Light-Induced Conformational Changes in Photosynthetic Reaction Centers: Redox-Regulated Proton Pathway near the Dimer
Bibliographic record
Abstract
The influence of the hydrogen bonds on the light-induced structural changes were studied in the wild type and 11 mutants with different hydrogen bonding patterns of the primary electron donor of reaction centers from Rhodobacter sphaeroides. Previously, using the same set of mutants at pH 8, a marked light-induced change of the local dielectric constant in the vicinity of the dimer was reported in wild type and in mutants retaining Leu L131 that correlated with the recovery kinetics of the charge-separated state [ Deshmukh et al. (2011) Biochemistry, 50, 340-348]. In this work after prolonged illumination the recovery of the oxidized dimer was found to be multiphasic in all mutants. The fraction of the slowest phase, assigned to a recovery from a conformationally altered state, was strongly pH dependent and found to be extremely long at room temperature, at pH 6, with rate constants of ∼10(-3) s(-1). In wild type and in mutants with Leu at L131 the very long recovery kinetics was coupled to a large proton release at pH 6 and a decrease of up to 79 mV of the oxidation potential of the dimer. In contrast, in the mutants carrying the Leu to His mutation at the L131 position, only a negligible fraction of the dimer exhibited lowered potential, the large proton release was not observed, the oxidized dimer recovered 1 or 2 orders of magnitude faster depending on the pH, and the very long-lived state was not or barely detectable. These results are modeled as arising from the loss of a proton pathway from the bacteriochlorophyll dimer to the solvent when His is present at the L131 position.
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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".