211 resultados para ELECTROPHORESIS-MASS SPECTROMETRY
Resumo:
A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 muL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized. (C) 2004 American Society for Mass Spectrometry.
Resumo:
Direct-injection electrospray ionization mass spectrometry in combination with information-dependent data acquisition (IDA), using a triple-quadrupole/linear ion trap combination, allows high-throughput qualitative analysis of complex phospholipid species from child whole blood. In the IDA experiments, scans to detect specific head groups (precursor ion or neutral loss scans) were used as survey scans to detect phospholipid classes. An enhanced resolution scan was then used to confirm the mass assignments, and the enhanced product ion scan was implemented as a dependent scan to determine the composition of each phospholipid class. These survey and dependent scans were performed sequentially and repeated for the entire duration of analysis, thus providing the maximum information from a single injection. In this way, 50 different phospholipids belonging to the phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidylcholine and sphingomyelin classes were identified in child whole blood. Copyright (C) 2005 John Wiley & Sons, Ltd.
Resumo:
A sample of tobacco essential oil was analyzed using gas chromatography-mass spectrometry (GUMS)and comprehensive two-dimensional gas chromatography coupled to a time-of-flight mass spectrometry (GC x GC/TOFMS), respectively. In the GUMS analysis, serially coupled columns were used. By comparing the GUMS results with GC x GC/TOFMS result,,, many more components in the essential oil could be found within the two-dimensional separation space of GC x GC. The quantitative determination of components in the essential oil was performed by GC x GC with flame ionization detection (FID), using a method of multiple internal standards calibration, (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
A quantitative analysis of the individual compounds in tobacco essential oils is performed by comprehensive two-dimensional gas chromatography (GC x GC) combined with flame ionization detector (FID). A time-of-flight mass spectrometer (TOF/MS) was coupled to GC x GC for the identification of the resolved peaks. The response of a flame ionization detector to different compound classes was calibrated using multiple internal standards. In total, 172 compounds were identified with good match and 61 compounds with high probability value were reliably quantified. For comparative purposes, the essential oil sample was also quantified by one-dimensional gas chromatography-mass spectrometry (GC/MS) with multiple internal standards method. The results showed that there was close agreement between the two analysis methods when the peak purity and match quality in one-dimensional GC/MS are high enough. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for environmental analysis has been mainly focused on qualitative analysis of high-mass molecules, such as toxins, humic acid, and microorganisms. Herein,we describe a novel MALDI-TOF-MS method with a matrix of oxidized carbon nanotubes for analysis of low-mass compounds in environmental samples. A number of chemicals in the environment were qualitatively analyzed by the present method, and it was found that most of them, especially the highly polar chemicals, were measurable with high sensitivity. With the intrinsic ability to measure high-mass chemicals, this method can compensate for the current shortage of methods for environmental analysis for the measurement of highly polar or high-mass chemicals. For sample analysis, arsenic speciation in Chinese traditional medicines was qualified and diphenylolpropane in water samples was quantified. With the relatively high tolerance of the method to interfering molecules, a simple pretreatment or even no pretreatment could be employed before MS detection. Furthermore, this method can be employed in a high-throughput format.
Resumo:
An approach for the separation and identification of components in a traditional Chinese medicine Psoralea corylifolia was developed. Ion-exchange chromatography (IEC) was applied for the fractionation of P corylifolia extract, and then followed by concentration of all the fractions with rotary vacuum evaporator. Each of the enriched fractions was then further separated on an ODS column with detection of UV absorbance and atmospheric pressure chemical ionization mass spectrometer (APCI/MS), respectively, and also analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) with matrix of oxidized carbon nanotubes. Totally more than 188 components in P. corylifolia extract were detected with this integrated approach, and 12 of them were preliminary identified according to their UV spectra and mass spectra performed by APCI/MS and MALDI-TOF/MS. The obtained analytical results not only demonstrated the powerful resolution of integration IEC fractionation with reversed-phase liquid chromatography (RPLC)-APCI/MS and MALDI-TOF/MS for analysis of compounds in a complex sample, but also exhibited the superiority of APCI/MS and MALDI-TOF/MS for identification of low-mass compounds, such as for study of traditional Chinese medicines (TCMs) and metabolome. (c) 2005 Published by Elsevier B.V.
