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51.
We have developed a simple, sensitive, and robust liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method to determine free 3-nitrotyrosine concentrations in human plasma of patients receiving on-pump coronary artery bypass grafting surgery. A one-step solid-phase extraction protocol was optimized to enrich the analyte at low nanomolar concentrations. The processed samples were analyzed by LC-MS/MS with a 2.1 × 100 mm Kinetex PFP column and a triple quadrupole mass spectrometer. The method was validated for 3-nitrotyrosine concentrations close to real patient plasma levels. The relative standard deviations or relative errors of the intraday and interday determinations were all within 10%. Limit of detection and limit of quantitation were determined to be 0.034 nM and 0.112 nM, respectively, while lower limit of quantitation was below 0.625 nM. No deterioration of the column performance was noticed after running a large number of patient samples. The results showed that the 3-nitrotyrosine concentrations in coronary sinus plasma samples were elevated after cardiopulmonary bypass (CPB) procedure. The pre-CPB and post-CPB concentrations of 3-nitrotyrosine in patient plasmas were 1.494 ± 0.107 nM and 2.167 ± 0.177 nM (mean ± SEM), respectively. Application of this method to more patients in clinical studies may help validate 3-nitrotyrosine as a meaningful biomarker for nitrosative stress and link patient characteristics, clinical outcomes, and cardioprotective treatments to endogenous nitrosative stress levels. 相似文献
52.
53.
MR evaluation of giant cell tumors of the tendon sheath 总被引:1,自引:0,他引:1
Giant cell tumor of the tendon sheath (GCTTS) is a benign condition that involves the synovium of the tendon sheaths. Histologically, GCTTS is similar to pigmented villonodular synovitis. The MRI findings in two cases of GCTTS are reported. In both cases, predominantly low signal is seen on T1-weighted, proton density weighted, and T2-weighted images. This information may be useful in distinguishing GCTTS from other mass lesions involving the tendon sheaths. 相似文献
54.
Andre Rosowsky Clara E. Mota Sherry F. Queener 《Journal of heterocyclic chemistry》1995,32(1):335-340
2,4-Diamino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidines with di- and trimethoxyaralkyl substitution at the 6-position were synthesized from the N6-unsubstituted compound and appropriate aralkyl bromides in N,N-dimethylformamide solution containing a catalytic amount of sodium iodide. An improved method of preparation of 2,4-diamino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine from 2-amino-6-benzyl-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-4(3H)-one was also developed, in which N2 was protected by reaction with pivalic anhydride and the resulting product was subjected consecutively to reaction with 4-chlorophenylphosphorodichloridate and 1,2,4-triazole, ammonolysis to replace the 4-imidazolido group and remove the N2-pivaloyl group, and catalytic hydrogenolysis to remove the 6-benzyl group. In assays of the ability of the products to inhibit dihydrofolate reductase from Pneumocystis carinii, and Toxoplasma gondii, and rat liver the most active of the compounds tested was 2,4-diamino-6-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine. The concentration of this compound needed to inhibit enzyme activity by 50% was 0.51 μM against the P. carinii enzyme, 0.09 μM against the T. gondii enzyme, and 0.35 μM against the rat enzyme. Thus, there was selectivity of binding to T. gondii enzyme, but not P. carinii enzyme, relative to rat enzyme. 2′,5′-Dimethoxybenzyl analogues were less active than the corresponding 3′,4′,5′-trimethoxybenzyl analogues, and compounds with a CH2CH2 or CH2CH2CH2 bridge were less active than those with a CH2 bridge. 2,4-Diamino-6-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine showed greater selectivity than trimetrexate or piritrexim for the P. carinii and T. gondii enzyme, but was less selective than trimethoprim or pyrimethamine. However its molar potency against both enzymes was greater than that of trimethoprim, the antifolate most commonly used, in combination with sulfamethoxazole, for initial treatment of opportunistic P. carinii and T. gondii infections in patients with AIDS and other disorders of the immune system. 相似文献
55.
Yang E Wang S Bowen C Kratz J Cyronak MJ Dunbar JR 《Rapid communications in mass spectrometry : RCM》2005,19(6):759-766
A quantitative bioanalytical method involving chemical derivatization, solid phase extraction (SPE) and high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) was developed for the determination of 4-fluorobenzyl chloride (4FBCl) in human plasma. 4FBCl is a volatile and reactive molecule that is very unstable in human plasma. In order to stabilize 4FBCl in plasma samples prior to storage, 4-dimethylaminopyridine (DMAP) was added, forming a stable quaternary amine salt derivative. A three-step weak cation-exchange SPE procedure was then employed to remove excess DMAP. The plasma extracts were analyzed by HPLC/MS/MS using a TurboIonspray interface and multiple reaction monitoring. Unlike 4FBCl, the quaternary amine derivative shows excellent sensitivity in electrospray mass spectrometry. The method was validated over a concentration range of 0.5-500 ng/mL using 45 microL of plasma. The maximum within-run and between-run precision observed in a three-run validation for quality control (QC) samples was 12.5 and 7.6%, respectively. The maximum percentage bias observed at all QC sample concentrations was 11.9%. The method has proven to be robust and compatible with high-throughput bioanalysis. 相似文献
56.
Tom Otieno Jaime R. Blanton M. Jason Hatfield Sherry L. Asher Sean Parkin 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m182-m185
The reaction of Cu(ClO4)2·6H2O, NaAsF6 and excess pyrazole yields hexakis(pyrazole‐κN2)copper(II) bis(hexafluoroarsenate), [Cu(C3H4N2)6](AsF6)2 or [Cu(pzH)6](AsF6)2 (pzH is pyrazole), (I). The analogous hexakis(pyrazole‐κN2)copper(II) hexafluorophosphate perchlorate complex, [Cu(C3H4N2)6](PF6)1.29(ClO4)0.71 or [Cu(pzH)6](PF6)1.29(ClO4)0.71, (II), is obtained in a similar fashion, using KPF6 in place of NaAsF6. Both compounds contain the hitherto unknown [Cu(pzH)6]2+ complex cation, in which the copper(II) ion lies at the center of a regular octahedron of coordinated N atoms. The cation has crystallographically imposed symmetry. The X‐ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn–Teller disorder or dynamic Jahn–Teller distortion. 相似文献
57.
The enthalpy of hydrolysis of solid tungsten azide pentafluoride in alkaline aqueous solution (1.O mol dm?3 KOH; 298.2K) is ?578 kJ mol?1. Hence its enthalpy of formation is ?1170 kJ mol?1. 相似文献
58.
Brian G. Sherry Hirotsugu K. Yasuda Magda El-Nokaly Stig E. Friberg 《Journal of Dispersion Science and Technology》2013,34(3):275-290
Polypropylene surfaces were rendered cationic by hydrophobic implantation and by grafting a quaternized polyvinyl pyridine onto a plasma treated surface. The polypropylene surface with the grafted polymer showed a strong adsorption of an anionic surfactant, corresponding to about ten monomolecular layers. High concentration of electrolyte caused a reduction of the adsorption at low concentrations of surfactant. 相似文献
59.