Intracrystalline incorporation of nacre protein hydrogels modifies the mechanical properties of calcite crystals: a microcompression study
Bibliographic record
Abstract
The fracture toughness of mollusk shell nacre has been attributed to many factors, one of which is the intracrystalline incorporation of nacre-specific proteins. Although mechanical force measurements have been made on the nacre layer and on individual calcium carbonate crystals containing occluded organic molecules and macromolecules, there are few if any studies which examine the impact of occluded proteins on the mechanical properties of calcium carbonate crystals. To remedy this, we performed microcompression studies of calcite crystals grown in the presence and absence of two recombinant nacre proteins, r-AP7 (H. rufescens, intracrystalline proteome) and r-n16.3 (P. fucata, framework proteome), both of which are known aggregators that form hydrogel nanoinclusions within in vitro calcite. We find that, relative to protein-free calcite, the intracrystalline inclusion of either r-AP7 or r-n16.3 nacre protein hydrogels within the calcite crystals leads to a reduction in strength. However, nacre protein-modified crystals were found to exhibit elastic deformation under force compared to control scenarios, with no discernable differences noted between intracrystalline or framework protein-modified crystals. We conclude from our in vitro microcompression studies that the intracrystalline incorporation of nacre proteins can contribute to fracture-resistance of the crystalline phase by significantly reducing both modulus AND critical strength.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.001 | 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 teacher head, 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".