Resumo:
A hyphenated method for the isolation and identification of components in a traditional Chinese medicine of Honeysuckle was developed. Ion-exchange chromatography (IEC) was chosen for the fractionation of Honeysuckle extract, and then followed by concentration of all the fractions with rotary vacuum evaporator. Each of the enriched fractions was then further analyzed by reversed-phase liquid chromatography-atmospheric pressure chemical ionization mass spectrometer (RPLC-APCI/MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) with matrix of oxidized carbon nanotubes, respectively. It can be noted totally more than 117 components were detected by UV detector, APCI/MS and MALDI-TOF/MS in Honeysuckle extract except the, 145 components identified by MALDI-TOF/MS alone with this integrated approach, and 7 of them were preliminary identified according to their UV spectra and mass spectra performed by APCI/MS and MALDI-TOF/MS, respectively. The obtained analytical results not only indicated the approach of integration IEC fractionation with RPLC-APCI/MS and MALDI-TOF/MS is capable of analyzing complex samples, but also exhibited the potential power of the mass spectrometer in detection of low-mass compounds, such as traditional Chinese medicines (TCMs) and complex biological samples. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
High-performance liquid chromatography-tandem mass spectrometry has been used to identify isoflavone aglycones and glycosides in kudzu root. Fourteen isoflavones were detected. Among these, six were identified by comparison with authentic standards. Tentative identifications of the other isoflavones are based on UV spectra, mass spectra of protonated and deprotonated molecules, and MS-MS data. Several are reported for the first time in kudzu root. The bioactivity and bioavailability of isoflavone aglycones are usually greater than those of their glycosides. To improve the bioavailability of kudzu root isoflavones, crude beta-glycosidases prepared from microbes were used to hydrolyze the isoflavone glycosides. Several MS modes are combined not only to identify the isoflavones in kudzu root, but also to describe the biotransformation of kudzu root isoflavone glycosides. It is also proved that crude beta-glycosidases have high selectivity toward the O-glycosides of isoflavones.
Resumo:
水稻既是我国三大粮食作物之一,又是基因组学研究的模式材料,在生产实践和科学研究中都占有极其重要的地位。基因组学研究取得的巨大成就以前所未有的深度和广度推动了生命科学各个研究领域的飞速发展。水稻基因组的破译是水稻科学研究的重要里程碑,同时也宣告了功能基因组学时代的到来。蛋白质组学是研究细胞内全部蛋白质的动态表达及其相互关系的新兴学科,是功能基因组学研究的重要组成部分和战略制高点。 本论文采用高分辨率的蛋白质双向电泳分离技术和高通量的蛋白质质谱分析技术以及生物信息学等手段,开展水稻灌浆期茎蛋白质组表达模式和水稻幼苗脱黄化过程的比较蛋白质组学研究,探讨茎生长发育规律和水稻应答光信号相关蛋白质及其网络调控机制,是学科前沿与实际应用的有机结合,在科研和生产实践中都具有重要的意义。 首先,分别构建了灌浆期水稻顶端茎段和水稻黄化幼苗的蛋白质组表达谱。并对其中185个目的蛋白点进行了MALDI-TOF/MS分析和数据库检索鉴定。共有149个蛋白质得到了鉴定,蛋白质鉴定的成功率为80.5%。这些被鉴定的蛋白质分属118个基因的表达产物,根据它们功能可以分为13种不同的类别,其中绝大多数为能量产生和代谢以及抗性相关的蛋白质。 在水稻灌浆期顶端茎段表达的蛋白质中,与能量和物质代谢相关的蛋白质例如ATPase、磷酸丙糖异构酶,6-磷酸葡萄糖异构酶等占有很高比例,说明茎段组织中具有很强的代谢活动。与生长发育相关的蛋白质包括beta-tubulins、无机焦磷酸酶(inorganic pyrophosphatase)、液泡质子ATP酶(vacuolar proton-ATPase)以及UDP葡萄糖焦磷酸酶等的大量累积,显示出顶端茎段细胞分裂和生长迅速;同时,贮存多糖和结构多糖也在旺盛合成。G蛋白、GDP释放抑制因子等信号传导蛋白以及苯丙氨酸氨解酶、谷胱苷肽S转移酶(glutathione S-transferase,GST)、抗坏血酸过氧化酶(ascorbate peroxidase,APX)以及超氧化物歧化酶(superoxide dismutase,SOD)等抗性相关蛋白质在该时期丰度表达,表明在灌浆期水稻顶端茎段能够迅速感受并传递外界信号,从而使得其在遭受胁迫时能够立刻启动抗逆防御系统,最大限度地降低不利环境对种子发育的影响。 