Femtosecond Pumping Rate Dependence of Fragmentation Mechanisms in Matrix-Assisted Laser Desorption Ionization
Bibliographic record
Abstract
The benzyltriphenylphosphonium (BTP) thermometer ion is utilized to characterize the fragmentation mechanisms of matrix-assisted laser desorption/ionization (MALDI) for femtosecond ultraviolet laser pulses. We demonstrate that the survival yield of BTP approaches unity under these conditions, which suggests that a minimal amount of fragmentation is occurring. It is also shown that the survival yield of BTP is insensitive to the laser fluence. However, the magnitude of fragmentation for the matrix increased notably for the same fluence range. These results indicate that the amount of energy transferred from the matrix ions to the BTP thermometer ions is minimal because the femtosecond desorption applied here occur within the stress-confinement regime. This observation is in agreement with recent molecular dynamics simulations which predict that it should be possible to separate both desorption and ionization processes in the regime of stress-confined desorption. Our results indicate that angiotensin is the largest biomolecule which could be routinely measured with these pulses. A mass upper-limit supports the hypothesis that ionization is hindered by the increased thermal gradients imposed in the lattice and associated velocity distribution within the ablation process from the much higher lattice heating rate with femtosecond pulses. This effect results in the temporal overlap between the neutral molecules and the matrix ions being too small to result in sufficient proton exchange for ionization.
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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) | 0.004 | 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 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".