| 11. |
- Eriksson, Anna, et al.
(författare)
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Cooperative adsorption behavior of phosphopeptides on TiO2 leads to biased enrichment, detection and quantification
- 2015
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Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 140:1, s. 303-312
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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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| 12. |
- Fernandes, Daniel L. A., et al.
(författare)
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A 3D printed microliquid jet with an adjustable nozzle diameter
- 2015
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:18, s. 6234-6238
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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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| 13. |
- Fuentes, Catalina, et al.
(författare)
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Comparison between conventional and frit-inlet channels in separation of biopolymers by asymmetric flow field-flow fractionation
- 2019
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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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| 14. |
- Haas, Julian, et al.
(författare)
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Infrared Spectroscopy Based on Broadly Tunable Quantum Cascade Lasers and Polycrystalline Diamond Waveguides
- 2018
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 143:21, s. 5112-5119
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Tidskriftsartikel (refereegranskat)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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| 15. |
- Herr, Amy E., et al.
(författare)
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Next wave advances in single-cell analyses
- 2019
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Ingår i: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 144:3, s. 735-737
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)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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| 16. |
- Kanje, Sara, et al.
(författare)
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Next generation of labeling reagents for quantitative and multiplexing immunoassays by the use of LA-ICP-MS
- 2016
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Ingår i: ANALYST. - : Royal Society of Chemistry. - 0003-2654. ; 141:23, s. 6374-6380
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Tidskriftsartikel (refereegranskat)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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| 17. |
- Kumar, Keshav, et al.
(författare)
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Constraint randomised non-negative factor analysis (CRNNFA) : an alternate chemometrics approach for analysing the biochemical data sets
- 2017
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Ingår i: The Analyst. - : ROYAL SOC CHEMISTRY. - 0003-2654 .- 1364-5528. ; 142:11, s. 1916-1928
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Tidskriftsartikel (refereegranskat)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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| 18. |
- Kumar, Saroj, et al.
(författare)
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Sensing protein antigen and microvesicle analytes using high-capacity biopolymer nano-carriers
- 2016
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 141:3, s. 836-846
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Tidskriftsartikel (refereegranskat)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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| 19. |
- Källsten, Malin, et al.
(författare)
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Qualitative analysis of antibody-drug conjugates (ADCs) : an experimental comparison of analytical techniques of cysteine-linked ADCs.
- 2018
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 143:22, s. 5487-5496
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Tidskriftsartikel (refereegranskat)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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| 20. |
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