the crystals completely biogenic.     

Synthesis of hydroxyapatite crystals using amino acid-capped gold nanoparticles as a scaffold

Inorganic composites are of special interest for biomedical applications such as in dental and bone implants wherein the ability to modulate the morphology and size of the inorganic crystals is important. One interesting possibility to control the size of inorganic crystals is to grow them on nanoparticles. We report here the use of surface-modified gold nanoparticles as templates for the growth of hydroxyapatite crystals. Crystal growth is promoted by a monolayer of aspartic acid bound to the surface of the gold nanoparticles; the carboxylate ions in aspartic acid are excellent binging sites for Ca(2+) ions. Isothermal titration calorimetry studies of Ca(2+) ion binding with aspartic acid-capped gold nanoparticles indicates that the process is entropically driven and that screening of the negative charge by the metal ions leads to their aggregation. The aggregates of gold nanoparticles are believed to be responsible for assembly of the platelike hydroxyapatite crystals into quasi-spherical superstructures. Control experiments using uncapped gold nanoparticles and pure aspartic acid indicate that the amino acid bound to the nanogold surface plays a key role in inducing and directing hydroxyapatite crystal growth.     

Ligand-induced reorganization and assembly in synthetic lipid membranes

Membrane targetting of soluble ligands accompanied by assembly of membrane components into functional superstructures underlies biological signal transduction and a variety of other processes ranging from blood coagulation to biomineralization. Protein or lipid components provide the interactions required for targetting and specific orientation of bound molecules; the membrane's fluidity allows reorganization and sampling of intermolecular contacts required for assembly into superstructures. We are developing synthetic membrane-based recognition systems capable of reproducing important features of biological targetting and assembly. Systems such as these may open up new routes to controlling molecular architecture in materials and devices. Specially designed metal-chelating receptor/reporter lipids have been used to study lipid reorganization induced by binding of metal-complexing ligands. Proteins and peptides are targetted to the Cu²⁺- and Ni²⁺-complexing lipids via coordination interactions with surface histidines. Binding and assembly of multivalent ligands are accompanied by reorganization of the lipid receptors, as measured by fluorescence spectroscopy and fluorescence microscopy. Coordination interactions between protein and chelating lipid components can be used for direct assembly into superstructures such as patterned lipid monolayers and two-dimensional protein crystals.     

A selective fluorescent sensor for detecting lead in living cells

We present the synthesis, properties, and biological applications of Leadfluor-1 (LF1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively imaging Pb2+ in aqueous solution and in living cells. LF1 combines a fluorescein chromophore and a pseudocrown receptor to provide good selectivity for Pb2+ over a range of biologically and environmentally relevant metal ions in aqueous solution, with sensitivity to parts per billion EPA limits for allowable lead in drinking water. In addition to these attributes, imaging experiments further show that LF1 is the first small-molecule reagent that can be delivered into living cells and report changes in intracellular Pb2+ levels.     

Nonclassical crystallization: mesocrystals and morphology change of CaCO3 crystals in the presence of a polyelectrolyte additive

Crystallization of calcite from differently concentrated calcium chloride solutions by the CO2 gas diffusion technique in the presence of polystyrene sulfonate yields crystal superstructures with unusual morphology. From the typical calcite rhombohedra as a starting situation, the morphology can be systematically varied via rounded edges and truncated triangles to finally concavely bended lens-like superstructures. Although these "crystals" are apparently well-faceted in light microscopy, electron microscopy analysis and BET reveal that the structures are highly porous and are composed of almost perfectly 3D-aligned calcite nanocrystals scaffolded to the final, partly nicely curved superstructures. At high supersaturations, superstructures with changed symmetry indicative of dipolar interaction potentials between the building blocks are found. The present model case also gives evidence for the importance of nonclassical, mesoscopic processes in crystallization in general.     

