Promotion of <i>α</i>-cyano-4-hydroxycinnamic acid and peptide cocrystallization within levitated droplets with net charge
Bibliographic record
Abstract
Many reactions occur as a result of charge imbalance within or between reactive species in reaction vessels that have zero net charge. Here, chemical processes taking place within reaction vessels having net excess charge were studied. For mass spectroscopists, a familiar example of vessels that defy electroneutrality are the charged droplets produced by an electrospray ion source. Evidence is presented that control of the magnitude of the net charge contained in a reaction vessel, in this case a levitated droplet, can be used to promote nucleation and crystal growth of a mixture of an organic acid, alpha-cyano-4-hydroxycinnamic acid (CHCA), with one or more peptides. This phenomenon was first observed during our ongoing development of wall-less sample preparation (WaSP), electrodynamic charged droplet processing methodology capable of creating micrometer-sized sample spots for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) from subnanoliter volumes of sample material. Peptide ion signal-to-noise (S/N) ratios obtained by MALDI-TOF-MS from sample spots created from droplets that had high relative magnitude of net charge were consistently greater than those detected from sample spots created from droplets that had lower net charge. To study this unexpected phenomenon further, WaSP methodology was developed to process different mass-to-charge (m/z) droplets levitated in an electrodynamic balance (EDB), facilitating their deposition onto different positions of a target to create arrays of droplet residues ordered from highest to lowest m/z. This capability allowed simultaneous levitation with subsequent separation of a population of droplets created from a single starting solution, but the droplets had varied magnitudes of net charge. After the droplets were ejected from the EDB and collected on a glass slide or MALDI plate, the solids contained in the deposited droplets were characterized using microscopy and MALDI-TOF-MS. Factors impacting the chemical processing in droplets having net excess charge levitated in an EDB are discussed with particular emphasis on their possible roles in the promotion of crystal nucleation and growth.
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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".