skip to main content


Title: Ultraviolet Photodissociation Induced by Light‐Emitting Diodes in a Planar Ion Trap
Abstract

The first application of light‐emitting diodes (LEDs) for ultraviolet photodissociation (UVPD) mass spectrometry is reported. LEDs provide a compact, low cost light source and have been incorporated directly into the trapping cell of an Orbitrap mass spectrometer. MS/MS efficiencies of over 50 % were obtained using an extended irradiation period, and UVPD was optimized by modulating the ion trapping parameters to maximize the overlap between the ion cloud and the irradiation volume.

 
more » « less
NSF-PAR ID:
10236048
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie
Volume:
128
Issue:
40
ISSN:
0044-8249
Format(s):
Medium: X Size: p. 12605-12609
Size(s):
["p. 12605-12609"]
Sponsoring Org:
National Science Foundation
More Like this
  1. Rationale

    Tandem‐ion mobility spectrometry/mass spectrometry methods have recently gained traction for the structural characterization of proteins and protein complexes. However, ion activation techniques currently coupled with tandem‐ion mobility spectrometry/mass spectrometry methods are limited in their ability to characterize structures of proteins and protein complexes.

    Methods

    Here, we describe the coupling of the separation capabilities of tandem‐trapped ion mobility spectrometry/mass spectrometry (tTIMS/MS) with the dissociation capabilities of ultraviolet photodissociation (UVPD) for protein structure analysis.

    Results

    We establish the feasibility of dissociating intact proteins by UV irradiation at 213 nm between the two TIMS devices in tTIMS/MS and at pressure conditions compatible with ion mobility spectrometry (2–3 mbar). We validate that the fragments produced by UVPD under these conditions result from a radical‐based mechanism in accordance with prior literature on UVPD. The data suggest stabilization of fragment ions produced from UVPD by collisional cooling due to the elevated pressures used here (“UVnoD2”), which otherwise do not survive to detection. The data account for a sequence coverage for the protein ubiquitin comparable to recent reports, demonstrating the analytical utility of our instrument in mobility‐separating fragment ions produced from UVPD.

    Conclusions

    The data demonstrate that UVPD carried out at elevated pressures of 2–3 mbar yields extensive fragment ions rich in information about the protein and that their exhaustive analysis requires IMS separation post‐UVPD. Therefore, because UVPD and tTIMS/MS each have been shown to be valuable techniques on their own merit in proteomics, our contribution here underscores the potential of combining tTIMS/MS with UVPD for structural proteomics.

