Sensitive Detection of Selenoproteins in Gel Electrophoresis by High Repetition Rate Femtosecond Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

A laser ablation-ICPMS method using an infrared (1030 nm), low-energy (39 μJ/pulse), high repetition rate (10 kHz), femtosecond laser was developed to improve the sensitivity of detection of heteroatom-containing proteins in 1D polyacrylamide gels. A 2-mm-wide lane was ablated by ultrafast (10 cm s-1) back-and-forth movement of a 20-μm laser beam parallel to the protein bands while the gel advanced perpendicularly. This procedure resulted in a considerable increase in detection sensitivity (>40-fold) compared to the nanosecond 266-nm laser ablation-ICPMS, mainly because of the much larger amount of ablated material introduced into the plasma on the time scale of the dwell time of the mass spectrometer. The method was applied to the specific detection in the gel of formate dehydrogenase expressed in Escherichia coli and of selenoproteins in Desulfococcus multivorans with detection limits at the low-femtomolar levels.