Publications by authors named "Asa Emmer"

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) based on micro/nanostructured materials with different natures has received increasing attention for the analysis of a wide variety of analytes. However, up to now, only a few studies have shown the application of simple platforms in MALDI-MS for the identification of intact proteins. The present work reports on the application of copper oxide particles (CuO PS), obtained by a greener route, in combination with low amounts of 2,5-dihydroxybenzoic acid (DHB) as a novel hybrid platform.

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There is need for well-defined lignin macromolecules for research related to their use in biomaterial and biochemical applications. Lignin biorefining efforts are therefore under investigation to meet these needs. The detailed knowledge of the molecular structure of the native lignin and of the biorefinery lignins is essential for understanding the extraction mechanisms as well as chemical properties of the molecules.

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Today, the reactions of gas-phase organic peroxy radicals (RO) with unsaturated Volatile Organic Compounds (VOC) are expected to be negligible at room temperature and ignored in atmospheric chemistry. This assumption is based on combustion studies ( ≥ 360 K), which were the only experimental data available for these reactions until recently. These studies also reported epoxide formation as the only reaction channel.

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Rationale: Chemical mass shifts in quadrupolar ion traps have been studied previously but only for a limited number of analytes and mass ranges. Here, mass shifts of cluster ions, commonly used as calibrants, and other analytes are qualitatively evaluated on the Bruker amaZon spherical ion trap (QIT) and the Finnigan LXQ linear ion trap (LIT). To extend the mass range from previous experiments m/z up to 4000 are investigated.

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The increased use of biopharmaceuticals calls for improved means of bioprocess monitoring. In this work, capillary electrophoresis (CE) and microchip electrophoresis (MCE) methods were developed and applied for the analysis of amino acids (AAs) in cell culture supernatant. In samples from different days of a Chinese hamster ovary cell cultivation process, all 19 proteinogenic AAs containing primary amine groups could be detected using CE, and 17 out of 19 AAs using MCE.

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In recent work, it was shown that the graminoid plants (), (), and () have an ovipositional effect on the malaria vector in olfactometric bioassays. In order to get a view of the diversity of semiochemicals present in the environment of the vector during olfactometric trials, in the present work, the volatile profiles of these graminoid plants were analyzed using headspace solid-phase microextraction (HS-SPME) together with gas chromatography-mass spectrometry (GC-MS). In addition, one-way ANOVA comparison of compounds detected in two or more headspace samples are presented in order to provide a basis for comparison of compounds that could constitute a starting point for novel blends of volatile organic compounds to be tested as oviposition attractants.

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Background: Understanding the ecology and behaviour of disease vectors, including the olfactory cues used to orient and select hosts and egg-laying sites, are essential for the development of novel, insecticide-free control tools. Selected graminoid plants have been shown to release volatile chemicals attracting malaria vectors; however, whether the attraction is selective to individual plants or more general across genera and families is still unclear.

Methods: To contribute to the current evidence, we implemented bioassays in two-port airflow olfactometers and in large field cages with four live graminoid plant species commonly found associated with malaria vector breeding sites in western Kenya: Cyperus rotundus and C.

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The rapidly growing, competitive biopharmaceutical market requires tight bioprocess monitoring. An integrated, automated platform for the routine online/at-line monitoring of key factors in the cell culture medium could greatly improve process monitoring. Mono- and disaccharides, as the main energy and carbon source, are one of these key factors.

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CE-C D methods for the analysis of amino acids (AAs) are presented. Combining the results from two methods with acetic acid and cyclodextrin-based BGEs, 20 proteinogenic AAs could be analyzed using CE. CE-C D was also, for the first time, applied to analyze free AAs in samples of mammalian cell culture supernatant.

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Background: Tattoo inks have been reported to elicit allergic contact dermatitis.

Objectives: To investigate the labels and the contents of metals and pigments in tattoo inks, considering restrictions within the European Union.

Methods: Seventy-three tattoo inks currently available on the market, either bought or donated (already used), were investigated for trace metals and pigments by inductively coupled plasma mass spectrometry and by matrix-assisted laser desorption/ionization time of flight tandem mass spectrometry.

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Rationale: A calibration solution for mass spectrometry needs to cover the range of interest with intense and sufficiently narrowly spaced peaks. Limited options fulfilling this may lead to compromises between performance and ease of use. SpheriCal -ESI was designed to combine high calibration performance for electrospray ionization (ESI) mass spectrometric analysis of peptides in positive mode with quick and easy use.

