| 51. |
- Haas, Julian, et al.
(author)
-
Infrared Spectroscopy Based on Broadly Tunable Quantum Cascade Lasers and Polycrystalline Diamond Waveguides
- 2018
-
In: The Analyst. - 0003-2654 .- 1364-5528. ; 143:21, s. 5112-5119
-
Journal article (peer-reviewed)abstract
- Recently emerging broadly tunable quantum cascade lasers (tQCL) emitting in the mid-infrared (MIR) are a versatile alternative to well established thermal emitters in combination with interferometers as applied in Fourier transform infrared (FTIR) spectroscopy. The wide and highly spectrally resolved wavelength tuning characteristics along with superior spectral energy density renders laser-based vibrational spectroscopy methods an efficient alternative vs. conventional molecular spectroscopies. Using diamond in attenuated total reflection (ATR) sensing formats benefits from the physical robustness and chemical resistivity of the internal reflective element (IRE) material. While inherent material absorption frequently limits the optical path length within diamond ATR elements, the herein presented design combining bright tQCLs with a multi-reflection polycrystalline diamond (PCD) ATR element enables an optical beam path length of approximately 5 cm. Thereby, sensitive spectroscopic measurements in the MIR are enabled. As an example, non-invasive glucose monitoring in human saliva is examined, highlighting the potential benefits of the proposed analytical concept with regards to exquisite sensitivity and selectivity in combination with a robust sensing interface, i.e., diamond. This approach paves the way towards directly analyzing molecular constituents in complex and potentially corrosive biomedical and biochemical matrices.
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| 52. |
- Hagenbjörk-Gustafsson, Annika, et al.
(author)
-
Validation of the Willems badge diffusive sampler for nitrogen dioxide determinations in occupational environments
- 2002
-
In: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 127:1, s. 163-168
-
Journal article (peer-reviewed)abstract
- The Willems badge, a diffusive sampler for nitrogen dioxide, has previously been validated for ambient air measurements. This paper describes the laboratory and field validation of the Willems badge for personal sampling under working environment conditions. The mean sampling rate in the laboratory tests was 46 ml min(-1), with an RSD of 12%. No statistically significant effects on sampling rate of the sampling time, concentration of NO2 or relative humidity were found. A slightly decreased sampling rate was observed at low wind velocity. This was also confirmed during static sampling, which makes the sampler less appropriate for static sampling indoors. No back diffusion was observed. Storage of the samplers for two weeks before or after exposure did not affect the sampling rate. Our analysis is based on a modified colorimetric method, performed by FIA (flow injection analysis). This technique was compared to ion chromatography analysis. The use of ion chromatography lowered the detection limit from 11 to 2 microg m(-3) for an 8 h sample, and furthermore enabled the detection of other anions. In conclusion, the diffusive sampler was found to perform well for personal measurements in industrial environments.
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| 53. |
- Hakonen, Aron, 1970, et al.
(author)
-
Diffusion consistent calibrations for improved chemical imaging using nanoparticle enhanced optical sensors
- 2012
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 137, s. 315-321
-
Journal article (peer-reviewed)abstract
- A basic square root function was successfully used as a diffusion consistent calibration function that considers depletion mechanisms often occurring within optical chemical sensors. This continuous function improved image quality and simplified the calibration process. It may be a universal tool for the typical response function of reversible diffusion controlled sensing reactions. Further, we demonstrate that the gold nanoparticle interaction based ammonium fluorosensor is suitable for non-invasive high-resolution quantitative imaging of complex samples. The plasmon sensitized optical sensors were utilized as a bioanalytical tool for chemical imaging of natural degradation processes occurring in biological tissues. Analytical performance of the nanoparticle enhanced sensors confirmed superior sensitivity, reversibility, durability and overall image quality over non-doped sensing membranes. Although applied in a complex matrix of high potassium (major interferent) and very high sodium (interferent) excellent performance is achieved. The nanoparticle interaction/coextraction based sensing scheme utilized in this study is general and can be used for numerous ions, preferably combined with the diffusion consistent calibrations for superior analytical performance. A table with 44 commercially available ionophores is provided to guide potential users of this sensor configuration. © 2012 The Royal Society of Chemistry.
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| 54. |
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| 55. |
- Hartfelder, Urs, et al.
(author)
-
Determination of catalytic reaction mechanisms by isotopic frequency response.
- 2012
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 137:22, s. 5374-81
-
Journal article (peer-reviewed)abstract
- Efficient catalysts are of extraordinary importance for the development of efficient chemical processes as well as applications such as energy storage. Rational development of catalysts requires a mechanistic understanding of the catalytic reaction. Since steady-state investigations are insufficient to gain mechanistic understanding, transient methods such as SSITKA and frequency response have been developed. In this paper we provide a theoretical basis for a frequency response method based on variations in the isotopic composition of the reactant. This approach is particularly useful, since it permits transient investigations under quasi-steady state conditions and because the response is linear.
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| 56. |
- Herr, Amy E., et al.
(author)
-
Next wave advances in single-cell analyses
- 2019
-
In: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 144:3, s. 735-737
-
Journal article (other academic/artistic)abstract
- Welcome to this Analyst themed issue highlighting next wave advances in single cell analyses, Guest Edited by Amy Herr (University of California, Berkeley, USA) Takehiko Kitamori (University of Tokyo, Japan), Ulf Landegren (Uppsala University, Sweden) and Masood Kamali-Moghaddam (Uppsala University, Sweden).
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| 57. |
- Isetun, Sindra, et al.
(author)
-
Dynamic field sampling of airborne organophosphate triesters using solid-phase microextraction under equilibrium and non-equilibrium conditions
- 2005
-
In: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 30, s. 94-98
-
Journal article (peer-reviewed)abstract
- A simple setup for dynamic air sampling using a solid-phase microextraction (SPME) device designed for use in the field was evaluated for organophosphate triester vapour under both equilibrium and non-equilibrium conditions. The effects of varying the applied airflows in the sampling device were evaluated in order to optimise the system with respect to the Reynolds number and magnitude of the boundary layer that developed near the surface. Further, the storage stability of the analytes was studied for both capped and uncapped 100- m m PDMS fibres. Organophosphate triesters are utilized on large scales as flame-retardants and/or plasticizers, for instance in upholstered furniture. In indoor working environments these compounds have become common components in the surrounding air. Measurements were performed in a recently furnished working environment and the concentration of tris(2-choropropyl) phosphate was found to be 7 mg m23 .
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| 58. |
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| 59. |
- Johansson, Ursula, et al.
