| 1. |
- Ahlford, Annika, et al.
(författare)
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Dried reagents for multiplex genotyping by tag-array minisequencing to be used in microfluidic devices
- 2010
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 135:9, s. 2377-2385
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Tidskriftsartikel (refereegranskat)abstract
- We present an optimized procedure for freeze-drying and storing reagents for multiplex PCR followed by genotyping using a tag-array minisequencing assay with four color fluorescence detection which is suitable for microfluidic assay formats. A test panel was established for five cancer mutations in three codons (175, 248 and 273) of the tumor protein gene (TP53) and for 13 common single nucleotide polymorphisms (SNPs) in the TP53 gene. The activity of DNA polymerase was preserved for six months of storage after freeze-drying, and the half-life of activities of exonuclease I and shrimp alkaline phosphatase were estimated to 55 and 200 days, respectively. We conducted a systematic genotyping comparison using freeze-dried and liquid reagents. The accuracy of successful genotyping was 99.1% using freeze-dried reagents compared to liquid reagents. As a proof of concept, the genotyping protocol was carried out with freeze-dried reagents stored in reaction chambers fabricated by micromilling in a cyclic olefin copolymer substrate. The results reported in this study are a key step towards the development of an integrated microfluidic device for point-of-care DNA-based diagnostics.
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| 2. |
- Artemenko, Konstantin A., et al.
(författare)
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Optimization of immunoaffinity enrichment and detection : toward a comprehensive characterization of the phosphotyrosine proteome of K562 cells by liquid chromatography-mass spectrometry
- 2011
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 136:9, s. 1971-1978
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorylation of protein tyrosine residues regulates many cell functions and has also been proved to be involved in oncogenesis. Thus, the identification of the phosphotyrosine (pTyr) proteome of cells is a very important task. Since tyrosine phosphorylation represents only around 1% of the total human phosphoproteome, the study of pTyr proteins is rather challenging. Here we report the optimization study of the phosphotyrosine proteome using K562 cells as a model system. A substantial segment of the phosphotyrosine proteome of K562 cells was characterized by immunoaffinity enrichment with 4G10 and PYKD1 antibodies followed by LC-MS/MS analysis. 480 non-redundant pTyr peptides corresponding to 342 pTyr proteins were found. 141 pTyr peptides were not described elsewhere. The mass spectrometry approach involving high-resolving FTMS analysis of precursor ions and subsequent detection of CID fragments in a linear ion trap was considered as optimal. For detection of low abundant pTyr peptides pooling of individual immunoaffinity enrichments for one LC-MS/MS analysis was crucial. The enrichment properties of the monoclonal PYKD1 antibody were presented for the first time, also in comparison to the 4G10 antibody. PYKD1 was found to be more effective for protein enrichment (1.2 and 5% efficiency at peptide and protein level correspondingly), while 4G10 showed better results when peptide enrichment was performed (15% efficiency versus 3.6% at protein level). Substantially different subsets of the phosphoproteome were enriched by these antibodies. This finding together with previous studies demonstrates that comprehensive pTyr proteome characterization by immunoprecipitation requires multiple antibodies to be used for the affinity enrichment.
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| 3. |
- Axelsson, Mikael D., et al.
(författare)
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Multielemental analysis of Mn–Fe nodules by ICP-MS: optimisation of analytical method
- 2002
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 127:1, s. 76-82
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Tidskriftsartikel (refereegranskat)abstract
- Two acid digestion procedures (microwave-assisted and room temperature) were developed for the quantitative analysis of ferromanganese nodules by inductively coupled plasma double focusing sector field mass spectrometry (ICP-SFMS). Different compositions of the acid mixture, dilution factors and corrections for spectral interferences were tested. A combination of nitric, hydrochloric and hydrofluoric acids is necessary for complete sample digestion, with lowest acid to sample ratios (v/m) of 15 and 1.5. respectively, for the last two acids. Sample dilution factors higher than 2 X 104 should be used in order to decrease matrix effects and provide robust long-term instrumental operation. In spite of high dilution. method detection limits in the sub-mug g(-1) range were obtained for 54 out of 71 elements tested. due to the high detection capability of ICP-SFMS, as well as the special care taken to ensure the purity of reagents, to clean the instrument sample introduction system and to minimise sample handling. Owing to the presence of unresolved (at the resolution available) spectral interferences, accurate determination of Au, Hg, Os, Pd, Re and Rh is impossible without matrix separation. The accuracy of the entire analytical method was tested by the analysis of two nodule reference materials. The results generated agreed to within +/-2% for about 10, within +/-10% for more than 40 and within +/-20% for about 50 of 53 elements for which certified, recommended or literature values are available. A precision better than 3%, expressed as the between-digestion relative standard deviation (n=4). was obtained for the majority of elements, except in cases limited by low analyte concentrations
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| 4. |
- Azmi, Jahanara, et al.
(författare)
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Metabolic trajectory characterisation of xenobiotic-induced hepatotoxic lesions using statistical batch processing of NMR data : Nicholson Jeremy K., Holmes Elaine
- 2002
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). ; 127, s. 271-6
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Tidskriftsartikel (refereegranskat)abstract
- Multivariate statistical batch processing (BP) analysis of 1H NMR urine spectra was employed to establish time-dependent metabolic variations in animals treated with the model hepatotoxin, -naphthylisothiocyanate (ANIT). ANIT (100 mg kg-1) was administered orally to rats (n = 5) and urine samples were collected from dosed and matching control rats at time-points up to 168 h post-dose. Urine samples were measured via1H NMR spectroscopy and partial least squares (PLS) based batch processing analysis was used to interpret the spectral data, treating each rat as an individual batch comprising a series of timed urine samples. A model defining the mean urine profile over the 7 day study period was established, together with model confidence limits (±3 standard deviation), for the control group. Samples obtained from ANIT treated animals were evaluated using the control model. Time-dependent deviations from the control model were evident in all ANIT treated animals consisting of glycosuria, bile aciduria, an initial decrease in taurine levels followed by taurinuria and a reduction of tricarboxylic acid cycle intermediate excretion. BP provided an efficient means of visualising the biochemical response to ANIT in terms of both inter-animal variation and net variation in metabolite excretion profiles. BP also allowed multivariate statistical limits for normality to be established and provided a template for defining the sequence of time-dependent metabolic consequences of toxicity in NMR based metabonomic studies.
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| 5. |
- Badea, M, et al.
