TEM provided the first visualizatio

TEM provided the first visualization of the large GroEL protein complex’s tertiary structures. In that study, the GroEL complex was generated using native mass spectrometry and deposited onto TEM grids using ion soft landing [60]. Although this field still is in its infancy, the results demonstrate the potential of preparatory mass spectrometry for structural characterization of well-defined biomolecular complexes on substrates.

17. Conclusions and outlook
Collisions of polyatomic ions with surfaces have been systematically investigated for more than 30 years. These studies have resulted in development of SID as a powerful tool for the structural characterization of complex molecules, as well as for detailed understanding of the energetics and mechanisms of gas-phase fragmentation of large molecules. Future SID applications will focus on quantitative studies of non-covalent interactions and structural characterization of large protein complexes using mass spectrometry. Detailed and progressive understanding of the physical and chemical processes underlying soft and reactive landing of mass-selected ions provided the foundation for preparatory mass spectrometry. With advanced development of ionization sources, preparatory mass spectrometry may be transformed into a widely used technique for surface modification complementary to solution-phase deposition and molecular beam epitaxy. Some of the most promising future applications of preparatory mass spectrometry include fabrication of catalytically active substrates, thin film ultracapacitors and magnetic devices, and separation and structural characterization of large biomolecular complexes, among others.

Acknowledgments
I would like to thank all of the students, postdoctoral fellows, and colleagues who contributed to development of the research area described in this perspective article. In particular, I express my appreciation to my former research advisor, Dr. Jean Futrell, who introduced me to this field, as well as current group members Drs. Grant Johnson and Don Gunaratne and former group members Drs. Eduard Denisov, Sergey Rakov, Anil Shukla, Omar Hadjar, Peng Wang, Zhibo Yang, and Qichi Hu—who all worked on various aspects of ion–surface collisions. I also thank Profs. Graham Cooks, Bill Hase, and Vicki Wysocki for helpful discussions and continued collaboration. Our ongoing research involving ion–surface collisions in mass spectrometry is supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Chemical Sciences, Geosciences & Biosciences Division. The research is performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the DOE under Contract DE-AC05-76RL01830.