Spectrophotometric characterization of diazacrown ethers having two carbodithioate groups

HILIC LC-MS for the determination of 2'-C-methyl-cytidine-triphosphate in rat liver

A very accurate and selective LC-MS/MS method was developed and validated for the quantification of 2'-C-modified nucleoside triphosphate in liver tissue samples. An efficient pretreatment procedure of liver tissue samples was developed, using a fully automated SPE procedure with 96-well SPE plate (weak anion exchange sorbent, 30 mg). Nucleotide hydrophilic interaction chromatography has been performed on an aminopropyl column (100 mm x 2.0 mm, 3 microm) using a gradient mixture of ACN and ACN/water (5:95 v/v) with 20 mM ammonium acetate at pH 9.45 as mobile phase at 300 microL/min flow rate. The 2'-C-modified nucleoside triphosphate was detected in the negative ESI mode in multiple reaction monitoring (MRM) mode. Calibration curve was linear over the 0.05-50 microM concentration range. Satisfying results, confirming the high reliability of the established LC-MS/MS method, were obtained for intraday precision (CV = 2.5-9.1%) and accuracy (92.6-94.8%) and interday precision (CV = 9.6-11.5%) and accuracy (94.4-102.4%) as well as for recovery (82.0-112.6%) and selectivity. The method has been successfully applied for pharmacokinetic studies of 2'-C-methyl-cytidine-triphosphate in liver tissue samples.

Analysis of adenosine phosphates in HepG-2 cell by a HPLC-ESI-MS system with porous graphitic carbon as stationary phase

A high performance liquid chromatography coupled with electrospray ionization/mass spectrometry method was developed for the determination of adenosine 5'-monophosphate (AMP), adenosine 5'-diphosphate (ADP), and adenosine 5'-triphosphate (ATP) in the extract of HepG-2 cells. The chromatographic conditions were optimized by using porous graphitic carbon as the stationary phase for the retention and separation of the AMP, ADP and ATP. Negative-ion mode ESI-MS in basic mobile phase was applied to improve the method sensitivity. An external calibration method with linear ranges from 0.22 to 57.80 microM for AMP, from 0.59 to 117.37 microM for ADP, and from 0.49 to 98.81 microM for ATP was used for quantitative analysis. The levels of ATP, ADP, and AMP in HepG-2 cells treated with benzo[a]pyrene with different time periods were determined. Total adenine nucleotides and the energy charge potential were calculated for the investigation of the effect of benzo[a]pyrene on cell energy metabolism.

Simultaneous quantification of GMP, AMP, cyclic GMP and cyclic AMP by liquid chromatography coupled to tandem mass spectrometry

Phosphodiesterases are drug targets for treating various diseases. Inhibition of these can increase cAMP and cGMP levels, which can affect a variety of physiological responses. Here we report a new method for determining PDE activity by combining high-performance liquid chromatography and tandem mass spectrometry. Characteristic peaks of the substrates, cGMP or cAMP and products, GMP or AMP, were identified in positive-ion electrospray ionization using multiple reaction monitoring. The method can be applied to determine activity of PDE inhibitors. Our results showed that this new method was fast, sensitive and highly reproducible.

Determination of adenosine nucleotides in cultured cells by ion-pairing liquid chromatography-electrospray ionization mass spectrometry

A method using ion-pairing liquid chromatography-mass spectrometry (MS) was developed for analyzing adenosine 5(')-monophosphate (AMP), adenosine 5(')-diphosphate (ADP), and adenosine 5(')-triphosphate (ATP) in cellular extracts. Dimethylhexylamine (DMHA) was used as ion-pairing agent to retain and separate the analytes on a reversed-phase microbore column with a gradient program. Positive-ion electrospray ionization-MS was applied for the detection because of the use of the ion-pairing agent. Adduct ions of DMHA with AMP, ADP, and ATP were found to be the most intensive peaks and thus selected as quantitative ions. An external calibration method with linear ranges from 0.1 to 20 microM for AMP, 2 to 20 microM for ADP, and 2.5 to 20 microM for ATP was used for the quantitation. The method was applied to determine concentrations of AMP, ADP, and ATP in extracts of cultured rat C6 glioma cells that were pretreated with various concentrations of Zn. The detected levels of the adenosine nucleotides have been used to calculate total adenosine nucleotide and energy charge potential. Changes in cellular energy status upon exposure to increasing concentration of Zn in the culture medium were analyzed. The results indicated that the addition of Zn in a range of 40 to 120 microg/ml cause a gradual increased in energy charge potential of the cells.