(författare)
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A flow immunoassay for alkylphenol ethoxylate surfactants and their metabolites - questions associated with cross-reactivity, matrix effects, and validation by chromatographic techniques
- 2003
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 128:7, s. 849-856
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the application and evaluation of a competitive enzyme flow injection immunoassay (EFIIA) for screening of alkylphenol ethoxylate (APEO) surfactants in different water samples based on a generic immunoassay system previously developed ( see E. Burestedt, C Nistor, U. Schagerlof and J. Emneus, Anal. Chem., 2000, 72, 4171 - 4177). The detection limits for octylphenol ethoxylates (OPEOs), nonylphenol ethoxylates (NPEOs), and nonylphenol (NP) were 0.5 mug l(-1), between 2 and 3 mug l(-1), and 50 mug l(-1), respectively, with a sample throughput of 6 h(-1) (i.e., for triplicate analysis of each sample). Different OPEOs and NPEOs were highly cross-reactive within the assay, with sensitivities in the same order of magnitude for all the ethoxylates tested, thus the result obtained by the EFIIA method could be used as an "alkylphenol ethoxylate index". No or minor matrix effects with recoveries between 70 - 120% for the reference analyte NPEO10 in tap, and surface water, and acceptable for rainwater, were observed. Influent and effluent surfactant containing wastewater samples were analysed by EFIIA, LC-MS, LC-Fluoresence (LC-FL), and a commercial microplate ELISA. High recoveries for different concentrations of APEO(10) spiked into a 200 times diluted raw influent and effluent wastewater were achieved with the EFIIA method, however, the found APEO content of the same diluted wastewater samples, before spiking, could not be correlated directly to the chromatographic result by any of the immunoassays, and the possible reasons for this are discussed. The same trend of decreasing APEO content from influent to effluent wastewater could, however, be followed for all methods employed.
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| 6. |
- Bailly-Chouriberry, Ludovic, et al.
(författare)
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A new analytical method based on anti-EPO monolith column and LC-FAIMS-MS/MS for the detection of rHuEPOs in horse plasma and urine samples
- 2012
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 137:10, s. 2445-2453
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Tidskriftsartikel (refereegranskat)abstract
- Recombinant human erythropoietin (rHuEPO) is a 30-34 kDa glycoprotein banned by the racing authorities. For some years this molecule has been detected in race horses in USA and in Europe, and even in racing camels. Although direct methods to differentiate horse endogenous EPO and rHuEPO have been developed either by LC-MS/MS or by isoelectric focusing (IEF) with double-blotting, the short confirmation time of such prohibited hormone in plasma remains a problem for horseracing doping control laboratories. In order to improve the rHuEPOs confirmation process in horse plasma or urine in terms of reliability and delay, a small anti-EPO monolith membrane contained in a disposable column (anti-EPO monolith column) has been successfully used and validated (n = 10). This new sample preparation, combined with LC-FAIMS-MS/MS, has been performed on plasma and urine samples collected from one horse which received an Eprex[registered sign] treatment during six consecutive days and a second one with a single injection of Aranesp[registered sign]. This inventive technology allowed the possibility to confirm the presence of rHuEPO within one day with a limit of detection validated for both urine and plasma at 250 pg mL-1 by means of a disposable, ready to use immunoaffinity column. The lower limit of detection (LLOD) obtained for each matrix was 100 pg mL-1. These results provide an important improvement for rHuEPO doping control in horseracing especially the possibility to confirm these banned molecules in both matrices, urine and plasma, with a confidence of two specific target peptides.
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| 7. |
- Baldassarre, Maurizio, et al.
(författare)
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Pushing the detection limit of infrared spectroscopy for structural analysis of dilute protein samples.
- 2014
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 139:21, s. 5393-5399
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Tidskriftsartikel (refereegranskat)abstract
- Fourier-transform infrared spectroscopy is a powerful and versatile tool to investigate the structure and dynamics of proteins in solution. The intrinsically low extinction coefficient of the amide I mode, the main structure-related oscillator, together with the high infrared absorptivity of aqueous media, requires that proteins are studied at high concentrations (>10 mg L(-1)). This may represent a challenge in the study of aggregation-prone proteins and peptides, and questions the significance of structural data obtained for proteins physiologically existing at much lower concentrations. Here we describe the development of a simple experimental approach that increases the detection limit of protein structure analysis by infrared spectroscopy. Our approach relies on custom-made filters to isolate the amide I region (1700-1600 cm(-1)) from irrelevant spectral regions. The sensitivity of the instrument is then increased by background attenuation, an approach consisting in the use of a neutral density filter, such as a non-scattering metal grid, to attentuate the intensity of the background spectrum. When the filters and grid are combined, a 2.4-fold improvement in the noise level can be obtained. We have successfully tested this approach using a highly diluted solution of pyruvate kinase in deuterated medium (0.2% w/v), and found that it provides spectra of a quality comparable to those recorded with a 10-fold higher protein concentration.
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| 8. |
- Baldassarre, Maurizio, et al.
(författare)
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Simultaneous acquisition of infrared, fluorescence and light scattering spectra of proteins : direct evidence for pre-fibrillar species in amyloid fibril formation
- 2016
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 141:3, s. 963-973
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Tidskriftsartikel (refereegranskat)abstract
- Different spectroscopic approaches are often used to probe specific aspects of amyloid fibril formation but are usually performed separately and under different conditions. This makes it problematic to relate different aspects of the aggregation process when these are monitored by different methods. We report on a multispectral approach for simultaneous acquisition of infrared, fluorescence and light scattering spectra of proteins undergoing aggregation. We have applied our approach to study beta-lactoglobulin, a milk protein known to form amyloid fibrils under well-established conditions. Our real-time multispectral measurements show that unfolding of this protein is followed by formation of early aggregates consisting of intermolecular beta-sheets with a typical infrared absorption at similar to 1619 cm(-1) in (H2O)-H-2. These aggregates, which lead to an increase in the light scattering signal, do not bind the amyloid-specific fluorophore ThT and therefore consist of oligomers or protofibrils. Fibril growth is then observed as a sigmoidal increase in ThT fluorescence. After similar to 25 h, a plateau is observed in the intensities of ThT emission and of the band at 1619 cm(-1), indicating that no new fibrils are forming. However, a second phase in the light scattering signal taking place after similar to 25 h suggests that the fibrils are assembling into larger structures, known as mature fibrils. This is associated with an upshift of the main beta-sheet band in the infrared spectrum. TEM analyses confirmed the existence of thick fibrils comprising 3-5 filaments.
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| 9. |
- Baldassarre, Maurizio, et al.
(författare)
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The carbonate/bicarbonate system as a pH indicator for infrared spectroscopy
- 2014
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 139:9, s. 2167-2176
-
Tidskriftsartikel (refereegranskat)abstract
- Caged compounds capable of inducing large pH-jumps upon UV illumination have represented a breakthrough in time-resolved infrared spectroscopy of acidification-triggered phenomena, but their use is hampered by the inability to control the initial pH as well as to measure the final pH in mu L volumes. We have developed an experimental approach that accurately measures the initial and final pH values in pH-jump experiments. Our approach exploits the concomitant presence of two or more inorganic ions, such as carbonate and bicarbonate, that are added to the sample at a known concentration. The difference spectrum obtained in the infrared measurement is fitted to isolate the bands arising from the appearance or disappearance of either protonation state, and is then compared to a synthetic library of difference spectra generated using both qualitative (band position and width, extinction coefficient, pK) and quantitative (concentration, pathlength) parameters of the reporter ions. We have tested this approach in UV-photolysis experiments of 1-(2-nitrophenyl)ethyl sulfate in the presence of different concentrations of Na2CO3 and successfully used the infrared absorption of the carbonate and the bicarbonate ions to determine the initial and final pH values before and after the pH-jump, respectively.
