The Effect of Copper Limitation on the Bioavailability of Cu-Organic Complexes
Bibliographic record
Abstract
We examined the bioavailability of synthetic organic Cu complexes (Cu-L) and inorganic Cu species (Cu′) to Thalassiosira oceanica growing under Cu-limiting and Cu-inhibiting conditions. Copper bioavailability depended on the phytoplankton Cu nutritional state and whether Cu′ diffusion to the cell surface was sufficient to meet the cellular demands for growth. Under Cu-limiting conditions when [Cu′] was less than the diffusion concentration threshold (DCT: 10 –14.13 M), growth rate was a hyperbolic function of [Cu-L]. Increasing [Cu′] above the DCT caused growth rate to increase proportionally, but growth rate also increased with increasing [Cu-L] so that both Cu′ and Cu-L were bioavailable. Short-term photosynthesis assays conducted under Cu-limiting conditions showed a similar response to Cu speciation. In contrast, the growth rate of Cu-inhibited cells at high [Cu′] varied inversely with [Cu 2+ ] and was independent of [Cu-L], as previously reported. The change in Cu-L bioavailability correlated with expression levels of genes encoding the reduction-dependent, high-affinity Cu uptake pathway, which was regulated by [Cu′]. Our analysis shows that at [Cu′] typical of the open sea, T. oceanica -like phytoplankton are diffusion limited and must rely on Cu-organic complexes to fulfill their Cu requirements for growth.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".