Alkaline phosphatase (AP) is a membrane-bound glycoprotein that is widely distributed in the plasma membrane of cells of various organs and also found in many organisms from bacteria to humans. The complete amino acid sequence and three-dimensional structure of human placental alkaline phosphatase have been reported. Based on the literature data, AP con- sists of two presumptive glycosylation sites, at Asn-144 and Asn-271. However, it only contains a single occupied N-linked gly- cosylation site and no occupied O-linked glycosylation sites. Hydrophilic interaction chromatography (HILIC) has been primarily employed for the characterization of the glycan structures derived from glycoproteins. N-glycan structures from human placental alkaline phosphatase (PLAP) were investigated using HILIC-Orbitrap MS, and subsequent data processing and glycan assignment software. 16 structures including 10 sialylated N-glycans were identified from PLAP.
The number of matched peaks (NMP) is estimated as the spectral similarity measure in tandem mass spectral library searches of small molecules. In the high resolution mode, NMP provides the same reliable identification as in the case of a com-mon dot-product function. Corresponding true positive rates are (94±3) % and (96±3) %, respectively.
The focus of this paper is to present techniques to overcome certain difficulties in quantitative analysis with a time- of-flight mass spectrometer (TOF-MS). The method is based on conventional solid-phase extraction, followed by reversed- phase ultra high performance liquid chromatography of the extract, and mass spectrometric analysis. The target compounds included atenolol, atrazine, caffeine, carbamazepine, diclofenac, estrone, ibuprofen, naproxen, simazine, sucralose, sulfamethox- azole, and triclosan. The matrix effects caused by high concentrations of organic compounds in wastewater are especially signif- icant in electrospray ionization mass spectroscopy. Internal-standard calibration with isotopically labeled standards corrects the results for many matrix effects, but some peculiarities were observed. The problems encountered in quantitation of carbamaze- pine and triclosan, due to nonlinear calibration were solved by changing the internal standard and using a narrower mass win- dow. With simazine, the use of a quadratic calibration curve was the best solution.
In this study, the chemical composition of bacterial melanin isolated from the Streptomyces glaucescens strain was elucidated by ultra-high-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Ultra-high-resolu- tion mass profiles of the microbial melanin product were acquired using a 15 Tesla FT-ICR mass spectrometer in positive and negative ion modes via electrospray ionization to obtain more complete descriptions of the molecular compositions of melanin- derived organic constituents. A mass resolving power of 500,000 (at m/z 400) was achieved for all spectra while collecting 400 scans per sample with a 4 M transient. The results of this analysis revealed that the melanin pigment isolated from S. glaucescens predominantly exhibits CHON and CHO species, which belong to the proteins class of compounds, with the mean C/O and C/N ratios of 4.3 and 13.1, thus suggesting that the melanin could be eumelanin. This analytical approach could be utilized to investi- gate the molecular compositions of a variety of natural or synthetic melanins. The compositional features of melanins are important for understanding their formation mechanisms and physico-chemical properties.
Methallylescaline, 2-(3,5-dimethoxy-4-[(2-methylprop-2-en-1-yl)oxy]phenyl)ethanamine, is a new psychoactive substance with potent agonist of 5-HT receptor, but there is little information on its pharmacological effect, metabolism, and tox- icity. It is necessary to characterize the metabolic profiling of methallylescaline in human hepatocytes using liquid chromatogra- phy-high resolution mass spectrometry. Methallylescaline was metabolized to three hydroxy-methallylescaline (M1-M3) and dihydroxy-methallylescaline (M4) via hydroxylation in human hepatocytes. CYP2D6, CYP2J2, CYP1A2, and CYP3A4 enzymes were responsible for the metabolism of methallylescaline. The metabolites as well as methallylescaline would be used for monitoring the abuse of methallylescaline,