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| 10. |
- Bassan, Paul, et al.
(författare)
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The inherent problem of transflection-mode infrared spectroscopic microscopy and the ramifications for biomedical single point and imaging applications.
- 2013
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528 .- 0003-2654. ; 138:1, s. 144-57
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Tidskriftsartikel (refereegranskat)abstract
- Transflection-mode FTIR spectroscopy has become a popular method of measuring spectra from biomedical and other samples due to the relative low cost of substrates compared to transmission windows, and a higher absorbance due to a double pass through the same sample approximately doubling the effective path length. In this publication we state an optical description of samples on multilayer low-e reflective substrates. Using this model we are able to explain in detail the so-called electric-field standing wave effect and rationalise the non-linear change in absorbance with sample thickness. The ramifications of this non-linear change, for imaging and classification systems, where a model is built from tissue sectioned at a particular thickness and compared with tissue of a different thickness are discussed. We show that spectra can be distorted such that classification fails leading to inaccurate tissue segmentation which may have subsequent implications for disease diagnostics applications.
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| 11. |
- Bergman, Hilde-Marlene, et al.
(författare)
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Profiling and quantifying endogenous molecules in single cells using nano-DESI MS
- 2017
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Ingår i: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 142:19, s. 3639-3647
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Tidskriftsartikel (refereegranskat)abstract
- Molecular profiling of single cells has the potential to significantly advance our understanding of cell function and cellular processes of importance to health and disease. In particular, small molecules with rapid turn-over rates can reveal activated metabolic pathways resulting from an altered chemical environment or cellular events such as differentiation. Consequently, techniques for quantitative metabolite detection acquired in a higher throughput manner are needed to characterize the biological variability between seemingly homogenous cells. Here, we show that nanospray desorption electrospray ionization (nano-DESI) mass spectrometry ( MS) enables sensitive molecular profiling and quantification of endogenous species in single cells in a higher throughput manner. Specifically, we show a large number of detected amino acids and phospholipids, including plasmalogens, readily detected from single cheek cells. Further, by incorporating a phosphatidylcholine ( PC) internal standard into the nano-DESI solvent, we determined the total amount of PC in one cell to be 1.2 pmoles. Finally, we describe a higher throughput approach where molecules in single cells are automatically profiled. These developments in single cell analysis provide a basis for future studies to understand cellular processes related to drug effects, cell differentiation and altered chemical microenvironments.
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| 12. |
- Bergman, Hilde-Marléne, et al.
(författare)
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Quantitative mass spectrometry imaging of small-molecule neurotransmitters in rat brain tissue sections using nanospray desorption electrospray ionization
- 2016
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 141:12, s. 3686-3695
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Tidskriftsartikel (refereegranskat)abstract
- Small molecule neurotransmitters are essential for the function of the nervous system, and neurotransmitter imbalances are often connected to neurological disorders. The ability to quantify such imbalances is important to provide insights into the biochemical mechanisms underlying the disorder. This proof-of-principle study presents online quantification of small molecule neurotransmitters, specifically acetylcholine, γ-aminobutyric acid (GABA) and glutamate, in rat brain tissue sections using nanospray desorption electrospray ionization (nano-DESI) mass spectrometry imaging. By incorporating deuterated internal standards in the nano-DESI solvent we show identification, accurate mapping, and quantification of these small neurotransmitters in rat brain tissue without introducing any additional sample preparation steps. We find that GABA is about twice as abundant in the medial septum-diagonal band complex (MSDB) as in the cortex, while glutamate is about twice as abundant in the cortex as compared to the MSDB. The study shows that nano-DESI is well suited for imaging of small molecule neurotransmitters in health and disease.
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| 13. |
- Bergman, Nina, et al.
(författare)
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Recent developments in proteomic methods and disease biomarkers
- 2014
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 139, s. 3836-3851
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Tidskriftsartikel (refereegranskat)abstract
- Proteomic methodologies for identification and analysis of biomarkers have gained more attention during recent years and have evolved rapidly. Identification and detection of disease biomarkers are important to foresee outbreaks of certain diseases thereby avoiding surgery and other invasive and expensive medical treatments for patients. Thus, more research into discovering new biomarkers and new methods for faster and more accurate detection is needed. It is often difficult to detect and measure biomarkers because of their low concentrations and the complexity of their respective matrices. Therefore it is hard to find and validate methods for accurate screening methods suitable for clinical use. The most recent developments during the last three years and also some historical considerations of proteomic methodologies for identification and validation of disease biomarkers are presented in this review.
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| 14. |
- Bergström, Sara K., et al.
(författare)
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A simplified multidimensional approach for analysis of complex biological samples : on-line LC-CE-MS
- 2006
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 131:7, s. 791-798
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Tidskriftsartikel (refereegranskat)abstract
- Information on protein expression, disease biomarkers or surrogate markers and genetic disorders can nowadays be achieved from analysis of complex biological samples by liquid separation coupled to mass spectrometric (MS) detection. This paper describes fast multidimensional separation by on-line liquid chromatography (LC) and capillary electrophoresis (CE), followed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) MS detection. This detector provides ultrahigh resolution of the detected ions, mass accuracy at the ppm-level and high sensitivity. Most of the challenge of this system lies in the development of a new interface for the on-line coupling of LC to CE. The interface developed in poly(dimethylsiloxane) provides a RSD for injection repeatability of <3.5% and surface control for unspecific binding by deactivation with a cationic polymer, PolyE-323. We have evaluated the interface, as well as the overall system, with respect to robustness and deconvolution ability. Sequence coverage for bovine serum albumin (BSA) of 93% showed a high recovery of sample in the different transfer steps through the system. The detection limit for identification is 277 ng mL−1 (or 280 nM) on average for peptides. In the future, we expect LC-CE-MS to be a novel strategy for elucidating the chemistry of biological matrices.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Briand, Elisabeth, 1979, et al.
(författare)
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Combined QCM-D and EIS study of supported lipid bilayer formation and interaction with pore-forming peptides
- 2010
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 135:2, s. 343-350
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Tidskriftsartikel (refereegranskat)abstract
- A novel set-up combining the quartz crystal microbalance with dissipation monitoring technique (QCM-D) and electrochemical impedance spectroscopy (EIS) under flow conditions was successfully used to follow supported lipid bilayer (SLB) formation on SiO(2). This study demonstrates the simultaneous detection, in real time, of both the electrical and the structural properties of the SLB. The combination of the two techniques provided novel insights regarding the mechanism of SLB formation: we found indications for an annealing process of the lipid alkyl chains after the mass corresponding to complete bilayer coverage had been deposited. Moreover, the interaction of the SLB with the pore-forming toxin, gramicidin D (grD) was studied for grD concentrations ranging from 0.05 to 40 mg L(-1). Membrane properties were altered depending on the toxin concentration. For low grD concentrations, the electrical properties of the SLB changed upon insertion of active ion channels. For higher concentrations, the QCM-D data showed dramatic changes in the viscoelastic properties of the membrane while the EIS spectra did not change. AFM confirmed significant structural changes of the membrane at higher grD concentrations. Thus, the application of combined QCM-D and EIS detection provides complementary information about the system under study. This information will be particularly important for the continued detailed investigation of interactions at model membrane surfaces
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| 19. |
- Candefjord, Stefan, et al.