在黑暗中萌发和生长的水稻黄化幼苗随着光照时间(0~24小时)的延长,能通过双向电泳后检测到的蛋白质逐渐变少,24小时后趋于稳定,相当于正常光照条件下生长的水稻幼苗蛋白质组表达谱。进一步分析表明,在黄化苗中,分解代谢及能量产生相关的蛋白如丙糖磷酸异构酶、琥珀酰辅酶A连接酶、异戊酰辅酶A脱氢酶与ATPase等的表达量比较丰富;另外,还可能启动了脂肪酸的α氧化分解途径,以供黑暗中生长所需的物质和能量。当黄化幼苗光照后,与光合作用及物质合成相关的一些蛋白质表达量增加,而那些分解代谢相关酶类则有所下降。同时,鸟核苷酸结合蛋白β亚基类似蛋白、20S proteasome以及Bowman Birk trypsin inhibitor等信号传递及抗性相关蛋白随着光照时间的延长而减少,说明黑暗胁迫条件下水稻幼苗启动了相关的抗逆途径。叶绿素合成途径中的蛋白酶胆色素原脱氨基酶和金属鳌合酶在脱黄化过程中表达量有所下降,可能是因为叶绿素合成产物具有反馈抑制作用。 本研究首次利用蛋白质组学方法来解析水稻灌浆期茎蛋白质组表达模式和水稻黄化幼苗响应光因子的蛋白质组变化情况,鉴定了一些有价值的蛋白质,并得到了它们的表达特点和相关数据,为更好地理解水稻顶端茎秆的生长特点和功效、水稻应答黑暗胁迫和光形态建成以及光合作用机理等提供了分子证据。
Resumo:
In this work, a new fluorescent method for sensitive detection of biological thiols in human plasma was developed using a near-infrared (NIR) fluorescent dye, FR 730. The sensing approach was based on the strong affinity of thiols to gold and highly efficient fluorescent quenching ability of gold nanoparticles (Au NPs). In the presence of thiols, the NIR fluorescence would enhance dramatically due to desorption of FR 730 from the surfaces of Au NPs, which allowed the analysis of thiol-containing amino acids in a very simple approach. The size of Au NPs was found to affect the fluorescent assay and the best response for cysteine detection was achieved when using Au NPs with the diameter of 24 nm, where a linear range of 2.5 x 10(-8) M to 4.0 x 10(-6) M and a detection limit of as low as 10 nM was obtained. This method also demonstrated a high selectivity to thiol-containing amino acids due to the strong affinity of thiols to gold.
CE coupling with end-column electrochemiluminescence detection for chiral separation of disopyramide
Resumo:
CE with electrochemiluminescence, (ECL) detection technique was successfully applied for the chiral separation of a kind of class IA antiarrhythmic racemic drug. To the best of our knowledge, this is the first report of ECL detection used in chiral CE. To get better detection sensitivity and good enantioresolution at the same time, the conditions of capillary inlet and outlet buffer were systematically optimized. Unlike the traditional chiral separation method, the buffers we used in the capillary inlet and outlet differed from each other in terms of buffer pH, ionic strength, type of BGE as well as buffer composition. Under the optimum conditions, baseline enantioseparation and highly sensitive detection of the enantiomers were achieved. Wide linear relationship of each enantiomer was achieved in the range of 5 x 10(-7) to 2 x 10(-5) mol/L with relative coefficients of 0.996 and 0.997, respectively. The detection limits were estimated to be 8 x 10(-8) and 1.0 X 10(-7) mol/L (S/N = 3) for the enantiomers, respectively. In addition, a successful application of this new method to the chiral separation of the racemic drug in spiked plasma samples confirmed the validity and applicability of the chiral CE-ECL method.
Resumo:
Amphetamines including methamphetamine, 3,4-methylenedioxyamphetamine and 3,4-methylenedioxymethamphetamine were separated and detected by CE using simultaneous electrochemical (EC) and electrochemiluminescence (ECL) detection (CE-EC/ ECL). Factors that influenced the separation and detection performance, such as the detection potential, the pH value and concentration of the running buffer, the separation voltage and the pH of the detection buffer, were investigated.