Electrospray ionization mass spectrometry is applied for the selective detection of metal ligands after a post-column continuous-flow ligand-exchange reaction. The detection is based on the specific release of a reporter ligand from a metal-reporter ligand complex by a high affinity ligand. Constant infusion and direct-injection experiments are performed to optimize the method. The on-line coupling of a liquid chromatographic separation prior to the continuous flow ligand-exchange reaction enables the screening for high affinity ligands in complex samples. The feasibility of the method is demonstrated by using several ligands with a different affinity for either Cu(II) or Zn(II) ions. The selectivity of the ligand-exchange detection method can be tuned by the choice of the reporter ligand. This is demonstrated by using either 2,2'-bipyridyl or 5-methyl-1,10-phenanthroline as reporter ligands. 相似文献
A novel methodology is shown enabling the screening of mixtures of compounds for their affinity to a receptor protein. The system presented, dynamic protein-affinity chromatography solid-phase extraction (DPAC-SPE), overcomes the limitations of the existing methods by performing an incubation of the His-tagged protein with a mixture of possible ligands, which are still in their native conditions. This is followed by a fully automated affinity trapping step, coupled on-line to an LC-MS system in order to detect and identify the bound ligands. The system has been optimized using a commercially available on-line SPE system, using the estrogen receptor alpha (ERalpha) as model protein. A representative range of ligands with sub-nanomolar to millimolar affinities has been identified successfully from a mixture. The weakest binder that can be identified is norethindrone (approximately K(d)=0.1-1mM). The same setup also provides the possibilities to measure EC50 curves of both weak and strong binders. 相似文献
Turbulent-flow chromatography (TFC) on-line coupled to liquid chromatography mass spectrometry (LC-MS) is used to determine flavonoids and resveratrol in different types of wines. A fully automated system was developed in which 10 mL of sample (diluted wine) was passed over a TFC column, after which the retained analytes were separated by reversed-phase LC and detected by negative ion mode atmospheric-pressure chemical ionization (APCI) MS. The method proved to be fast, non-laborious, robust and sensitive. The feasibility of the method was tested on several red, white and rose wines. Quantitation of resveratrol was possible using the standard addition procedure. Red wine showed the highest amount of resveratrol (4 mg L−1), while rose and white wine contained concentrations which were about ten fold lower.
Low levels of peptide drugs in human plasma can be determined employing off-line solid-phase extraction, followed by capillary zone electrophoresis with UV detection. A bioanalytical procedure is presented, using gonadorelin and angiotensin II in human plasma as model compounds. The solid-phase extraction method, based on a weak cation exchange mechanism, is able to remove interfering endogenous components from the plasma sample, extract the model peptides quantitatively, and give a possibility of concentrating the sample at the same time. Transient isotachophoretic conditions were kept to increase the sample loadability by about two orders of magnitude. Up to about 70% of the capillary was filled with the reconstituted extract, whereafter the peptides were selectively concentrated during the first 15 min. Subsequently, the concentrated sample zones were separated under capillary zone electrophoresis conditions, showing the technique's high resolution. For the model cationic peptides (gonadorelin, angiotensin II) good linearity and reproducibility was observed in the 20-100 ng/mL concentration range. A more extensive washing procedure permits quantitation of gonadorelin at the 5 ng/mL level. In comparison with a liquid chromatography analysis, superior mass sensitivity and separation are obtained with the transient isotachophoretic capillary zone electrophoresis method. Moreover, in this case equivalent sensitivity is achieved when it is directly compared with a liquid chromatography method with UV detection, keeping in mind that 60 times more sample is needed for the latter method. A further gain in sensitivity can be obtained when the analysis is combined with native fluorescence detection, as is demonstrated by combining liquid chromatography separation with fluorescence detection. 相似文献
This review article summarizes the applications of bismuth(III) compounds in organic synthesis since 2002. Although there are an increasing number of reports on applications of bismuth(III) salts in polymerization reactions, and their importance is acknowledged, they are not included in this review. This review is largely organized by the reaction type although some reactions can clearly be placed in multiple sections. While every effort has been made to include all relevant reports in this field, any omission is inadvertent and we apologize in advance for the same (358 references). 相似文献