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Advanced Materials 07/2011; · 13.88 Impact Factor
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ABSTRACT: To further improve the selectivity and throughput of phosphopeptide analysis for the samples from real-time cell lysates, here we demonstrate a highly efficient method for phosphopeptide enrichment via newly synthesized magnetite microparticles and the concurrent mass spectrometric analysis. The magnetite microparticles show excellent magnetic responsivity and redispersibility for a quick enrichment of those phosphopeptides in solution. The selectivity and sensitivity of magnetite microparticles in phosphopeptide enrichment are first evaluated by a known mixture containing both phosphorylated and nonphosphorylated proteins. Compared with the titanium dioxide-coated magnetic beads commercially available, our magnetite microparticles show a better specificity toward phosphopeptides. The selectively-enriched phosphopeptides from tryptic digests of β-casein can be detected down to 0.4 fmol μl⁻¹, whereas the recovery efficiency is approximately 90% for monophosphopeptides. This magnetite microparticle-based affinity technology with optimized enrichment conditions is then immediately applied to identify all possible phosphorylation sites on a signal protein isolated in real time from a stress-stimulated mammalian cell culture. A large fraction of peptides eluted from the magnetic particle enrichment step were identified and characterized as either single- or multiphosphorylated species by tandem mass spectrometry. With their high efficiency and utility for phosphopeptide enrichment, the magnetite microparticles hold great potential in the phosphoproteomic studies on real-time samples from cell lysates.
Analytical Biochemistry 01/2011; 408(1):19-31. · 3.00 Impact Factor
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ABSTRACT: Highly ordered mesoporous crystalline MoO(2) materials with bicontinuous Ia3d mesostructure were synthesized by using phosphomolybdic acid as a precursor and mesoporous silica KIT-6 as a hard template in a 10% H(2) atmosphere via nanocasting strategy. The prepared mesoporous MoO(2) material shows a typical metallic conductivity with a low resistivity ( approximately 0.01Omega cm at 300 K), which makes it different from all previously reported mesoporous metal oxides materials. Primary test found that mesoporous MoO(2) material exhibits a reversible electrochemical lithium storage capacity as high as 750 mA h g(-1) at C/20 after 30 cycles, rendering it as a promising anode material for lithium ion batteries.
Nano Letters 09/2009; 9(12):4215-20. · 13.20 Impact Factor
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Small 01/2009; 4(12):2166-70. · 8.35 Impact Factor
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ABSTRACT: Magnetic permanently confined micelle arrays (Mag-PCMAs) have been successfully synthesized as sorbents for hydrophobic organic compound (HOC) removal from contaminated media. The synthesis of Mag-PCMAs involves coating a silica/surfactant mesostructured hybrid layer on the negatively charged Fe(3)O(4) microparticles to create a core/shell structure. The surfactant, 3-(trimethoxysily)propyl-octadecyldimethyl-ammonium chloride (TPODAC), has a reactive endgroup -Si(OCH(3))(3) on its hydrophilic groups, which allows the surfactant micelles to permanently anchor on the silica framework through covalent bonding. This unique structural property avoids surfactant loss during application and allows for sorbent regeneration. The isotherms and kinetics of four representative HOCs (atrazine, diuron, naphthalene, and biphenyl) onto Mag-PCMAs were determined, and the regeneration and reusability of Mag-PCMAs for diuron removal was also investigated. As a proof of principle for application of Mag-PCMAs for soil-washing, the use of Mag-PCMAs for removal of diuron from a contaminated soil was also demonstrated. All of the results showed that Mag-PCMAs are reusable sorbents for fast, convenient, and highly efficient removal of HOCs from contaminated media.
