3,551 research outputs found
Applying mini-bore HPAEC-MS/MS for the characterization and quantification of Fc N-glycans from heterogeneously glycosylated IgGs
No full textAbstractHigh-performance anion-exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD) is a highly sensitive method for the analysis of oligosaccharides without the need for prior derivatization. However, the method suffers from the lack of chemical information with peak assignments based on the retention times of authentic standards or known peaks of reference materials. Here we applied HPAEC coupled on-line with electrospray ion trap mass spectrometry (HPAEC-MS) using a prototype mini-bore (1mm I.D.) CarboPac PA200 column and challenged the analytical separation based method for the structural assignment of heterogeneous mixtures of N-glycans derived from immunoglobulin G from human plasma, glyco-engineered CHO cells, and Sp2/0 mouse myeloma cells. Compared to an analytical scale 3mm I.D. column, the mini-bore column demonstrated a superior performance with up to 8-fold improved limit of detection for specific N-glycans determined by PAD. Quantitative evaluation by extracted ion current chromatograms revealed detection limits in the 50⿿100 femtomole range using ion trap MS operated in positive ionization mode. In our hands HPAEC-MS/MS allowed the detection and quantification of even low abundant glycan species including biantennary complex-type, high mannose, hybrid and hybrid bisected structures. In comparison to the detection of N-glycans as lithiated or sodiated adducts, we obtained a 65-fold improved signal-to-noise ratio with protonated ions only. Relative quantitative evaluation by single ion current chromatograms was successfully applied and demonstrated an excellent performance with respect to selectivity in the relative quantification of heterogeneous samples of N-glycans compared to HPAEC-PAD and HILIC-UPLC of 2-AB labelled N-glycans
Fluoxetine as disease modifying treatment in multiple sclerosis : rationale, evaluation of the use of MRI to monitor treatment, and preliminary findings
No full textPatients with multiple sclerosis (MS) lack astrocytic β2-adrenergic receptors and this may contribute to the focal inflammatory demyelinating lesions and axonal degeneration that characterize this disease. We hypothesized that the antidepressant fluoxetine might be able to compensate for the loss of the β2-adrenergic receptors. In this thesis we evaluated the use of cerebral MRI scans to monitor disease activity and we performed several exploratory studies to evaluate effects of fluoxetine on patients with MS.
A convenient way to find out whether a drug is able to reduce disease activity in MS is by measuring the development of new focal lesions on serial MRI scans of the brain.
MS patients who received fluoxetine during 6 months had a trend towards the development of less new focal lesions compared to patients receiving placebo. To assess whether preventing new lesions formation reduces disability on the long term, we studied the relationship between the focal (T2) lesions and disease progression. The number of focal lesions predicted progression of disability and conversion to a progressive disease course in patients with relapsing remitting MS. However, once patients had entered the progressive phase, T2 lesions were no longer predictive for further progression of disability. In another study, we found that 2 weeks use of fluoxetine resulted in an increase in NAA/Cr (a marker of axonal function) in the white matter of MS patients.
These preliminary studies suggest that fluoxetine reduces new focal lesion formation and may improve axonal metabolism in MS patients.
Evaluation of Differences in MS/MS Spectra from Two Different-generation Q-TOF Instruments: Implications for Metabolomic Database Use
No full textGenerating reproducible fragmentation patterns is a problem in electrospray ionization mass spectrometry. Two generations of quadrupole time-of-flight(Q-TOF) instruments were selected to evaluate the reproducibility of tandem mass spectrometry(MS/MS) spectra: an old-and a new-generation instrument. Ninety-four MS/MS and MS/MS/MS spectra with information-rich product ions were obtained in positive-or negative-ion mode with two different-generation Q-TOF instruments, BioTOF-Q and micrOTOF-Q. Two principles were selected to optimize the collision energy. On the one hand, maximal structural information is obtained when the collision energy is increased; on the other hand, when most product ions show relative abundance of more than 10%, the lowest collision energy should be selected. The Paired-Samples T Test method was used to analysis these paired-spectra. We found that most product ions were the same and the profiles of the product ions were similar with both Q-TOF instruments. Interestingly, at the low signal to-noise ratio (S/N) of the precursor ion (ion intensity low to 180 counts), the profile of the MS/MS spectrum is very similar to that at a high S/N. Furthermore, when spectra were generated with micrOTOF-Q even before and after a four-year interval, the profiles and product ions were virtually identical. In summary, databases built with different-generation Q-TOF instruments may be universally applicable
Preparation and Characterization of Biodegradable Modified Chitosan Films for Food Packaging
No full textThis Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page
Validation data for the quantification of the Annonaceous acetogenin annonacin in Rat brain by UPLC-MS/MS
No full textAbstractAnnonaceous acetogenins (AAGs) are environmental neurotoxins from the fruit pulp of several Annonaceae species, whose consumption was linked to the occurrence of sporadic atypical Parkinsonism with dementia. The quantification of the prototypical AAG annonacin in Rat brain homogenates was performed by UPLC-MS/MS in selected reaction monitoring (SRM) mode, using a triple quadrupole mass analyzer. A natural analog of annonacin was used as an internal standard. Analyzed data set of the analytical validation of this method is presented, including stability of the samples, extraction recovery and matrix effect, supporting the results described in the article “Quantification of the environmental neurotoxin annonacin in Rat brain by UPLC-MS/MS” N. Bonneau, I. Schmitz-Afonso, D. Touboul, A. Brunelle, P. Champy (2016) [1]
Highly sensitive CE-ESI-MS analysis of N-glycans from complex biological samples
