LAUSR

Photoactivation and photodissociation have long proven useful tools in tandem mass spectrometry, but implementation often involves cumbersome and potentially dangerous configurations. Here we redress this problem by using a fiber optic cable to couple an infrared (IR) laser to a mass spectrometer for robust, efficient, and safe photoactivation experiments. Transmitting 10.6 µm IR photons through a hollow-core fiber, we show that such fiber-assisted activated ion-electron transfer dissociation (AI-ETD) and infrared multiphoton dissociation (IRMPD) experiments can be carried out as effectively as traditional mirror-based implementations. We report on transmission efficiency of the hollow-core fiber for conducting photoactivation experiments and perform various intact protein and peptide analyses to illustrate the benefits of fiber-assisted AI-ETD: namely a simplified system for irradiating the two-dimensional linear ion trap volume concurrent with ETD reactions to limit uninformative non-dissociative events and thereby amplify sequence coverage. We also describe a calibration scheme for the routine analysis of IR laser alignment and power through the fiber and into the dual cell quadrupolar linear ion trap. In all, these advances allow for a more robust, straightforward, and safe instrumentation platform, permitting implementation of AI-ETD and IRMPD on commercial mass spectrometers and broadening the accessibility of these techniques.