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Molecular-level characterization of reactive and refractory dissolved natural organic nitrogen compounds by atmospheric pressure photoionization coupled to Fourier transform ion cyclotron resonance mass spectrometry.
Dissolved organic nitrogen (DON) represents a significant fraction of the total dissolved nitrogen pool in most surface waters and serves as an important nitrogen source for phytoplankton and bacteria. As with other natural organic matter mixtures, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) is the only technique currently able to provide molecular composition information on DON. Although electrospray ionization (ESI) is the most commonly used ionization method...
Ferrocene derivatives have become very popular molecules for biological applications. Although considerable experimental and theoretical calculation studies have demonstrated that ferrocene derivatives are easily oxidized during electrospray ionization (ESI), the details of the single electron redox reaction for protonated benzoylferrocenes in collision-induced dissociation (CID) mass spectrometry (MS) has not been obtained. Characterizing this mechanism is useful for further understanding the properties of...
Mass spectrometry based comparative glycomics is essential for disease biomarker discovery. However, developing a reliable quantification method is still a challenging task.
For the matrix-assisted laser desorption/ionization (MALDI) imaging of proteins and tryptic peptides it is recommendable to remove salts, lipids, and phospholipids prior to analysis. However, thorough investigations of the influence of commonly used washing protocols on the entire protein content and the spectral quality have not been carried out.
In order to deepen the understanding of electrospray ionisation collision-induced dissociation (ESI-CID) fragmentation reactions of xanthine derivatives for the identification of metabolites using low-resolution liquid chromatography/mass spectrometry (LC/MS) analysis, basic experiments using caffeine (1,3,7-trimethylxanthine) as model compound have been performed.
The fast and univocal identification of different species in mixtures of pollen grains is still a challenge. Apart from microscopic evaluation and Raman spectroscopy, no other techniques are available.
Although the electrospray method is widely used in biomedical mass spectrometry and ion-drift spectrometry, the electrospray system can generate large drops that are the cause of electrical breakdowns, and of the fast clogging of the inlet diaphragm of the differential pumping first stage and system of ion transportation to the analyzer. Thus, a system free of such problems would be of benefit.
Stable isotope analysis is a critical tool for understanding ecological food webs; however, results can be sensitive to sample preparation methods. To limit the possibility of sample contamination, freezing is commonly used to euthanize invertebrates and preserve non-lethal samples from vertebrates. For destructive sampling of vertebrates, more humane euthanasia methods are preferred to freezing and it is essential to evaluate how these euthanasia methods affect stable isotope results.
Multiplexed liquid chromatography (LC) coupled with multiple-injection-chromatogram acquisition has emerged as the method of choice for high-speed discovery bioanalysis, because it significantly reduces injection-to-injection cycle time while maintaining the chromatography quality. Historically, systems utilizing this approach had been custom built, and therefore relied on custom software tools to communicate with multiple vendor software for system control, which lacked transferability, flexibility and rob...
A sensitive liquid chromatography/tandem mass spectrometry method for the determination of natural and synthetic steroid estrogens in seawater and marine biota, with a focus on proposed Water Framework Directive Environmental Quality Standards.
Trace levels of natural and synthetic steroid estrogens estrone (E1), 17β-estradiol (E2) and 17α-ethynyl estradiol (EE2) have been demonstrated to exert adverse effects in exposed organisms. E2 and EE2 have been proposed for inclusion in the Water Framework Directive (WFD) list of priority pollutants; however, the detection and accurate quantification of these compounds provide significant challenges, due to the low detection limits required.
Poly(amidoamine) PAMAM dendrimers are highly water soluble and are used as flexible scaffolding or nanocontainers to conjugate, complex or encapsulate therapeutic drugs to overcome intrinsically weak characteristics such as solubilization in aqueous medium. To provide a reliable method for the quantitation of PAMAM dendrimers in aqueous medium, we report here a validation study which was developed in a complex wastewater matrix to evaluate the matrix effect in the electrospray ionization (ESI) source.
