THIN GOLD FILM-ASSISTED LASER-DESORPTION IONIZATION FOURIER-TRANSFORMION-CYCLOTRON RESONANCE MASS-SPECTROMETRY OF BIOMOLECULES

A new thin gold film-assisted (TGFA) laser desorption/ionization (LDI) technique has been combined with Fourier transform ion cyclotron reso nance (FT-ICR) high-resolution mass analysis. A thermally labile organ ic sample is coated onto a thin gold film deposited on a glass plate a nd desorbed and ionized by Nd:YAG laser irradiation. The wavelength fo r maximum light absorption may be tuned by varying the thickness of th e metal film; e.g., a 10-nm-thick gold film absorbs maximally near the Nd:YAG fundamental wavelength (1064 nm). A key advantage of the metho d is the stability of the gold film, which facilitates deposition of s amples from any of a variety of solvent systems. Coupled with recently introduced quadrupolar excitation and collisional cooling for ion axi alization, TGFA-LDI FT-ICR mass spectra provide high sensitivity (e.g. , 100-fmol single-shot detection limit and mass resolving power, m/DEL TAm almost-equal-to 113 000, for (M + K)+ ions from gramicidin S at m/ z 1180).