共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Seven columns with embedded polar functionality were evaluated for use in liquid chromatography with a focus on molecular
shape recognition. Tests based on Standard Reference Material 869b Column Selectivity Test Mixture for Liquid Chromatography
and the Tanaka test indicate that only two of the phases are slightly shape selective at 20 °C. The shape recognition characteristics
of the phases appear to be directly related to the density of the embedded polar ligands and the temperature of the separation,
consistent with trends observed with conventional hydrocarbon phases.
Catherine Rimmer is a Research Chemist at the National Institute of Standards and Technology where she began as a National Research Council Postdoctoral Fellow. Her research efforts are currently directed towards an improved understanding of chromatographic processes to advance the “state of the art” in chemical metrology. 相似文献
Catherine A. RimmerEmail: |
Catherine Rimmer is a Research Chemist at the National Institute of Standards and Technology where she began as a National Research Council Postdoctoral Fellow. Her research efforts are currently directed towards an improved understanding of chromatographic processes to advance the “state of the art” in chemical metrology. 相似文献
3.
Edgar D. Goluch Bernhard Wolfrum Pradyumna S. Singh Marcel A. G. Zevenbergen Serge G. Lemay 《Analytical and bioanalytical chemistry》2009,394(2):447-456
Amperometric detection is ideally suited for integration into micro- and nanofluidic systems as it directly yields an electrical
signal and does not necessitate optical components. However, the range of systems to which it can be applied is constrained
by the limited sensitivity and specificity of the method. These limitations can be partially alleviated through the use of
redox cycling, in which multiple electrodes are employed to repeatedly reduce and oxidize analyte molecules and thereby amplify
the detected signal. We have developed an interdigitated electrode device that is encased in a nanofluidic channel to provide
a hundred-fold amplification of the amperometric signal from paracetamol. Due to the nanochannel design, the sensor is resistant
to interference from molecules undergoing irreversible redox reactions. We demonstrate this selectivity by detecting paracetamol
in the presence of excess ascorbic acid.
Figure
相似文献
Serge G. LemayEmail: |
4.
Hitoshi Shirase Yurie Miura Yutaka Fukuda 《Monatshefte für Chemie / Chemical Monthly》2009,140(7):807-814
Abstract Mixed-ligand NiII complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined
by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky
ligands on the coordination distances and spectral properties are discussed.
Graphical Abstract
相似文献
Yutaka FukudaEmail: |
5.
Abstract The synthesis and acid-catalyzed rearrangement of novel thiazolomorphinandienes have been presented. An isomerization was
observed simultaneously with the backbone transformation. An extensive study was performed to determine the major effects
of the isomerization of 2′-alkyl- and aryl-substituted thiazoloapocodeines into 3′-alkyl- and arylisothiazoloapocodeines.
The obtained results provided another practical example of the reversible benzisothiazole–benzothiazole-type isomerization
emphasizing the determining role of the thermal effects in the occurrence of these isomerization products. The obtained experimental
results and the proposed mechanism were in agreement with the calculated DFT data.
Graphical abstract
相似文献
Attila SiposEmail: |
6.
Gerard P. O’Sullivan Norma M. Scully Jean-Marie Prat Jeremy D. Glennon Benjamin Dietrich Volker Friebolin Klaus Albert 《Analytical and bioanalytical chemistry》2009,394(5):1261-1272
Supercritical carbon dioxide has attracted attention as a potential replacement for traditional organic solvents due to its
simplified workup procedures and reduced environmental impact—providing a green chemistry approach for organic solvent-free
functionalisation. In addition to the environmental benefits, the enhanced diffusivity observed in supercritical solvents
can often enhance reaction rates. We have applied these valuable features to the preparation of silica-bonded stationary phases
and examined their potential in liquid chromatography. We report the successful preparation and characterisation of polyether
silica based on Frechet dendrimers—this significantly enhances the range of stationary-phase chemistries that can be prepared
in supercritical fluids. First- and second-generation polyether silicas were prepared, characterised, end-capped and evaluated
for use as stationary phases for liquid chromatography.
Figure SRM1649 on 2nd generation polyether silica
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Jeremy D. GlennonEmail: |
7.