(author)
-
Isotopic exchange of kaolinite hydroxyl protons: a diffuse reflectance infrared Fourier transform spectroscopy study
- 1998
-
In: The Analyst. - 0003-2654 .- 1364-5528. ; 123:4, s. 641-645
-
Journal article (peer-reviewed)abstract
- Specific surface reactions on kaolinite were investigated by deuterium exchange of the hydroxyl protons of kaolinite, The kaolinite samples were reacted with deuterium oxide for 48 h and 2.5 and 5 weeks, at various pH values (3, natural and 8) and at different temperatures (ambient, and 30, 60 and 100 degrees C), Analyses were performed using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The spectral results show that it is very difficult at room temperature to exchange the hydroxyl protons isotopically with deuterons at the surface of kaolinite, The temperature and the reaction time must be increased for successful exchange. It was found that the most suitable temperature for isotopic exchange was 60 degrees C. The pH did not significantly influence the deuteration, Only at high pH were changes of the OD bands in the DRIFT spectra observed, This study shows that it is possible to deuterate kaolinite without using intercalation. All three types of hydroxyl protons from the inner, inner surface and edge were exchanged.
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| 60. |
- Jonsson, Pär, et al.
(author)
-
Extraction, interpretation and validation of information for comparing samples in metabolic LC/MS data sets
- 2005
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 130:5, s. 701-707
-
Journal article (pop. science, debate, etc.)abstract
- LC/MS is an analytical technique that, due to its high sensitivity, has become increasingly popular for the generation of metabolic signatures in biological samples and for the building of metabolic data bases. However, to be able to create robust and interpretable ( transparent) multivariate models for the comparison of many samples, the data must fulfil certain specific criteria: (i) that each sample is characterized by the same number of variables, (ii) that each of these variables is represented across all observations, and (iii) that a variable in one sample has the same biological meaning or represents the same metabolite in all other samples. In addition, the obtained models must have the ability to make predictions of, e. g. related and independent samples characterized accordingly to the model samples. This method involves the construction of a representative data set, including automatic peak detection, alignment, setting of retention time windows, summing in the chromatographic dimension and data compression by means of alternating regression, where the relevant metabolic variation is retained for further modelling using multivariate analysis. This approach has the advantage of allowing the comparison of large numbers of samples based on their LC/MS metabolic profiles, but also of creating a means for the interpretation of the investigated biological system. This includes finding relevant systematic patterns among samples, identifying influential variables, verifying the findings in the raw data, and finally using the models for predictions. The presented strategy was here applied to a population study using urine samples from two cohorts, Shanxi (People's Republic of China) and Honolulu ( USA). The results showed that the evaluation of the extracted information data using partial least square discriminant analysis (PLS-DA) provided a robust, predictive and transparent model for the metabolic differences between the two populations. The presented findings suggest that this is a general approach for data handling, analysis, and evaluation of large metabolic LC/MS data sets.
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| 61. |
- Kanje, Sara, et al.
(author)
-
Next generation of labeling reagents for quantitative and multiplexing immunoassays by the use of LA-ICP-MS
- 2016
-
In: ANALYST. - : Royal Society of Chemistry. - 0003-2654. ; 141:23, s. 6374-6380
-
Journal article (peer-reviewed)abstract
- Immuno imaging by the use of Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) is a growing research field in life sciences such as biology and biomedicine. Various element labeling strategies for antibodies have been developed for the application of multiplex immunoassays analyzed by the use of LA-ICP-MS. High multiplexing capabilities, a wide linear dynamic range and the possibility of absolute quantification are the main advantages of ICP-MS. But in the context of immuno imaging by the use of LA-ICP-MS, quantification of analytes is limited due to non-controllable antibody labeling chemistry. In the presented proof-of-principle a novel antibody labeling technique has been investigated which results in a controlled labeling degree. A small affinity protein based on the C2 domain of protein G was modified with conventional metal coded tags (MeCAT) after introducing a cysteine into the C-terminus of the protein. The modified C2 domain photo-crosslinks to the Fc or Fab region of the IgG and allows specific and covalent labeling of antibodies for multiplex immunoassay analysis by the use of LA-ICP-MS. In combination with a house-made calibration membrane the amount of labeled antibody-antigen complexes in a multiplex western blot immuno-assay was determined by LA-ICP-MS.
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| 62. |
- Kaya, Ibrahim, 1989, et al.
(author)
-
Multimodal chemical imaging of a single brain tissue section using ToF-SIMS, MALDI-ToF and immuno/histochemical staining
- 2021
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 146:4, s. 1169-1177
-
Journal article (peer-reviewed)abstract
- Cluster ion beam ToF-SIMS and/or MALDI-ToF mass spectrometry imaging (using 1,5-DAN matrix via sublimation) of a single coronal rat brain tissue section followed by classical-or immuno-histochemical staining faclilated a new multimodal chemical imaging workflow allowing complementary correlation of the lipid molecular ion images with the immuno/histological features within cerebellum region of the same brain tisue section.
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| 63. |
- Keighron, Jacqueline, 1982, et al.
(author)
-
Analytical tools to monitor exocytosis: A focus on new fluorescent probes and methods
- 2012
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 137:8, s. 1755-1763
-
Research review (peer-reviewed)abstract
- A great deal of research has been focused on unraveling the processes governing the exocytotic pathway and the extent of release during the process. Arguments abound for and against both the occurrence and significance of full release during exocytosis and partial release including kiss-and-run events. Several optical methods to directly observe the exocytosis process have been developed and here we focus on fluorescence methods and probes for this work. Although fluorescence imaging has been used for cell experiments for decades, in the last two decades a plethora of new approaches have arrived on the scene. These include application of new microscopy techniques, like total internal reflectance and stimulated emission depletion that are offering new ways to circumvent the limits of far field microscopy with a diffraction limit of 200 nm, and allow tracking of single synaptic vesicles. For selective imaging of synaptic vesicles the introduction of methods to stain the vesicular compartment has involved developing probes of the vesicular membrane and intravesicular solution, nanoparticle quantum dots that can be observed during exocytosis but not via the fusion pore, and fluorescent false neurotransmitters.
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| 64. |
- Kelly, Orla, et al.
(author)
-
Femtosecond lasers for mass spectrometry : proposed application to catalytic hydrogenation of butadiene.
- 2012
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 137:1, s. 64-9
-
Journal article (peer-reviewed)abstract
- Mass spectra from the interaction of intense, femtosecond laser pulses with 1,3-butadiene, 1-butene, and n-butane have been obtained. The proportion of the fragment ions produced as a function of intensity, pulse length, and wavelength was investigated. Potential mass spectrometry applications, for example in the analysis of catalytic reaction products, are discussed.
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| 65. |
- Kjeldsen, Frank, et al.
