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1.
Justina Grabowska Karuna Kar Nanda R.T. Rajendra Kumar J.P. Mosnier M.O. Henry Simon B. Newcomb Patrick McNally Lisa OReilly Xu Lu Enda McGlynn 《Superlattices and Microstructures》2007,42(1-6):327
Self-organized ZnAl2O4 nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl2O4, formed by the reaction of Zn and O with the sapphire substrate. 相似文献
2.
A new protocol for synthesis of 2-heterocylylacetic acid derivatives involving conjugate addition of allyl mercaptan to an acrylate containing a tethered olefinic site followed by RCM (ring-closing metathesis) is described. In this series, sulfanyl derivatives were unreactive, while sulfoxide and sulfone analogues provided the corresponding thiazocines in fair to excellent yields. Use of the sulfoxide oxidation state as a protecting group for sulfides inert to RCM is demonstrated also. Thus, oxidation of sulfide 9 [N-allyl-N-[2-(allylthio)-4-(1H-indol-1-yl)-4-oxobutyl]-4-methylbenzenesulfonamide] followed by cyclization yielded the corresponding thiazocine sulfoxide 12. Deprotection (deoxygenation) of 12 was accomplished using Lawesson's reagent, producing 1-[[4-[4-(methylphenyl)sulfonyl]-3,4,5,8-tetrahydro-2H-1,4-thiazocin-2-yl]acetyl]-1H-indole (21) in 67% unoptimized yield. 相似文献
3.
The effects of anionic, non-ionic, and cationic surfactants and thallium(I) nitrate on the paper-substrate room-temperature phosphorescence (RTP) of eleven phenothiazine derivatives are described. Enhancement factors within the range 1.5–10 are observed after addition of sodium dodecylsulfate, dodecyltrimethylammonium chloride and thallium(I) nitrate. The influence of surfactant on phosphor characteristics as well as effects of moisture are discussed. Limits of detection were in the range 0.2–2 ng. Results are also reported for p-aminobenzoic acid, carbazole and o-terphenyl. 相似文献
4.
Field SJ Thornton NP Anderson LJ Gates AJ Reilly A Jepson BJ Richardson DJ George SJ Cheesman MR Butt JN 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3580-3586
Protein film voltammetry of Paracoccus pantotrophus respiratory nitrate reductase (NarGH) and Synechococcus elongatus assimilatory nitrate reductase (NarB) shows that reductive activation of these enzymes may be required before steady state catalysis is observed. For NarGH complementary spectroscopic studies suggest a structural context for the activation. Catalytic protein film voltammetry at a range of temperatures has allowed quantitation of the activation energies for nitrate reduction. For NarGH with an operating potential of ca. 0.05 V the activation energy of ca. 35 kJ mol-1 is over twice that measured for NarB whose operating potential is ca. -0.35 V. 相似文献
5.
Christian NP Reilly JP Mokler VR Wincott FE Ellington AD 《Journal of the American Society for Mass Spectrometry》2001,12(6):744-753
To probe the mechanism of gas-phase oligonucleotide ion fragmentation, modified oligonucleotides were studied using matrix-assisted laser desorption/ionization. The oligonucleotides were of the form 5'-TTTTXTTTTT, where X was a modified nucleotide. Modifications included substitution of hydroxy, methoxy, amino, and allyl groups at the 2'-position of the deoxyribose. The modified ribose contained adenine, guanine, cytosine, or uracil bases. For comparison, we studied oligomers where X was an unmodified adenosine, guanosine, cytidine, thymidine, or uridine deoxyribonucleotide. We found a very strong dependence of the matrix-to-analyte ratio on fragmentation for these oligomers. Analysis of these modifications suggests that the initial fragmentation step in MALDI-MS involves a two-step (E1) elimination of the base. 相似文献
6.
7.
