共查询到20条相似文献,搜索用时 859 毫秒
1.
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: |
2.
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: |
3.
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: |
4.
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: |
5.
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: |
6.
José ángel Rodríguez-Castrillón Mariella Moldovan J. Ignacio García Alonso 《Analytical and bioanalytical chemistry》2009,394(1):351-362
A method has been developed for the accurate determination of platinum by isotope dilution analysis, using enriched 194Pt, in environmental samples containing comparatively high levels of hafnium without any chemical separation. The method is
based on the computation of the contribution of hafnium oxide as an independent factor in the observed isotope pattern of
platinum in the spiked sample. Under these conditions, the ratio of molar fractions between natural abundance and isotopically
enriched platinum was independent of the amount of hafnium present in the sample. Additionally, mass bias was corrected by
an internal procedure in which the regression variance was minimised. This was possible as the mass bias factor for hafnium
oxide was very close to that of platinum. The final procedure required the measurement of three platinum isotope ratios (192/194,
195/194 and 196/194) to calculate the concentration of platinum in the sample. The methodology has been validated using the
reference material “BCR-723 road dust” and has been applied to different environmental matrices (road dust, air particles,
bulk wet deposition and epiphytic lichens) collected in the Aspe Valley (Pyrenees Mountains). A full uncertainty budget, using
Kragten’s spreadsheet method, showed that the total uncertainty was limited only by the uncertainty in the measured isotope
ratios and not by the uncertainties of the isotopic composition of platinum and hafnium.
Figure Simultaneous correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental
samples using isotope dilution analysis
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Mariella MoldovanEmail: |
7.
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: |
8.
Wei Wang Shu-Hui Zhang Lin-Mei Li Zong-Li Wang Jie-Ke Cheng Wei-Hua Huang 《Analytical and bioanalytical chemistry》2009,394(1):17-32
Communication between cells by release of specific chemical messengers via exocytosis plays crucial roles in biological process.
Electrochemical detection based on ultramicroelectrodes (UMEs) has become one of the most powerful techniques in real-time
monitoring of an extremely small number of released molecules during very short time scales, owing to its intrinsic advantages
such as fast response, excellent sensitivity, and high spatiotemporal resolution. Great successes have been achieved in the
use of UME methods to obtain quantitative and kinetic information about released chemical messengers and to reveal the molecular
mechanism in vesicular exocytosis. In this paper, we review recent developments in monitoring exocytosis by use of UMEs-electrochemical-based
techniques including electrochemical detection using micrometer and nanometer-sized sensors, scanning electrochemical microscopy
(SECM), and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a
better understanding of vesicular exocytosis and chemical communications between cells, and will facilitate developments in
many fields, including analytical chemistry, biological science, and medicine. Furthermore, future developments in electrochemical
probing of exocytosis are also proposed.
Figure In this paper, we review recent developments in monitoring the exocytosis by use of UMEs-electrochemical-based techniques
including electrochemical detection using micrometer and nanometer-sized sensors, Scanning Electrochemical Microscopy (SECM)
and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a better understanding
of vesicular exocytosis and chemical communications between cells, and will facilitate developments in many fields including
analytical chemistry, biological science and medicine. Furthermore, future developments in electrochemical probing of exocytosis
are proposed.
相似文献
Wei-Hua HuangEmail: |
9.
Heavy metal ions are highly toxic species which can cause long-term damage to biological systems. These species are known
to disrupt biological events at the cellular level, cause significant oxidative damage, and are carcinogens. The production
of simple, in-field detection methods that are highly sensitive for these cations is highly desirable in response to global
pollution. In that regard, bio-inspired colorimetric sensing systems have been developed to detect Hg2+ and Pb2+, and other cations, down to nmol L−1 concentrations. The benefits of these systems, which are reviewed herein, include cost-effective production, facile usage,
and a visual color change for the detection method. Such advantages are significant positive steps for heavy metal ion detection,
especially in regions where sophisticated laboratory studies are prohibited.
Figure Biological-based colorimetric detection of heavy metal cations. The materials on the left are independent Au nanoparticles
in solution, functionalized with heavy metal binding biomolecules, which, upon metal addition, aggregate to evolve a detectable
solution color change.
