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131.
Samuel K Yin W Stearns RA Tang YS Chaudhary AG Jewell JP Lanza T Lin LS Hagmann WK Evans DC Kumar S 《Journal of mass spectrometry : JMS》2003,38(2):211-221
Metabolic activation of drug candidates to electrophilic reactive metabolites that can covalently modify cellular macromolecules may result in acute and/or idiosyncratic immune system-mediated toxicities in humans. This presents a significant potential liability for the future development of these compounds as safe therapeutic agents. We present here an example of an approach where sites of metabolic activation within a new drug candidate series were rapidly identified using online liquid chromatography/multi-stage mass spectrometry on an ion trap mass spectrometer. This was accomplished by trapping the reactive intermediates formed upon incubation of compounds with rat and human liver microsomes as their corresponding glutathione conjugates and mass spectral characterization of these thiol adducts. Based on the structures of the GSH adducts identified, potential sites and mechanisms of bioactivation within the chemical structure were proposed. These metabolism studies were interfaced with iterative structural modifications of the chemical series in order to block these bioactivation sites within the molecule. This strategy led to a significant reduction in the propensity of the compounds to undergo metabolic activation as evidenced by reductions in the irreversible binding of radioactivity to liver microsomal material upon incubation of tritium-labeled compounds with this in vitro system. With the efficiency and throughput achievable with such an approach, it appears feasible to identify and address the metabolic activation potential of new drug leads during routine metabolite identification studies in an early drug discovery setting. 相似文献
132.
Three new serratanes were isolated from the nonsaponifiable fraction of western white pine ( Dougl.) bark. The compounds were shown to be 3β-methoxyserrat-14-ene-21α,30-diol (), 3β-methoxyserrat-14-ene-21α, 29-diol (), and 3β-methoxyserrat-14-ene-21β,30-diol (), by a combination of chemical, and spectral methods. 相似文献
133.
本研究采用直接曝热技术,分别以氢气和甲烷为反应气,测定了10个血卟啉衍生物和13个金属血卟啉衍生物的正、负离子解吸化学电离质谱,探讨了各种化学电离质谱法在结构测定中的应用。 相似文献
134.
Marina Lulla Jelena Asari Jaan Aarik Kaupo Kukli Raul Rammula Unto Tapper Eero Kauppinen Väino Sammelselg 《Mikrochimica acta》2006,155(1-2):195-198
Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating
samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage
and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed.
For comparison, Al2O3, Ta2O5 and TiO2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized
by atomic layer deposition method. 相似文献
135.
Relative mass transport efficiencies of near infrared (λ = 795 nm) femtosecond laser generated brass aerosols in helium were measured by ICP-MS applying different ablation cells with short and long washout times. It was found that the transport efficiencies are independent of the cell used within the mutual experimental uncertainties. This finding was confirmed by additional measurements providing the absolute particle mass transport efficiencies of femtosecond laser ablation in He. Here, the transport efficiencies were determined by weighing the samples before and after ablation with a micro-balance, collecting the particles by low-pressure impaction, and evaluating the impacted masses quantitatively by total reflection X-ray fluorescence. Within the experimental uncertainties (± 9–19%) the same absolute transport efficiency (about 77%) was found for all cells applied. This efficiency value can be regarded as a lower limit of the absolute mass transport efficiency since mass losses in the impactor are difficult to quantify. 相似文献
136.
建立了酱油中1,3-二氯-2-丙醇、2,3-二氯-1-丙醇、3-氯-1,2-丙二醇和2-氯-1,3-丙二醇的分散固相萃取-气相色谱-高分辨质谱快速筛查检测方法。样品采用乙酸乙酯提取,提取液浓缩后经N-丙基乙二胺净化,气相色谱-高分辨质谱测定,内标法定量。结果表明,该方法对于酱油中4种氯丙醇的定量限为0.5~10 μg/kg。在3个浓度水平下的加标回收率为78%~103%;相对标准偏差均不大于8.8%。该方法快速、简便、准确、灵敏,可作为酱油中4种氯丙醇的有效检测方法。 相似文献
137.
V. G. Nefedov O. A. Artyushenko E. V. Kashevarova 《Russian Journal of Electrochemistry》2006,42(6):638-642
Mass transfer to a horizontal electrode during electrolytic evolution of oxygen and hydrogen at current densities of 100 to 10 000 A/m2 is studied. The mass transfer intensity is evaluated from the diffusion layer thickness, which varies from 60 to 5 μm at such current densities. Calculations show that the decrease in the diffusion layer thickness is due to bubbles with a stationary interphase surface crossing the diffusion layer. During the hydrogen evolution, the diffusion layer thickness is nearly the same for vertical and horizontal electrodes. During the oxygen evolution, the diffusion layer is much thinner for a horizontal electrode. Additional decrease of the diffusion layer thickness during the evolution of oxygen is associated with the lesser solution density in the near-electrode layer and with its transport away by means of natural convection. 相似文献
138.