No full textThe in-depth, high-sensitivity characterization of the glycome from complex biological samples, such as biofluids and tissues, is of utmost importance in basic biological research and biomarker discovery. Major challenges often arise from the vast structural diversity of glycans in combination with limited sample amounts. Here, we present a method for the highly sensitive characterization of released N-glycans by combining a capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) approach with linkage-specific derivatization of sialic acids and uniform cationic reducing end labelling of all glycans. This method allows the analysis of glycans at the attomole level, provides information on sialic acid isomers and enables the in-depth characterization of complex samples, even when available in minute amounts.BN/Chirlmin Joo La
A Class-D Piezoelectric Speaker Driver Using A Quadrature Feedback Chopping Scheme achieving 29dB Large-Signal THD+N Improvement
No full textThis paper presents a Class-D piezoelectric speaker driver that employs a quadrature feedback chopping scheme (QCS). Compared to a conventional single feedback chopping scheme (SCS), the use of QCS can eliminate the timing skew between low-voltage (LV) and high-voltage (HV) choppers, greatly improving large-signal linearity. A prototype implemented in a 180nm BCD process achieves a peak THD+N of 88dB/-92.5dB for a 1kHz/6kHz input frequency and 37μ VR MS output noise (A-weighted) while driving a 4μ F load. Thanks to QCS, the large-signal THD+N has been improved by 29 dB, while the output voltage swing achieving -60dB THD+N has been extended from 86.9% to 99.5% of the full-scale (FS). Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationElectronic Components, Technology and Material
Phytochemical profile of Allmania nodiflora through in vitro antioxidant assays and GC-MS analysis
No full textDepartment of Chemistry, Periyar University, Salem-636 011, Tamilnadu, India
E-mail : [email protected]
Green leafy vegetables attain an important place among the food crops as they possess intense amounts of essential proteins, β-carotene and carbohydrates for trade. Allmania nodiflora [F : Amaranthaceae] is chosen to investigate their phenolic, flavonoid, carbohydrate, protein, DPPH-radical scavenging activity, reducing power accompanied with GC-MS, for their various solvent extracts [hexane, ethyl acetate, acetone, methanol]. Results indicate that methanol extract of Allmania nodiflora have marked amount of total phenolic and total flavonoid which could be responsible for antioxidant activity. Among the extracts assayed, methanol extract exhibited significant activity, thereby presenting its antioxidant activity potential by scavenging free radicals. This was evident from the SC50 values against standard ascorbic acid. In competence, better significance was reported by acetone fractions, which has articulated in identifying numerous constituents through GC-MS. Hence, this present study would endow the scientific validation for their medicinal, therapeutic and dietary applications
The analysis of lipophilic marine toxins : development of an alternative method
No full textLipophilic marine toxins are produced by certain algae species and can accumulate in filter feeding shellfish such as mussels, scallops and oysters. Consumption of contaminated shellfish can lead to severe intoxications such as diarrhea, abdominal cramps and vomiting. Methods described in European Union (EU) legislation to test for the presence of these toxins are based on a mouse or rat bioassay. These assays are unethical and have a poor sensitivity and selectivity. The aim of this thesis is to develop an alternative method based on liquid chromatography - tandem mass spectrometry (LC-MS/MS) for the quantitative analysis of lipophilic marine toxins. LC-MS/MS methods described in literature for the determination of lipophilic marine toxins used an acidic chromatographic system. Under acidic conditions peak shape and separation of a number of toxins preferably analyzed in electrospray ionization negative (ESI–) and positive (ESI+) were poor. A LC-MS/MS method with alkaline chromatographic conditions in which we were able to analyze 28 different toxins in a single analysis in separated retention time windows operating in either ESI– or ESI+ was developed. Furthermore, a clean up procedure based on solid phase extraction (SPE) was developed to reduce the amount of matrix effects (ion suppression and enhancement). A combination of SPE clean up and alkaline chromatographic conditions resulted in reduced matrix effects for all matrices tested (mussel, scallop and oyster). The developed SPE & LC-MS/MS method was in-house validated at regulatory limits based on EU Commission Decision 2002/657/EC. With respect to accuracy, repeatability, reproducibility, decision limit, specificity and ruggedness the method performed well. The method also performed excellently in view of possible new limits that are four- to five-fold lower than current limits for some toxins. Finally a screening method based on LC orbitrap MS was developed for 85 marine toxins of which most are not stated in EU legislation. The screening used in-house developed software which made it possible to reduce the complex data files and screen for a large number of toxins within seconds. This thesis will contribute to the replacement of the animal assays that are still prescribed in EU legislation for the determination of lipophilic marine toxins in shellfish. </p
N-¹, N-¹⁴-diferuloylspermine as an antioxidative phytochemical contained in leaves of Cardamine fauriei
No full textMost Brassicaceae vegetables are ideal dietary sources of antioxidants beneficial for human health. Cardamine fauriei (Ezo-wasabi in Japanese) is a wild, edible Brassicaceae herb native to Hokkaido, Japan. To clarify the main antioxidative phytochemical, an 80% methanol extraction from the leaves was fractionated with Diaion (R) HP-20, Sephadex (R) LH-20, and Sep-Pak (R) C18 cartridges, and the fraction with strong antioxidant activity depending on DPPH method was purified by HPLC. Based on the analyses using HRESIMS and MS/MS, the compound might be N-1, N-14-diferuloylspermine. This rare phenol compound was chemically synthesized, whose data on HPLC, MS and H-1 NMR were compared with those of naturally derived compound from C. fauriei. All results indicated they were the same compound. The radical-scavenging properties of diferuloylspermine were evaluated by ORAC and ESR spin trapping methods, with the diferuloylspermine showing high scavenging activities of the ROO, O-2(-), and HO radicals as was those of conventional antioxidants
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