A label-free method based on MALDI-TOF mass spectrometry for the absolute quantitation of troponin T in mouse cardiac tissue

A label-free absolute quantitation method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been developed. This methodology was applied to mouse heart in order to quantify cardiac troponin T (cTnT), which is considered to be a sensitive marker of heart damage. The cTnT was extracted, isolated by reversed-phase high-performance liquid chromatography, digested, and analyzed by MALDI-TOF MS. The MS-based quantitation was performed using matrix-matched calibration curves (due to a matrix effect) of two synthetic peptides, one cTnT-specific peptide and one internal standard peptide, respectively. Recoveries at three spiking levels ranged from 87–96%, with relative standard deviations of below 10%. The method detection limit and the method quantitation limit, expressed as the amount of cTnT for the amount of total sarcomeric protein extract, were 0.03 mg g−1 and 0.15 mg g−1, respectively. This method appears to be accurate and generally suitable for improving absolute protein quantitation.