Mitamura K Setaka M Shimada K Honma S Namiki M Koh E Mizokami A 《Biomedical chromatography : BMC》2005,19(10):796-801
A promising liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) for analysis of the sulfates of 5alpha-androgen, androsterone and epiandrosterone (A-S and EpiA-S) in human serum was developed. The method was used to assess one of the markers of 5alpha-reductase activity of males including patients with prostate cancer (PC). After deproteinization with acetonitrile, the androgen sulfates and the internal standard, [7,7,16,16-2H4]dehydroepiandrosterone-S, were extracted from human serum using a solid-phase extraction cartridge and washed with hexane. The extract was reconstituted and applied to the LC/ESI-MS system operated in the selected ion monitoring mode. The method was validated over the range 0.02-5 microg/mL (A-S) and 0.005-1.5 microg/mL (EpiA-S) using 10 microL of human serum. The method was a concise procedure without chemical or enzymatic hydrolysis of the conjugates, purification by high-performance liquid chromatography and/or derivatization, and proved to be satisfactory in its reproducibility and accuracy. The levels of these androgen sulfates tended to decrease during aging, and the A-S levels in the sera obtained from both healthy males and patients with PC were correlated with their EpiA-S levels. 相似文献
139.
Kratzsch C Tenberken O Peters FT Weber AA Kraemer T Maurer HH 《Journal of mass spectrometry : JMS》2004,39(8):856-872
A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (LC/APCI-MS) is presented for fast and reliable screening and identification and also for precise and sensitive quantification in plasma of the 23 benzodiazepines alprazolam, bromazepam, brotizolam, camazepam, chlordiazepoxide, clobazam, clonazepam, diazepam, flunitrazepam, flurazepam, desalkylflurazepam, lorazepam, lormetazepam, medazepam, metaclazepam, midazolam, nitrazepam, nordazepam, oxazepam, prazepam, temazepam and tetrazepam, triazolam, their antagonist flumazenil and the benzodiazepine BZ1 (omega 1) receptor agonists zaleplone, zolpidem and zopiclone. It allows confirmation of the diagnosis of an overdose situation and monitoring of psychiatric patients' compliance. The analytes were isolated from plasma using liquid-liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' LC/MS library, the analytes were quantified in the selected-ion monitoring mode. The quantification assay was fully validated. It was found to be selective proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes, except bromazepam. The corresponding reference levels the assay's accuracy and precision data for all studied substances are listed. The accuracy and precision data were within the required limits with the exception of those for bromazepam. The analytes were stable in frozen plasma for at least 1 month. The validated assay was successfully applied to several authentic plasma samples from patients treated or intoxicated with various benzodiazepines or with zaleplone, zolpidem or zopiclone. It has proven to be appropriate for the isolation, separation, screening, identification and quantification of the drugs mentioned above in plasma for clinical toxicology, e.g. in cases of poisoning, and forensic toxicology, e.g. in cases of driving under the influence of drugs. 相似文献
140.
Crommentuyn KM Rosing H Nan-Offeringa LG Hillebrand MJ Huitema AD Beijnen JH 《Journal of mass spectrometry : JMS》2003,38(2):157-166
HIV protease inhibitors are important antiretroviral drugs which have substantially reduced the morbidity and mortality associated with HIV-1 infection. Recent data have shown relationships between plasma concentrations of the protease inhibitors and clinical response, which makes therapeutic drug monitoring valuable. We have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), for the routine quantification of the six licensed protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir) and the pharmacologically active nelfinavir metabolite M8 in plasma. The sample pretreatment consisted of protein precipitation with a mixture of methanol and acetronitrile using only 100 microl of plasma. Chromatographic separation was performed on an Inertsil ODS3 column (50 x 2.0 mm i.d., particle size 5 microm), with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.5 ml min(-1). The analytical run time was 5.5 min. The use of a 96-well plate autosampler allowed batch sizes up to 150 patient samples. The triple-quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges 0.01-10 microg ml(-1) for indinavir and saquinavir, 0.1-10 microg ml(-1) for amprenavir, 0.05-10 microg ml(-1) for nelfinavir and ritonavir, 0.1-20 microg ml(-1) for lopinavir and 0.01-5 microg ml(-1) for M8. Saquinavir-d(5) and indinavir-d(6) were used as internal standards. The coefficients of variation were always <10% for both intra-day and inter-day precisions for each compound. Mean accuracies were also between the designated limits (+/-15%). The validated concentration ranges proved to be adequate in daily practice. This robust and fast LC/MS/MS assay is now successfully applied for routine therapeutic drug monitoring and pharmacokinetic studies in our hospital. 相似文献