(author)
-
On studying protein phosphorylation patterns using bottom-up LC-MS/MS : the case of human alpha-casein
- 2007
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 132:8, s. 768-776
-
Journal article (peer-reviewed)abstract
- Most proteomics studies involving mapping post-translational modifications, such as the phosphorylation of serine and threonine, are performed today using the 'bottom-up' approach. This approach involves enzymatic cleavage of proteins, most often by trypsin, with subsequent nano-LC-MS/MS. The occupancy rates of phosphosites in proteins may differ by orders of magnitude, and thus the occupancy rate must be reported for each occupied phosphosite. To highlight potential pitfalls in quantifying the occupancy rates, αs1- casein from human milk was selected as a model molecule representing moderately phosphorylated proteins. For this purpose, human milk from one Caucasian woman in the eighth month of lactation was used. The phosphorylation level of caseins is believed to have major implications for the formation of micelles that are involved in delivering valuable calcium phosphate and other minerals to the new-born. Human αs1-casein has been reported to be much less phosphorylated than ruminant caseins, which may indicate a different function of caseins in humans. Revealing the phosphorylation pattern in human casein can thus shed light on its function. The current study found that the sequence region between the residues Ser70 and Ser76 in human αs1-casein is in fact phosphorylated, contrary to previous knowledge. The site of the most abundant phosphorylation is Ser75, in agreement with the known action of the mammary gland casein kinase. There is evidence for the second phosphorylation in that region, possibly at Ser73. Earlier reported positions of phosphorylations at Ser18 and Ser26 are also confirmed, but not the dominance of Ser18 phosphorylation. The occupancy rates at Ser18, Ser26 and Ser75 are estimated to be (7 ± 2), (20 ± 6) and (27 ± 9)%, respectively. Owing to differences in the ionization efficiency between phosphorylated and unphosphorylated peptides a 30% error margin is added to the occupancy rates. The highlighted pitfalls of the bottom-up strategy include the sensitivity of enzymes to proximal acidic and phosphorylated residues and the presence of multiple isoforms, including unexpected ones, of the tryptic peptides. The utility of the earlier introduced PhosTS_hunter and ModifiComb approaches for evading the latter pitfall is demonstrated.
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| 66. |
- Kumar, Keshav, et al.
(author)
-
Constraint randomised non-negative factor analysis (CRNNFA) : an alternate chemometrics approach for analysing the biochemical data sets
- 2017
-
In: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 142:11, s. 1916-1928
-
Journal article (peer-reviewed)abstract
- The present work introduces an alternate chemometrics approach constraint randomised non-negative factor analysis (CRNNFA) for analysing the bioanalytical data sets. The CRNNFA algorithm provides the outputs that are easy to interpret and correlate with the real chromatograms. The CRNNFA algorithm achieves termination when the iteration limit is reached circumventing the premature convergence. Theoretical and computational aspects of the proposed method are also described. The analytical and computational potential of CRNNFA are successfully tested by analysing the complex chromatograms of the peptidoglycan samples belonging to the Alphaproteobacterium members. The obtained results clearly show that CRNNFA can easily trace the compositional variability of the peptidoglycan samples. In summary, the proposed method in general can be a potential alternate approach for analysing the data sets obtained from different analytical and clinical fields.
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| 67. |
- Kumar, Saroj, et al.
(author)
-
Sensing protein antigen and microvesicle analytes using high-capacity biopolymer nano-carriers
- 2016
-
In: The Analyst. - 0003-2654 .- 1364-5528. ; 141:3, s. 836-846
-
Journal article (peer-reviewed)abstract
- Lab-on-a-chip systems with molecular motor driven transport of analytes attached to cytoskeletal filament shuttles (actin filaments, microtubules) circumvent challenges with nanoscale liquid transport. However, the filaments have limited cargo-carrying capacity and limitations either in transportation speed (microtubules) or control over motility direction (actin). To overcome these constraints we here report incorporation of covalently attached antibodies into self-propelled actin bundles (nanocarriers) formed by cross-linking antibody conjugated actin filaments viafascin, a natural actin-bundling protein. We demonstrate high maximum antigen binding activity and propulsion by surface adsorbed myosin motors. Analyte transport capacity is tested using both protein antigens and microvesicles, a novel class of diagnostic markers. Increased incubation concentration with protein antigen in the 0.1–100 nM range (1 min) reduces the fraction of motile bundles and their velocity but maximum transportation capacity of >1 antigen per nm of bundle length is feasible. At sub-nanomolar protein analyte concentration, motility is very well preserved opening for orders of magnitude improved limit of detection using motor driven concentration on nanoscale sensors. Microvesicle-complexing to monoclonal antibodies on the nanocarriers compromises motility but nanocarrier aggregation via microvesicles shows unique potential in label-free detection with the aggregates themselves as non-toxic reporter elements.
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| 68. |
- Källsten, Malin, et al.
(author)
-
Qualitative analysis of antibody-drug conjugates (ADCs) : an experimental comparison of analytical techniques of cysteine-linked ADCs.
- 2018
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 143:22, s. 5487-5496
-
Journal article (peer-reviewed)abstract
- Antibody-drug conjugates (ADCs) are an emerging type of biotherapeutics that utilize multiple tissue-specific antibodies combined with a range of linker designs to enable the transportation and selective release of cytotoxic drugs in close proximity to tumours. Consisting of antibodies conjugated to small drug molecules through a variety of linkers, ADCs are chemically complex analytes. Here we present a unique experimental comparison of four techniques for ADC analysis: hydrophobic interaction chromatography (HIC-UV/Vis), reversed phase liquid chromatography mass spectrometry (RPLC-MS), using either a QToF or an Orbitrap analyser, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Four different ADCs consisting of Trastuzumab, monomethyl auristatin E (MMAE) and a peptidic linker moiety differing in their respective stoichiometric ratios in regard to drug-to-antibody ratio (DAR) were used for the comparison. We found that the determined DAR from all techniques was comparable, while the accuracy of the molecular weights for the conjugated light and heavy chain differed more extensively. This indicates that the choice of a mass analyser is more crucial for determining the accurate weights of the light and heavy chains than to evaluate the DAR of a given batch. However, ambiguous DAR assignment in HIC-UV/Vis or bias for either the light or heavy chain fragments in the mass spectrometry-based techniques can influence the obtained average DAR value and the use of complementary techniques is advisable. Out of the four techniques evaluated, HIC-UV/Vis and MALDI required less time to obtain an average DAR value and would therefore be good for initial screenings in the early stages of the discovery phase of new ADCs.
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| 69. |
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| 70. |
- Lanekoff, Ingela, et al.
