Excitation energy transfer and charge separation dynamics in photosystem II: hole-burning study
Bibliographic record
Abstract
The constituents of oxygen-evolving photosystem II core complexes-antenna proteins (CP43 and CP47) and reaction center (RC)-have been the subject of many studies over the years.However, the various issues related to electronic structure, including the origin/composition of the lowest-energy traps, origin of various emission bands, excitation energy transfer (EET), primary charge separation (CS) processes and pigment site energies remain yet to be fully resolved.Exploiting our state-of-the-art techniques such as low-T absorption, fluorescence, and hole burning (HB) spectroscopies, we resolved some of the issues particularly related to CP47 and isolated RC protein complexes.For example, we demonstrated that the fluorescence origin band maximum (~695 nm) originates from the lowest-energy state ~693 nm of intact CP47.In intact CP47 in contrast to destablished protein complexes, the band (~695 nm) does not shift in the temperature range of 5-77 K unless hole-burning takes place.We also studied a large number of isolated RC preparations from spinach, and wild-typeChlamydomonas reinhardtii (at different levels of intactness), as well as its mutant (D2-L209H), in which the active branch pheophytin (Pheo D1 ) has been genetically replaced with chlorophyll a (Chl a).We showed that the Q x -/Q y -region site-energies of Pheo D1 and Pheo D2 are ~545/680 nm and ~541.5/670nm, respectively, in good agreement with our previous assignment [Jankowiak et al.J. Phys.Chem.B 2002, 106, 8803].Finally, we demonstrated that the primary electron donor in isolated algal RCs from C. reinhardtii (referred to as RC684) is P D1 and/or P D2 of the special Chl pair (analogous to P L and P M , the special BChl pair of the bacterial RC) and not Chl D1 .However, the latter can also be the primary electron donor (minor pathway) in RC684 depending on the realization of the energetic disorder.We further demonstrate that transient HB spectra in RC684 are very similar to P + Q A -PQ A spectra measured in PSII core, providing the first evidence that RC684 represent intact isolated RC that also possesses the secondary electron acceptor, Q A .In summary, a new insight into possible charge separation pathways in isolated PSII RCs has been provided.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".