Characterizing degradation products of peptides containing N‐terminal Cys residues by (off‐line high‐performance liquid chromatography)/matrix‐assisted laser desorption/ionization quadrupole time‐of‐flight measurements
Bibliographic record
Abstract
A transformation analogous to the well-known conversion of an N-terminal glutamine residue to pyroglutamic acid is the cyclization of an N-terminal carboxyamidomethylated cysteine residue (the normal product of alkylation with iodoacetamide). This yields 5-oxothiomorpholine-3-carboxylic acid, with the same 17 Da mass loss observed in the Gln reaction. Nineteen tryptic peptides with Cys at the N-terminal were identified for this study, and compared with eight with N-terminal Gln. When examined by MALDI-QqTOF and (off-line HPLC)/MALDI-QqTOF measurements, these were all found to undergo the cyclization reactions. The average degree of degradation during overnight digestion was found to be approximately 51 and approximately 34% for Cys and Gln, respectively; more detailed information on the time course of the reactions was obtained for the peptides CCTESLVNR and QYYTVFDR. Taking this modification into account while sequencing is likely to increase the probability of protein identification by peptide mass fingerprinting, especially for cysteine-rich proteins.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".