(författare)
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Effects of snap-freezing and near-infrared laser illumination on porcine prostate tissue as measured by Raman spectroscopy
- 2009
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 134:9, s. 1815-1821
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Tidskriftsartikel (refereegranskat)abstract
- Most Raman spectroscopic studies on tissue are performed in vitro. To assure that the results are applicable to in vivo examinations, preparation protocols and measurement procedures of tissue for in vitro studies should preserve tissue characteristics close to the native state. This study had two aims. The first was to elucidate if photoinduced effects arise during 5 minutes' continuous illumination of tissue with an 830 nm laser at an irradiance of 3 × 1010 W/m2. The second was to investigate the effects of snap-freezing of porcine prostate tissue in liquid nitrogen and subsequent storage at -80 °C, by means of multivariate analysis. 830 nm laser illumination of the specified irradiance did not affect the Raman spectra. A decrease of the spectral background was observed, likely due to photobleaching of tissue fluorophores. Snap-freezing and subsequent storage at -80 °C gave rise to subtle but significant alterations in Raman spectra, most likely related to changes in the protein conformations
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| 20. |
- Casanova, Ana, et al.
(författare)
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A sustainable amperometric biosensor for the analysis of ascorbic, benzoic, gallic and kojic acids through catechol detection. Innovation and signal processing
- 2020
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 145:10, s. 3645-3655
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a new catechol amperometric biosensor fabricated on the basis of naturally available enzymes in common mushrooms. The biosensor response mechanism comprises the reduction of the quinone exclusively produced in the oxidation of the catechol present in the sample, which is catalyzed by tyrosinase enzyme. The new catechol biosensor has demonstrated excellent analytical performance at increasing catechol concentrations in the sample solution, which includes superior reproducibility for several electrodes and long-term stability. On top of that, the biosensing element used in the fabrication is a sustainable material, of low-cost and presents an excellent lifetime of years. Whether the catechol biosensor is operating in the presence of a compound influencing the reactions underlying the amperometric response (such as ascorbic, benzoic, gallic and kojic acids), this serves as an analytical platform to detect these compounds in real samples. Particularly, we introduce herein for the first time different treatments to process the current signal of the biosensor pursuing the linearity needed for the analytical application in real samples. In this sense, the catechol biosensor has been successfully applied to the detection of benzoic, gallic and kojic acids in juices, teas and cosmetic products, respectively.
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| 21. |
- Casanova, Ana, et al.
(författare)
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Recent progress in the development of porous carbon-based electrodes for sensing applications
- 2022
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 147:5, s. 767-783
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Forskningsöversikt (refereegranskat)abstract
- Electrochemical (bio)sensors are considered clean and powerful analytical tools capable of converting an electrochemical reaction between analytes and electrodes into a quantitative signal. They are an important part of our daily lives integrated in various fields such as healthcare, food and environmental monitoring. Several strategies including the incorporation of porous carbon materials in its configuration have been applied to improve their sensitivity and selectivity in the last decade. The porosity, surface area, graphitic structure as well as chemical composition of materials greatly influence the electrochemical performance of the sensors. In this review, activated carbons, ordered mesoporous carbons, graphene-based materials, and MOF-derived carbons, which are used to date as crucial elements of electrochemical devices, are described, starting from their textural and chemical compositions to their role in the outcome of electrochemical sensors. Several relevant and meaningful examples about material synthesis, sensor fabrication and applications are illustrated and described. The closer perspectives of these fascinating materials forecast a promising future for the electrochemical sensing field.
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| 22. |
- Chinnasamy, Thiruppathiraja, et al.
(författare)
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A lateral flow paper microarray for rapid allergy point of care diagnostics
- 2014
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Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 139:10, s. 2348-2354
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing need for multiplexed specific IgE tests that can accurately evaluate patient sensitization profiles. However, currently available commercial tests are either single/low-plexed or require sophisticated instrumentation at considerable cost per assay. Here, we present a novel convenient lateral flow microarray-based device that employs a novel dual labelled gold nanoparticle-strategy for rapid and sensitive detection of a panel of 15 specific IgE responses in 35 clinical serum samples. Each gold nanoparticle was conjugated to an optimized ratio of HRP and anti-IgE, allowing significant enzymatic amplification to improve the sensitivity of the assay as compared to commercially available detection reagents. The mean inter-assay variability of the developed LFM assay was 12% CV, and analysis of a cohort of clinical samples (n = 35) revealed good general agreement with ImmunoCAP, yet with a varying performance among allergens (AUC = [0.54-0.88], threshold 1 kU). Due to the rapid and simple procedure, inexpensive materials and read-out by means of a consumer flatbed scanner, the presented assay may provide an interesting low-cost alternative to existing multiplexed methods when thresholds > 1 kU are acceptable.
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| 23. |
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| 24. |
- Cuartero, Maria, et al.
(författare)
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Why ammonium detection is particularly challenging but insightful with ionophore-based potentiometric sensors - an overview of the progress in the last 20 years
- 2020
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 145:9, s. 3188-3210
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Forskningsöversikt (refereegranskat)abstract
- The monitoring of ammonium ion concentration has gained the attention of researchers from multiple fields since it is a crucial parameter with respect to environmental and biomedical applications. For example, ammonium is considered to be a quality indicator of natural waters as well as a potential biomarker of an enzymatic byproduct in key physiological reactions. Among the classical analytical methods used for the detection of ammonium ions, potentiometric ion-selective electrodes (ISEs) have attracted special attention in the scientific community because of their advantages such as cost-effectiveness, user-friendly features, and miniaturization ability, which facilitate easy portable measurements. Regarding the analytical performance, the key component of ISEs is the selective receptor, labelled as an ionophore in ISE jargon. Indeed, the preference of an ionophore for ammonium amongst other ions (i.e., selectivity) is a factor that primarily dictates the limit of detection of the electrode when performing measurements in real samples. A careful assessment of the literature for the last 20 years reveals that nonactin is by far the most employed ammonium ionophore to date. Despite the remarkable cross-interference of potassium over the ammonium response of nonactin-based ISEs, analytical applications comprising water quality assessment, clinical tests in biological fluids, and sweat monitoring during sports practice have been successfully researched. Nevertheless, there is evident difficulty in the determination of close-to-micromolar levels of ammonium in real samples with a significant potassium background level (i.e., millimolar concentration). This fact has fostered the search for a large variety of ammonium ionophores over the years, which are critically inspected herein. Overall, we provide an easily readable state of the art accompanied by a comprehensive description of other types of ammonium electrodes, including commercially available units. We conclude that newer breakthroughs are still required in the field to reach the desired analytical applications.