(author)
-
Matrix effects in biological mass spectrometry imaging : identification and compensation
- 2014
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 139:14, s. 3528-3532
-
Journal article (peer-reviewed)abstract
- Matrix effects in mass spectrometry imaging (MSI) may affect the observed molecular distribution in chemical and biological systems. In this study, we use mouse brain tissue of a middle cerebral artery occlusion (MCAO) stroke model to examine matrix effects in nanospray desorption electrospray ionization MSI (nano-DESI MSI). This is achieved by normalizing the intensity of the sodium and potassium adducts of endogenous phosphatidylcholine (PC) species to the intensity of the corresponding adduct of the PC standard supplied at a constant rate with the nano-DESI solvent. The use of MCAO model with an ischemic region localized to one hemisphere of the brain enables immediate comparison of matrix effects within one ion image. Furthermore, significant differences in sodium and potassium concentrations in the ischemic region in comparison with the healthy tissue allowed us to distinguish between two types of matrix effects. Specifically, we discuss matrix effects originating from variations in alkali metal concentrations and matrix effects originating from variations in the molecular composition of the tissue. Compensation for both types of matrix effects was achieved by normalizing the signals corresponding to endogenous PC to the signals of the standards. This approach, which does not introduce any complexity in sample preparation, efficiently compensates for signal variations resulting from differences in the local concentrations of sodium and potassium in tissue sections and from the complexity of the extracted analyte mixture derived from local variations in molecular composition.
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| 71. |
- Lanekoff, Ingela, et al.
(author)
-
Spatially resolved analysis of glycolipids and metabolites in living Synechococcus sp. PCC 7002 using nanospray desorption electrospray ionization
- 2013
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 138:7, s. 1971-1978
-
Journal article (peer-reviewed)abstract
- Microorganisms release a diversity of organic compounds that couple interspecies metabolism, enable communication, or provide benefits to other microbes. Increased knowledge of microbial metabolite production will contribute to understanding of the dynamic microbial world and can potentially lead to new developments in drug discovery, biofuel production, and clinical research. Nanospray desorption electrospray ionization (nano-DESI) is an ambient ionization technique that enables detailed chemical characterization of molecules from a specific location on a surface without special sample pretreatment. Due to its ambient nature, living bacterial colonies growing on agar plates can be rapidly analyzed without affecting the viability of the colony. In this study we demonstrate for the first time the utility of nano-DESI for spatial profiling of chemical gradients generated by microbial communities on agar plates. We found that despite the high salt content of the agar used in this study (~350 mM), nano-DESI analysis enables detailed characterization of metabolites produced by the Synechococcus sp. PCC 7002 colonies. High resolution mass spectrometry and MS/MS analysis of the living Synechococcus sp. PCC 7002 colonies allowed us to detect metabolites and lipids on the colony and on the surrounding agar, and confirm their identities. High sensitivity of nano-DESI enabled identification of several glycolipids that have not been previously reported by extracting the cells using conventional methods. Spatial profiling demonstrated that a majority of lipids and metabolites were localized on the colony while sucrose and glucosylglycerol, an osmoprotective compound produced by cyanobacteria, were secreted onto agar. Furthermore, we demonstrated that the chemical gradients of sucrose and glucosylglycerol on agar depend on the age of the colony. The methodology presented in this study will facilitate future studies focused on molecular-level characterization of interactions between bacterial colonies.
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| 72. |
- Larsson, Tom, et al.
(author)
-
Studies of transport and collection characteristics of gaseous mercury in natural gases using amalgamation and isotope dilution analysis
- 2007
-
In: The Analyst. - : RSC Publishing. - 0003-2654 .- 1364-5528. ; 132:6, s. 579-586
-
Journal article (peer-reviewed)abstract
- Transport and collection characteristics were studied for gaseous elemental mercury (Hg0(g)) in natural gases using newly developed methodology based on amalgamation, isotope dilution with permeation tubes and inductively coupled plasma mass spectrometry. The study involved different Au–Pt collection tube designs, tubing materials and gaseous matrices, including air, natural and sales gas, as well as methane and sales gas to which hydrogen sulfide (H2S) had been added. The Hg0(g) capacity of the Au–Pt tubes was determined to 3.5 ± 0.1 µg. Blanks and detection limits of gaseous mercury (Hg(g)) were 58 ± 17 pg m–3 and 50 pg m–3, respectively, for a 60 L sample volume. For the gases tested, added Hg0(g) tracers could be collected with 90% or higher efficiency at flow rates and volumes of up to 10 L min–1 and 100 L, respectively. The collection efficiency was found to be independent of the type of gas tested, even in the presence of H2S. However, for the gases containing H2S, the apparent transport efficiency of added Hg0(g) tracers through stainless steel tubing varied from 50 to 150% upon changing the temperature from 25 to 100 °C. The interaction of stainless steel with Hg0(g) leading to either a sink, or source of Hg, was not observed in the absence of H2S, nor was it observed for PTFE tubing in the presence of H2S. These observations raise questions about the applicability of currently used sampling procedures for determination of Hg(g) in H2S rich natural gases, including the 6978-2 ISO standard method, in which stainless steel is a prescribed material for tubing and valves of the sampling apparatus.
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| 73. |
- Li, Chenge, et al.
(author)
-
Quality assessment of recombinant proteins by infrared spectroscopy. Characterisation of a protein aggregation related band of the Ca2+-ATPase
- 2014
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 139:17, s. 4231-4240
-
Journal article (peer-reviewed)abstract
- Infrared spectroscopy was used to characterise recombinant sarcoplasmic reticulum Ca2+-ATPase (SERCA1a). In the amide I region, its spectrum differed from that of Ca2+-ATPase prepared from rabbit fast twitch muscle below 1650 cm(-1). A band at 1642 cm(-1) is reduced in the spectrum of the recombinant protein and a band at 1631 cm(-1) is more prominent. By comparison of amide 1 band areas with the known secondary structure content of the protein, we assigned the 1642 cm(-1) band to beta-sheet structure. Further investigation revealed that the 1642 cm(-1) band decreased and the 1631 cm-1 band increased upon storage at room temperature and upon repeated washing of a protein film with water. Also protein aggregates obtained after solubilisation of the rabbit muscle enzyme showed a prominent band at 1631 cm(-1), whereas the spectrum of solubilised ATPase resembled that of the membrane bound protein. The spectral position of the 1631 cm(-1) band is similar to that of a band observed for inclusion bodies of other proteins. The findings show that the absence of the 1642 cm(-1) band and the presence of a prominent band at 1631 cm(-1) indicate protein aggregation and can be used as a quality marker for the optimisation of recombinant protein production. We conclude that recombinant production of SERCA1a, storage at room temperature, repeated washing and aggregation after solubilisation all modify existing beta-sheets in the cytosolic domains so that they become similar to those found in inclusion bodies of other proteins.
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| 74. |
- Li, C. Y., et al.
