A Simple Two-Step Approach for Introducing a Protected Diaminedithiol Chelator during Solid-Phase Assembly of Peptides
Bibliographic record
Abstract
A simple synthetic strategy is described to incorporate a protected diaminedithiol (N(2)S(2)) chelator during Fmoc solid-phase synthesis of short peptides. The resulting constructs could be efficiently labeled with technetium-99m (99mTc). The chelator was assembled at the N-terminus of peptides in a two-step procedure where the deprotected terminal amino group was first reacted with di-Fmoc-diaminopropionic acid (Fmoc-DAP-[Fmoc]-OH). The two protected amino groups were then simultaneously deprotected and subsequently reacted with S-benzoylthiolglycolic acid (TGA) to generate a protected N(2)S(2) chelator. This metal binding site was introduced into di- and tripeptides. Each peptide construct was composed of a C-terminal lysine residue and an N-terminal diaminopropionic moiety modified to create the chelator site. The epsilon-amino group at the C-terminal lysine was further derivatized with a nitroimidazole group to facilitate cellular retention. The resulting constructs were then cleaved from the resin support, purified, and labeled with [99mTc]pertechnetate. Six constructs were prepared differing by a single amino acid inserted between the diaminopropionic acid and lysine residues. Optimal labeling yields of >70% were achieved around neutral pH and heating at 75 degrees C for 10 min. Purified 99mTc-labeled constructs were found to accumulate in Chinese hamster ovary (CHO) cells in vitro as a function of charge and hydrophobicity.
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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) | 0.000 | 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".