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Leaf-like hollow cobalt sulfides with a sulfur-gold-cysteine (S-Au-Cys) structure on the surface have been synthesized for efficient N-glycopeptide enrichment. A two-dimensional (2D) zeolitic imidazolate framework with cobalt (ZIF-L-Co, L for leaf) was used as a self-sacrificed template. After sulfidation, the S-Au-Cys architecture was created on the surface of the leaf-like hollow cobalt sulfide to obtain a material denoted ZIF-L-Co-S-Au-Cys.

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Article Synopsis
  • Osteopontin is a protein secreted by osteoblasts that plays a role in bone diseases, cancers, and inflammation due to its ability to bind various molecules.
  • DEAE-Cibacron blue 3GA was utilized to extract recombinant osteopontin from human plasma, effectively removing major abundant proteins without using antibodies.
  • The process involved using specific buffer systems to separate osteopontin from other proteins, which was later identified using MALDI-TOF MS/MS after digestion with trypsin.
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Amyloid-like protein nanofibrils (PNFs) can assemble from a range of different proteins including disease-associated proteins, functional amyloid proteins and several proteins for which the PNFs are neither related to disease nor function. We here examined the core building blocks of PNFs formed by soy proteins. Fibril formation at pH 2 and 90 °C is coupled to peptide hydrolysis which allows isolation of the PNF-forming peptides and identification of them by mass spectrometry.

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A method for off-line CE-MALDI-TOF-MS and MS, and on-target digestion under a fluorocarbon lid was developed and applied for the analysis of proteins in the spermatophore of the butterfly Pieris napi. Fractionation revealed many peptides otherwise not detected or resolved. Automated fractionation was performed with an in-lab developed robotic system, and automated on-target tryptic digestion under a fluorocarbon lid was demonstrated with the same system.

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A method for analysis of proteins from spermatophores transferred from male to female Pieris napi butterflies during mating has been developed. The proteins were solubilized from the dissected spermatophores using different solubilization agents (water, methanol, acetonitrile and hexafluoroisopropanol). Capillary electrophoresis (CE) analysis was performed using an acidic background electrolyte containing a fluorosurfactant to avoid protein-wall adsorption, and to increase separation performance.

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Here we present a method to manufacture peptide-concentrating MALDI-plates with alkyl ketene dimer (AKD) as a new superhydrophobic coating. The fabrication of the hydrophobic plates included application of AKD by airbrush, and negative contact printing to generate the concentration sites. Deposited sample droplets were contained within the prestructured sites, and self-adjusted onto the site if slightly misplaced.

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A novel method for preconcentration and purification of the Alzheimer's disease related amyloid beta (Aβ) peptides by isoelectric focusing (IEF) in 75 nL microchannels combined with their analysis by micropillar-matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) is presented. A semiopen chip-based setup, consisting of open microchannels covered by a lid of a liquid fluorocarbon, was used. IEF was performed in a mixture of four small and chemically well-defined amphoteric carriers, glutamic acid, aspartyl-histidine (Asp-His), cycloserine (cSer), and arginine, which provided a stepwise pH gradient tailored for focusing of the C-terminal Aβ peptides with a pI of 5.

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Recently, a new type of ultrasound contrast agent that consists of air-filled microbubbles stabilized with a shell of polyvinyl alcohol was developed. When superparamagnetic nanoparticles of iron oxide are incorporated in the polymer shell, a multimodal contrast agent can be obtained. The biodistribution and elimination pathways of the polyvinyl alcohol microbubbles are essential to investigate, which is limited with today's techniques.

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In this work, electrophoretic preconcentration of protein and peptide samples in microchannels was studied theoretically using the 1D dynamic simulator GENTRANS, and experimentally combined with MS. In all configurations studied, the sample was uniformly distributed throughout the channel before power application, and driving electrodes were used as microchannel ends. In the first part, previously obtained experimental results from carrier-free systems are compared to simulation results, and the effects of atmospheric carbon dioxide and impurities in the sample solution are examined.

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A new instrumental concept for extraction of nanovolumes from open microchannels (dimensions 150 μm × 50 μm, length 10 mm) manufactured on silicon microchips has been used in combination with a previously developed method for preconcentrating proteins and peptides in the open channels through electromigration. The extracted nanovolumes were further analyzed using nanoelectrospray ionization (nESI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) directly or with subsequent enzymatic protein digestion in a nanodroplet prior to the MS analysis. Preconcentration of the samples resulted in a 15-fold sensitivity increase in nESI for a neurotensin solution, and using MALDI-MS, amyloid beta (Aβ) peptides could be detected in concentrations down to 1 nM.

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