Light-Induced Conformational Changes in Photosynthetic Reaction Centers: Impact of Detergents and Lipids on the Electronic Structure of the Primary Electron Donor
Bibliographic record
Abstract
Light-induced hypsochromic shifts of the Q(y) absorption band of the bacteriochlorophyll dimer (P) from 865 to 850 nm were identified using continuous illumination of dark-adapted reaction centers (RCs) from Rhodobacter capsulatus when dispersed in the most commonly used detergent, the zwitterionic lauryl N-dimethylamine-N-oxide. Such a shift is known to be the consequence of the decreased degree of delocalization of P. A 2-fold acceleration of the recovery kinetics of P(+) was found in RCs that underwent light-induced structural changes compared to those where the P-band position did not change. The light-induced shift was irreversible except in the presence of a secondary electron donor. Prolonged (15 min) illumination resulted in a shift in the position of the P-band even in neutral or negatively charged detergents. In contrast, RCs reconstituted into liposomes made from lipids with different headgroup charges showed light-induced shifts only if shorter fatty acid chains were used. The light-induced conformational changes caused a prominent decrease of the redox potential of P ranging from 120 to 160 mV depending on the detergent compared to the potential of P in dark-adapted reaction centers. The measured light-induced potential decreases were 55 to 85 mV larger than those reported for reaction centers where the P-band position remained at 865 nm. The influence of structural factors, such as the delocalization of the electron hole on P(+), the involvement of Tyr M210, and the hydrophobic mismatch between the thickness of the hydrophobic belt of the detergent micelles or the lipid bilayer and the RC protein, on the spectral features and electron transfer kinetics is discussed.
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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".