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Query: UMLS:C1275122 (TEM)
 21,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A de novo peptide that self-assembles into fibrillar structures and serves as a substrate for the cross-linking enzyme tissue transglutaminase was developed (Ac-QQKFQFQFEQQ-Am). Congo red staining, circular dichroism, and FTIR spectroscopy showed that this 11-amino acid peptide produced predominantly beta-sheet structures. TEM with negative staining and quick-freeze deep etch (QFDE) TEM showed that the peptide structures were composed of a highly entangled fibrillar network. These beta-sheet fibrillar nanostructures were then covalently coupled to pendant amine-containing biomolecules via tissue transglutaminase. MALDI-TOF mass spectrometry and HPLC were utilized to monitor the extent of the transglutaminase modification of the peptide, showing that as many as five glutamines in the peptide were reactive via transglutaminase for covalent conjugation. This strategy, based on the post-assembly modification of a self-assembling peptide, has potential applications for tailoring supramolecular structures for drug delivery, tissue engineering, or other biomedical applications.
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PMID:Enzymatic modification of self-assembled peptide structures with tissue transglutaminase. 1286 27

We present a methodology for mass and size dispersity analysis by MALDI-TOF mass spectrometry of lyothermally grown 2.5-3.7 nm ZnS nanocrystals having a Zn blende crystal structure. These results correlate with information obtained by TEM and absorption spectroscopy. The use of MS methods to probe size and size dispersity provides a convenient method to rapidly analyze II-VI materials at the nanoscale. We believe these results represent the first mass spectrometric analysis of size and size dispersities on II-VI nanocrystals.
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PMID:ZnS nanomaterial characterization by MALDI-TOF mass spectrometry. 1292 72

Simple bile acid amide synthesis of lithocholic and deoxycholic acids with 2-aminoethanol and 3-aminopropanol are reported. The structural properties of these amides were examined by NMR spectroscopic, ESI-TOF mass spectral, and X-ray crystallographic methods. The gelation properties of these amides in common organic solvents and in three different water solutions were also investigated using Tyndall effect, SEM, TEM, and optical microscopy. 2-Hydroxyethylamides were found to be effective gelators in chlorinated organic solvents and 3-hydroxypropylamides in aromatic solvents. Both derivatives thicken neutral and acidic water solutions.
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PMID:Bile acid amidoalcohols: simple organogelators. 1555 72

Recombinant human serum albumin (rHSA) clusters have been synthesized and physicochemically characterized. Cross-linking between the Lys groups of the core albumin and a unique Cys-34 of the shell albumins with an N-succinimidyl-6-[3'-(2-pyridyldithio)propionamido]hexanoate produced the structurally defined rHSA trimer and tetramer. MALDI-TOF-MS showed a single peak with the triple and quadruple masses of rHSA. Their molar ellipticities and the isoelectric points (pI = 4.8) are all identical to those of the monomer, suggesting that the essential structures of the albumin units were intact. TEM observations demonstrated a uniform morphology of the rHSA tetramer with a diameter of 20-30 nm. The circulation half-life (tau1/2) of the 125I-labeled rHSA tetramer in rat (5.5 h) was significantly longer than that of the monomer (2.3 h) due to the low ratio of the distribution phase (alpha-phase). A total of 24 and 32 molecules of the synthetic iron(II) porphyrins (FePs) are incorporated into the hydrophobic cavities of the rHSA trimer and tetramer, respectively, producing huge artificial hemoproteins. These albumin-heme clusters can reversibly bind and release O2 under physiological conditions (37 degrees C, pH 7.3) and showed similar O2-binding properties (O2-binding affinity, association and dissociation rate constants) to those of the corresponding monomer. A large volume of O2 can be chemically dissolved into the albumin-heme cluster solutions relative to the monomeric rHSA-FeP when the molar concentration of the albumin scaffold is identical.
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PMID:Albumin clusters: structurally defined protein tetramer and oxygen carrier including thirty-two iron(II) porphyrins. 1628 71

The surface properties of bimetallic Ni-Pt/SiO2 catalysts with variable Ni/Ni + Pt atomic ratio (0.75, 0.50, and 0.25) were studied using N2O decomposition and N2O reduction by hydrogen reactions as probes. Catalysts were prepared by incipient wetness impregnation of the silica support with aqueous solutions of the metal precursors to a total metal loading of 2 wt %. For both model reactions, Pt/SiO2 catalyst was substantially more active than Ni/SiO2 catalyst. Mean particle size by TEM was about the same (in the range 6-8 nm) for all catalysts and truly bimetallic particles (more than 95%) were evidenced by EDS in the Ni-Pt/SiO2 catalysts. CO adsorption on the bimetallic catalysts showed differences in the linear CO absorption band as a function of the Ni/Pt atomic ratio. Bimetallic Ni-Pt/SiO2 catalysts showed, for the N2O decomposition, a catalytic behavior that points out an ensemble-size sensitive behavior for Ni-rich compositions. For the N2O + H2 reaction, the bimetallic catalysts were very active at low temperature. The following activity order at 300 K was observed: Ni75Pt25 > Ni25Pt75 approximately Ni50Pt50 > Pt. TOF values for these catalysts increased 2-5 times compared to the most active reference catalyst (Pt/SiO2). The enhancement of the activity in the Ni75Pt25 bimetallic catalysts is explained in terms of the presence of mixed Ni-Pt ensembles.
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PMID:Surface properties of Ni-Pt/SiO2 catalysts for N2O decomposition and reduction by H2. 1685 Dec 31

