Novel Analytical Method (novel + analytical_method)

Distribution by Scientific Domains


Selected Abstracts


Indirect identification of isoprenoid quinones in Escherichia coli by LC-MS with atmospheric pressure chemical ionization in negative mode

JOURNAL OF BASIC MICROBIOLOGY, Issue 6 2004
Mengchun Gao Dr.
A novel analytical method was applied for identification of isoprenoid quinones in Escherichia coli by liquid chromatography atmospheric press chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS). Extraction and clean-up of sample were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges. Ubiquinone-7 (UQ-7), Ubiquinone-8 (UQ-8) and Mequinone-8 (MK-8) were determined directly using combined information on retention time, molecular ion mass, fragment ion masses and UV characteristic spectrometry without any standard reagent. It was found that UQ-8 was the major component of isoprenoid quinones in Escherichia coli under aerobic condition. Compared with UQ-8, the relative abundance of UQ-7 and MK-8 is only 15% and 14%, respectively. The average recoveries of UQ-6, UQ-10 and vitamin K1 in Escherichia coli were investigated by standard spiking experiment. The recoveries were achieved in the range from 94 to 106%, and the relative standard deviations (RSD) of the triplicate analysis of the spiked samples (UQ-6, UQ-10 and vitamin K1) ranged from 3 to 8%. The detection limits of LC-NI-APCI-MS were estimated to be 5, 40 and 0.8 ,g/g dry cell for UQ-6, UQ-10 and vitamin K1, respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Population differences in the testosterone levels of young men are associated with prostate cancer disparities in older men

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2010
Louis Calistro Alvarado
Although there is evidence that greater exposure to testosterone is associated with an increased risk of prostate cancer, a recent analysis of 18 prospective studies found no relationship between levels of endogenous sex hormones and prostate cancer development. However, the reviewed studies were subject to methodological constraints that would obscure any potential relationship between prostate cancer and androgenic hormones. If prostate cancer risk is mediated by lifetime exposure to testosterone, then case-control studies that concentrate on endogenous sex hormones near the ages that prostate cancer is diagnosed would provide limited information on cumulative testosterone exposure across the lifespan. Alternately, early adulthood has been suggested as the most salient period to evaluate the influence of steroid physiology on prostate carcinogenesis. As such, an exhaustive literature search was completed to obtain testosterone values reported for study samples of younger men, along with prostate cancer incidences for the larger populations from which the study populations were sampled. A novel analytical method was developed to standardize, organize, and examine 12 studies reporting testosterone levels for 28 population samples. Study populations were generally apportioned according to ethnicity and geographic residence: Americans of African, Asian, Caucasian, and Hispanic ancestry from several different regions within the United States as well as men from China, Germany, Japan, Kuwait, New Zealand, South Korea, and Sweden. Population differences in the testosterone levels of young men were significantly associated with population disparities in the prostate cancer incidence of older men (Spearman's rho = 0.634, p = 0.002). Am. J. Hum. Biol. 2010. © 2010 Wiley-Liss, Inc. [source]


Development of a validated liquid chromatography/tandem mass spectrometry method for the distinction of thyronine and thyronamine constitutional isomers and for the identification of new deiodinase substrates

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2008
Susanne Piehl
Thyronines (THs) and thyronamines (TAMs) are two groups of endogenous iodine-containing signaling molecules whose representatives differ from each other only regarding the number and/or the position of the iodine atoms. Both groups of compounds are substrates of three deiodinase isozymes, which catalyze the sequential reductive removal of iodine from the respective precursor molecule. In this study, a novel analytical method applying liquid chromatography/tandem mass spectrometry (LC-MS/MS) was developed. This method permitted the unequivocal, simultaneous identification and quantification of all THs and TAMs in the same biological sample. Furthermore, a liquid-liquid extraction procedure permitting the concurrent isolation of all THs and TAMs from biological matrices, namely deiodinase (Dio) reaction mixtures, was established. Method validation experiments with extracted TH and TAM analytes demonstrated that the method was selective, devoid of matrix effects, sensitive, linear over a wide range of analyte concentrations and robust in terms of reproducible recoveries, process efficiencies as well as intra-assay and inter-assay stability parameters. The method was applied to study the deiodination reactions of iodinated THs catalyzed by the three deiodinase isozymes. With the HPLC protocol developed herein, sufficient chromatographic separation of all constitutional TH and TAM isomers was achieved. Accordingly, the position of each iodine atom removed from a TH substrate in a Dio-catalyzed reaction was backtracked unequivocally. While several established deiodination reactions were verified, two as yet unknown reactions, namely the phenolic ring deiodination of 3,,5,-diiodothyronine (3,,5,-T2) by Dio2 and the tyrosyl ring deiodination of 3-monoiodothyronine (3-T1) by Dio3, were newly identified. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Quantitative determination of capsaicin, a transient receptor potential channel vanilloid 1 agonist, by liquid chromatography quadrupole ion trap mass spectrometry: evaluation of in vitro metabolic stability

BIOMEDICAL CHROMATOGRAPHY, Issue 2 2009
Francis Beaudry
Abstract Capsaicin is the most abundant pungent molecule present in red peppers and it is widely used for food flavoring, in pepper spray in self-defense devices and more recently in ointments for the relief of neuropathic pain. Capsaicin is a selective agonist of transient receptor potential channel, vanilloid subfamily member 1. A selective and sensitive quantitative method for the determination of capsaicin by LC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray quadrupole ion trap mass spectrometry. The chromatographic separation was achieved using a 100 × 2 mm C18 Waters Symmetry column combined with a gradient mobile phase composed of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 220 µL/min. The mass spectrometer was operating in full-scan MS/MS mode using two-segment analysis. An analytical range of 10,5000 ng/mL was used in the calibration curve constructed in rat plasma. The interbatch precision and accuracy observed were 6.5, 6.7, 5.3 and 101.2, 102.7, 103.5% at 50, 500 and 5000 ng/mL, respectively. An in vitro metabolic stability study was performed in rat, dog and mouse liver microsomes and the novel analytical method was adapted and used to determine intrinsic clearance of capsaicin. Results suggest very rapid degradation with T1/2 ranging from 2.3 to 4.1 min and high clearance values suggesting that drug bioavailability will be considerably reduced, consequently affecting drug response and efficacy. Copyright © 2008 John Wiley & Sons, Ltd. [source]