Rapid synthesis of Au, Ag, and bimetallic Au core-Ag shell nanoparticles using Neem (Azadirachta indica) leaf broth

We report on the use of Neem (Azadirachta indica) leaf broth in the extracellular synthesis of pure metallic silver and gold nanoparticles and bimetallic Au/Ag nanoparticles. On treatment of aqueous solutions of silver nitrate and chloroauric acid with Neem leaf extract, the rapid formation of stable silver and gold nanoparticles at high concentrations is observed to occur. The silver and gold nanoparticles are polydisperse, with a large percentage of gold particles exhibiting an interesting flat, platelike morphology. Competitive reduction of Au3+ and Ag+ ions present simultaneously in solution during exposure to Neem leaf extract leads to the synthesis of bimetallic Au core-Ag shell nanoparticles in solution. Transmission electron microscopy revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core-shell structure. The rates of reduction of the metal ions by Neem leaf extract are much faster than those observed by us in our earlier studies using microorganisms such as fungi, highlighting the possibility that nanoparticle biological synthesis methodologies will achieve rates of synthesis comparable to those of chemical methods.     

Enzyme mediated extracellular synthesis of CdS nanoparticles by the fungus,Fusarium oxysporum

The biosynthesis of Q-state CdS nanoparticles by reaction of aqueous CdSO4 solution with the fungus, Fusarium oxysporum, is demonstrated. Nanoparticle formation proceeds by release of sulfate reductase enzymes by the fungus, conversion of sulfate ions to sulfide ions that subsequently react with aqueous Cd2+ ions to yield highly stable CdS nanoparticles. Elucidation of an enzymatic pathway using fungi opens up the exciting possibility of developing a rational, biosynthesis strategy for nanomaterials over a range of chemical compositions which is currently not possible.     

A selective turn-on fluorescent sensor for imaging copper in living cells

We present the synthesis, properties, and biological applications of Coppersensor-1 (CS1), a new water-soluble, turn-on fluorescent sensor for intracellular imaging of copper in living biological samples. CS1 utilizes a BODIPY reporter and thioether-rich receptor to provide high selectivity and sensitivity for Cu+ over other biologically relevant metal ions, including Cu2+, in aqueous solution. This BODIPY-based probe is the first Cu+-responsive sensor with visible excitation and emission profiles and gives a 10-fold turn-on response for detecting this ion. Confocal microscopy experiments further establish that CS1 is membrane-permeable and can successfully monitor intracellular Cu+ levels within living cells.     

Polymer-controlled crystallization of zinc oxide hexagonal nanorings and disks

In this study, we have developed a novel route to the synthesis of ZnO nanorings, disks, and diskoidlike crystals on a large scale by a facile solution-based method by using polymers as crystal growth modifiers. The crystals precipitated with polyacrylamide (PAM) as the additive show ringlike morphology. A possible growth mechanism of the ZnO nanostructures based on typical polymer-crystals interactions in a mild aqueous solution is given. The polymer contains in the side chain a large number of amide ligands that are able to coordinate with Zn(2+) ions, that is, the otherwise just weakly exposed (001) face, leading to a lowering of surface energy and inhibition of growth along this direction and the formation of ringlike morphologies. While in the presence of carboxyl-functionalized polyacrylamide (PAM-COOH), nearly monodispersed disklike crystals were observed and finally evolved into diskoidlike microstructures with the reaction time prolonged. Polymer-directed crystal growth and mediated self-assembly of nanocrystals may provide promising routes to rational synthesis of various ordered inorganic and inorganic-organic hybrid materials with complex form and structural specialization.     

NMR, UV-vis and CD study on the interaction of pradimicin BMY-28864 with divalent cations of alkaline earth metal

In order to clarify the mechanism of the calcium-activated anti-fungal action of pradimicin derivatives, we investigated the compatibility of four divalent metal cations, Ca2+, Mg2+, Sr2+ and Ba2+, when combined with pradimicin BMY-28864 in an aqueous solution. The 1H NMR studies suggest that all the tested cations can induce a chemical exchange between two types of aggregation of BMY-28864 in an aqueous solution. The exchange rate, however, varies according to the cation species. In descending order they are: Ba2+ > Sr2+ > Ca2+ > Mg2+. The differences in the binding ability of BMY-28864 to the cations and the solubility of the chloride salts are explained by the electronegativity of these cations. The UV-Vis and CD spectra of these solutions show isosbestic points that correspond to an exchange process in the cations' binding to BMY-28864. The results provide experimental support for the hypothesis that there is a common mechanism underlying their cations interactions with the antibiotic. The CD study also provided evidence about the stoichiometric relation of the divalent metal ions to the antibiotic, 1:2, which was obtained by NMR analyses.     

