oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 56 )

2018 ( 253 )

2017 ( 277 )

2016 ( 300 )

Custom range...

Search Results: 1 - 10 of 8006 matches for " mass spectrometry "
All listed articles are free for downloading (OA Articles)
Page 1 /8006
Display every page Item
Reduction of Internal Standard Signals in Quantitative MALDI-TOF Mass Spectrometry  [PDF]
Walter B. Wilson, Dickson M. Wambua, Norman H. L. Chiu
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2012, DOI: 10.4236/jasmi.2012.23021
Abstract: The advantages of combining qualitative and quantitative analysis on a single analytical technique have further extended the applications of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to the quantitation of various biomolecules. To achieve absolute quantitation, it is necessary to perform a calibration with standard dilutions. For the purpose of measuring DNA samples, a pure DNA oligonucleotide at different concentrations was chosen as a standard to perform the calibration of MALDI-TOF MS. In order to overcome the variation of signal intensity from repeated measurements of each DNA standard dilution, fixed amount of an internal standard was added into each DNA standard dilution. Instead of maintaining at a constant level, the signals of fixed amount of internal standard were decreased 73% from its initial level while the signals of DNA standard continued to increase within a linear dynamic range for quantitation from 0.20 μM to 12.5 μM of DNA. Attempts to identify the cause of signal reduction were systematically carried out. This is the first report on the extent of signal reduction in quantitative MALDI-TOF MS. These results represent a limitation on using MALDI-TOF MS to monitor the changes in concentration of two different compounds within a chemical or biological system.
Structure Elucidation of a New Toxin from the Mushroom Cortinarius rubellus Using Gas Chromatography-Mass Spectrometry (GC-MS)  [PDF]
Ilia Brondz
International Journal of Analytical Mass Spectrometry and Chromatography (IJAMSC) , 2013, DOI: 10.4236/ijamsc.2013.12014
Abstract:

Cortinarius orellanus (Fries) and C. rubellus (Cooke),which were formerly also known as C. speciosissimus, are poisonous mushrooms containing the toxin orellanine and several degradation products of orellanine,includingorelline and orellinine. Mass intoxication by poisonous mushrooms was observed in Poland in 1952-1957 [1]. In 1957, the cause of these outbreaks was described by Grzymala as poisoning by a member of the Cortinarius family. The toxin orellanine was first isolated from C. orellanusby Grzymala in 1962; the chemical structure of orellanine was later determined to be 3,3',4,4'-tetrahydroxy-2,2'-bipyridine-N,N'-dioxide. Poisoning with C. orellanus and C. rubellus has a very specific character. The first symptoms of intoxication usually do not appear until 2-3 days after ingestion, but in some cases intoxication appears after three weeks. The target organ for the toxin is the kidney. Histologically, it is easy to record the specific damage. The presence of degradation products of orellanine in kidney can be confirmed chromatographically, suggesting that the cause of poisoning is orellanine. However, the presence of orellanine in the blood of intoxicated persons has not been directly detected. A specific model was developed by Brondz et al. for the detection of orellanine, orelline, and orellininein animal stomach fluids [2-4]. The hypothesis that the fungal toxin orellanine as a diglucoside can be transported from the digestive system by the blood to the kidney could not be supported. The toxin orellanine as a diglucoside is very unstable in an aqueous acidic environment.[i1] However, in the present study, it was possible to record an additional substance in animal stomach fluids using GC-MSafter ingestion ofC. rubellus. This substance, which has been namedrubelline, is part of a toxic mixture inC. orellanusandC. rubellusand is closely related to orellanine. The structure of rubelline is more suitable than orellanine for absorptionfromthe digestive tract and for transport in the blood. The presented hypothesis is that rubellineis absorbed in the digestive tract and transportedin the blood to the kidney, where it is biotransformed to orellanine and accumulatedto toxic levels. The process of biotransformationis in itself also

Formation of Mercury(II)-Glutathione Conjugates Examined Using High Mass Accuracy Mass Spectrometry  [PDF]
Zachary Fine, Troy D. Wood
International Journal of Analytical Mass Spectrometry and Chromatography (IJAMSC) , 2013, DOI: 10.4236/ijamsc.2013.12011
Abstract:

