Top‐down lignomic matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry analysis of lignin oligomers extracted from date palm wood
Bibliographic record
Abstract
Rationale We report for the first time the top‐down lignomic analysis of the virgin released lignin (VRL) oligomers obtained from the Saudi date palm wood (SDPW), using a matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight (MALDI‐TOF/TOF) instrument. In addition, we are proposing new collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) fragmentation routes for this series of unreported VRL oligomers. Methods We have used direct MALDI‐TOF‐MS analysis of the mixture of lignin oligomers without any chromatographic pre‐separation. High‐energy CID‐MS/MS analyses were used to confirm the precursor ion structures. Results Six protonated lignin oligomer molecules were identified: [C 19 H 24 O 8 + H] + as H(8‐O‐4')G; [C 50 H 52 O 19 + H] + as H(8‐O‐4')H(8‐O‐4'')S(8‐O‐4''')S(8‐O‐4'''')G; [C 58 H 54 O 18 + H] + as H(8‐O‐4')H(8‐O‐4'')H(8‐O‐4''')G(8‐O‐4'''')S(8‐O‐4''''')G; [C 58 H 54 O 19 + H] + as H(8‐O‐4')H(8‐O‐4'')H(8‐O‐4''')S(8‐O‐4'''')S(8‐O‐4''''')G; [C 61 H 68 O 25 + H] + as H(8‐O‐4')G(8‐O‐4'')G(8‐O‐4''')S(8‐O‐4'''')S(8‐O‐4''''')G; and [C 61 H 68 O 26 + H] + as C(8‐O‐4')G(8‐O‐4'')G(8‐O‐4''')S(8‐O‐4'''')S(8‐O‐4''''')G units (H = coniferyl, S = sinapyl, and G = p ‐coumaryl). Two distonic cations were identified as [C 39 H 43 O 15 + H] +• and [C 40 H 43 O 16 + H] +• deriving from two tetrameric lignin oligomers. The high‐energy MS/MS analyses allowed the confirmation of the proposed structures of this series of lignin oligomers. Conclusions To our knowledge, this is the first elucidation of the lignin structure of the Saudi seedling date palm wood that was accomplished using a top‐down lignomic strategy that has not previously been published. The complex high‐energy CID‐MS/MS fragmentations presented herein are novel and have never been described before.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".