Titania represents an important material that has wide applications. The bactericidal efficiency of TiO(2) has been shown to be dependent on the size of the nanoparticles, so it is important to be able to reliably estimate their dimensions. In this study, a stable TiO(2) cluster suspension is produced by the thermal solvent process, and ultrasmall clusters (<1 nm) with different sizes are obtained by size-selection treatment. MALDI-TOF-MS and LDI-TOF-MS are shown to be useful for characterization of these ultrasmall nanoparticles. Peak maxima are found to correlate with nanoparticle size, and the possibility of using these mass spectrometry-based approaches to estimate nanoparticle size is affirmed. The size distributions of TiO(2) nanoparticles obtained from MALDI- and LDI-TOF-MS are in good agreement with parallel TEM observations. Finally, PSD analysis of inorganic nanomaterials is performed and valuable information about the structure of analytes has been obtained.
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PMID:Characterization of synthesized titanium oxide nanoclusters by MALDI-TOF mass spectrometry. 1714 21

A novel class of organic-inorganic hybrids, the so-called cerasomes, which have a bilayer vesicular structure and a silicate surface, has been synthesized by combination of sol-gel reaction and self-assembly of organoalkoxysilanes with a molecular structure analogous to lipids. We have synthesized two cerasome-forming organoalkoxysilanes, N-[N-(3-triethoxysilyl)propylsuccinamoyl]dihexadecylamine (1) and N,N-dihexadecyl-N (alpha)-[6-[(3-triethoxysilyl)propyldimethylammonio]hexanoyl]glycinamide bromide (2), and investigated the synthetic conditions of the cerasomes and their structural characteristics. For the proamphiphilic 1, the cerasome was obtained under restricted pH conditions where acid-catalyzed hydrolysis of the triethoxysilyl moiety proceeded without disturbing the vesicle formation. In contrast, the amphiphilic 2, additionally having a hydrophilic quaternary ammonium group, formed stable dispersions of the cerasome in a wide pH range. The hydrolysis behavior of the triethoxysilyl groups was monitored by (1)H NMR spectroscopy. Morphology of the cerasomes having the liposomal vesicular structure was confirmed by TEM observations. Extent of the development of siloxane networks through condensation among the silanol groups on the cerasome surface was evaluated by using MALDI-TOF-MS spectrometry. Formation of oligomers of the cerasome-forming lipids in the vesicle was clearly confirmed. Due to the siloxane network formation, the cerasome showed remarkably high morphological stability compared with a reference liposome, as evaluated by surfactant dissolution measurements.
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PMID:Preparation and characterization of a novel organic-inorganic nanohybrid "cerasome" formed with a liposomal membrane and silicate surface. 1740 15

In this report, a four-component nanocomposite, trypsin-immobilized polyaniline-coated Fe(3)O(4)/carbon nanotube composite, was synthesized for highly efficient protein digestion. Fe(3)O(4) was deposited by the chemical coprecipitation of Fe(2+) and Fe(3+) in an alkaline solution containing carbon nanotubes (CNTs) to prepare nano-Fe(3)O(4)/CNT composite. Subsequently, polyaniline (PA) was assembled on the Fe(3)O(4)/CNT composite by the in situ polymerization of aniline in the presence of trypsin to obtain trypsin-immobilized PA/Fe(3)O(4)/CNT nanocomposite. The novel 1D superparamagnetic biomaterial has been characterized by TEM, SEM, XRD, and magnetometric analysis. The feasibility and performance of the unique magnetic biomaterial have been demonstrated by the tryptic digestion of bovine serum albumin, myoglobin, and lysozyme within 5min. The digests were identified by MALDI-TOF MS with sequence coverages that were comparable to those obtained from the conventional in-solution tryptic digestion. The present biocomposite offers considerable promise for protein analysis due to its high magnetic responsivity and excellent dispersibility. It can be easily isolated from the digests with the aid of an external magnetic field. Because the enzyme-immobilized nanocomposite can be prepared by a simple two-step deposition approach at low cost, it may find a wide range of biological applications including proteome research.
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PMID:Immobilization of trypsin in polyaniline-coated nano-Fe3O4/carbon nanotube composite for protein digestion. 1835 64

A minisequencing method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) was developed for rapid identification of single nucleotide polymorphisms at bla(TEM) gene codons 104, 164 and 238 associated with extended-spectrum activity on TEM-type beta-lactamases. The method was validated by testing the Escherichia coli and Klebsiella pneumoniae strains possessing the known bla(TEM) gene sequences.
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PMID:A MALDI TOF MS-based minisequencing method for rapid detection of TEM-type extended-spectrum beta-lactamases in clinical strains of Enterobacteriaceae. 1869 87

Novel triangular macrocycle isomers were synthesized through metathesis cyclization with high yield (77%). HPLC and MALDI-TOF showed that the purity of the macrocycles was higher than 99%, while (1)H NMR clearly showed that these macrocycles contain C2 and C3 isomers in a ratio of 1:3. AFM and TEM showed that they spontaneously formed vesicular structures in a chloroform/water system with an average diameter of 460 nm, which was corroborated by DLS results.
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PMID:Synthesis of macrocycle isomers via metathesis cyclization and their self-assembly from aqueous solutions. 1880 29


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