Attila Sipos Miklós Tóth Franziska K. U. Mueller Jochen Lehmann Sándor Berényi 《Monatshefte für Chemie / Chemical Monthly》2009,140(4):473-478
Abstract The synthesis of 4H-thiochromene derivatives of apomorphines, a novel class of isoquinoline alkaloid-related compounds, has been achieved by
different O-dealkylation methods applied on previously published heteroring-fused aporphinoids. Detailed DFT study has been presented
regarding the mechanism of the L-selectride-mediated multiple O-dealkylation of a seven-ring aporphine analogue. Dopamine-binding tests confirmed the essential function of 11-hydroxy moiety
of the aporphine skeleton and revealed a remarkable D1 over D2 specificity for the derivative having the 4H-thiochromene ring system attached to positions 2 and 3 of the aporphine backbone.
Graphical Abstract
相似文献
Attila SiposEmail: |
8.
Leonard Nyadong Edward G. Hohenstein Asiri Galhena Amy L. Lane Julia Kubanek C. David Sherrill Facundo M. Fernández 《Analytical and bioanalytical chemistry》2009,394(1):245-254
Presented here is the optimization and development of a desorption electrospray ionization mass spectrometry (DESI-MS) method
for detecting natural products on tissue surfaces. Bromophycolides are algal diterpene-benzoate macrolide natural products
that have been shown to inhibit growth of the marine fungal pathogen Lindra thalassiae. As such, they have been implicated in antimicrobial chemical defense. However, the defense mechanisms are not yet completely
understood. Precise detection of these compounds on algal tissue surfaces under ambient conditions without any disruptive
sample processing could shed more light onto the processes involved in chemical defense of marine organisms. Conventional
DESI-MS directly on algal tissue showed relatively low sensitivity for bromophycolide detection. Sensitivity was greatly improved
by the addition of various anions including Cl−, Br−, and CF3COO− into the DESI spray solvent. Chloride adduction gave the highest sensitivity for all assayed anions. Density functional optimization
of the bromophycolide anionic complexes produced during DESI supported this observation by showing that the chloride complex
has the most favorable binding energy. Optimized DESI protocols allowed the direct and unambiguous detection of bromophycolides,
including A, B, and E, from the surface of untreated algal tissue.
Figure Desorption Electrospray Ionization, a novel technique for mass spectrometric analysis under open air conditions reveals the
presence of naturally-occurring antibiotics on the surface of marine algae. Ab-initio calculations and experimental results
indicate that sensitiviity could be greatly enhanced by means of dynamic complexation of these antibiotics with various small
anions during the dynamic desorption process.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Facundo M. FernándezEmail: |
9.
Sabine Borgmann 《Analytical and bioanalytical chemistry》2009,394(1):95-105
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) play a crucial role in chemical signaling processes of biological
cells. Electrochemistry is one of the rare methods able to directly detect these species. ROS and RNS can be monitored in
the local microenvironment of cells in real time at the site where the actual signaling takes place. This review presents
recent advances made with amperometric electrochemical techniques. Existing challenges for the quantification of ROS and RNS
in biological systems are discussed to promote the development of innovative and reliable cell-based assays.
Figure Reactive oxygen and nitrogen species (ROS & RNS) are produced biological cells. An amperometric sensor is placed in close
proximity. The recorded current I is used to determine fluxes of certain species.
相似文献
Sabine BorgmannEmail: |
10.
Masaya Murata Yukihiro Okamoto Yeon-Su Park Noritada Kaji Manabu Tokeshi Yoshinobu Baba 《Analytical and bioanalytical chemistry》2009,394(1):277-283
We investigated properties of cells affecting their optical trapping force and successfully established a novel cell separation
method based on the combined use of optical trapping force and microfluidics on a microchip. Our investigations reveal that
the morphology, size, light absorption, and refractive index of cells are important factors affecting their optical trapping
force. A sheath flow of sample solutions created in a microchip made sample cells flow in a narrow linear stream and an optical
trap created by a highly focused laser beam captured only target cells and altered their trajectory, resulting in high-efficiency
cell separation. An optimum balance between optical trapping force and sample flow rate was essential to achieve high cell
separation efficiency. Our investigations clearly indicate that the on-chip optical trapping method allows high-efficiency
cell separation without cumbersome and time-consuming cell pretreatments. In addition, our on-chip optical trapping method
requires small amounts of sample and may permit high-throughput cell separation and integration of other functions on microchips.
Figure Optical trapping in a microchannel allows high-efficiency separation of cells, e.g., dead and live HeLa cells
相似文献
Yukihiro OkamotoEmail: |
11.
