Demystifying and unravelling the molecular structure of the biopolymer sporopollenin
Bibliographic record
Abstract
RATIONALE: We report the unsolved molecular structure of the complex biopolymer sporopollenin exine extracted from Lycopodium clavatum pollen grains. METHODS: H} multi CP-MAS NMR experiments were used to confirm the structural assigments revealed by MS and MS/MS studies. Finally, high-resolution XPS was used to check for the presence of aromatic components in sporopollenin. RESULTS: The combined MS and NMR analyses showed that sporopollenin contained poly(hydroxy acid) dendrimer-like networks with glycerol as a core unit, which accounted for the sporopollenin empirical formula. In addition, these analyses showed that the hydroxy acid monomers forming this network contained a β-diketone moiety. Moreover, MALDI-TOF-MS and MS/MS allowed us to identify a unique macrocyclic oligomeric unit composed of polyhydroxylated tetraketide-like monomers. Lastly, high-resolution X-ray photoelectron spectroscopy (HR-XPS) showed the absence of aromaticity in sporopollenin. CONCLUSIONS: We report for the first time the two main building units that form the Lycopodium clavatum sporopollenin exine. The first building unit is a macrocyclic oligomer and/or polymer composed of polyhydroxylated tetraketide-like monomeric units, which represents the main rigid backbone of the sporopollenin biopolymer. The second building unit is the poly(hydroxy acid) network in which the hydroxyl end groups can be covalently attached by ether links to the hydroxylated macrocyclic backbone to form the sporopollenin biopolymer, a spherical dendrimer. Such spherical dendrimers are a typical type of microcapsule that have been used for drug delivery applications. Finally, HR-XPS indicated the total absence of aromaticity in the sporopollenin exine.
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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 | 0.001 |
| 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".