Maternal exposure to Hg(II) during pregnancy has been identified as a potential causal factor in the development of severe neurobehavioral disorders. Children with autism have been identified with lower reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios, and GSH is known to strongly bind Hg(II). In order to gain insight into the mechanism by which GSH binds Hg(II), high resolution mass spectrometry coupled with tandem mass spectrometry was utilized to examine the conjugation process. While the 1:1 Hg(II):GSH conjugate is not formed immediately upon mixing aqueous solutions of Hg(II) and GSH, two species containing Hg(II) are observed:the 1:2 Hg(II):GSH conjugate, [(GS)2 Hg + H+], and a second Hg(II)-containing species around m/z 544. Interestingly, this species at m/z 544 decreases in time while the presence of the 1:1 Hg(II):GSH conjugate increases, suggesting that m/z 544 is an intermediate in the formation of the 1:1 conjugate. Experiments using the high mass accuracy capability of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry coupled to an electrospray ionization source indicate that the intermediate species is [GSH + HgCl]+, andnotthe 1:1 conjugate [Hg(GSH) – H + 2H2O]+postulated in previous literature. Further confirmation of [GSH + HgCl]+ is supported by collisionofinduced dissociation experiments, which show neutral loss of HCl from the intermediate and loss of the N- and C-terminal amino acids, indicating binding of Hg(II) at the Cys residue.

MicrobIdentifier: A Microbial Identification Software Based on Mass-Spectrometry  [PDF]
Feng LIU, Lu LI, Chi ZHANG, Lingbing WANG, Pei LI
Journal of Software Engineering and Applications (JSEA) , 2009, DOI: 10.4236/jsea.2009.23028
Abstract: As the technology of microbial identification by mass cataloging has been widely used, we have developed the micro-bial identification software, MicrobIdentifier, which integrates and automates different steps in the procedure of rapid species identification based on mass-spectrometry. This software is written in Java for cross-platform intention.
The effect of milling on proteins in model Queso Fresco cheeses  [PDF]
Moushumi Paul, Alberto Nu?ez, Diane Van Hekken
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.31001
Abstract: Raw milk Queso Fresco (QF) made in Mexico contains contaminating bacterial strains that are not permitted in US foods. There is interest in developing a pasteurized milk version of Mexican Queso Fresco to be sold in the US. Milling is one of many manufacturing factors that may influence protein integrity. The aim of this study is to assess the effect of milling procedures on protein composition and cheese functional properties in a model QF, made without starter cultures. Mass spectrometric and gel electrophoretic analyses of aged milled cheeses show minimal changes in protein content without differences among the milling techniques. In these novel QF-like cheeses, eight weeks of aging, regardless of milling type, results in cheeses that is very similar to the non-aged samples. Aged cheeses with minimal proteolysis imply an extended shelf life and therefore, model cheeses from this study, relative to Mexican raw milk cheeses, would stay fresher in American households and supermarkets longer.
Exorphins in urine from schizoaffective psychotics  [PDF]
Dag Tveiten, Karl L. Reichelt
Open Journal of Psychiatry (OJPsych) , 2012, DOI: 10.4236/ojpsych.2012.23029
Abstract: Hyperpeptiduria and opioid excess have been reported in schizophrenia. According to Prof. Dr. L. Lindstrom, Sweden opioids may explain the patho-physiology of this syndrome. Therefore it is critical to elucidate the presence and nature of opioids in schizophrenia and diagnostic sub groups. First morning urine from untreated schizoaffective patients (ICD-10: F 25.1) was separated on HPLC and peaks that elute where different opioid standards appear, freeze dried, re-dissolved in methanol/water (50/50) and 10mM formic acid. Mass spectrometry and MS/MS or fragmentation mass spectrometry was performed. We found fragmentation pattern of beta-casomorphin 1-3 and 1-4 (bovine) identical to synthetic standards from Bachem. The aggregation tendency of peptides was much in evidence. The reported exorphins were found in the urine from 8 of 12 untreated schizoaffective patients.
Differential protein expression between EBV-positive and negative epithelial cells  [PDF]
Haibo Yu, Lian Zhao, Qijia Yan, Lielian Zuo, Zhengyuan Yu, Wei Xiong, Xiaoling Li, Shourong Sheng, Zhaojian Gong, Guiyuan Li, Jianhong Lu
Journal of Biophysical Chemistry (JBPC) , 2013, DOI: 10.4236/jbpc.2013.42011
Abstract:

Epstein Barr virus infection is believed to play a role in the development of nasopharyngeal carcinoma. In order to investigate the function of EBV in epithelial cell, proteomic methods were used to find and identify the differential proteins and expected to elucidate the mechanism of EBV. Altered protein expressions were found between 293 cell (HEK293) and EBV infected cell (293-EBV). In this study, we separated differential expressed proteins using 2D-DIGE method while matrix-assisted laser desorption/ionization tandem time of flight mass spectrometry (MALDI-TOF-MS) method was used to identify proteins. The results showed that 14 proteins were up regulated and 3 proteins were down regulated in 293-EBV cells. Bioinformatic analysis showed that these proteins are involved in cell proliferation, metastasis, apoptosis, metabolism, and signal transduction. Western blotting analysis was further carried out to verify the MS results. Thus, EBV may exert its functions by mediating differential expression of these proteins.

