Exploration of charge reduction on sequence coverage of proteins by 193 nm ultraviolet photodissociation
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo Sapiens (human) Cellular Organisms Equus Caballus Saccharomyces Cerevisiae (baker's Yeast) Bos Taurus
SUBMITTER: Jennifer S Brodbelt
PROVIDER: PXD065627 | JPOST Repository | Mon Jun 30 00:00:00 BST 2025
REPOSITORIES: jPOST
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| 5uMCA_80perACN_MS1.raw | Raw | |||
| 5uMCA_80perACN_PoCr2800V_Nw_3LminSF60V_MS1.raw | Raw | |||
| 5uMCA_SF30VMS1.raw | Raw | |||
| 5uMCA_SF45VMS1.raw | Raw | |||
| 5uMCA_SF60VMS1.raw | Raw |
Items per page: 5 1 - 5 of 20 |
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Project description:Characterization of all gas-phase charge sites of natively sprayed proteins and peptides is demonstrated using 193 nm UVPD. The high sequence coverage offered by UVPD is exploited for the accurate determination of charge sites in protein systems up to 18 kDa, allowing charge site to be studied as a function of protein conformation and the presence of disulfide bonds. Charging protons are found on both basic sidechains and on the amide backbone of less basic amino acids such as serine, glutamine, and proline. UVPD analysis was performed on the 3+ charge state of melittin, the 5+ to 8+ charge states of ubiquitin, and the 8+ charge state of reduced and oxidized β-lactoglobulin. The location of charges in gas-phase proteins is known to impact structure; molecular modeling of different charge site motifs of 3+ melittin demonstrates how placement of protons in simulations can dramatically impact the predicted structure of the molecule. The location of positive charge sites in ubiquitin and β-lactoglobulin are additionally found to depend on the presence or absence of salt-bridges, columbic repulsion across the length of the peptide, and protein conformation. Charge site isomers are demonstrated for ubiquitin and β-lactoglobulin but found to be much less numerous than previously predicted.
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Project description:We analyzed the backbone fragmentation behavior of tryptic peptides of a four protein mixture and of E. coli lysate subjected to Ultraviolet Photodissociation (UVPD) at 213 nm on a commercially available UVPD-equipped tribrid mass spectrometer. We obtained 15,178 high-confidence peptide-spectrum matches by additionally recording a reference beam-type collision-induced dissociation (HCD) spectrum of each precursor. Type a, b and y ions were most prominent in UVPD spectra and median sequence coverage ranged from 5.8% (at 5 ms laser excitation time) to 45.0% (at 100 ms). Overall sequence fragment intensity remained relatively low (median: 0.4% (5 ms) to 16.8% (100 ms) of total intensity) and remaining precursor intensity high. Sequence coverage and sequence fragment intensity ratio correlated with precursor charge density, suggesting that UVPD at 213 nm may suffer from newly formed fragments sticking together due to non-covalent interactions. UVPD fragmentation efficiency therefore might benefit from supplemental activation, as was shown for ETD. Aromatic amino acids, most prominently tryptophan, facilitated UVPD. This points at aromatic tags as possible enhancers of UVPD. Data are available via ProteomeXchange and on spectrumviewer.org/db/UVPD_213nm_trypPep
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Project description:Ultraviolet photodissociation (UVPD) has emerged as a useful technique for characterizing peptide, protein, and protein complex primary and secondary structure. 193 nm UVPD, specifically, enables extensive covalent fragmentation of the peptide backbone without the requirement of a specific side chain chromophore and with no precursor charge state dependence. We have modified a commercial quadrupole-ion mobility-time-of-flight (Q-IM-TOF) mass spectrometer to include 193 nm UVPD following ion mobility. Ion mobility (IM) is a gas-phase separation technique that enables separation of ions by their size, shape, and charge, providing an orthogonal dimension of separation to mass analysis. Following instrument modifications, we characterized the performance of, and information that could be generated from, this new setup using the model peptides substance P, melittin, and insulin chain B. These experiments show extensive fragmentation across the peptide backbone and a variety of ion types as expected from 193 nm UVPD. Additionally, y-2 ions (along with complementary a+2 and b+2 ions) N-terminal to proline were observed. Combining the IM separation and mobility gating capabilities with UVPD, we demonstrate the ability to accomplish both mass- and mobility-selection of bradykinin des-Arg9 and des-Arg1 peptides followed by complete sequence characterization by UVPD. The new capabilities of this modified instrument demonstrate the utility of combining IM with UVPD because isobaric species cannot be independently selected with a traditional quadrupole alone.
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