相似文献
Marc R. KnechtEmail: |
10.
The identification of ignitable liquid residues in fire debris is a key finding for determining the cause and origin of a
suspicious fire. However, the complex mixtures of organic compounds that comprise ignitable liquids are susceptible to microbiological
attack following collection of the sample. Biodegradation can result in selective removal of many of the compounds required
for identification of an ignitable liquid. Such degradation has been found to occur rapidly in substrates such as soil, rotting
wood, or other organic matter. Furthermore, fire debris evidence must often be stored for extended periods at room temperature
prior to analysis due to case backlogs and available evidence storage. Hence, extensive damage to ignitable liquid residues
by microbes poses a significant threat to subsequent laboratory work. In this work, the effects of microbial degradation of
ignitable liquids in soil have been evaluated as a function of time. Key findings include the loss of n-alkanes, particularly C9–C16, which showed the most dramatic decrease in gasoline as well as the petroleum distillates, while branched alkanes remained
unchanged. Monosubstituted benzenes also showed the most dramatic loss in gasoline. In the heavy petroleum distillates, n-alkanes with even carbon numbers were degraded more than n-alkanes with odd carbon numbers.
Figure A “fully involved” house fire in Indianapolis, IN
相似文献
John V. GoodpasterEmail: |
11.
Warunya Boonjob María Rosende Manuel Miró Víctor Cerdà 《Analytical and bioanalytical chemistry》2009,394(1):337-349
Two novel dynamic extraction approaches, the so-called sequential injection microcolumn extraction and sequential injection
stirred-flow chamber extraction, based on the implementation of a sample-containing container as an external extraction reactor
in a sequential injection network, are for the first time, optimized and critically appraised for fractionation assays. The
three steps of the original Community Bureau of Reference (BCR) sequential extraction scheme have been performed in both automated
dynamic fractionation systems to evaluate the extractability of Cr, Cu, Ni, Pb, and Zn in a standard reference material of
coal fly ash (NIST 1633b). In order to find the experimental conditions with the greatest influence on metal leachability
in dynamic BCR fractionation, a full-factorial design was applied, in which the solid sample weight (100–500 mg) and the extraction
flow rate (3.0–6.0 mL min−1) were selected as experimental factors. Identical cumulative extractabilities were found in both sequential injection (SI)-based
methods for most of assayed trace elements regardless of the extraction conditions selected, revealing that both dynamic fractionation
systems, as opposed to conventional steady-state BCR extraction, are not operationally defined within the selected range of
experimental conditions. Besides, the proposed automated SI assemblies offer a significant saving of operational time with
respect to classical BCR test, that is, 3.3 h versus 48 h, for complete fractionation with minimum analyst involvement.
Schematic illustration of automatic flow-based setups for dynamic fractionation of trace metals in fly ash
相似文献
Manuel MiróEmail: |
12.
Pérez Pavón JL García Pinto C Guerrero Peña A Moreno Cordero B 《Analytical and bioanalytical chemistry》2008,391(2):599-607
In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to
a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment,
the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the
mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to
the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization
of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired
information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation
are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach
for oil spill identification in soils.
Figure PCA score plots illustrate clear discrimination of types of crude oil in polluted soil samples (e.g. results are shown for
vertisol) 相似文献
13.
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: |
14.
A capillary-assembled microchip (CAs-CHIP), prepared by simply embedding square capillaries in a lattice polydimethylsiloxane
(PDMS) channel plate with the same channel dimensions as the outer dimensions of the square capillaries, has been used as
a diffusion-based pretreatment attachment in capillary electrophoresis (CE). Because the CAs-CHIPs employ square-section channels,
diffusion-based separation of small molecules from sample solutions containing proteins is possible by using the multilayer
flow formed in the square section channel. When a solution containing high-molecular-weight and low-molecular-weight species
makes contact with a buffer solution, the low-molecular-weight species, which have larger diffusion coefficients than the
high-molecular-weight species, can be collected in a buffer-solution phase. The collected solution containing the low-molecular-weight
species is introduced into the separation capillary to be analyzed by CE. This type of system can be used for CE analysis
in which pretreatment is required to remove proteins. In this work a fluorescently labeled protein and rhodamine-based molecules
were chosen as model species and a feasibility study was performed.