Rapid Quantification of Functional Carbohydrates in Food Products  [PDF]
Annabelle Le Parc, Hyeyoung Lee, Kevin Chen, Daniela Barile
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.51010
Abstract:

Current research on milk bioactive components, including complex oligosaccharides, stimulated development of novel milk-based ingredients; this in turn sparked the development of methods that are simultaneously simple and sensitive. Oligosaccharides and glycoproteins present interesting health benefits, including antibacterial and antiviral effects, stimulation of the immune system, and participation in the establishment of a balanced gut microbiome in infants. This work describes the application of a simple and rapid method—Total Carbohydrate Assay—to the determination of functional carbohydrate content in various dairy-based functional products. The miniaturization and optimization of the carbohydrate quantification on microplates afforded good repeatability and sensitivity. The optimized method consumed only minimal amounts of reagents and samples, and carbohydrates were detected in the range from 0 - 20 μg. This assay was successfully applied to determine the content of complicated oligosaccharide mixtures and N-glycans in dairy-derived products. Several complementary analytical techniques were applied to confirm the results. This method is faster and far less expensive than mass spectrometry and it gives a general picture of complex carbohydrate concentrations for instances in which detailed data are not required as needed for research in discrete differences among various biological samples. The ability to quantify glycans in novel food products will provide a unique understanding of the potential of these novel ingredients for use by the food industry.

GC/MS Analyses of Thiosemicarbazones Synthesized from Acetophenones: Thermal Decay and Mass Spectra Features  [PDF]
Belén Gastaca, Gastón Galletti, Hernán Rubén Sánchez, Reinaldo Pis Diez, María de las Mercedes Schiavoni, Jorge Javier Pedro Furlong
International Journal of Analytical Mass Spectrometry and Chromatography (IJAMSC) , 2015, DOI: 10.4236/ijamsc.2015.31001
Abstract: The mass spectral fragmentation of thiosemicarbazones synthesized from acetophenones has been studied by CG/MS. These carbonyl compounds exhibit chromatographic peaks which are not observed in aliphatic analogues or those synthesized from aldehydes. The analysis of the corresponding spectra has allowed structural assignment to the dimerization of gas phase neutral fragments. Theoretical calculations (DFT level) also provide evidence to support the experimental observations.
Initial Analysis of Lipid Metabolomic Profile Reveals Differential Expression Features in Myeloid Malignancies  [PDF]
Adriana Ramos de Oliveira, Ismael Dale Cotrim Guerreiro Da Silva, Edson G. Lo Turco, Helio Alves Martins Júnior, Maria de Lourdes L. Ferrari Chauffaille Chauffaille
Journal of Cancer Therapy (JCT) , 2015, DOI: 10.4236/jct.2015.615138
Abstract: The purpose of this preliminary study was to determine the comparative lipid profile of blood plasma samples of healthy individuals and patients with Myeloproliferative Neoplasms. Methods: Untargeted Shotgun MS/MS Analysis was performed to evaluate plasma samples from 153 participants, being 90 of the Control Group, 43 Myeloproliferative Neoplasms (MPN), 11 Myelodysplastic Syndromes (MDS) and 9 Acute Myeloid Leukemias (AML). Lipids were extracted from plasma using the Bligh-Dyer protocol. Data were acquired using the AB-Sciex Analyst TF, processed using the AB-Sciex LipidViewTM and the web-based analytical pipeline MetaboAnalyst 2.0 (www.metaboanalyst.ca). Results: Untargeted analysis identified in negative and positive-modes a total of 658 features at 2 ppm resolution. PCA and PLS-DA analysis revealed clear discrimination among groups, in particular for AML patients. Main lipid groups differentially expressed were: Monoacylglycerols (MAG), Glucosylceramide E (GlcdE), Ethyl Esters (EE), Lysophosphatidic acid (LPA), Sulfoquinovosil diacylglycerols (SQDG), Monoglycerols (MG), Methyl Ethanolamines (ME), Lysophosphatidylcholines (LPC), Dimethyl Phosfatidyletanolamines (DMPE), Monometylphosphatidiletanolamines (MMPE), Ceramide-1-phosphate (CerP), Glicerophosphoglycerols (GP), Lysomonomethyl-Phosphatidylethanolamines (LMMPE), Phosphatidic Acids (PA), Ergosterols (ERG), Glycerophosphoserine (PS), Diacylglycerols (DAG), Hexocylceramides (HexCer) and Lanosterol (Lan). ROC Curve Analysis revealed Total LMMPE as the strongest discriminating marker between Controls from Patients. In addition, these lipids were also able to differentiate MDS and AML from NPM. Conclusions: The Myeloproliferative Neoplasms from the point of view
Page 1 /8006
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.