X‐ray structure analysis reveals <i>β</i>‐turn mimicry by <i>N</i>‐amino‐imidazolidin‐2‐ones<sup>†</sup>
Bibliographic record
Abstract
The conformation of the N-amino-imidazolidin-2-one (Aid) peptidomimetic was investigated using NMR spectroscopy and X-ray crystallography. In solution, the tetrapeptide model p-bromobenzoyl-Aid-l-Phe-N'-iso-propylamide (1) exhibited shielded and solvent exposed amide protons indicative of a turn conformation. In the crystal lattice of 1, four turn conformers were present in the unit cell differing primarily by the ring puckering of the Aid residue. Two pairs of β-turn conformers were observed each possessing an intramolecular ten-member hydrogen bond between the benzamide carbonyl and iso-propylamine NH moieties. The pairs had types II and II' β-turn geometry that differed slightly about the ϕ and ψ torsion angles. Moreover, the X-ray analysis of 1 has been compared with that of the related unsaturated N-amino-imidazolin-2-one (Nai) analogs indicating the influences of ring flattening and substituents on conformation. Insertion of the preorganized Aid structure into biologically active peptides has thus been shown to offer a potentially valuable means for exploring the importance of turn geometry for activity, particularly in drug discovery.
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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".