Journal of the American Chemical Society 01/2009; 131(1):182-8. · 9.91 Impact Factor
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ABSTRACT: Porous silica materials are attractive for hemorrhage control because of their blood clot promoting surface chemistry, the wide variety of surface topologies and porous structures that can be created, and the potential ability to achieve high loading of therapeutic proteins within the silica support. We show that silica cell-window size variation in the nanometers to tens of nanometers range greatly affects the rate at which blood clots are formed in human plasma, indicating that window sizes in this size range directly impact the accessibility and diffusion of clotting-promoting proteins to and from the interior surfaces and pore volume of mesocellular foams (MCFs). These studies point toward a critical window size at which the clotting speed is minimized and serve as a model for the design of more effective wound-dressing materials. We demonstrate that the clotting times of plasma exposed to MCF materials are dramatically reduced by immobilizing thrombin in the pores of the MCF, validating the utility of enzyme-immobilized mesoporous silicas in biomedical applications.
Langmuir 12/2008; 24(24):14254-60. · 4.19 Impact Factor
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Angewandte Chemie International Edition 11/2008; 47(45):8682-6. · 13.45 Impact Factor
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Advanced Functional Materials 09/2008; 18(19):2956 - 2962. · 10.18 Impact Factor
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ABSTRACT: A "brick-and-mortar" assembly approach for creating porous carbon and carbon/metal oxide fibers on the micron scale with well-defined pore structure and interface is presented. A series of monodisperse silica@polyacrylonitrile (PAN) and silica@metal oxide@PAN core/shell particles were synthesized by emulsion polymerization and assembled into organic-inorganic composite fibers through a simple ice-templating strategy with the assistance of polyvinyl alcohol. Porous carbon and carbon/metal oxide fibers with well-controlled pores and interfaces were created by oxidative stabilization and carbonization of composite fibers followed by removal of silica cores with hydrofluoric acid or concentrated alkali. The pore structure and the carbon/metal oxide interfaces of the fibers impart to the fibers' lightweight and potential applications in catalysis, electrochemical energy, and gas or liquid separations and storage.
Journal of the American Chemical Society 05/2008; 130(15):5034-5. · 9.91 Impact Factor
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ABSTRACT: Molecular assembly enables the formation of material systems with multiple compositions and functions that are structured at the mesoscale (2−50 nm) and beyond. This approach allows structure control through the competitive tuning of bulk and surface interactions to yield new mechanical, catalytic, optoelectronic, biological, and other properties. The molecular-assembly process is governed by the interactions between different components of the assembling system and with their external environment. This review summarizes the fundamental principles of molecular assembly in the synthesis of mesostructured inorganic–organic materials and focuses on recent attempts to utilize external fields (magnetic, electric, or mechanical) and dimensional confinement (in one, two, and three dimensions) to direct the molecular assembly of mesostructured organic–inorganic hybrids with astonishing complexity.
12/2007;
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ABSTRACT: Water-soluble macromolecular chain transfer agents (Macro-CTAs) were developed for the microwave-assisted precipitation polymerization of N-isopropylacrylamide. Two types of Macro-CTAs, amphiphilic (Macro-CTA1) and hydrophilic (Macro-CTA2), were investigated regarding their activity for the facile formation of nanoparticles and double hydrophilic block copolymers by RAFT processes. While both Macro-CTAs functioned as steric stabilization agents, the variation in their surface activity afforded different levels of control over the resulting nanoparticles in the presence of cross-linkers. The cross-linked nanoparticles produced using the amphiphilic Macro-CTA1 were less uniform than those produced using the fully hydrophilic Macro-CTA2. The nanoparticles spontaneously formed core-shell structures with surface functionalities derived from those of the Macro-CTAs. In the absence of cross-linkers, both types of Macro-CTAs showed excellent control over the RAFT precipitation polymerization process with well-defined, double hydrophilic block copolymers being obtained. The power of combining microwave irradiation with RAFT procedures was evident in the high efficiency and high solids content of the polymerization systems. In addition, the "living" nature of the nanoparticles allowed for further copolymerization leading to multiresponsive nanostructured hydrogels containing surface functional groups, which were used for surface bioconjugation.
