Absolute quantification of nicotinamide mononucleotide in biological samples by double isotope-mediated liquid chromatography-tandem mass spectrometry (dimeLC-MS/MS).

Nicotinamide adenine dinucleotide (NAD) is an essential metabolite for fundamental biological phenomena, including aging. Nicotinamide mononucleotide (NMN) is a key NAD intermediate that has been extensively tested as an effective NAD-boosting compound in mice and humans. However, the accurate measurement of NMN in biological samples has long been a challenge in the field.

Solid-phase microextraction- probe electrospray ionization devices for screening and quantitating drugs of abuse in small amounts of biofluids.

Probe electrospray ionization (PESI) is an ambient ionization mass spectrometry technique (AIMS) that is primarily used in qualitative studies, though researchers have recently combined it with sample preparation for the quantitative analysis of various analytes in biological matrices. This study presents a method that integrates solid-phase microextraction with PESI for direct coupling to a triple quadrupole mass spectrometer, and examines its ability to quantitate drugs of abuse. Intra- and inter-probe reproducibility experiments were conducted to assess the stability and reproducibility of the extraction-phase-coated PESI probes (coating length: 2 mm; coating thickness: 6.

Multivariate approach to on-line supercritical fluid extraction - supercritical fluid chromatography - mass spectrometry method development.

Coupling supercritical fluid extraction (SFE) on-line with supercritical fluid chromatography (SFC) - tandem mass spectrometry (MS/MS) provides a single platform for efficient extraction, separation, and detection in a chemical analysis. SFE-SFC-MS/MS requires consideration of many extraction and chromatographic variables to not only provide the most efficient extraction, but also to analytically transfer the extracted analytes to the column for separation. There is a fundamental lack of understanding of how the variables in SFE affect those in SFC.

Optimization of microflow LC-MS/MS and its utility in quantitative discovery bioanalysis.

The sensitivity advantage of microflow LC (μFLC)-MS/MS is potentially impactful for challenging compounds not detectable by conventional flow LC-MS/MS in drug discovery bioanalysis. Relatively new to μFLC technology, discovery bioanalytical scientists would benefit from an effective strategy for method development and optimization. A systematic μFLC-MS/MS method optimization approach was developed in this study.

Simultaneous Detection of 13 Allergens in Thermally Processed Food Using Targeted LC-MS/MS Approach.

Food allergy is a major concern for public health and food industries. Because of the large numbers of food ingredients to be tested, MS is considered an alternative to existing techniques in terms of high selectivity, sensitivity, and capability to analyze multiple allergens simultaneously. In this study, we developed the method for monitoring significant peptides derived from 13 food allergens (milk, eggs, cod, shrimp, lobster, almonds, brazil nuts, cashew nuts, hazelnuts, walnuts, peanuts, wheat, and soybeans) and evaluated it in thermally processed foods (bread, cookie, fried fish, and frozen pasta).

Photoinduced Ligand Release from a Silicon Phthalocyanine Dye Conjugated with Monoclonal Antibodies: A Mechanism of Cancer Cell Cytotoxicity after Near-Infrared Photoimmunotherapy.

Photochemical reactions can dramatically alter physical characteristics of reacted molecules. In this study, we demonstrate that near-infrared (NIR) light induces an axial ligand-releasing reaction, which dramatically alters hydrophilicity of a silicon phthalocyanine derivative (IR700) dye leading to a change in the shape of the conjugate and its propensity to aggregate in aqueous solution. This photochemical reaction is proposed as a major mechanism of cell death induced by NIR photoimmunotherapy (NIR-PIT), which was recently developed as a molecularly targeted cancer therapy.

On-line supercritical fluid extraction-supercritical fluid chromatography-mass spectrometry of polycyclic aromatic hydrocarbons in soil.

On-line supercritical fluid extraction - supercritical fluid chromatography - mass spectrometry (SFE-SFC-MS) has been applied for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil. The purpose of this study was to develop and validate the first on-line SFE-SFC-MS method for the quantification of PAHs in various types of soil. By coupling the sample extraction on-line with chromatography and detection, sample preparation is minimized, diminishing sample loss and contamination, and significantly decreasing the required extraction time.

Method for the Compound Annotation of Conjugates in Nontargeted Metabolomics Using Accurate Mass Spectrometry, Multistage Product Ion Spectra and Compound Database Searching.

Owing to biotransformation, xenobiotics are often found in conjugated form in biological samples such as urine and plasma. Liquid chromatography coupled with accurate mass spectrometry with multistage collision-induced dissociation provides spectral information concerning these metabolites in complex materials. Unfortunately, compound databases typically do not contain a sufficient number of records for such conjugates.

Nano-scale liquid chromatography coupled to tandem mass spectrometry using the multiple reaction monitoring mode based quantitative platform for analyzing multiple enzymes associated with central metabolic pathways of Saccharomyces cerevisiae using ultra fast mass spectrometry.

A widely targeted quantitative proteome analysis of Saccharomyces cerevisiae enzymes was performed employing an ultra fast mass spectrometry (UFMS). Nano-liquid chromatography-UFMS analysis of trypsin digested peptide samples derived from yeast strains successfully determined relative abundances of 303 peptides of 137 proteins.

Development of a practical metabolite identification technique for non-targeted metabolomics.

Metabolite identification is one of the major challenges of non-targeted metabolomics involving liquid chromatography coupled with mass spectrometry (LC-MS). Compound databases contain enormous numbers of records, which makes compound identification difficult in practice because each search will return a large number of candidates. We therefore developed a practical compound identification system using LC-MS with high mass accuracy and MS(n) capability, combined with a compound database.