Influence of Calcium on Milk Protein Aggregation and Binding Dynamics Between Binder of Sperm (BSP) Proteins and Milk Proteins.
Bibliographic record
Abstract
Over the years, skim milk has been used as extender for cryopreservation of semen from domestic animals due to its protective role against cold shock. The protective effect is attributed to its protein fraction and approximately 80% of the total milk proteins are casein micelles. In skim milk, calcium ions are associated with casein micelles and also responsible for their internal stability. Calcium forms linkages between proteins as colloidal calcium phosphate or it directly binds to caseins. Recent studies have shown that major proteins of the bovine seminal plasma, named Binder of Sperm (BSP) proteins as well as their homologues from stallion, boar and ram interact with the constituents of milk-based extenders. This interaction is implicated in sperm protection during cooling and storage of semen. Thus, the aim of this study was to investigate if calcium ions modulate the interaction between milk proteins and BSP proteins from animals of agricultural importance. In order to evaluate such interaction, heated skim milk was incubated with seminal plasma proteins from bulls, stallions, boars and rams. Then, these solutions were loaded onto Sepharose CL-4B column previously equilibrated with buffer-C (20 mM Tris, 50 mM NaCl, 10 mM CaCl2, 0.02% sodium azide, pH 7.4). The proteins were eluted with buffer-C and fractions were analysed by immunobloting. In parallel, seminal plasma proteins alone was used as controls and subjected to gel filtration chromatography in buffer-C. In the presence of calcium, casein micelles and whey protein aggregated and co-eluted. Bull, stallion and boar BSP proteins also co-eluted with milk protein aggregates in the presence of calcium. These results suggest that, in these species, calcium modulates protein-protein interaction as a result of an increase in milk protein aggregation. In contrast, ram BSP proteins did not bind to milk protein aggregates, suggesting that ram BSP proteins may differ in structural organization as compared to the bull, boar and stallion BSP homologues. In conclusion, our results indicate that calcium influences the formation of larger casein aggregates and the binding of bull, stallion and boar BSP proteins to milk proteins. These findings are crucial to understand the mechanisms of sperm protection by extender components and for the development of novel extenders. (Supported by CAPES - Brazil and NSERC of Canada)
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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 | 0.000 |
| 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 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".