相似文献
15.
16.
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: |
17.
José I. Martínez-López Héctor Moncada-Hernández Javier L. Baylon-Cardiel Sergio O. Martínez-Chapa Marco Rito-Palomares Blanca H. Lapizco-Encinas 《Analytical and bioanalytical chemistry》2009,394(1):293-302
Insulator-based dielectrophoresis (iDEP), an efficient technique with great potential for miniaturization, has been successfully
applied for the manipulation of a wide variety of bioparticles. When iDEP is applied employing direct current (DC) electric
fields, other electrokinetic transport mechanisms are present: electrophoresis and electroosmotic flow. In order to concentrate
particles, iDEP has to overcome electrokinetics. This study presents the characterization of electrokinetic flow under the
operating conditions employed with iDEP; in order to identify the optimal conditions for particle concentration employing
DC-iDEP, microparticle image velocimetry (μPIV) was employed to measure the velocity of 1-μm-diameter inert polystyrene particles
suspended inside a microchannel made from glass. Experiments were carried out by varying the properties of the suspending
medium (conductivity from 25 to 100 μS/cm and pH from 6 to 9) and the strength of the applied electric field (50–300 V/cm);
the velocities values obtained ranged from 100 to 700 μm/s. These showed that higher conductivity and lower pH values for
the suspending medium produced the lowest electrokinetic flow, improving iDEP concentration of particles, which decreases
voltage requirements. These ideal conditions for iDEP trapping (pH = 6 and σ
m = 100 μS/cm) were tested experimentally and with the aid of mathematical modeling. The μPIV measurements allowed obtaining
values for the electrokinetic mobilities of the particles and the zeta potential of the glass surface; these values were used
with a mathematical model built with COMSOL Multiphysics software in order to predict the dielectrophoretic and electrokinetic
forces exerted on the particles; the modeling results confirmed the μPIV findings. Experiments with iDEP were carried out
employing the same microparticles and a glass microchannel that contained an array of cylindrical insulating structures. By
applying DC electric fields across the insulating structures array, it was seen that the dielectrophoretic trapping was improved
when the electrokinetic force was the lowest; as predicted by μPIV measurements and the mathematical model. The results of
this study provide guidelines for the selection of optimal operating conditions for improving insulator-based dielectrophoretic
separations and have the potential to be extended to bioparticle applications.
Figure Comparison of experimental measurements and mathematical modeling of electrokinetic and dielectrophoretic effects on microparticles
相似文献
Blanca H. Lapizco-EncinasEmail: |
18.
19.
Larissa S. Fenn Michal Kliman Ablatt Mahsut Sophie R. Zhao John A. McLean 《Analytical and bioanalytical chemistry》2009,394(1):235-244
The conformation space occupied by different classes of biomolecules measured by ion mobility-mass spectrometry (IM-MS) is
described for utility in the characterization of complex biological samples. Although the qualitative separation of different
classes of biomolecules on the basis of structure or collision cross section is known, there is relatively little quantitative
cross-section information available for species apart from peptides. In this report, collision cross sections are measured
for a large suite of biologically salient species, including oligonucleotides (n = 96), carbohydrates (n = 192), and lipids (n = 53), which are compared to reported values for peptides (n = 610). In general, signals for each class are highly correlated, and at a given mass, these correlations result in predicted
collision cross sections that increase in the order oligonucleotides < carbohydrates < peptides < lipids. The specific correlations
are described by logarithmic regressions, which best approximate the theoretical trend of increasing collision cross section
as a function of increasing mass. A statistical treatment of the signals observed within each molecular class suggests that
the breadth of conformation space occupied by each class increases in the order lipids < oligonucleotides < peptides < carbohydrates.
The utility of conformation space analysis in the direct analysis of complex biological samples is described, both in the
context of qualitative molecular class identification and in fine structure examination within a class. The latter is demonstrated
in IM-MS separations of isobaric oligonucleotides, which are interpreted by molecular dynamics simulations.
Figure Potential for performing simultaneous “omics” through the separation of biomolecular classes on the basis of structure and
mass using ion mobility-mass spectrometry
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
John A. McLeanEmail: |
20.
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: |