Cold ion spectroscopy for structural identifications of biomolecules

Over the last decade, the spectroscopy of cryogenically cold ions iso- lated in the gas phase has been developed as a new tool for structural elucidations of biological molecules. Cooling allows for vibrational resolution in UV and IR spectra of small to midsize peptides, enabling different multi-laser techniques of conformer-specific spectroscopy. In conjunction with quantum chemistry calculations, IR spectra of sin- gle conformers allows for solving their intrinsic geometries. Here, we briefly review some fundamental and technical aspects of the cold- ion spectroscopy (CIS) approach and illustrate its application for pro- tonated peptides, carbohydrates and for non-covalent complexes of biomolecules. The challenges and limitations of CIS in view of its rele- vance to life-science studies are critically assessed. Finally, we discuss and illustrate some approaches of CIS for the analytical identification of biomolecules, in particular the recently developed method of 2D UV-MS fingerprinting, which combines CIS with high-resolution mass spectrometry.