Edward B. Nikitin Sanjeev K. Dey David A. Lightner 《Monatshefte für Chemie / Chemical Monthly》2009,140(1):97-110
Abstract Six 10-nor-bilirubin analogs have been synthesized and investigated. Lacking the C(10) CH2 group, these linear tetrapyrroles have a bipyrrole core rather than a dipyrrylmethane core and thus a different shape. Whereas
the propionic acid groups of bilirubin are well engaged in intramolecular hydrogen bonding to the dipyrrinones, molecular
modeling studies of the 10-nor-rubins predict that propionic acid chains are too short to engage the CO2H hydrogen fully in intramolecular hydrogen bonding with the dipyrrinones. Butyric acid chains, however, can and do lead to
a stabilized conformation with a bipyrrole dihedral angle of approximately 115°. Spectroscopic studies verify the predictions
and vapor pressure osmometry indicates that the 10-nor-rubins with butyric acids are monomeric in CHCl3.
Graphical abstract
相似文献
David A. LightnerEmail: |
12.
Anti-lysozyme aptamers are found to preferentially bind to the edge of a tightly packed lysozyme pattern. Such edge-binding
is due to the better accessibility and flexibility of the edge lysozyme molecules. Kelvin probe force microscopy (KPFM) was
used to study the aptamer–lysozyme binding. Our results show that KPFM is capable of detecting the aptamer–protein binding
down to the 30 nm scale. The surface potential of the aptamer–lysozyme complex is approximately 12 mV lower than that of the
lysozyme. The surface potential images of the aptamer-bound lysozyme patterns have the characteristic shoulder steps around
the pattern edge, which is much wider than that of a clean lysozyme pattern. These results demonstrate the potentials of KPFM
as a label-free method for the detection of protein–DNA interactions.
Figure Aptamers preferentially bind on the edge of a protein pattern as revealed by Kelvin force microscopy.
相似文献
Yuguang CaiEmail: |
13.
Dae-Sik Kim Vincent M. Lynch Kent A. Nielsen Carsten Johnsen Jan O. Jeppesen Jonathan L. Sessler 《Analytical and bioanalytical chemistry》2009,395(2):393-400
A new receptor, the bisTTF-calix[2]thiophene[2]pyrrole derivative 3, has been prepared from the Lewis acid-catalyzed condensation of 2,5-bis(1-hydroxymethylethyl)thiopheno-TTF and pyrrole.
This new system is found to form complexes with the electron-deficient guests, trinitrobenzene (TNB) and picric acid (PA),
which serve as models for nitroaromatic explosives. The binding phenomenon, which has been studied in organic solution using
proton nuclear magnetic resonance and absorption spectroscopies, results in an easy-to-visualize color change in chloroform
that is independent of the presence of chloride anion, a known interferant for an earlier tetrakisTTF-calix[4]pyrrole TNB
chemosensor. Support for the proposed binding mode comes from a preliminary solid state structure of the complex formed from
TNB, namely TNB⊂3. A color change is also observed when dichloromethane solutions of chemosensor 3 are added to solvent-free samples of TNB, PA, and 2,4,6-trinitrotoluene supported on silica gel.
Figure A new bis-tetrathiafulvalene calix[2]thiophene[2]pyrrole derivative has been prepared that gives rise to an easy-to-visualize
color change in the presence of the model nitroaromatic explosives trinitrobenzene and picric acid.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Jonathan L. Sessler (Corresponding author)Email: |
14.
Marcus L. Young Suzanne Schnepp Francesca Casadio Andrew Lins Melissa Meighan Joseph B. Lambert David C. Dunand 《Analytical and bioanalytical chemistry》2009,395(1):171-184
Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to determine the bulk metal elemental composition
of 62 modern bronze sculptures cast in Paris in the first half of the twentieth century from the collections of The Art Institute
of Chicago and the Philadelphia Museum of Art. As a result, a comprehensive survey of the alloy composition of the sculptures
of many prominent European artists of the early twentieth century is presented here for the first time. The sculptures in
this study consist of predominantly copper with two main alloying elements (zinc and tin). By plotting the concentrations
of these two elements (zinc and tin) against each other for all the sculptures studied, three clusters of data become apparent:
(A) high-zinc brass; (B) low-zinc brass; (C) tin bronze. These clusters correlate to specific foundries, which used specific
casting methods (sand or lost wax) that were influenced by individual preferences and technical skills of the foundry masters.