(author)
-
A wide pH range optical sensing system based on a sol-gel encapsulated amino-functionalised corrole
- 2006
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 131:3, s. 388-393
-
Journal article (peer-reviewed)abstract
- The synthesis of a new compound, 10-(4-aminophenyl)-5,15-dimesitylcorrole, and its application for the preparation of optical chemical pH sensors is described. The dye materials were immobilized in a sol - gel glass matrix and characterised upon exposure to aqueous buffer solutions. The response of the sensor is based on the fluorescence intensity changing of corrole owing to multiple steps of protonation and deprotonation. Due to its containing several proton sensitive centers, the 10-(4-aminophenyl)- 5,15-dimesitylcorrole based optode shows a wider response range toward pH than that of tetraphenylporphyrin (TPPH2) and 5,10,15-tris( pentafluorophenyl) corrole (H-3(tpfc)). It shows a linear pH response in the range of 2.17 - 10.30. The effect of the composition of the sensor membrane has been studied and the experimental conditions were optimized. The optode showed good reproducibility and reversibility, and common co-existing inorganic ions did not show obvious interference to its pH measurement.
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| 75. |
- Lidén, H., et al.
(author)
-
On-line determination of non-volatile or low-concentration metabolites in a yeast cultivation using an electronic nose
- 2000
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 125:6, s. 1123-1128
-
Journal article (peer-reviewed)abstract
- An electronic nose was used for on-line gas phase monitoring of key metabolites in a Saccharomyces cerevisiae cultivation. The metabolites were either non-volatile or present at very low concentrations and therefore not detectable in the gas phase by the sensors in the electronic nose. It was found that it is still possible to make a prediction based on the off-gas emission. Artificial neural networks (ANNs) were trained using data acquired by the gas sensors and reference data obtained from on-line HPLC analyses, from a total of six cultivations to estimate concentrations of the metabolites glucose, glycerol, acetate and acetaldehyde. The ANNs were subsequently validated on an independent set of cultivation data resulting in a prediction accuracy described by the root mean square error (RMSE) of 0.13 (in the range 0-7.33), 0.015 (0.08-0.15), 0.012 (0-0.20) and 0.004 (0-0.11) g L-1, respectively. Data from a cultivation with higher initial glucose concentration were added to the original data and the extended set was used for training an ANN to determine concentration variables at higher concentration ranges than in the first study. The RMSE was 1.2 (0-9.31), 0.016 (0.09-0.20), 0.026 (0-0.19) and 0.010 (0-0.15) g L-1, respectively, when validating the ANNs.
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| 76. |
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| 77. |
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| 78. |
- Liljegren, Gustav, et al.
(author)
-
On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry
- 2005
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; :130, s. 1358-1368
-
Journal article (peer-reviewed)abstract
- Electrochemically controlled solid-phase extractions of anions were interfaced on-line to electrospray mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS), using polypyrrole coated electrodes and a thin-layer electrochemical (EC) flow cell. The results indicate that electrochemically controlled solid-phase extraction (EC-SPE) can be used as a versatile potential controlled sample preparation technique for a range of anions and that the properties of the polypyrrole coatings can be modified by altering the electrodeposition conditions. In the present study, the influence of interfering anions (i.e., fluoride and sulfate), and the anion used during the electropolymerisation, on the bromide extraction recovery was investigated for EC-SPE interfaced to ICP-MS. The results of these experiments show that the interference due to the presence of similar concentrations of sulfate can be reduced when using a polypyrrole coating electropolymerised in the presence of bromide ions. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were also used to study the morphology of the coatings, as well as the variations in the film thickness within the coatings. The effect of different desorption techniques on the bromide preconcentration factor in the ICP-MS on-line flow system was also examined. Stopped-flow desorption was found to give rise to significantly increased preconcentration factors in comparison with desorptions in flowing solutions. While the desorption efficiency depends on the type of desorption electrolyte (the electrolyte in which the desorption takes place), due to the competing influx of cations, the influence of the pH on the switching charge of the polypyrrole coating was found to be small, at constant ionic strength. To study the applicability of the EC-SPE technique with respect to real samples, investigations were also made with tap water samples spiked with different bromide concentrations. The results of these experiments, which were carried out using a modified thin-layer EC flow cell allowing in situ polymerisation of polypyrrole yielding a polymer plug covering the cross section of the channel, demonstrate that 3 uM concentrations of bromide could be detected in the tap water sample. This demonstrates that the extraction technique allows extractions of low concentrations of ions in the presence of significantly higher concentrations of other similar ions. The fact that the extraction and desorption steps are electrochemically controlled makes EC-SPE particularly well suited for inclusion in miniaturised lab-on-a-chip systems.
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| 79. |
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| 80. |
- Lin, Weifeng, et al.
(author)
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Sensitive mass spectrometric analysis of carbonyl metabolites in human urine and fecal samples using chemoselective modification
- 2020
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 145:11, s. 3822-3831
-
Journal article (peer-reviewed)abstract
- Metabolites with ketone or aldehyde functionalities comprise a large proportion of the human metabolome, most notably in the form of sugars. However, these reactive molecules are also generated through oxidative stress or gut microbiota metabolism and have been linked to disease development. The discovery and structural validation of this class of metabolites over the large concentration range found in human samples is crucial to identify their links to pathogenesis. Herein, we have utilized an advanced chemoselective probe methodology alongside bioinformatic analysis to identify carbonyl-metabolites in urine and fecal samples. In total, 99 metabolites were identified in urine samples and the chemical structure for 40 metabolites were unambiguously validated using a co-injection procedure. We also describe the preparation of a metabolite-conjugate library of 94 compounds utilized to efficiently validate these ketones and aldehydes. This method was used to validate 33 metabolites in a pooled fecal sample extract to demonstrate the potential for rapid and efficient metabolite detection over a wide metabolite concentration range. This analysis revealed the presence of six metabolites that have not previously been detected in either sample type. The constructed library can be utilized for straightforward, large-scale, and expeditious analysis of carbonyls in any sample type.
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| 81. |
- Lind, Pernilla, et al.
