| A method was demonstrated for determining dissociation energies of various biomolecules by surface-induced dissociation (SID). Energetic information on biomolecules will help not only understand their fragmentation patterns in the gas phase, but also analyze their primary and secondary structures via sequencing.;A method for extracting the dissociation energy for the formation of fragment ion that forms from SID was proposed by previous workers and was successfully applied to the dissociation of SiMe3+ ion [Wainhaus et al. J. Am. Chem. Soc. 1997, 119, 4001]. We improved this method and applied it to the dissociation of thiophene ions (C4H4S+) for which the dissociation energies were well known. Our method analyzes the energy-resolved mass spectra (ERMS) and kinetic energy distribution spectra (KEDS) of the parent and fragment ions that scatter off the hexanethiolate-covered Au(111) surface. The higher SID dissociation energies of the major fragment ions of C4H4S+ than literature values were explained in terms of delayed dissociation effect.;The data analysis method was then applied to several protonated polypeptides using a modified experimental apparatus. Relative dissociation energies (RDEs) were obtained for the major fragment ions produced by electrospray ionization/surface-induced dissociation of the protonated triglycine, tetraglycine, leucine enkephalin, and leucine enkephalin arginine. The overall trend in fragmentation order for all peptides was consistent with the results from other experiments. However, determination of absolute dissociation energies from SID data requires further refinement of the data analysis method. |
