Resonant multiphoton processes and excitation limits to structural dynamics
Bibliographic record
Abstract
Understanding the chemical reactions that give rise to functional biological systems is at the core of structural biology. As techniques are developed to study the chemical reactions that drive biological processes, it must be ensured that the reaction occurring is indeed a biologically relevant pathway. There is mounting evidence indicating that there has been a propagation of systematic error in the study of photoactive biological processes; the optical methods used to probe the structural dynamics of light activated protein functions have failed to ensure that the photoexcitation prepares a well-defined initial state relevant to the biological process of interest. Photoexcitation in nature occurs in the linear (one-photon per chromophore) regime; however, the extreme excitation conditions used experimentally give rise to biologically irrelevant multiphoton absorption. To evaluate and ensure the biological relevance of past and future experiments, a theoretical framework has been developed to determine the excitation conditions, which lead to resonant multiphoton absorption (RMPA) and thus define the excitation limit in general for the study of structural dynamics within the 1-photon excitation regime. Here, we apply the theoretical model to bacteriorhodopsin (bR) and show that RMPA occurs when excitation conditions exceed the linear saturation threshold, well below typical excitation conditions used in this class of experiments. This work provides the guidelines to ensure excitation in the linear 1-photon regime is relevant to biological and chemical processes.
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 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".