Differences on the conversion of celestite in solutions bearing monovalent ions under hydrothermal conditions

The replacement of SO₄²⁻ ions by monovalent ions in mineral SrSO₄ crystals was investigated under hydrothermal conditions by using aqueous solutions bearing F⁻ and OH⁻ ions. Experiments were conducted at various temperatures (150-250 °C) for different reaction intervals (1-96 h), with M⁻/SO₄²⁻ molar ratios of 1, 5 and 10, where M⁻=F⁻ or OH⁻. The celestite crystals were completely converted into SrF₂ crystals, at 200 °C using a F⁻/SO₄²⁻ molar ratio=5 for 24 h. The morphology of the converted SrF₂ crystals indicated that the heteroionic conversion proceeded by a pseudomorphic replacement process, because the transformed crystals maintained their original shape and dimensions. In contrast, the SrSO₄ crystals were instantaneously converted into the Sr(OH)₂ phase by a bulk dissolution-recrystallization mechanism, resulting in the formation of large transparent acicular Sr(OH)₂ crystals. The differences on the conversion process are mainly associated with the chemical interaction between the mineral crystal and the hydrothermal fluid. In addition, the chemical stability of the converted phase with low solubility is also essential for the heteroionic conversion to proceed by the pseudomorphic replacement process.     

水溶液中Mn2+对硫化锌纳米粒子形貌的调控作用

利用硫代乙酰胺在水溶液中缓慢释放的S2-与Zn2+反应制备了ZnS纳米颗粒,ZnS纳米颗粒沉积吸附在3-磺酸基丙基三甲氧基硅烷自组装单层膜上。 实验发现,溶液中添加少量Mn2+,可以显著影响ZnS纳米颗粒的形貌,对ZnS纳米晶的生长方向也有重要影响。 EDS和XRD谱证实Mn2+并没有掺杂到纳米颗粒中去。 这为纳米粒子形貌的调控提供了新途径。 并对ZnS的形成过程进行了探讨,并提出了可能的影响纳米材料形貌的机制。     

多种金属离子对一株双齿相手蟹肠道共生真菌生长代谢影响的研究

对一株双齿相手蟹肠道共生真菌Sporothrixsp．（ZJSEF-7）,测定了12种金属离子对该菌生长代谢的影响。结果表明,Fe^3＋、K^＋、Mn^2＋、Mg^2＋、Ca^2＋和Sb^3＋可明显促进菌体的生长;Cu^2＋、Sn^2＋和Pb^2＋对菌体生长没有明显的影响;Fe^2＋对菌体生长有强的抑制作用;Al^3＋和Zn^2＋完全抑制菌体生长。相手蟹共生菌对部分重金属显示了一定的抗性和强的化学防御功能,深入研究其作用机制,将有助于了解相手蟹共生菌的生物学本质及其生态学作用,对于保护红树林生态环境具有重要的意义。     

双模板体系中多级结构碳酸钡晶体的控制合成

在用细乳液聚合法制备聚合物微球的基础上,以此聚合物形成的不溶性自组装膜与可溶性的修饰剂聚丙烯酰胺组成的双模板为三维聚合物模板体系,成功完成了多孔、刺球等具有复杂多级结构碳酸钡晶体的制备.实验过程中发现,调节双模板的组成可精确调控碳酸钡晶体的成核与生长.同时,多孔碳酸钡晶体为典型的大孔材料,孔径为103.4 rm,BET...     

