Control of Calcium Oxalate Crystal Growth by Face-Specific Adsorption of an Osteopontin Phosphopeptide
Bibliographic record
Abstract
Mineral-associated proteins have been proposed to regulate many aspects of biomineralization, including the location, type, orientation, shape, and texture of crystals. To understand how proteins achieve this exquisite level of control, we are studying the interaction between the phosphoprotein osteopontin (OPN) and the biomineral calcium oxalate monohydrate (COM). In the present study, we have synthesized peptides corresponding to amino acids 220-235 of rat bone OPN (pSHEpSTEQSDAIDpSAEK), one of several highly phosphorylated, aspartic-, and glutamic acid-rich sequences found in the protein. To investigate the role of phosphorylation in interaction with crystals, peptides containing no (P0), one (P1), or all three (P3) phosphates were prepared. Using a novel combination of confocal microscopy and scanning electron microscopy, we show that these peptides adsorb preferentially to {100} faces of COM and inhibit growth of these faces in a phosphorylation-dependent manner. To characterize the mechanism of adsorption of OPN peptides to COM, we have performed the first atomic-scale molecular-dynamics simulation of a protein-crystal interaction. P3 adsorbs to the {100} face much more rapidly than P1, which in turn adsorbs more rapidly than P0. In all cases, aspartic and glutamic acid, not phosphoserine, are the amino acids in closest contact with the crystal surface. These studies have identified a COM face-specific adsorption motif in OPN and delineated separate roles for carboxylate and phosphate groups in inhibition of crystal growth by mineral-associated phosphoproteins. We propose that the formation of close-range, stable, and face-specific interactions is a key factor in the ability of phosphoproteins to regulate biomineralization processes.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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 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".