The utility of elemental sulfur as a matrix for inorganic salts such as CsI, AgI, and KI was investigated because the conventional matrices deployed to generate gaseous ions from organic compounds, upon irradiation with a laser beam, are not suitable for inorganic salts.
Synthetic polymers of molecular masses up to a few kDa can be analyzed without the use of any matrix by direct laser desorption/ionization mass spectrometry (LDI-MS). In this technique, the surface of the sample plate plays a crucial role, and many attempts have been made to understand the influence of the surface on the ease of desorption. Since this technique requires no tedious sample pretreatment, it is a promising method for the rapid characterization of various synthetic polymers.
Currently, most of the antioxidants and free radical neutralizers used in cosmetic compositions are absorbed quickly into deeper layers of skin, and then carried away by the blood stream. It would be beneficial to delay the penetration of antioxidants to the deeper layers of skin to control their delivery and release.
A considerable fraction of atmospheric particulate fine matter consists of organosulfates, with some of the most polar ones originating from the oxidation of isoprene. Their structural characterization provides insights into the nature of gas-phase precursors as well as into formation pathways.
Ion/molecule reactions are commonly used to characterize structures due to their high specificity. Herein, we present ambient ion/molecule reactions performed in the course of low-temperature plasma (LTP) ionization of condensed-phase analytes in order to increase the specificity of LTP-based ambient analysis.
Both traditional electron ionization and electrospray ionization tandem mass spectrometry have demonstrated limitations in the unambiguous identification of fatty acids. In the former case, high electron energies lead to extensive dissociation of the radical cations from which little specific structural information can be obtained. In the latter, conventional collision-induced dissociation (CID) of even-electron ions provides little intra-chain fragmentation and thus few structural diagnostics. New approach...
The use of quinonoid compounds against tropical diseases and as antitumor agents has prompted the search for new naturally occurring and synthetic derivatives. Among these quinonoid compounds, lapachol and its isomers (α- and β-lapachone) serve as models for the synthesis of new compounds with biological activity, and the use of electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis as a tool to elucidate and characterize these products has furnished important information about these compou...
The analysis of crude oil is a challenging task due to sample complexity. In mass spectrometry, several ionization techniques can be used to perform this task. Herein, we report the use of an atmospheric pressure low-temperature plasma (LTP) probe to desorb and ionize compounds of petroleum crude oil from different sources and residual fuel oil standard reference materials (SRMs). LTP is used to perform rapid screening of low molecular weight and relatively volatile components enabling characterization and...
Melphalan is a widely used cytotoxic agent in cancer treatments. This phenylalanine analog has been shown an effective drug in the treatment of breast cancer, multiple myeloma and melanoma of the extremities. A good knowledge of the drug's degradation and metabolism are crucial for understanding its activity during cancer treatments.
Enrichment and determination of crotonaldehyde using magnetic multiwalled carbon nanotubes as an adsorbent and a matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry provides the means to map the in situ distribution of tryptic peptides in formalin-fixed clinical tissue samples. The ability to analyze clinical samples is of great importance to further developments in the imaging field. However, there is a requirement in this field of research for additional methods describing the characterization of tryptic peptides by MALDI imaging.
Bisphenol A has been widely used in plastic containers and this has raised safety concerns for fetuses, infants, and young children. Aflatoxin B1, ochratoxin A, and patulin are among the most toxic regulated mycotoxins found as contaminants in agricultural crops and animal products. To facilitate the analysis of these chemicals for regulatory purposes, we have developed an analytical method enabling their simultaneous detection in beverages and food products.
Structural characterization of biosynthetic precursors is very important in assigning enzymatic function to proteins that have been identified as functional homologs on the basis of sequence homology alone. The objective of this study is to demonstrate the use of electrospray ionization tandem mass spectrometry (ESI-MS/MS) as a powerful technique for the characterization of enzymatic products in the biosynthetic pathway of deoxythymidine 5'-diphosphate-4-formamido-4,6-dideoxy-D-glucose (dTDP-D-Qui4NFo) in P...