Capillary electrophoretic approach to screen for enzyme inhibitors in natural extracts 总被引:2,自引:0,他引:2
This paper demonstrates development of electrophoretically mediated micro analysis (EMMA), for screening protein tyrosine phosphatase (PTP) inhibitors in natural extracts. It is demonstrated that capillary electrophoresis (CE) separation of the substrate and the product allows for using the assay in an on-column format to monitor the reaction without typically used fluorogenic substrates. Michaelis-Menten kinetics parameters calculated based on the EMMA results (Km = 1.2-1.5 microM) were in a good agreement (Km = 1.0-1.5 microM) obtained using an off-line CE functional assay (CE FA). EMMA of PTP titrated with different concentrations of ligand demonstrated the peak-shift phenomenon normally seen in affinity capillary electrophoresis. This feature of EMMA gives an indication of the binding affinity of the ligand in addition to its functional activity, providing another dimension in characterization of the protein-inhibitor interaction. It was demonstrated that simultaneous screening of the primary PTP target and a secondary, counter target (PTP-C) using the EMMA format can be used to prioritize hits based on their specificity. 相似文献
8.
Acyclic dithiol and cyclic disulfide forms of the peptides Ac-Cys-Pro-Xaa-Cys-NH2 (Xaa = Phe, His, Tyr, Gly, and Thr) and Ac-Cys-Gly-Pro-Cys-NH2 and the peptide Ac-Ala-Gly-Pro-Ala-NH2 were synthesized and characterized by mass spectrometry and NMR spectroscopy. Rate constants kct and ktc for cis-to-trans and trans-to-cis isomerization, respectively, across the Cys-Pro or Gly-Pro peptide bonds were determined by magnetization transfer NMR techniques over a range of temperatures, and activation parameters were derived from the temperature dependence of the rate constants. It was found that constraints imposed by the disulfide bond confer an unexpected rate enhancement for cis/trans isomerization, ranging from a factor of 2 to 13. It is proposed that the rate enhancements are a result of an intramolecular catalysis mechanism in which the NH proton of the Pro-Xaa peptide bond hydrogen bonds to the proline nitrogen in the transition state. The peptides Ac-Cys-Pro-Xaa-Cys-NH2 and Ac-Cys-Gly-Pro-Cys-NH2 are model compounds for proline-containing active sites of the thioredoxin superfamily of oxidoreductase enzymes; the results suggest that the backbones of the active sites of the oxidized form of these enzymes may have unusual conformational flexibility. 相似文献
9.
10.
Vladimir Gubala Jonathan Siegrist Ruairi Monaghan Brian O’Reilly Ram Prasad Gandhiraman Stephen Daniels David E. Williams Jens Ducrée 《Analytica chimica acta》2013
Herein a simple analytical method is presented for the characterization of biomolecule adsorption on cyclo olefin polymer (COP, trade name: Zeonor®) substrates which are widely used in microfluidic lab-on-a-chip devices. These Zeonor® substrates do not possess native functional groups for specific reactions with biomolecules. Therefore, depending on the application, such substrates must be functionalized by surface chemistry methods to either enhance or suppress biomolecular adsorption. This work demonstrates a microfluidic method for evaluating the adsorption of antibodies and oligonucleotides surfaces. The method uses centrifugal microfluidic flow-through chips and can easily be implemented using common equipment such as a spin coater. The working principle is very simple. The user adds 40 L of the solution containing the sample to the starting side of a microfluidic channel, where it is moved through by centrifugal force. Some molecules are adsorbed in the channel. The sample is then collected at the other end in a small reservoir and the biomolecule concentration is measured. As a pilot application, we characterized the adsorption of goat anti-human IgG and a 20-mer DNA on Zeonor®, and on three types of functionalized Zeonor: 3-aminopropyltriethoxysilane (APTES) modified surface with mainly positive charge, negatively charged surface with immobilized bovine serum albumin (BSA), and neutral, hydrogel-like film with polyethylene glycol (PEG) characteristics. This simple analytical approach adds to the fundamental understanding of the interaction forces in real, microfluidic systems. This method provides a straightforward and rapid way to screen surface compositions and chemistry, and relate these to their effects on the sensitivity and resistance to non-specific binding of bioassays using them. In an additional set of experiments, the surface area of the channels in this universal microfluidic chip was increased by precision milling of microscale trenches. This modified surface was then coated with APTES and tested for its potential to serve as a unique protein dilution feature. 相似文献