(author)
-
Albumin adducts in plasma from workers exposed to toluene diisocyanate
- 1997
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 122:2, s. 151-154
-
Journal article (peer-reviewed)abstract
- Desalted plasma from a 2,4- and 2,6-toluene diisocyanate (2,4- and 2,6-TDI) exposed worker at a factory producing flexible polyurethane foam was separated and fractionated into 200 fractions using ion-exchange chromatography followed by a gel-filtration separation and fractionation into 59 fractions. The corresponding amines (to the isocyanates), 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA), were determined in each fraction after sulfuric acid hydrolysis as pentafluoropropionic anhydride derivatives by capillary gas chromatography and chemical ionisation mass spectrometry monitoring negative ions. The ion exchange fractions containing TDA (81-115) were added together and the solution was separated and fractionated on the gel-filtration column. The fractions 81-115 contained 84 and 72% of 2,4- and 2,6-TDA, respectively, as compared to the unfractionated plasma. The gel filtration fractions 22-27 contained 107 and 119% of 2,4- and 2,6-TDA, respectively, as compared to the amounts in the ion exchange fractions (81-115). Agarose gel-electrophoresis and electroimmunoassay demonstrated that albumin, 2,4- and 2,6-TDA co-eluted in both ion-exchange and gel-filtration chromatography. Quantitative determination of albumin, 2,4- and 2,6-TDA also demonstrated that these components co-eluted using albumin-immunosorption chromatography. In addition, studies of affinity isolated IgG revealed that this fraction was devoid of 2,4- and 2,6-TDA. These results indicate that albumin is the major receptor molecule for 2,4- and 2,6-TDI in blood plasma and that these isocyanates form covalent bondings with albumin.
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| 82. |
- Lindahl, R, et al.
(author)
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Determination of morpholine in air by derivatisation with 1-naphthylisothiocyanate and HPLC analysis
- 2001
-
In: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 126:2, s. 152-154
-
Journal article (peer-reviewed)abstract
- A method for the determination of morpholine in air was developed. Samples were collected with adsorbent tubes containing XAD-2 resin coated with 1-naphthylisothiocyanate (NIT). The thiourea derivative formed was subsequently desorbed with acetonitrile and analysed by HPLC with UV detection. The recovery after gas phase spiking with morpholine (2.2-1570 micrograms) was 91% (86-100%) with a relative standard deviation of 5.5%. No effect on recovery from relative humidity or amount of morpholine was seen. The lowest level tested corresponded to 7 mg m-3 (1/10 threshold limit value) for a 15 min sampling period with a sampling rate of 20 ml min-1. Exposed NIT-coated XAD-2 tubes were stable at room temperature for at least 2 weeks.
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| 83. |
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| 84. |
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| 85. |
- Liu, Wenxin, et al.
(author)
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A flexible method of carbonate determination using an automatic gas analyzer equipped with an FTIR photoacoustic measurement chamber
- 1999
-
In: The Analyst. - 0003-2654 .- 1364-5528. ; 124:3, s. 361-365
-
Journal article (peer-reviewed)abstract
- A Fourier transform infrared spectrometer was employed to determine automatically the total inorganic carbonate (TIC) in solids and waters, based on active photoacoustic absorption of infrared light by carbon dioxide. A 2.0 l reactor, connected to the spectrometer, is immersed in water-bath at 20 °C. After purging with pure N2, 5 ml of 0.5 mol l–1 HClO4 are injected into 50 ml of solid suspension or solution with continuous stirring. The specific absorption of infrared light by the CO2 evolved induces corresponding fluctuations of temperature and pressure in a measurement chamber. Accordingly, photoacoustic signals, with frequencies dependent on the absorbed wavelengths, are generated and measured by the chamber microphones in the form of an absorption spectrum and concentration. For solids, the method exhibits a linear response up to 120 mg of CaCO3 with a detection limit of 0.02 mg; in the case of waters, these figures of merit are 36.4 mmol l–1 and 3 µmol l–1 NaHCO3, respectively. Since proton consumption by TIC in clay minerals may commonly influence the evaluation of surface acid–base properties, the methodology was applied to determine TIC in three natural illite samples of different origins. In addition, some potential interferences and modifications of this method are discussed.
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| 86. |
- Liu, Wei, et al.
(author)
-
Surface plasmon resonance imaging of limited glycoprotein samples
- 2008
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 133:9, s. 1268-1273
-
Journal article (peer-reviewed)abstract
- A surface plasmon resonance imaging method has been developed for high throughput recognition and determination of low level glycoproteins with limited sample volume at least down to 50 nL. Chicken ovalbumin and immunoglobulin G were chosen as model compounds while bovine serum albumin and lysozyme were used as control. Each protein, at a concentration of 0.0080-1.0 mg mL(-1), was printed on one gold sensing film, and the films were simultaneously reacted with a probe solution and viewed using a laboratory-built surface plasmon resonance imaging system. The imaging signals were dependent on the concentration and the type of analyte, with a limit of detection down to at least 0.5 ng. The glycoproteins dotted at either 1.0 mg mL(-1) or 0.010 mg mL(-1) were easily differentiated from the non-glycoproteins by reaction with 200 nM concanavalin A (con A), giving a limit of recognition down also to 0.5 ng glycoprotein. This imaging method was hence considered a new tool for analyzing glycoproteins.
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| 87. |
- Loughran, MG, et al.
(author)
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Ammonium ion requirement and stability of methanol dehydrogenase TTF TCNQ electrodes
- 1996
-
In: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 121:11, s. 1711-1715
-
Journal article (peer-reviewed)abstract
- The ammonium ion requirement and stability of quinoprotein methanol dehydrogenases were investigated with a view to incorporating them in enzyme electrodes for alcohol. This involved consideration of the effect of temperature and polyelectrolytes on enzyme stability. A packed cavity electrode was constructed using the organic conducting salt TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane). Methanol dehydrogenase isolated from Paracoccus denitrificans was more stable than the enzyme isolated from Methylophilus methylotrophus and was successfully used for repeated assay in packed cavity electrodes without significant loss in current output. These investigations also showed that, contrary to suggestions in the literature, ammonium ions are necessary for efficient re-oxidation of methanol dehydrogenase at the organic conducting salt electrode.
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| 88. |
- Lundahl, Johan, 1978, et al.
(author)
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A new highly adaptable design of shear-flow device for orientation of macromolecules for Linear Dichroism (LD) measurement
- 2011
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 136:16, s. 3303-3306
-
Journal article (peer-reviewed)abstract
- This article presents a new design of flow-orientation device for the study of bio-macromolecules, including DNA and protein complexes, as well as aggregates such as amyloid fibrils and liposome membranes, using Linear Dichroism (LD) spectroscopy. The design provides a number of technical advantages that should make the device inexpensive to manufacture, easier to use and more reliable than existing techniques. The degree of orientation achieved is of the same order of magnitude as that of the commonly used concentric cylinders Couette flow cell, however, since the device exploits a set of flat strain-free quartz plates, a number of problems associated with refraction and birefringence of light are eliminated, increasing the sensitivity and accuracy of measurement. The device provides similar shear rates to those of the Couette cell but is superior in that the shear rate is constant across the gap. Other major advantages of the design is the possibility to change parts and vary sample volume and path length easily and at a low cost.
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| 89. |
- Majdi, Soodabeh, 1980, et al.
