The molecular interaction of human salivary histatins with polyphenolic compounds
Why this work is in the frame
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Bibliographic record
Abstract
Dietary tannins are polyphenols that are effectively precipitated by salivary histatins (Hsts), a novel family of tannin binding proteins. Epigallocatechin gallate (EGCG), a flavan-3-ol ester related to condensed tannins (polymerized products of flavan-3-ols), and pentagalloyl glucose (PGG), a hydrolyzable tannin, were used to evaluate the molecular nature of Hst-polyphenol interaction. NMR demonstrated that Hst5, a representative Hst, bound to EGCG in a hydrophobic manner via basic and aromatic residues. In contrast, proline plays a dominant role in polyphenol binding to other tannin precipitating proteins. The role of basic and aromatic amino acids in EGCG binding was investigated using a series of modified Hsts in each of which one type of amino acid was substituted by Ala. EGCG bound to all modified Hsts, but the binding was diminished. Optimal EGCG binding also depended on the primary structure, as a polypeptide with randomised Hst5 sequence showed significantly diminished interaction with EGCG. Soluble EGCG/Hst5 complexes containing up to seven molecules of EGCG per mol of Hst5 had a 1-mM dissociation constant. In contrast to EGCG, PGG formed small soluble complexes with Hst5 consisting of only one molecule each of PGG and Hst5, as demonstrated by analytical ultracentrifugation. These complexes became insoluble upon binding of additional molecules of PGG. Diminished PGG binding was seen to a peptide with a Hst5 randomized sequence showing the importance of the primary structure. Hsts may serve to form insoluble complexes with tannins thereby preventing their absorption from the intestines and potentially harmful biological effects. In contrast the much weaker interaction with EGCG may allow its uptake into the organism and exploitation of its antioxidant effect.
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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 | 0.000 | 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 it