Cryogenic methods for the spectroscopy of large, biomolecular ions

Determining the conformation of biological molecules is key for understanding their function. The recent combination of mass spectrometry, cryogenic ion traps, and laser spectroscopy is providing new methods to interrogate individual conformations of peptides and proteins that have advantages over classical techniques of structure determination. This chapter provides an overview of these new state-of-the-art methods and illustrates several specific applications. After reviewing the fundamentals of ion production, trapping, cooling, and spectroscopic detection, we review how different combinations of these techniques have been implemented in various laboratories around the world. We then focus on applications of cryogenic ion spectroscopy from two specific laboratories to illustrate the potential of this general approach. Finally, we outline ways in which these powerful new techniques could be further improved.