Control of Energy Dissipation and Photochemical Activity in Photosystem I by NADP-Dependent Reversible Conformational Changes
Bibliographic record
Abstract
Addition of NADP(+) to thylakoid membranes or isolated photosystem I (PSI) submembrane fractions quenched chlorophyll fluorescence by up to 40% at low or room temperature. This quenching was reversed by NADPH. Similar quenching was also observed with the addition of heparin or thenoyltrifluoroacetone (TTFA), inhibitors that bind ferredoxin:NADP(+) reductase (FNR) and prevent reduction of NADP(+). The NADP(+)-induced quenching coincided with a reversible conformational change of the secondary protein structure in the PSI submembrane fractions where 20% of the alpha-helix conformations were transformed mainly into beta-sheet-like structures. Further, P700 photooxidation was retarded due to this conformational change, and about 25% of the centers could not be photooxidized, these changes being also reversible with addition of NADPH. The above modifications in the presence of NADP(+) also increased photodamage processes under strong illumination, and NADPH protected it. Conformational modification of FNR upon binding of NADP(+) or NADPH is proposed to trigger the macromolecular changes in a larger part of the protein complex of PSI. The conformational changes must increase the intermolecular distances and change the mutual orientation between the various cofactors in the PSI complex. This new control mechanism of energy dissipation and photochemical activity by NADP(+)/NADPH is proposed to increase the turnover rate of PSI under conditions when both linear and cyclic electron transport activities must be supported.
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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 | 0.000 | 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 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".