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| 25. |
- Dahlin, Andreas, 1980
(författare)
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Sensing applications based on plasmonic nanopores: The hole story
- 2015
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:14, s. 4748-4759
-
Forskningsöversikt (refereegranskat)abstract
- A review of sensing applications based on plasmonic nanopores is given. Many new types of plasmonic nanopores have recently been fabricated, including pores penetrating multilayers of thin films, using a great variety of fabrication techniques based on either serial nanolithography or self-assembly. One unique advantage with nanopores compared to other plasmonic sensors is that sample liquids can flow through the surface, which increases the rate of binding and improves the detection limit under certain conditions. Also, by utilizing the continuous metal films, electrical control can be implemented for electrochemistry, dielectrophoresis and resistive heating. Much effort is still spent on trying to improve sensor performance in various ways, but the literature uses inconsistent benchmark parameters. Recently plasmonic nanopores have been used to analyse targets of high clinical or academic interest. Although this is an important step forward, one should probably reflect upon whether the same results could have been achieved with another optical technique. Overall, this critical review suggests that the research field would benefit by focusing on applications where plasmonic nanopores truly can offer unique advantages over similar techniques.
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| 26. |
- Dennison, MJ, et al.
(författare)
-
Direct monitoring of formaldehyde vapour and detection of ethanol vapour using dehydrogenase-based biosensors
- 1996
-
Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 121:12, s. 1769-1773
-
Tidskriftsartikel (refereegranskat)abstract
- Biosensors capable of directly detecting low levels of formaldehyde and ethanol vapour were constructed, Both biosensors are based on dehydrogenase enzymes which produce reduced nicotinamide adenine dinucleotide as part of the oxidation of formaldehyde and ethanol, The enzymes were immobilized in a reverse micelle medium which did not dehydrate significantly over time, and allowed direct gas-phase monitoring, A screen-printed electrode was used as transducer. Formaldehyde and ethanol vapour partitioned into the reverse micelle media, where it was acted upon by the relevant enzyme, Reduced nicotinamide adenine dinucleotide was oxidized at the working electrode at a potential of 800 mV versus an Ag/AgCl reference electrode, Formaldehyde could be measured over the concentration range 1 ppb-1.3 ppm and ethanol could be detected over the range 50-250 ppm.
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| 27. |
- Dini, Francesca, et al.
(författare)
-
Polymers with embedded chemical indicators as an artificial olfactory mucosa
- 2010
-
Ingår i: ANALYST. - : Royal Society of Chemistry. - 0003-2654. ; 135:6, s. 1245-1252
-
Tidskriftsartikel (refereegranskat)abstract
- Physiological investigations suggest that the olfactory mucosa probably plays an ancillary role in the recognition of odours introducing a sort of chromatographic separation that, together with the zonal distribution of olfactory receptors, gives place to selective spatio-temporal response patterns. It has been recently suggested that this behaviour may be simulated by chemical sensors embedded in continuous polymer layers. In this paper, in analogy to the biology of olfaction, a simple and compact platform able to separate and detect gases and vapours on the basis of their diffusion properties is proposed. In such a system, broadly selective colour indicators, such as metalloporphyrins, are embedded in continuous layers of polymers with different sorption properties. The exposure to various alcohols and amines shows that the porphyrins are mainly responsible for the recognition of the molecular family, while the occurring spatio-temporal signal patterns make possible the identification of the individual chemical species.
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| 28. |
- Dorlo, Thomas P C, et al.
(författare)
-
Characterization and identification of suspected counterfeit miltefosine capsules.
- 2012
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 137:5, s. 1265-74
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, it was revealed that generic miltefosine capsules for the treatment of visceral leishmaniasis, a fatal parasitic disease, were possibly counterfeit products. Here we report on the methods to characterize and identify miltefosine in pharmaceutical products and the procedures that were used to assess the quality of these suspected counterfeit products. Characterization and identification of miltefosine were done with liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), Fourier transform infrared (FT-IR) spectroscopy and near-infrared (NIR) spectroscopy. Moreover, a simple, rapid and inexpensive colorimetric test was developed and evaluated for the detection of miltefosine in pharmaceutical products that can be used in the field. The complementary analytical techniques presented here were able to determine qualitatively or (semi-)quantitatively the presence or absence of miltefosine in pharmaceutical preparations and could identify suspected counterfeit miltefosine capsules. This finding of a suspected counterfeit drug intended to treat a neglected disease in a resource-poor country emphasizes the urgent need to develop more simple inexpensive assays to evaluate drug quality for use in the field.
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| 29. |
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| 30. |
- Duncan, Kyle D., et al.
(författare)
-
A pneumatically assisted nanospray desorption electrospray ionization source for increased solvent versatility and enhanced metabolite detection from tissue
- 2017
-
Ingår i: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 142:18, s. 3424-3431
-
Tidskriftsartikel (refereegranskat)abstract
- Nanospray desorption electrospray ionization (nano-DESI) has been established as a powerful technique for mass spectrometry imaging (MSI) of biomolecules from tissue samples. The direct liquid extraction of analytes from a surface at ambient pressure negates the need for significant sample preparation or matrix application. Although many recent studies have applied nano-DESI to new and exciting applications, there has not been much work in the development and improvement of the nano-DESI source. Here, we incorporate a nebulizer to replace the self-aspirating secondary capillary in the conventional nano-DESI setup, and characterize the device by use of rat kidney tissue sections. We find that the pneumatically assisted nano-DESI device offers improved sensitivity for metabolite species by 1-3 orders of magnitude through more complete desolvation and reduced ionization suppression. Further, the pneumatically assisted nano-DESI device reduces the dependence on probe-to-surface distance and enables sampling and imaging using pure water as the nano-DESI solvent. This provides exclusive detection and imaging of many highly polar endogenous species. Overall, the developed pneumatically assisted nano-DESI device provides more versatile solvent selection and an increased sensitivity for metabolites, which generates ion images of higher contrast - allowing for more intricate studies of metabolite distribution.
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| 31. |
- Duncan, Kyle D., et al.
(författare)
-
Advances in mass spectrometry based single-cell metabolomics
- 2019
-
Ingår i: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 144:3, s. 782-793
-
Forskningsöversikt (refereegranskat)abstract
- Metabolomics has grown into a prominent field contributing to the molecular understanding of complex biological processes in both health and disease. Furthermore, single-cells are known to display metabolic differences between seemingly homogeneous populations of cells. Single-cell metabolomics attempts to analyze many cellular metabolites from single cells to understand phenotypic heterogeneity, which is a significant challenge due to the low analyte abundances and limited sample volumes. Label-free metabolite detection can be achieved with mass spectrometry, which is capable of simultaneously analyzing hundreds of metabolites. Herein, we review the recent advances in mass spectrometry based single-cell metabolomics, highlighting the current state-of-the-art within the last three years, and identify the challenges to move the field forward.
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| 32. |
- Duner, Gunnar, et al.