(author)
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Selected recent in vivo studies on chemical measurements in invertebrates
- 2015
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:11, s. 3676-3686
-
Journal article (peer-reviewed)abstract
- In vivo measurements of neurotransmitters and related compounds have provided a better understanding of the chemical interactions that are a major part in functioning of brains. In addition, a great deal of technology has been developed to measure chemical species in other areas of living organisms. A key part of this work has been sampling technologies as well as direct measurements in vivo. This is extremely important when sampling from the smallest animal systems. Yet, very small invertebrate systems are excellent models and often have better defined and more easily manipulated genetics. This review focuses on in vivo measurements, electrochemical methods, fluorescence techniques, and sampling and is further narrowed to work over approximately the last three years. Rapid developments of in vivo studies in these model systems should aid in finding solutions to biological and bioanalytical challenges related to human physiological functions and neurodegenerative diseases.
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| 90. |
- Manzano, J., et al.
(author)
-
Principal component analysis of sample response to RGB light
- 2004
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 129:2, s. 182-189
-
Journal article (peer-reviewed)abstract
- In this article we present a principal component analysis (PCA) for data generated by a web camera recording of a two dimensional array of samples illuminated with CRT and TFT screens. In order to create a robust cross-platform identification system useful in bio-analysis we investigate a "buoyant" approach to PCA. Using such approach we assess the relevance of keeping local reference samples to compensate for the spurious angle dependence introduced by TFT screens. We show how local references allow for the detection of such screen dependent angular anisotropy and the construction of a new coordinate space where this effect is considerably reduced. This new coordinate space is built using only the RGB coordinates provided by the camera without resorting to the screen RGB coordinates. Finally we investigate the sensitivity of sample tagging with respect to the number of illuminating colours. We show that 3 quasi-pure R, G and B colours are enough to obtain good separation of data and robust CRT/TFT cross platform tagging.
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| 91. |
- Marand, Åsa, et al.
(author)
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Determination of amines as pentafluoropropionic acid anhydride derivatives in biological samples using liquid chromatography and tandem mass spectrometry
- 2004
-
In: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 129:6, s. 522-528
-
Journal article (peer-reviewed)abstract
- Determination of amines in biological samples as markers of exposure to the amines or the corresponding isocyanates is an important tool for industrial exposure assessment. In this study, a liquid chromatography and tandem mass spectrometry (LC- MS/ MS) method for determination of amines in biological samples as perfluorofatty amides derivatives is presented. The method enables determination of diamines such as methylene diamine (MDA), toluene diamine (TDA), naphthalene diamine (NDA), hexamethylene diamine (HDA), isophorone diamine (IPDA), methylenedi( cyclohexylamine) (HMDA) and 4,4'-methylene-(2-chloroaniline) (MOCA) in human urine and plasma. The work-up procedure included hydrolysis of the biological samples with 3 M H2SO4 at 100degreesC for 16 h and extraction of the amines into toluene, where derivatisation of the amines with perfluorofatty acid anhydride was performed. Following removal of excess reagent and the acid formed and an exchange of solvent, the derivatives were analysed using gradient elution with an acetonitrile/water mobile phase composition and electrospray ionisation (ESI) with multiple reaction monitoring (MRM) of [M - H](-) --> [M - H - 120](-) or [119](-). Several perfluorofatty acid anhydrides were evaluated as derivatisation reagents, but the LC chromatographic properties of the pentafluoropropionic acid anhydride (PFPA) derivatives were favourable. Quantification of amine - PFPA derivatives was performed using deuterium labelled amine - PFPA derivatives as internals standards with good precision and linearity in the investigated range of 0 - 20 ng ml(-1) urine. The instrumental detection limits for the amine - PFPA derivatives were 0.2 - 3 fmol for MRM of [M - H](-) --> [119](-) and 0.3 - 8 fmol for [M - H](-) --> [M - H - 120](-). In 10 urine and 6 plasma samples from workers exposed to isocyanates, determination of TDA and MDA as PFPA derivatives was performed using LC- MS/ MS and a reference GC-MS method. No significant difference between the two methods was observed.
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| 92. |
- Matos, Tiago, et al.
(author)
-
Nucleic acid and protein extraction from electropermeabilized E. coli cells on a microfluidic chip.
- 2013
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 138:24, s. 7347-7353
-
Journal article (peer-reviewed)abstract
- Due to the extensive use of nucleic acid and protein analysis of bacterial samples, there is a need for simple and rapid extraction protocols for both plasmid DNA and RNA molecules as well as reporter proteins like the green fluorescent protein (GFP). In this report, an electropermeability technique has been developed which is based on exposing E. coli cells to low voltages to allow extraction of nucleic acids and proteins. The flow-through electropermeability chip used consists of a microfluidic channel with integrated gold electrodes that promote cell envelope channel formation at low applied voltages. This will allow small biomolecules with diameters less than 30 A to rapidly diffuse from the permeabilized cells to the surrounding solution. By controlling the applied voltage, partial and transient to complete cell opening can be obtained. By using DC voltages below 0.5 V, cell lysis can be avoided and the transiently formed pores can be closed again and the cells survive. This method has been used to extract RNA and GFP molecules under conditions of electropermeability. Plasmid DNA could be recovered when the applied voltage was increased to 2 V, thus causing complete cell lysis.
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| 93. |
- Mellqvist, Johan, 1965, et al.
(author)
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Temperature dependence of the absorption spectra of nitrogen oxide, nitrogen dioxide and sulfur dioxide in the application of differential optical absorption spectroscopy
- 1992
-
In: The Analyst. - 0003-2654 .- 1364-5528. ; 117:3, s. 417-418
-
Journal article (peer-reviewed)abstract
- An experimental set-up has been designed for measurements of differential absorption cross-sections ofgases at different temperatures. Preliminary measurements on NO, NO2 and SO2 have been carried out attemperatures between 20 and 400°C by using spectral resolutions in the range 0.26-0.95 nm. Thesemeasurements show that the differential absorption cross-sections for all three gases decrease continuouslywith increasing temperature. Large relative errors resulted when differential absorption cross-sectionsobtained at room temperature were used in the differential optical absorption spectroscopic technique forevaluation of the concentration of gases at high temperatures. The relative errors were of the order of 70% forSO2 and NOz and of the order of 20% for NO at 400°C.
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| 94. |
- Meyer, Tobias, et al.
