Frequency-Domain Spectroscopic Study of the PS I−CP43‘ Supercomplex from the Cyanobacterium <i>Synechocystis</i> PCC 6803 Grown under Iron Stress Conditions
Bibliographic record
Abstract
Absorption, fluorescence excitation, emission, and hole-burning (HB) spectra were measured at liquid helium temperatures for the PS I-CP43' supercomplexes of Synechocystis PCC 6803 grown under iron stress conditions and for respective trimeric PS I cores. Results are compared with those of room temperature, time-domain experiments (Biochemistry 2003, 42, 3893) as well as with the low-temperature steady-state experiments on PS I-CP43' supercomplexes of Synechococcus PCC 7942 (Biochim. Biophys. Acta 2002, 1556, 265). In contrast to the CP43' of Synechococcus PCC 7942, CP43' of Synechocystis PCC 6803 possesses two low-energy states analogous to the quasidegenerate states A and B of CP43 of photosystem II (J. Phys. Chem. B 2000, 104, 11805). Energy transfer between the CP43' and the PS I core occurs, to a significant degree, through the state A, characterized with a broader site distribution function (SDF). It is demonstrated that the low temperature (T = 5 K) excitation energy transfer (EET) time between the state A of CP43' (IsiA) and the PS I core in PS I-CP43' supercomplexes from Synechocystis PCC 6803 is about 60 ps, which is significantly slower than the EET observed at room temperature. Our results are consistent with fast (< or =10 ps) energy transfer from state B to state A in CP43'. Energy absorbed by the CP43' manifold has, on average, a greater chance of being transferred to the reaction center (RC) and utilized for charge separation than energy absorbed by the PS I core antenna. This indicates that energy is likely transferred from the CP43' to the RC along a well-defined path and that the "red antenna states" of the PS I core are localized far away from that path, most likely on the B7-A32 and B37-B38 dimers in the vicinity of the PS I trimerization domain (near PsaL subunit). We argue that the A38-A39 dimer does not contribute to the red antenna region.
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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".