(författare)
-
Signal Enhancement in Ligand-Receptor Interactions using Dynamic Polymers at Quartz Crystal Microbalance Surfaces
- 2016
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 141:13, s. 3993-3996
-
Tidskriftsartikel (refereegranskat)abstract
- The potential for signal amplification on QCM sensors by use of in situ polymerized poly(acrylic acid) brushes has been studied. A biotin derivative was immobilized on these surfaces and the interaction with anti-biotin Fabs was evaluated. Interaction data was found to be specific for the studied binding events, and the level of non-specific binding was shown to be low. The surface was proven to be suitable for regeneration, of importance for biomolecular interaction analysis and repetitive immunoassays.For comparison, the same interaction system was tested using commercial sensor surfaces with carboxylated self-assembled monolayers. The poly(acrylic acid) surface showed a dramatic increase in signal response with more than ten times the signal of the carboxylated self-assembled monolayer surface. Thus, the present study shows that polymers can be successfully applied to amplify responses on QCM sensors, valuable for studies of interactions between receptors and low molecular weight compounds.
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| 33. |
- Duong-Thi, Minh-Dao, et al.
(författare)
-
Lipodisks integrated with weak affinity chromatography enable fragment screening of integral membrane proteins
- 2016
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 141:3, s. 981-988
-
Tidskriftsartikel (refereegranskat)abstract
- Membrane proteins constitute the largest class of drug targets but they present many challenges in drug discovery. Importantly, the discovery of potential drug candidates is hampered by the limited availability of efficient methods for screening drug-protein interactions. In this work we present a novel strategy for rapid identification of molecules capable of binding to a selected membrane protein. An integral membrane protein (human aquaporin-1) was incorporated into planar lipid bilayer disks (lipodisks), which were subsequently covalently coupled to porous derivatized silica and packed into HPLC columns. The obtained affinity columns were used in a typical protocol for fragment screening by weak affinity chromatography (WAC), in which one hit was identified out of a 200 compound collection. The lipodisk-based strategy, which ensures a stable and native-like lipid environment for the protein, is expected to work also with other membrane proteins and screening procedures.
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| 34. |
- Duong-Thi, Minh-Dao, et al.
(författare)
-
Lipodisks integrated with weak affinity chromatography enable fragment screening of integral membrane proteins
- 2016
-
Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 141:3, s. 981-988
-
Tidskriftsartikel (refereegranskat)abstract
- Membrane proteins constitute the largest class of drug targets but they present many challenges in drug discovery. Importantly, the discovery of potential drug candidates is hampered by the limited availability of efficient methods for screening drug-protein interactions. In this work we present a novel strategy for rapid identification of molecules capable of binding to a selected membrane protein. An integral membrane protein (human aquaporin-1) was incorporated into planar lipid bilayer disks (lipodisks), which were subsequently covalently coupled to porous derivatized silica and packed into HPLC columns. The obtained affinity columns were used in a typical protocol for fragment screening by weak affinity chromatography (WAC), in which one hit was identified out of a 200 compound collection. The lipodisk-based strategy, which ensures a stable and native-like lipid environment for the protein, is expected to work also with other membrane proteins and screening procedures.
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| 35. |
- Dyukova, I., et al.
(författare)
-
A new approach for identifying positional isomers of glycans cleaved from monoclonal antibodies
- 2021
-
Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 146:15, s. 4789-4795
-
Tidskriftsartikel (refereegranskat)abstract
- Glycosylation patterns in monoclonal antibodies (mAbs) can vary significantly between different host cell types, and these differences may affect mAbs safety, efficacy, and immunogenicity. Recent studies have demonstrated that glycan isomers with the terminal galactose position on either the Man alpha 1-3 arm or the Man alpha 1-6 arm have an impact on the effector functions and dynamic structure of mAbs. The development of a robust method to distinguish positional isomers of glycans is thus critical to guarantee mAb quality. In this work, we apply high-resolution ion mobility combined with cryogenic infrared spectroscopy to distinguish isomeric glycans with different terminal galactose positions, using G1F as an example. Selective enzymatic synthesis of the G1(alpha 1-6)F isomer allows us to assign the peaks in the arrival-time distributions and the infrared spectra to their respective isomeric forms. Moreover, we demonstrate the impact of the host cell line (CHO and HEK-293) on the IgG G1F gycan profile at the isomer level. This work illustrates the potential of our approach for glycan analysis of mAbs.
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| 36. |
- Edvardsson, Malin, 1973, et al.
(författare)
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Investigation of binding event perturbations caused by elevated QCM-D oscillation amplitude
- 2006
-
Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 131:7, s. 822-828
-
Tidskriftsartikel (refereegranskat)abstract
- We report measurements with the quartz crystal microbalance with dissipation monitoring (QCM-D) technique, with focus on how the shear oscillation amplitude of the sensor surface influences biorecognition binding events. Technically, this is made as reported recently ( M. Edvardsson, M. Rodahl, B. Kasemo, F. Hook, Anal. Chem., 2005, 77( 15), 4918-4926) by operating the QCM in dual frequency mode; one harmonic (n = n(1)) is utilized for continuous excitation of the QCM-D sensor at resonance at variable driving amplitudes (1-10 V), while the second harmonic (n not equal n(1)) is used for combined f and D measurements. By using one harmonic as a "probe" and the other one as an "actuator", elevated amplitudes can be used to perturb - or activate - binding reactions in a controlled way, while simultaneously maintaining the possibility of probing the adsorption and/or desorption events in a non-perturbative manner using combined f and D measurements. In this work we investigate the influence of oscillation amplitude variations on the binding of NeutrAvidin-modified polystyrene beads (O similar to 200 nm) to a planar biotin-modified lipid bilayer supported on an SiO2-modified QCM-D sensor. These results are further compared with data on an identical system, except that the NeutrAvidin-biotin recognition was replaced by fully complementary DNA hybridization. Supported by micrographs of the binding pattern, the results demonstrate that there exists, for both systems, a unique critical oscillation amplitude, A(c), below which binding is unaffected by the oscillation, and above which binding is efficiently prevented. Associated with A(c), there is a critical crystal radius, r(c), defining the central part of the crystal where binding is prevented. From QCM-D data, A(c) for the present system was estimated to be similar to 6.5 nm, yielding a value of r(c) of similar to 3 mm - the latter number was nicely confirmed by fluorescent- and dark-field micrographs of the crystal. Furthermore, the fact that A(c) is observed to be identical for the two types of biorecognition reactions suggests that it is neither the strength, nor the number of contact points, that determine the amplitude at which binding is prevented. Rather, particle size seems to be the determining parameter.
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| 37. |
- Ekman, Jenny, et al.