Journal of the American Chemical Society 12/2007; 129(46):14493-9. · 9.91 Impact Factor
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ABSTRACT: Blood coagulates faster upon contact with polar glasslike surfaces than on nonpolar plastic surfaces; this phenomenon is commonly termed the glass effect. However, the variable hemostatic response that we report here for contact-activated coagulation by different metal oxides, all of which are polar substrates, requires a refinement of this simple polarity model of how inorganic metal oxides activate the intrinsic pathway of blood coagulation. To our knowledge, the role of metal oxide surface charge as determined at the physiological pH and Ca2+ concentration of blood has not been previously investigated. We find that basic oxides with an isoelectric point above the pH of blood are anticoagulant while acidic oxides with an isoelectric point below the pH of blood are procoagulant. Using a thromboelastograph, we find that the onset time for coagulation and rate of coagulation post-initiation depend on both the sign and the magnitude of the initial surface charge density of the metal oxide. This work presents a useful strategy based on a quantifiable material parameter to select metal oxides to elicit a predictable and tunable biological response when they are in contact with blood.
Langmuir 11/2007; 23(22):11233-8. · 4.19 Impact Factor
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ABSTRACT: Mesostructured non-silicate oxides, with well-defined organization on the 2-50 nm size scale, may play a pivotal role in advancing vital disciplines such as catalysis, energy conversion, and biotechnology. Herein, we present selected methodologies for utilizing the sol-gel process, in conjunction with organic-directed assembly, to synthesize a variety of mesostructured oxides. The nature of the inorganic precursor is critical for this process. We discuss the development of general routes for yielding stable, nanoscopic, hydrophilic, inorganic precursors compatible with organic co-assembly. In particular, we highlight the use and characterization of organic-acid-modified transition metal oxide sol-gel precursors that allow for the synthesis and processing of designer mesostructured oxides such as titania hybrids for optical applications and porous multicomponent metal oxides useful for catalysis.
Accounts of Chemical Research 10/2007; 40(9):784-92. · 21.64 Impact Factor
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ABSTRACT: Gold nanorods, nanospheres, and bipyramids have been assembled using glutathione and cysteine into three types of necklace structures, which might be useful for the fabrication of nanoscale photonic, electronic, and optoelectronic devices.
Chemical Communications 06/2007; · 6.17 Impact Factor
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Small 12/2006; 2(11):1261-5. · 8.35 Impact Factor
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ABSTRACT: Gold nanorods and bipyramids have been synthesized using the seed-mediated approach in aqueous cetyltriethylammonium bromide (CTEAB) solutions in the presence of silver nitrate. Gold nanoparticle seeds that are stabilized with either CTEAB or sodium citrate have been used. The use of the CTEAB-stabilized seeds gives gold nanorods in high yield in one step with the longitudinal plasmon wavelength ranging from 750 to 1030 nm, depending on the amount of the seeds. The longitudinal plasmon wavelength can be extended to 1100 nm by the use of a two-step growth method. The growth of gold nanorods in CTEAB solutions takes 5-10 h, more than 5 times slower than that in cetyltrimethylammonium bromide solutions at the same concentration of surfactants. The use of the citrate-stabilized seeds gives both gold bipyramids and a small percentage of gold nanorods. The longitudinal plasmon wavelength of the bipyramids is tunable from 700 to 1100 nm by varying the amount of the citrate-stabilized seeds. The growth of gold bipyramids takes more than 1 day. Transmission electron microscopy characterizations reveal that the gold nanorods grown from both types of gold nanoparticle seeds are single-crystalline and that the gold bipyramids are penta-twinned.
The Journal of Physical Chemistry B 09/2006; 110(33):16377-83. · 3.70 Impact Factor
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ABSTRACT: The tunable in vitro blood clotting activity of high-surface-area hemostatic bioactive glass is evaluated by Thromboelastograph, a clinical instrument for quantifying changes in blood during coagulation. The hemostatic trends associated with hemostatic bioactive glass and a new preparation of spherical hemostatic bioactive glass, along with similar Si- and Ca-containing oxides, are described and related to Si:Ca ratios, Ca2+ availability and coordination environment, porosity, DeltaHHydration, and surface area. Hemostatic bioactive glass is a new material with an excellent efficacy for inducing hemostasis and is chemically distinct from the traditional bioglass employed for bone growth.
