Unusual chemical and enzymatic stability of polysialic acid containing <i>N</i> ‐glycolylneuraminic acid
Bibliographic record
Abstract
The sialic acid N ‐glycolylneuraminic acid (Neu5Gc) is present only at trace levels in the brains of all vertebrates tested to date, suggesting a detrimental effect of Neu5Gc. As a candidate mechanism for this potential toxicity, we hypothesized a reduced enzymatic breakdown of polysialic acid (PSA), a polymer of α2–8 linked N ‐acetylneuraminic acid (Neu5Ac) found on the neural cell adhesion molecule (NCAM) and critical in many neurodevelopmental processes. We demonstrate that cultured neuroblastoma cells are able to incorporate Neu5Gc into PSA. Chemically synthesized polymers containing Neu5Gc exhibit resistance to the mammalian sialidase NEU1, an effect abolished by replacing the N ‐glycolyl group with N ‐propyl. Additional enzymatic and acidic conditions are being evaluated. Molecular modeling predicts similar tertiary structures of α2–8 linked Neu5Ac and Neu5Gc, but the presence of a glycolyl group creates a potentially stabilizing hydrogen bond with the adjacent carboxylate. This intrinsic stability of α2–8 linked Neu5Gc in PSA provides a potential explanation for the evolutionarily conserved absence of Neu5Gc from the vertebrate brain.
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 | 0.000 | 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) | 0.000 | 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".