A frequency tripled Nd:YLF laser (Explorer One, Spectra Physics, Mountain View, CA) emitting at 349 nm operating at 300 Hz was used for desorption and MALDI (referred to throughout as the MALDI laser). The MALDI laser was operated at a diode current of 1.8 A, with the pulse energy fine-tuned with an external attenuator (PowerXP, Altechna, Vilnius, Lithuania) positioned immediately in front of the laser. A pulse energy of 1.44 µj was used for laser desorption.