Deep Ultraviolet Laser Ablation Surface Sampling for Native Mass Spectrometry

Abstract

A pulsed 193 nm deep ultraviolet (DUV) laser was used to ablate proteins and a noncovalently bound protein assembly deposited on surfaces. DUV laser ablation has been used for ablation of proteins from surfaces without fragmentation; however, DUV ablation of native proteins from surfaces without the loss of higher-order structure of proteins has not been demonstrated. Here, protein charge state distribution (CSD) and collision-induced unfolding (CIU) were used to probe the structure of DUV laser-ablated native proteins. Standard solutions containing native bovine serum albumin (BSA), jack-bean concanavalin A (ConA), and bovine carbonic anhydrase (CA) were deposited on a quartz microscope slide, laser-ablated, and captured for ion mobility-mass spectrometry (IM-MS) analysis. Observed CSD from native MS of conventionally extracted and DUV laser-ablated proteins were comparable. CIU plots for all charge states of laser-ablated proteins exhibited the same ion mobility features and comparable transition voltages (CIU50) as the extracted samples. These results suggest that DUV laser ablation can yield intact proteins with conserved higher-order structures.