     
    more » « less
  2. Mutations in the GTPase enzyme K-Ras, specifically at codon G12, remain the most common genetic alterations in human cancers. The mechanisms governing activation of downstream signaling pathways and how they relate back to the identity of the mutation have yet to be completely defined. Here we use native mass spectrometry (MS) combined with ultraviolet photodissociation (UVPD) to investigate the impact of three G12X mutations (G12C, G12V, G12S) on the homodimerization of K-Ras as well as heterodimerization with a downstream effector protein, Raf. Electrospray ionization (ESI) was used to transfer complexes of WT or G12X K-Ras bound to guanosine 5′-diphosphate (GDP) or GppNHp (non-hydrolyzable analogue of GTP) into the gas phase. Relative abundances of homo- or hetero-dimer complexes were estimated from ESI-MS spectra. K-Ras + Raf heterocomplexes were activated with UVPD to probe structural changes responsible for observed differences in the amount of heterocomplex formed for each variant. Holo (ligand-bound) fragment ions resulting from photodissociation suggest the G12X mutants bind Raf along the expected effector binding region (β-interface) but may interact with Raf via an alternative α-interface as well. Variations in backbone cleavage efficiencies during UV photoactivation of each variant were used to relate mutation identity to structural changes that might impact downstream signaling. Specifically, oncogenic upregulation for hydrogen-bonding amino acid substitutions (G12C, G12S) is achieved by stabilizing β-interface interactions with Raf, while a bulkier, hydrophobic G12V substitution leads to destabilization of this interface and instead increases the proximity of residues along the α-helical bundles. This study deciphers new pieces of the complex puzzle of how different K-Ras mutations exert influence in downstream signaling. 
    more » « less
  3. As one candidate alloy for future Generation IV and fusion reactors, a dual-phase 12Cr oxide-dispersion-strengthened (ODS) alloy was developed for high temperature strength and creep resistance and has shown good void swelling resistance under high damage self-ion irradiation at high temperature. However, the effect of helium and its combination with radiation damage on oxide dispersoid stability needs to be investigated. In this study, 120 keV energy helium was preloaded into specimens at doses of 1 × 1015 and 1 × 1016 ions/cm2 at room temperature, and 3.5 MeV Fe self-ions were sequentially implanted to reach 100 peak displacement-per-atom at 475 °C. He implantation alone in the control sample did not affect the dispersoid morphology. After Fe ion irradiation, a dramatic increase in density of coherent oxide dispersoids was observed at low He dose, but no such increase was observed at high He dose. The study suggests that helium bubbles act as sinks for nucleation of coherent oxide dispersoids, but dispersoid growth may become difficult if too many sinks are introduced, suggesting that a critical mass of trapping is required for stable dispersoid growth. 
    more » « less
  4. Non-covalent complexes of the short amyloid peptide motif Gly-Asn-Asn-Gln-Gln-Asn-Tyr (GNNQQNY) with peptide counterparts that were tagged with a diazirine ring at the N-termini (*GNNQQNY) were generated as singly charged ions in the gas phase. Specific laser photodissociation (UVPD) of the diazirine tag in the gas-phase complexes at 355 nm generated transient carbene intermediates that underwent covalent cross-linking with the target GNNQQNY peptide. The crosslinking yields ranged between 0.8 and 4.5%, depending on the combinations of peptide C-terminal amides and carboxylates. The covalent complexes were analyzed by collision-induced dissociation tandem mass spectrometry (CID-MS 3 ), providing distributions of cross-links at the target peptide amino acid residues. A general preference for cross-linking at the target peptide Gln-4-Gln-5-Asn-6-Tyr-7 segment was observed. Born–Oppenheimer molecular dynamics calculations were used to obtain 100 ps trajectories for nine lowest free-energy conformers identified by ωB97X-D/6-31+G(d,p) gradient geometry optimizations. The trajectories were analyzed for close contacts between the incipient carbene atom and the X–H bonds in the target peptide. The close-contact analysis pointed to the Gln-5 and Tyr-7 residues as the most likely sites of cross-linking, consistent with the experimental CID-MS 3 results. Non-covalent binding in the amide complexes was evaluated by DFT calculations of structures and energies. Although antiparallel arrangements of the GNNQQNY and *GNNQQNY peptides were favored in low-energy gas-phase and solvated complexes, the conformations and peptide–peptide interface surfaces were found to differ from the secondary structure of the dry interface in GNNQQNY motifs of amyloid aggregates. 
    more » « less
  5. Abstract

    Organometal halide perovskite light emitting diodes (LEDs) have attracted a lot of attention in recent years, owing to the rapid progress in device efficiency. However, their short operational lifetime severely impedes the practical uses of these devices. The operating stability of perovskite LEDs are due to degradation due to ambient environment and degradation during operation. The former can be suppressed by encapsulation while the latter one is the intrinsic degradation due to the electrochemical stability of the perovskite materials. In addition, perovskites also suffer from ion migration which is a major degradation mechanism in perovskite LEDs. In this review, we specifically focus on the operational stability of perovskite LEDs. The review is divided into two parts: the first part contains a summary of various degradation mechanisms and some insight on the degradation behavior and the second part is the strategies how to improve the operational stability, especially the strategies to suppress ion migration. Based on the current advances in the literature, we finally present our perspectives to improve the device stability.

     
    more » « less