Immobilization of biogenic gold nanoparticles in thermally evaporated fatty acid and amine thin films

We have recently demonstrated the biological synthesis of gold nanoparticles by the reduction of aqueous chloroaurate ions by the fungus Fusarium oxysporum and with extract of geranium (Pelargonium graveolens) leaf. In this paper, we demonstrate the immobilization of biogenic gold nanoparticles in lipid thin films deposited by thermal evaporation. The charge on the gold nanoparticles synthesized by both the fungus and the geranium plant extract is used to facilitate their immobilization in both anionic and cationic lipid thin films. A rough estimate of the isoelectric point of the proteins capping the gold nanoparticles synthesized using the fungus could be made by pH-dependent microgravimetry studies of the immobilization process. An interesting size and shape selectivity in the immobilized gold nanoparticles is observed in the lipid thin films. The biogenic gold nanoparticle-lipid composite films were characterized using quartz crystal microgravimetry, UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy.     

Sr[C2(COO)2]: the first anhydrous salt of acetylenedicarboxylic acid

Single crystals of Sr[C(2)(COO)(2)] were formed at the phase boundary of an aqueous silica gel that contained acetylenedicarboxylic acid and an aqueous solution of SrCl(2). The crystal structure (I4(1)/amd, Z=4) shows a diamond-like topology, with the strontium ions in an eightfold co-ordination by the oxygen atoms of six carboxylate ligands with two of them co-ordinating in a chelating-type bidentate mode. As each oxygen atom of the carboxylate groups is involved in both a chelating-type bidentate and unidentate co-ordination and, therefore, bridging two strontium atoms, a three-dimensional framework results. Sr[C(2)(COO)(2)] exhibits a surprising thermal stability. In air decomposition starts at about 720 K and in an argon atmosphere around 750 K. This decomposition is accompanied by a mass loss of approximately 12 %, which is probably due to the loss of one CO molecule. The resulting residue is amorphous to X-rays. A small negative thermal expansion is found between 30 and 280 K, whereas between room temperature and 573 K almost no thermal expansion is observed. Single-crystal investigations at different temperatures show a strong "guitar string" vibration of the oxygen atom perpendicular to the contacts to the strontium atoms; this could be responsible for the thermal expansion behaviour.     

Room temperature antiferromagnetic order in the Mn(II) Oxide 4H-Ba(0.5)Sr(0.5)MnO(2+delta)

The synthesis of the Mn(II) phase 4H-Ba(0.5)Sr(0.5)MnO(2+delta) via the topotactic reduction of 4H-Ba(0.5)Sr(0.5)MnO(3-x) with the novel reducing agent LiH, is described. Neutron powder diffraction data show that oxide ions are deintercalated from the host structure in a disordered manner to yield "tetrahedral" MnO(4) coordination sites. Magnetic susceptibility and neutron powder diffraction data show that the title phase adopts a canted antiferromagnetically ordered state below T(N) = 355K, consistent with the strong magnetic coupling expected between d(5) centers.     

1-乙酰基-3-(2-羟基-4,6-二甲氧基苯基)-5-苯基-2-吡唑啉的合成及锌离子探针的研究

设计合成了1-乙酰基-3-(2-羟基-4,6-二甲氧基苯基)-5-苯基-2-吡唑啉(4), 测试了其紫外光谱和荧光光谱, 研究了其对锌离子的选择性识别作用. 结果表明, 化合物4作为锌离子荧光探针, 受常见离子的干扰较小, 对于锌离子有着较高的选择性和较低的检出限.     

Phenol solubilization in aqueous Pluronic® solutions: investigating the micellar growth and interaction as a function of Pluronic® composition

Regular one-dimensional (1D) parallel chains composed of CdS nanoparticles with cubic zinc blende crystal structure were prepared at the air/water interface via one-step synthesis and assembly process. These nanostructures were produced through an interfacial reaction between Cd(2+) ions in the aqueous solution of cadmium acetate and H(2)S in the gaseous phase under Langmuir monolayers of 10,12-pentacosadiynoic acid (PDA). It was demonstrated that PDA molecules self-assembled into parallelly aligned linear supermolecules at the air/water interface with the aid of π-π interactions and acted as templates for the formation of the superstructures. The experimental conditions including temperature and reaction time have great influences on the superstructure formation and the parameters of the parallel chains.