For instance, the high-zinc brass alloys (with the highest levels of tin and zinc and the lowest melting temperature) correspond
to most of the Picasso sculptures, correlate with the Valsuani foundry, and are associated with the most recent sculptures
(post-WWII) and with the lost-wax casting method. By expanding the ICP-OES database of objects studied, these material correlations
may become useful for identifying, dating, or possibly even authenticating other bronzes that do not bear foundry marks.
Figure
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Francesca CasadioEmail: |
15.
Partition layer-modified substrates for reversible surface-enhanced Raman scattering detection of polycyclic aromatic hydrocarbons 总被引:1,自引:0,他引:1
Courtney L. Jones Kyle C. Bantz Christy L. Haynes 《Analytical and bioanalytical chemistry》2009,394(1):303-311
Herein, we present progress towards an analytical sensor for polycyclic aromatic hydrocarbons (PAHs) using surface-enhanced
Raman scattering (SERS) on partition layer-modified nanostructured substrates. Specifically, a 1-decanethiol monolayer has
been assembled on a silver film over nanospheres substrate to concentrate PAHs within the zone of SERS detection. Both anthracene
and pyrene were detected with limits of detection at 300 and 700 pM, respectively. The measured SERS spectra allowed for easy
distinction of the two PAH compounds, due to varying peak locations, and insight into the partitioning mechanism. Additionally,
exposure to a common environmental interferant, Suwannee River fulvic acid, did not impede the measurement of the PAHs, and
the sensor is reusable after a short exposure to 1-octanol. Finally, the utility of this sensing platform for PAH detection
was compared to that achievable for other classes of organic pollutants such as polychlorinated biphenyls and polybrominated
diphenyl ethers.
Figure SERS detection of polycyclic aromatic hydrocarbons facilitated via partition layer modified substrates.
相似文献
Christy L. HaynesEmail: |
16.
Hideki Kuramitz 《Analytical and bioanalytical chemistry》2009,394(1):61-69
This review provides a summary of recent works concerning electrochemical immunoassays using magnetic microbeads as a solid
phase. Recent research activity has led to innovative and powerful detection strategies that have been resulted in sensitive
electrochemical detection. Coupling of magnetic microbeads with highly sensitive electrochemical detection provides a useful
analytical method for environmental evaluation and clinical diagnostics, etc. The huge surface area and high dispersion capability
of magnetic microbeads strongly contributes towards the development of new sensitive, rapid, user-friendly, and miniaturized
electrochemical immunoassay systems. Moreover, the immunocomplexes formed on the magnetic microbead surface can be easily
detected without pretreatment steps such as preconcentration or purification, which are normally required for standard methods.
The discussion in this review is organized in two main subjects that include magnetic-microbead-based assays using enzyme
labels and nanoparticle tags.
Figure SEM image of Dynabeads M-280 (12% γ-Fe2O3 in polystyrene, diameter is 2.8 μm)
相似文献
Hideki KuramitzEmail: |
17.
Environmental metabolomics is a growing and emerging sub-discipline of metabolomics. Studies with earthworms have progressed
from the initial stages of simple contact exposure tests to detailed studies of earthworm responses in soil. Over the past
decade, a variety of endogenous metabolites have been identified as potential biomarkers of contaminant exposure. Furthermore,
metabolomic methods have delineated responses from sub-lethal exposure of earthworms to polycyclic aromatic hydrocarbons and
metals in soil suggesting that environmental metabolomics may be used as a direct measure of contaminant bioavailability in
soil. Environmental metabolomics has the potential to fill knowledge gaps related to earthworm toxicity and contaminant bioavailability.
However, challenges with metabolite quantification and limited systems-level models of metabolic data require improvement
before detailed models of “normal” responses can be developed and used routinely in assessment of contaminated sites. Nonetheless,
environmental metabolomics is poised to improve our fundamental understanding of earthworm responses and toxicity to contaminants
in soil.
Figure Principal component analysis (PCA) scores plots of earthworm metabolic profiles measured by 1H NMR spectroscopy after exposure to sub-lethal concentrations of phenanthrene in soil.
相似文献
Myrna J. SimpsonEmail: |
18.