(författare)
-
Comparison of sampling methods for 1,6-hexamethylene diisocyanate, (HDI) in a commercial spray box
- 2002
-
Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 127:1, s. 169-173
-
Tidskriftsartikel (refereegranskat)abstract
- In this study three different types of samplers for the determination of 1,6-hexamethylene diisocyanate in air were compared. The experimental set up was a simulation of real life conditions with spray painting operations performed inside a commercial, full sized, spray box. The sampling methods were 1-(2-methoxyphenyl)-piperazine impregnated on glass fibre filter, and the same reagent in impinger, and also dibutylamine in impinger. All analyses were performed by LC-MS-MS. The determined concentrations varied between 20 and 90 microg m(-3) with relative standard deviations from 7 to 17% for each method. No significant difference was found between the three methods using ANOVA with a significance level of alpha = 0.05.
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| 38. |
- Emteborg, Håkan, et al.
(författare)
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Determination of methylmercury in sediments using supercritical fluid extraction and gas chromatography coupled with microwave-induced plasma atomic emission spectrometry
- 1996
-
Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 121:1, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- A method employing supercritical fluid extraction (SFE) and GC coupled with microwave-induced plasma atomic emission spectrometry (MIP–AES) is presented for the determination of methylmercury in sediments. Butylmagnesium chloride was used to derivatize the target compound to butylmethylmercury which is amenable to GC. Using a commercially available reference sediment (PACS-1, National Research Council of Canada) as the model sample, a factorial design was utilized to investigate the effect of three variables; density, temperature and flow rate, on the extraction efficiency. An extraction efficiency of 49 ± 0.5% could be obtained for a 37.5 min dynamic extraction, corresponding to 25 thimble volumes of supercritical CO2, and using purified support sand. Studies on the efficacy of SFE for another sediment matrix as a function of time have also been undertaken. Repeated pressure reductions in combination with support sand were found to increase the extraction efficiency of methylmercury from PACS-1 but not from a sediment issued by the Community Bureau of Reference (BCR) as part of an interlaboratory comparison. For PACS-1 this resulted in an increase in the average extraction efficiency to 96% for duplicate determinations following 50 thimble volume sweeps. Distillation was used as a reference method for isolation of methylmercury from sediments. Parallel extractions of the BCR sediment, using GC–MIP–AES for the final determination, gave results that were in good agreement and corresponded well with data submitted during the intercomparison exercise. The detection limit for the methylmercury in sediment using the described SFE GC–MIP–AES method is estimated to be 0.1 ng g–1 based on a 20 µl injection, 0.5 g of sample and three times the blank level. It is proposed that the co-extracted sulfur from the sediment mediates the transport of methylmercury and, to some extent, inorganic mercury from the sediments. This is supported by the strong correlation between the concentrations of butylmethylmercury and dibutylsulfide found in the toluene extract. Using a stable isotope tracer, 199Hg, and ICP-MS, evidence for the spurious formation of methylmercury during SFE under certain conditions is also presented.
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| 39. |
- Enger, Jonas, et al.
(författare)
-
Laser-induced fluorescence in a graphite furnace as a sensitive technique for assessment of traces in North Arctic atmospheric aerosol samples
- 1995
-
Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 120:3, s. 635-641
-
Tidskriftsartikel (refereegranskat)abstract
- An improved version of the highly sensitive laser-based spectroscopic trace-element detection technique, laser-induced fluorescence in a graphite furnace, LIF-GF (often also referred to as laser-excited atomic fluorescence spectrometry in electrothermal atomizer, ETA-LEAFS) has been used to assess the trace-element content of Al and Pb in size-fractionated aerosol samples from the Norwegian Arctic. The ordinary LIF-GF technique has been modified for improved selectivity by the incorporation of a multi-channel intensified CCD detector (ICCD) which mikes constant monitoring of various background signals possible (scattered laser light, concomitant fluorescence light, and black body radiation). It is shown that the sensitivity and selectivity of the LIF-GF-ICCD technique is sufficient for efficient detection of the trace contents of Al and Pb in dissolved aerosol samples from the Norwegian Arctic (0-75 pg for each furnace heating). The Al and Pb concentrations in air from Ny Alesund, Svalbard, at the time of sampling (March-April 1992) were found to be 1-50 ng m-3.
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| 40. |
- Eriksson, Anna, et al.
(författare)
-
Cooperative adsorption behavior of phosphopeptides on TiO2 leads to biased enrichment, detection and quantification
- 2015
-
Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 140:1, s. 303-312
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption behavior of phosphopeptides onto TiO2 surfaces was studied using the quartz crystal microbalance with dissipation monitoring (QCM-D) as the main experimental technique. The main focus is the characterization of the emergence of positive cooperativity under conditions where the peptides have a positively charged C-term. It is shown that when carrying no net charge, small water-soluble peptides as a rule develop positive cooperativity. The impact of the adsorption mechanism on the outcome of TiO2 based enrichment methods was investigated with the help of matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS). The data presented illustrate how the phosphopeptide profile in the enriched material may deviate from that in the native sample, as cooperative phosphopeptides are overrepresented in the former. Furthermore, commonly employed washing and elution solutions may facilitate preferential release of certain peptides, leading to further bias in the recovered sample. Taken together, the results of the present study demonstrate that thorough understanding of the mechanisms behind the adsorption of phosphopeptides on the enrichment material is necessary in order to develop reliable qualitative and quantitative methods for phosphoproteomics.
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| 41. |
- Fernandes, Daniel L. A., et al.
(författare)
-
A 3D printed microliquid jet with an adjustable nozzle diameter
- 2015
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:18, s. 6234-6238
-
Tidskriftsartikel (refereegranskat)abstract
- Microliquid jets have many applications, in particular in the fields of spectroscopy/analysis of samples susceptible to beam damage. Herein, we report a microliquid jet, manufactured with 3D printing technology, with a tuneable nozzle diameter output. This strategy increases the breadth of techniques that can be covered with a single microliquid jet.
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| 42. |
- Filippini, Daniel, 1968-, et al.
(författare)
-
Effect of fingerprint conformation and spectral scaling on the performance of computer screen photo-assisted experiments
- 2006
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 131:1, s. 118-125
-
Tidskriftsartikel (refereegranskat)abstract
- The use of computer screens as controlled light sources and web cameras as image detectors (the so-called computer screen photo-assisted technique, CSPT) is an ubiquitous alternative for the evaluation of colorimetric quick tests at homes or in primary care units. The performance of CSPT for such evaluations depends on several factors, from which the most relevant are the composition of illuminating sequences and the conformation of CSPT substance signatures. In this work, with the aid of a CSPT model, the effect of the construction of the substance signatures on the classification performance of different representative substance sets is studied. The correlation of illuminating colors with such classification is investigated, allowing one to determine redundancy and limitations with respect to visible spectroscopy. The concept of spectral scaling is introduced and its properties compared with standard procedures. © The Royal Society of Chemistry 2006.
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| 43. |
- Filippini, Daniel, 1968-, et al.
