Mass spectrometry of biological molecules in ices and gels enabled by resonant picosecond IR laser excitation

Summary form only given. In proteomics and molecular biology, there is a significant unmet need for identifying proteins and peptides in either their native aqueous environment or in the gel media used for diffusion based separation and sequencing of proteins and nucleotides. Here we report the first observations of desorption and ionization of peptides and proteins directly from water ices and electrophoresis gels, without any additional sample preparation. This procedure, if further developed, could open the way to direct, high-speed molecular imaging of proteins that have undergone preliminary separation in a gel. In our experiments, picosecond laser pulses from a tunable, mid-infrared free-electron laser (FEL) ablate microscopic volumes of gel or ice containing polypeptides and proteins from a cryogenically cooled probe stage in a reflectron time-of-flight mass spectrometer at a temperature low enough to be vacuum-compatible.