Hydrazo‐CEST: Hydrazone‐Dependent Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agents
Bibliographic record
Abstract
Abstract The rapid formation of hydrazones under physiological conditions was exploited for the detection of aldehydes through chemical exchange saturation transfer magnetic resonance imaging (CEST‐MRI). A metal‐free, diamagnetic contrast agent derived from N‐amino anthranilic acid was introduced, which selectively “turned‐on” upon hydrazone formation through an effect termed Hydrazo‐CEST. While the hydrazine form of the probe produced no CEST‐MRI signal enhancement, the formation of the aryl hydrazone resulted in >20 % intensity decrease in the bulk water signal through the CEST effect, as measured by 300 MHz 1 H NMR, 3 T and 7 T MRI. Both the electronic contributions of the N‐amino anthranilate and the aldehyde binding partner were shown to directly impact the exchange rate of the proton on the ring‐proximal nitrogen, and thus the imaging signal. Additionally, the presence of the carboxylic acid moiety ortho to the hydrazine was necessary not only for contrast production, but also for rapid hydrazone formation and prolonged hydrazone product stability under physiological conditions. This work provided the first example of an MRI‐based contrast agent capable of a “turn on” response upon reaction with bioactive aldehydes, and outlined both the structural and electronic requirements to expand on Hydrazo‐CEST, a novel, hydrazone‐dependent subtype of diamagnetic CEST‐MRI.
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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 | 0.001 | 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) | 0.006 | 0.001 |
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".