(författare)
-
Measurement strategy and instrumental performance of a computer screen photo-assisted technique for the evaluation of a multi-parameter colorimetric test strip
- 2006
-
Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 131:1, s. 111-117
-
Tidskriftsartikel (refereegranskat)abstract
- A measuring strategy for the evaluation of a seven parameters colorimetric test using a computer screen photo-assisted technique (CSPT) is demonstrated. CSPT is a versatile approach aimed at point of care or home tests that uses regular computer sets and web cameras as the whole instrument. Issues such as the stability and the equivalency on different platforms of the determinations have been addressed in the present work. The method uses an embedded local reference simultaneously measured with the tests and solves the evaluation as a classification problem. The achieved performance tested along 580 classifications covering all the ranges of the assay, using synthetic samples, yielded 97.2% correct determinations compared with 89.7% for the case of colorimetric determinations. The errors were concentrated in only two parameters that show a significant correlation with a set of quality indices used to assess the performance of the classification. © The Royal Society of Chemistry 2006.
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| 44. |
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| 45. |
- Forchheimer, Daniel, et al.
(författare)
-
Molecularly imprinted nanostructures by nanoimprint lithography
- 2010
-
Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 135:6, s. 1219-1223
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous imprinting on two length scales (nanometer and ångström) delivers highly specific molecular recognition sites in polymer patterns.
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| 46. |
- Forsberg, Pontus, 1981-, et al.
(författare)
-
High sensitivity infrared spectroscopy with a diamond waveguide on aluminium nitride
- 2021
-
Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 146:22, s. 6981-6989
-
Tidskriftsartikel (refereegranskat)abstract
- Mid-infrared waveguide spectroscopy promises highly sensitive detection and characterization of organic molecules. Different material combinations for waveguides and cladding have been demonstrated with promising results, each with its own strengths and weaknesses in terms of sensitivity, transmission window and robustness. In this article we present a 5 μm thick diamond planar waveguide on aluminium nitride cladding, using a new fabrication and polishing method. Diamond has a very wide transmission window in the infrared, and its hardness and high chemical stability allows for chemistries and cleaning protocols that may damage other materials. With an aluminium nitride cladding the waveguide has a useable range between 1000 and 1900 cm−1, which we demonstrate using a tunable quantum cascade laser (QCL). This is a large improvement over silicon dioxide cladding. Compared to previously demonstrated free-standing diamond waveguides, the robustness of the sensor is greatly improved, which allows for a thinner diamond layer and increased sensitivity. The new waveguide was used in a QCL-based optical setup to detect acetone in deuterium oxide and isopropyl alcohol in water. The measurements showed higher sensitivity and lower noise level than previous demonstrations of mid-infrared diamond waveguides, resulting in a two orders of magnitude lower detectable concentration.
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| 47. |
- Fuentes, Catalina, et al.
(författare)
-
Comparison between conventional and frit-inlet channels in separation of biopolymers by asymmetric flow field-flow fractionation
- 2019
-
Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 144:15, s. 4559-4568
-
Tidskriftsartikel (refereegranskat)abstract
- Asymmetric flow field-flow fractionation (AF4) is a separation technique in which a focusing/relaxation step is used after the sample is injected onto the separation channel. During the focusing/relaxation step, the sample is focused by two counter-directed flows. This allows sample components to establish a diffusion-dependent equilibrium concentration profile. The focusing step may, in some cases, cause a loss of sample due to adsorption into the accumulation wall (i.e. the membrane) or due to aggregation of the sample. In addition, the increase in sample concentration during the focusing step may prevent complete relaxation and cause overloading effects. In this study, a modified AF4 channel equipped with a frit inlet (FI-AF4) is utilized, where the sample is relaxed hydrodynamically as it enters to the channel through the frit. The main advantage of the FI-AF4 channel is to omit the focusing step. The FI-AF4 channel could also allow higher injection mass than in a conventional channel while still avoiding overloading. The purpose of the present study is to compare two channels (conventional and FI-AF4 channels) in terms of the plate height (H), resolution (Rs) and the mass recovery for analysis of a mixture of glycogen and pullulan. In addition, waxy maize (WM) starch was used to compare the mass overloading of the two channels. The results show that the type of relaxation method (i.e. focusing or hydrodynamic relaxation) had no significant effect on mass recovery. The resolution (Rs), was higher in the conventional AF4 channel than in the FI-AF4 channel for the separation of glycogen and pullulan. The results also show that it was possible to inject a higher mass of WM starch (i.e. twice the mass) onto the FI-AF4 channel, compared to a conventional AF4 channel, without observing an overloading effect.
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| 48. |
- Gadomska, J, et al.
(författare)
-
Mass transport-controlled steady-state currents for methanol in a flow injection system
- 1996
-
Ingår i: ANALYST. - : ROYAL SOC CHEMISTRY. - 0003-2654. ; 121:12, s. 1869-1871
-
Tidskriftsartikel (refereegranskat)abstract
- It is known that undiluted methanol can give mass transport-controlled steady-state oxidation currents at Pt microelectrodes. In the present study, the steady-state currents were examined under flow injection conditions. It was found that the methanol ox
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| 49. |
- Goikoetxea, Garazi, et al.
(författare)
-
Fluorescent and electrochemical detection of nuclease activity associated with Streptococcus pneumoniae using specific oligonucleotide probes
- 2024
-
Ingår i: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528.
-
Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pneumoniae (S. pneumoniae) represents a significant pathogenic threat, often responsible for community-acquired pneumonia with potentially life-threatening consequences if left untreated. This underscores the pressing clinical need for rapid and accurate detection of this harmful bacteria. In this study, we report the screening and discovery of a novel biomarker for S. pneumoniae detection. We used S. pneumoniae nucleases as biomarker and we have identified a specific oligonucleotide that works as substrate. This biomarker relies on a specific nuclease activity found on the bacterial membrane, forming the basis for the development of both fluorescence and electrochemical biosensors. We observed an exceptionally high sensitivity in the performance of the electrochemical biosensor, detecting as low as 10(2) CFU mL(-1), whereas the fluorescence sensor demonstrated comparatively lower efficiency, with a detection limit of 10(6) CFU mL(-1). Moreover, the specificity studies have demonstrated the biosensors' remarkable capacity to identify S. pneumoniae from other pathogenic bacteria. Significantly, both biosensors have demonstrated the ability to identify S. pneumoniae cultured from clinical samples, providing compelling evidence of the potential clinical utility of this innovative detection system.
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| 50. |
- Guinovart, Tomas, et al.
(författare)
-
Potentiometric sensors using cotton yarns, carbon nanotubes and polymeric membranes
- 2013
-
Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 138:18, s. 5208-5215
-
Tidskriftsartikel (refereegranskat)abstract
- A simple and generalized approach to build electrochemical sensors for wearable devices is presented. Commercial cotton yarns are first turned into electrical conductors through a simple dyeing process using a carbon nanotube ink. These conductive yarns are then partially coated with a suitable polymeric membrane to build ion-selective electrodes. Potentiometric measurements using these yarn-potentiometric sensors are demonstrated. Examples of yarns that can sense pH, K+ and NH4+ are presented. In all cases, these sensing yarns show limits of detection and linear ranges that are similar to those obtained with lab-made solid-state ion-selective electrodes. Through the immobilization of these sensors in a band-aid, it is shown that this approach could be easily implemented in a wearable device. Factors affecting the performance of the sensors and future potential applications are discussed.
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