Journal of the American Chemical Society 08/2006; 128(26):8384-5. · 9.91 Impact Factor
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ABSTRACT: Gold nanorods (NRs) have received much attention due to their size-dependent surface plasmon-related optical properties. A seed-mediated approach has recently been developed for the synthesis of Au NRs with varying length-to-diameter aspect ratios. With the introduction of silver ions in the growth solution, Au NRs of narrow size distributions can be produced in high yields. Herein we describe an approach for the continuous and selective shortening of Au NRs synthesized by the silver ion-assisted seed-mediated method through oxidation with environmentally benign oxygen at slightly elevated temperatures. UV-visible extinction measurements indicate that the longitudinal surface plasmon band of Au NRs decreases in intensity and blue-shifts as a function of the oxidation time. Transmission electron microscopy (TEM) imaging shows that the length of Au NRs decreases with oxidation and their diameter stays almost constant, which suggests that oxidation starts at the ends of Au NRs. The size distributions of shortened Au NRs are similar to those of starting NRs. Further oxidation transforms Au NRs into nanospheres, which become smaller in diameter and finally completely disappear. It has been found that the oxidation rate of Au NRs can be controlled by temperature and acid concentration. Furthermore, high-resolution TEM studies reveal that Au NRs synthesized by the silver ion-assisted seed-mediated method are single crystalline and they stay single crystalline during oxidation. It is expected that Au NRs of any aspect ratio with narrow size distributions within the limit of that possessed by starting NRs can be produced by this mild oxidation approach.
Journal of the American Chemical Society 05/2006; 128(16):5352-3. · 9.91 Impact Factor
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ABSTRACT: Micropatterning has important applications in a wide range of areas, including microelectronics, optics, information displays, and biotechnology. Herein, we describe a vesicle-array templating approach for the generation of surface patterns of micrometer-sized silica features on the surfaces of silica monoliths. The approach makes use of tetraethyl orthosilicate as silica precursor, a poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) triblock copolymer, EO2PO16EO2, as surfactants, and water, ethanol, and dimethylformamide as solvents. The morphological shapes of produced silica features are synthetically controlled through varying the sequence of silica precursor hydrolysis, vesicle formation, and silica condensation. Prehydrolysis of the silica precursor, before being mixed with the copolymer, gives hollow convex protrusions. Direct mixing of the silica precursor and the copolymer produces concave depressions. An increase in the amount of water in the mixture solution without prehydrolysis of the silica precursor results in hierarchical patterns of larger concave depressions attached with smaller convex protrusions. It has further been demonstrated that concave surface patterns can function as microlens arrays that are capable of producing numerous optical images from a common object.
Journal of the American Chemical Society 08/2005; 127(29):10154-5. · 9.91 Impact Factor
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ABSTRACT: A one-step nanocasting route has been demonstrated to prepare highly ordered single-crystal indium oxide nanowire (IONW) arrays with mesostructured frameworks. Unlike the reported multistep nanocasting process (synthesis of mesoporous materials, and then incorporation of precursors and formation of inorganic frameworks), a highly ordered mesostructured surfactant-silica monolith with low external surface serves as both the template and the reducing agent and makes the formation of single-crystal IONWs in its channels easily in one step by using normal In(NO(3))(3) as an inorganic precursor. After silica is removed, highly ordered uniform single-crystal IONW arrays with hexagonal (p6mm) or cubic (Ia3d) mesostructures are derived. These new materials are studied by XRD, SEM, TEM, N(2) adsoption, and UV spectrum. Furthermore, this one-step nanocasting synthesis route is a generalized method and can be used to synthesized a highly ordered mesoporous silica monolith with metal oxide nanocrystals in its channels. To the best of our knowledge, this is the first report of a single crystalline mesostructured In(2)O(3) framework.
Journal of the American Chemical Society 05/2003; 125(16):4724-5. · 9.91 Impact Factor