Lutz F. Tietze Birgit Krewer Holm Frauendorf 《Analytical and bioanalytical chemistry》2009,395(2):437-448
One of the main problems of anti-cancer therapy is an insufficient differentiation between normal and malignant cells by the
known anti-proliferant agents. The antibody-directed enzyme prodrug therapy is a promising approach for a selective treatment
of cancer, in which a non-toxic prodrug is enzymatically converted into a highly cytotoxic drug at the surface of malignant
cells by a targeted antibody–enzyme conjugate. The transformations and the stability of a very promising novel prodrug and
its corresponding cytotoxic derivative were now investigated in detail by high-performance liquid chromatography (HPLC)–mass
spectrometry (MS). In order to determine the time-dependent DNA alkylation efficiency and the sequence selectivity of the
novel compounds, DNA binding studies using direct electrospray–Fourier transform ion cyclotron resonance–MS (ESI–FTICR–MS)
have been performed. These measurements were accompanied by HPLC analyses followed by MS of the separated species to confirm
the results of the direct ESI–FTICR–MS measurements. The sites of DNA alkylation could be identified unambiguously by the
mass spectrometric fragmentation pattern of the alkylated oligodeoxynucleotides as well as by the results of HPLC followed
by MS. A combination of all techniques applied led to a better understanding of the mode of action of the new therapeutics
and might be used for an estimation of the cytotoxicity of different prodrugs and drugs since the alkylation efficiency correlates
with the bioactivity of the compounds in cell culture investigations.
After enzymatic cleavage of the sugar moiety, the untoxic prodrug is converted rapidly into the corresponding highly cytotoxic
drug that alkylates DNA with high efficiency
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Lutz F. TietzeEmail: |
19.
Ina Reiche Stefan R?hrs Joseph Salomon Birgit Kanngie?er Yvonne H?hn Wolfgang Malzer Friederike Voigt 《Analytical and bioanalytical chemistry》2009,393(3):1025-1041
The paper presents an analytical method developed for the nondestructive study of nineteenth-century Persian polychrome underglaze
painted tiles. As an example, 9 tiles from French and German museum collections were investigated. Before this work was undertaken
little was known about the materials used in pottery at that time, although the broad range of colors and shades, together
with their brilliant glazes, made these objects stand out when compared with Iranian ceramics of the preceding periods and
suggested the use of new pigments, colorants, and glaze compositions. These materials are thought to be related to provenance
and as such appropriate criteria for art-historical attribution. The analytical method is based on the combination of different
nondestructive spectroscopic techniques using microfocused beams such as proton-induced X-ray emission/proton-induced γ-ray
emission, X-ray fluorescence, 3D X-ray absorption near edge structure, and confocal Raman spectroscopy and also visible spectroscopy.
It was established to address the specific difficulties these objects and the technique of underglaze painting raise. The
exact definition of the colors observed on the tiles using the Natural Color System?? helped to attribute them to different colorants. It was possible to establish the presence of Cr- and U-based colorants as
new materials in nineteenth-century Persian tilemaking. The difference in glaze composition (Pb, Sn, Na, and K contents) as
well as the use of B and Sn were identified as a potential marker for different workshops.
Figure UV fluorescence and visible spectroscopy are two of the non-destructive analytical methods used to investigate the coloring
agents of underglaze painted tiles. Imaging of the uranium-containing areas was carried out by UV photography and identification
of the chemical species by visible spectroscopy.
相似文献
Ina ReicheEmail: |
20.
Stephanie L. Daniels Johnpeter N. Ngunjiri Jayne C. Garno 《Analytical and bioanalytical chemistry》2009,394(1):215-223
Individual ferritin molecules can be sensitively detected using magnetic sample modulation (MSM) combined with contact mode
atomic force microscopy (AFM). To generate an oscillating magnetic field, an alternating current (AC) was applied to a solenoid
placed within the base of the AFM sample stage. When a modulated electromagnetic field is applied to samples, ferromagnetic
and paramagnetic nanomaterials are induced to vibrate. The flux of the AC electromagnetic field causes the ferritin samples
to vibrate with corresponding rhythm and periodicity of the applied field. This motion can be detected and mapped using contact
mode AFM with a soft, nonmagnetic cantilever. Changes in the phase and amplitude of the periodic motion of the sample are
sensed by the tip to selectively map vibrating magnetic nanomaterials. Particle lithography was used to create nanopatterned
test platforms of ferritin for MSM measurements. Regularly spaced structures of proteins provide precise reproducible dimensions
for multiple successive surface measurements at dimensions of tens of nanometers.
Figure Ring patterns of ferritin were used as nanoscale test platforms to characterize magnetic properties at the level of individual
proteins with AFM imaging
相似文献
Jayne C. GarnoEmail: |