In a recent publication, Kohnosuke Kinoshita and colleagues present their data on a surrogate analyte method to determine D-serine in the murine brain. Their method utilizes LC–MS/MS to determine the endogenous levels of the amino acid.
D-serine is thought to be involved in neuronal signaling through its role as a co-agonist of the NMDA receptor. Therefore, it is thought that this protein might be an important biomarker for monitoring the effect of new drug compounds on the CNS. As the research team describe in their paper, “The accurate measurement of D-serine in biological matrices is … an essential part of the evaluation of drug candidates.”
The Japanese research group, based at Taisho Pharmaceutical Company, used [2,3,3-(2)H]D-serine as a surrogate analyte and [(15)N]D-serine as an internal standard, adding the analyte to mouse brain homogenate. The protein was precipitated from the homogenate, followed by a solid phase extraction step. A chiral crown ether column was then used to separate the enantomers (with a reported analysis time of 6 minutes for this step). The eluent was then analyzed using a triple-quadrupole mass spectrometer.
The team demonstrated accuracy and precision at all QC concentration levels. In addition, the teams’ method showed comparable results – in terms of measuring brain D-serine levels in normal mice – to the standard addition method; however offers a faster process time.
The authors conclude, “We think that the currently reported method would also be applicable to the measurement of brain D-serine levels for the monitoring of certain effects of drug candidates on the central nervous system.”
Source: Kinoshita K, Jingu S, Yamaguchi J. A surrogate analyte method to determine D-serine in mouse brain using liquid chromatography-tandem mass spectrometry. Anal. Biochem. 432(2), 124–130 (2013).