The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Peter H Santschi - One of the best experts on this subject based on the ideXlab platform.
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analysis of biogenic thiols in natural water samples by high performance liquid chromatographic separation and fluorescence detection with ammonium 7 fluorobenzo 2 oxa 1 3 Diazole 4 sulfonate sbd f
Analytica Chimica Acta, 2000Co-Authors: Degui Tang, Liangsaw Wen, Peter H SantschiAbstract:Abstract A sensitive and reliable reversed-phase high-performance liquid chromatography (HPLC) method has been developed to analyze naturally occurring low-molecular weight thiols using pre-column derivatization with ammonium 7-fluorobenzo-2-oxa-1,3-Diazole-4-sulfonate (SBD-F) and fluorescence detection in a gradient elution. The derivatization procedure and separation conditions were optimized by careful control of the reaction conditions in terms of time, temperature, pH and reducing agent. A linear calibration in the nM range was obtained for all the standard compounds, allowing measurement of thiols in natural water samples. Results show that the reducing agent tri-n-butylphosphine (TBP) not only acts as an anti-oxidant/disulfide cleaving agent, but also enables the SBD-F to react with thiols complexed by soft metals. This is the first study reported using the SBD-F labeling technique to measure phytochelatin concentrations. The methodology has been successfully applied to estuarine water samples from Galveston Bay.
J S Silberberg - One of the best experts on this subject based on the ideXlab platform.
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assay of plasma homocysteine light sensitivity of the fluorescent 7 benzo 2 oxa 1 3 Diazole 4 sulfonic acid derivative and use of appropriate calibrators
Clinical Chemistry, 1996Co-Authors: Nicholas P B Dudman, X W Guo, R Crooks, L Xie, J S SilberbergAbstract:The recognition of homocysteine as a vascular risk factor has led to increased clinical interest in assaying plasma homocysteine concentrations. Our aim was to improve the reliability of a widely used assay based on HPLC of the fluorescent 7-benzo-2-oxa-1, 3-Diazole-4-sulfonic acid (SBD) derivative. We found that SBD derivatives of homocysteine, cysteine, and N-acetylhomocysteine were highly unstable in light but essentially stable in the dark for several hours at either 0 degree C or 25 degrees C. As our primary calibrator, we chose homocystine added to human serum for more consistent results than homocysteine or homocystine in an aqueous buffer. N-acetylcysteine was effective as an internal recovery standard. We observed a previously unreported peak with a prolonged elution time in some plasma samples from subjects who had ingested methionine. Our findings suggest improvements in this and other assay procedures for plasma homocysteine.
G A M S Van Dongen - One of the best experts on this subject based on the ideXlab platform.
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platinum ii as bifunctional linker in antibody drug conjugate formation coupling of a 4 nitrobenzo 2 oxa 1 3 Diazole fluorophore to trastuzumab as a model
ChemMedChem, 2015Co-Authors: Dennis Christian Johannes Waalboer, Joey A Muns, Niels J Sijbrandi, Richardus B M Schasfoort, Rob Haselberg, Govert W Somsen, Hendrikjan Houthoff, G A M S Van DongenAbstract:The potential of platinum(II) as a bifunctional linker in the coordination of small molecules, such as imaging agents or (cytotoxic) drugs, to monoclonal antibodies (mAbs) was investigated with a 4-nitrobenzo-2-oxa-1,3-Diazole (NBD) fluorophore and trastuzumab (Herceptin™) as a model antibody. The effect of ligand and reaction conditions on conjugation efficiency was explored for [Pt(en)(L-NBD)Cl](NO
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platinum ii as bifunctional linker in antibody drug conjugate formation coupling of a 4 nitrobenzo 2 oxa 1 3 Diazole fluorophore to trastuzumab as a model
ChemMedChem, 2015Co-Authors: Dennis Christian Johannes Waalboer, Joey A Muns, Niels J Sijbrandi, Richardus B M Schasfoort, Rob Haselberg, Govert W Somsen, Hendrikjan Houthoff, G A M S Van DongenAbstract:The potential of platinum(II) as a bifunctional linker in the coordination of small molecules, such as imaging agents or (cytotoxic) drugs, to monoclonal antibodies (mAbs) was investigated with a 4-nitrobenzo-2-oxa-1,3-Diazole (NBD) fluorophore and trastuzumab (Herceptin™) as a model antibody. The effect of ligand and reaction conditions on conjugation efficiency was explored for [Pt(en)(L-NBD)Cl](NO3 ) (en=ethylenediamine), with L=N-heteroaromatic, N-alkyl amine, or thioether. Conjugation proceeded most efficiently at pH 8.0 in the presence of NaClO4 or Na2 SO4 in tricine or HEPES buffer. Reaction of N-coordinated complexes (20 equiv) with trastuzumab at 37 °C for 2 h, followed by removal of weakly bound complexes with excess thiourea, afforded conjugates with an NBD/mAb ratio of 1.5-2.9 that were stable in phosphate-buffered saline at room temperature for at least 48 h. In contrast, thioether-coordinated complexes afforded unstable conjugates. Finally, surface plasmon resonance analysis showed no loss in binding affinity of trastuzumab after conjugation.
Denis Blache - One of the best experts on this subject based on the ideXlab platform.
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hyperhomocysteinemia induced by folic acid deficiency and methionine load applications of a modified hplc method
Clinica Chimica Acta, 1996Co-Authors: Philippe Durand, L J Fortin, S Lussiercacan, Jean Davignon, Denis BlacheAbstract:Abstract The increasing possibility that homocysteine might be involved in atherosclerosis in non-homocysteinuric subjects has required the measurement of low concentrations of this aminothiol in biological samples. The procedure described here represents an improvement of different HPLC methods. We utilized an isocratic HPLC system with fluorescence detection of plasma total homocysteine derivatized after reaction with ammonium 7-fluoro-benzo-2-oxa-1,3-Diazole-4-sulphonate. With the help of the rapidly eluting internal standard N -acetyl-cysteine, the method ensures very good recovery (∼100%), reproducibility and precision (within-assay: 2.31%; day-to-day: 2.8%) in the physiological concentration range. This procedure allowed us to validate various animal models of hyperhomocysteinemia such as dietary folic acid deficiency in rat and acute methionine loads in rat and hamster. Using this method, we also confirmed that men have higher plasma total homocysteine levels than women. Due to its simplicity and reliability, our procedure is suitable for routine analysis of total homocysteine and other aminothiols (cysteine, cysteinyl-glycine and glutathione) in biological samples, as required in clinical and research laboratories.
Junbiao Chang - One of the best experts on this subject based on the ideXlab platform.
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synthesis of 2 amino 1 3 4 oxaDiazoles and 2 amino 1 3 4 thiaDiazoles via sequential condensation and i2 mediated oxidative c o c s bond formation
Journal of Organic Chemistry, 2015Co-Authors: Jinfeng Kang, Xianhai Tian, Lina Song, Jie Wu, Wenquan Yu, Junbiao ChangAbstract:2-Amino-substituted 1,3,4-oxaDiazoles and 1,3,4-thiaDiazoles were synthesized via condensation of semicarbazide/thiosemicarbazide and the corresponding aldehydes followed by I2-mediated oxidative C–O/C–S bond formation. This transition-metal-free sequential synthesis process is compatible with aromatic, aliphatic, and cinnamic aldehydes, providing facile access to a variety of Diazole derivatives bearing a 2-amino substituent in an efficient and scalable fashion.