(author)
-
A compact microscope setup for multimodal nonlinear imaging in clinics and its application to disease diagnostics
- 2013
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 138:14, s. 4048-4057
-
Journal article (peer-reviewed)abstract
- The past years have seen increasing interest in nonlinear optical microscopic imaging approaches for the investigation of diseases due to the method's unique capabilities of deep tissue penetration, 3D sectioning and molecular contrast. Its application in clinical routine diagnostics, however, is hampered by large and costly equipment requiring trained staff and regular maintenance, hence it has not yet matured to a reliable tool for application in clinics. In this contribution implementing a novel compact fiber laser system into a tailored designed laser scanning microscope results in a small footprint easy to use multimodal imaging platform enabling simultaneously highly efficient generation and acquisition of second harmonic generation (SHG), two-photon excited fluorescence (TPEF) as well as coherent anti-Stokes Raman scattering (CARS) signals with optimized CARS contrast for lipid imaging for label-free investigation of tissue samples. The instrument combining a laser source and a microscope features a unique combination of the highest NIR transmission and a fourfold enlarged field of view suited for investigating large tissue specimens. Despite its small size and turnkey operation rendering daily alignment dispensable the system provides the highest flexibility, an imaging speed of 1 megapixel per second and diffraction limited spatial resolution. This is illustrated by imaging samples of squamous cell carcinoma of the head and neck (HNSCC) and an animal model of atherosclerosis allowing for a complete characterization of the tissue composition and morphology, i.e. the tissue's morphochemistry. Highly valuable information for clinical diagnostics, e. g. monitoring the disease progression at the cellular level with molecular specificity, can be retrieved. Future combination with microscopic probes for in vivo imaging or even implementation in endoscopes will allow for in vivo grading of HNSCC and characterization of plaque deposits towards the detection of high risk plaques.
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| 95. |
- Minero, Antonio S. Gabriel, et al.
(author)
-
Sequence-specific validation of LAMP amplicons in real-time optomagnetic detection of Dengue serotype 2 synthetic DNA
- 2017
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 142:18, s. 3441-3450
-
Journal article (peer-reviewed)abstract
- We report on an optomagnetic technique optimised for real-time molecular detection of Dengue fever virus under ideal as well as non-ideal laboratory conditions using two different detection approaches. The first approach is based on the detection of the hydrodynamic volume of streptavidin coated magnetic nanoparticles attached to biotinylated LAMP amplicons. We demonstrate detection of sub-femtomolar Dengue DNA target concentrations in the ideal contamination-free lab environment within 20 min. The second detection approach is based on sequence-specific binding of functionalised magnetic nanoparticles to loops of LAMP amplicons. Melting studies reveal that true positive and spurious amplicons have different melting points and this allows us to discriminate between them. This is found to be in a good agreement with subsequent studies on real-time sequence-specific discrimination of LAMP amplicons. The specific binding causes clustering of magnetic nanoparticles via binding to multiple sites (loops) emerging in the elongation phase of LAMP. Formation of nanoclusters is monitored via the depletion of the optomagnetic signal due to free nanoparticles. After sequence-specific validation, we claim detection of down to 100 fM of Dengue target after 20 min of LAMP with a contamination background.
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| 96. |
- Moberg, My, et al.
(author)
-
Optimization strategy for liquid chromatography-electrospray ionization mass spectrometry methods
- 2000
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 125, s. 1970-1976
-
Journal article (peer-reviewed)abstract
- A strategy for the optimization of liquid chromatography (LC)–electrospray ionization mass spectrometry methods is proposed. The optimization aims at good chromatographic quality and a high signal-to-noise ratio for the analyte. The three-step strategy comprises screening experiments, LC studies and infusion experiments, using empirical modelling to evaluate the experimental data. The optimization route was examined for three different cases: (a) estriol in a mixture of estrogens, (b) ibuprofen and related metabolites in urine and (c) morphine in the presence of codeine
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| 97. |
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| 98. |
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| 99. |
- Moein, Mohammad Mahdi, et al.
(author)
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A new strategy for surface modification of polysulfone membrane by in situ imprinted sol-gel method for the selective separation and screening of L-Tyrosine as a lung cancer biomarker
- 2015
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:6, s. 1939-1946
-
Journal article (peer-reviewed)abstract
- In this work, a novel method based on in situ molecularly imprinted sol-gel for the surface modification of a polysulfone membrane (PSM) was developed. A modified molecularly imprinted sol-gel polysulfone membrane (MSM) was placed in a homemade plastic tube and coupled on-line with LC/MS/MS for the selective extraction and screening of L-Tyrosine (Tyr) as a tentative lung cancer biomarker in human plasma samples. The existence of molecularly imprinted sol-gel layers on both sides of a PSM was examined using scanning electron microscopy (SEM). To evaluate the role of precursor in the extraction performance, repeatability, and selectivity of developed method, three precursors, 3-(propylmethacrylate) trimethoxysilane (P1), 3-(triethoxysilyl)-propylamine (P2), tetraethyl orthosilicate (P3), individually and together were used for treatment of PSM. Our investigation showed that a single precursor's route is more repeatable, straightforward, precise, accurate, and selective for the extraction of Tyr in plasma samples. Moreover, to achieve the best conditions and extraction efficiency, the effect of influential parameters, including the conditioning, washing, and elution of solvents, sample flow rate, loading time, desorption time, loading sample volume, salt effect, pH, and adsorption capacity for the most efficiently prepared membranes were truly investigated. The non-molecularly imprinted sol-gel polysulfone membrane (NSM) was prepared as a blank via the same process but in the absence of the Tyr. The LOD (S/N = 3/1) was 0.1 nmol L-1 and the LOQ (S/N = 10/1) was 0.34 nmol L-1 for Tyr in the plasma samples. The linearity for the Tyr was in the range of 0.34-2000 nmol L-1 in the plasma samples. The coefficients of determination values were >= 0.998 for all runs. The extraction recovery was between 80%-85% for Tyr in the plasma samples. In addition, MSM could be used for up to 50 extractions without a significant change in recovery percentage.
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| 100. |
- Nielsen, Annika T., et al.
(author)
-
Trace determination of volatile sulfur compounds by solid-phase microextraction and GC-MS
- 2002
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 127:8, s. 1045-1049
-
Journal article (peer-reviewed)abstract
- A method was developed for the simultaneous determination of the following nine volatile sulfur compounds in gas samples: carbon disulfide, carbonyl sulfide, ethyl sulfide, ethyl methyl sulfide, hydrogen sulfide, isopropanethiol, methanethiol, methyl disulfide and methyl sulfide. The target compounds were preconcentrated by solid-phase microextraction (SPME) and determined by gas chromatography combined with mass spectrometry. Experimental design was employed to optimize the extraction time and temperature and concurrent detection of the nine compounds was achieved by using an SPME fiber coated with Carboxen-polydimethylsiloxane (75 ╡m). Detection limits ranged from 1 ppt (v/v) for carbon disulfide to 350 ppt (v/v) for hydrogen sulfide and calibration functions were linear up to 20 ppb (v/v) for all the compounds investigated.
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