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排序方式: 共有45条查询结果,搜索用时 15 毫秒
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El-Khoury JM Bunch DR Reineks E Jackson R Steinle R Wang S 《Analytical and bioanalytical chemistry》2012,402(2):771-779
Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and an established biomarker for endothelial
function, while symmetric dimethylarginine (SDMA), an emerging biomarker for renal function, has been shown to outperform
creatinine-based equations for estimated glomerular filtration rate. In order to study these analytes for clinical research,
a fast and simple method for measuring arginine (ARG), SDMA, and ADMA in plasma by liquid chromatography–tandem mass spectrometry
(LC-MS/MS) has been developed. Plasma (50 μL) was mixed with 50 μL of internal standard of 13C-arginine and d7-ADMA followed by protein precipitation with methanol containing 1% ammonium acetate (300 μL). After centrifugation, the supernatant
(100 μL) was mixed with 300 μL of acetonitrile with 1% formic acid, and the mixture was injected onto a silica column monitored
by a mass spectrometer. The analytical cycle time was 5.0 min. The method was linear from 5.7 to 489.7 μM for ARG, 0.06 to
5.15 μM for SDMA, and from 0.34 to 5.65 μM for ADMA, with an accuracy of 99.0–120.0%. Total coefficients of variation for
all analytes ranged from 2.7% to 7.7% for three concentration levels. The effects of hemolysis, lipemia, uremia, icterus,
specimen tube types, storage at different temperature, and freeze/thaw were thoroughly investigated. Reference ranges were
established using 51 well-defined reference subjects (12 men and 39 women, age 19–64 years): 53.1–129.7 μM for ARG, 0.32–0.65 μM
for SDMA, and 0.36–0.67 μM for ADMA. In conclusion, the validated LC-MS/MS method described here offers a fast and reliable
ARG, SDMA, and ADMA quantitation in plasma with minimum sample preparation. 相似文献
24.
Rebecca L. Edwards Paul Griffiths Josephine Bunch Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2012,23(11):1921-1930
We have previously shown that liquid microjunction surface sampling of dried blood spots coupled with high resolution top-down mass spectrometry may be used for screening of common hemoglobin variants HbS, HbC, and HbD. In order to test the robustness of the approach, we have applied the approach to unknown hemoglobin variants. Six neonatal dried blood spot samples that had been identified as variants, but which could not be diagnosed by current screening methods, were analyzed by direct surface sampling top-down mass spectrometry. Both collision-induced dissociation and electron transfer dissociation mass spectrometry were employed. Four of the samples were identified as ??-chain variants: two were heterozygous Hb D-Iran, one was heterozygous Hb Headington, and one was heterozygous Hb J-Baltimore. The fifth sample was identified as the ??-chain variant heterozygous Hb Phnom Penh. Analysis of the sixth sample suggested that it did not in fact contain a variant. Adoption of the approach in the clinic would require speed in both data collection and interpretation. To address that issue, we have compared manual data analysis with freely available data analysis software (ProsightPTM). The results demonstrate the power of top-down proteomics for hemoglobin variant analysis in newborn samples. 相似文献
25.
Rory T. Steven Alan M. Race Josephine Bunch 《Journal of the American Society for Mass Spectrometry》2013,24(5):801-804
para-Nitroaniline (PNA) is presented as a promising matrix for matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) on an intermediate-pressure ion source (~1 Torr) QqTOF instrument using an Nd:YVO4 laser operated at 5 kHz. An imaging study was carried out to determine the utility of PNA at this pressure by analyzing 14 tissue sections. We demonstrate acquisition of high-quality imaging data over a 6-h period in the ion source. In this study, comparisons were made between PNA and α-cyano-4-hydroxycinnamic acid (CHCA) in positive ion mode to demonstrate the utility of PNA in these circumstances. PNA performed as well as or better than CHCA in terms of lipid ion intensities, resulting in lower levels of ion fragmentation and in lower incidences of analyte migration at the edges of the tissue sections when using airspray matrix deposition. 相似文献
26.
The pivoting strategy of Bunch and Marcia for solving systems involving symmetric indefinite tridiagonal matrices uses two different methods for solving 2 × 2 systems when a 2 × 2 pivot is chosen. In this paper, we eliminate this need for two methods by adding another criterion for choosing a 1 × 1 pivot. We demonstrate that all the results from the Bunch and Marcia pivoting strategy still hold. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
27.
Direct functionalization of the 3-oxygenated isothiazole heteroaromatic parental system has not yet been reported in the literature. Here, we report the first regioselective lithiation of the 5-position of 3-(benzyloxy)isothiazole (4) using LDA in diethyl ether. The versatility of the methodology was explored by quenching with a variety of electrophiles to give the desired products 7a,b,d-g in 54-68% yield. Only benzoylation aiming at the synthesis of 7c was unsuccessful. Furthermore, a highly convergent synthesis of thioibotenic acid (1), the sulfur analogue of the neurotoxic natural product ibotenic acid, was carried out. 相似文献
28.
Andrew D. Palmer Rian Griffiths Iain Styles Ela Claridge Antonio Calcagni Josephine Bunch 《Journal of mass spectrometry : JMS》2012,47(2):237-241
Sucrose is used as a cryo‐preservation agent on large mammalian eyes post formalin fixation and is shown to reduce freezing artefacts allowing the collection of 12‐µm thick sections from these large aqueous samples. The suitability of this technique for use in MALDI imaging experiments is demonstrated by the acquisition of the first images of lipid distributions within whole sagittal porcine eye sections. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Pugh JA Cox AG McLeod CW Bunch J Writer MJ Hart SL Bienemann A White E Bell J 《Analytical and bioanalytical chemistry》2012,403(6):1641-1649
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used to map the spatial distribution of magnetic resonance imaging (MRI) contrast agents (Gd-based) in histological sections in order to explore synergies with in vivo MRI. Images from respective techniques are presented for two separate studies namely (1) convection enhanced delivery of a Gd nanocomplex (developmental therapeutic) into rat brain and (2) convection enhanced delivery, with co-infusion of Magnevist (commercial Gd contrast agent) and Carboplatin (chemotherapy drug), into pig brain. The LA technique was shown to be a powerful compliment to MRI not only in offering improved sensitivity, spatial resolution and signal quantitation but also in giving added value regarding the fate of administered agents (Gd and Pt agents). Furthermore simultaneous measurement of Fe enabled assignment of an anomalous contrast enhancement region in rat brain to haemorrhage at the infusion site. 相似文献