Y. Xu, M.W. Little, D.J. Rousell, J.L. Laboy, K.K. Murray, “Direct from polyacrylamide gel infrared laser desorption/ionization,” Anal. Chem. 76 (2004) 1078–1082. doi:10.1021/ac034879n.


FT-IR-ATR spectra of gel
FT-IR-ATR spectra of dry (black solid line) and wet (dashed line) polyacrylamide gel.

The direct combination of gel electrophoresis and infrared laser desorption/ionization time-of-flight mass spectrometry has been demonstrated. We present results for infrared laser desorption and ionization mass spectrometry of peptides and proteins directly from a polyacrylamide gel without the addition of a matrix. Analyte molecules up to 6 kDa were ionized directly from a vacuum-dried sodium dodecyl sulfate-polyacrylamide gel after electrophoretic separation. Mass spectra were obtained at the wavelength of 2.94 Β΅m, which is consistent with IR absorption by N-H and O-H stretch vibrations of water and other constituents of the gel. A 5-nmol quantity of peptide or protein was loaded per gel slot, although it was possible to obtain mass spectra from a small fraction of the gel spot. This technique shows promise for the direct identification of both parent and fragment masses of proteins contained in polyacrylamide gels.