Structure and stability of solid oligoglycines
Bibliographic record
Abstract
Although peptides have been extensively studied within many disciplines, their solid state chemistry is not sufficiently explored. Crystalline peptide materials could present new opportunities in solid state organic synthesis as well as pharmaceutical, cosmetic and food industries. In order to facilitate these future applications, a better understanding of the relationship between the solid state structure and chemical reactivity in peptide crystals is required. In this work, a series of linear glycine oligomers was studied to see how their crystal structure and thermal reactivity changes with the chains growth. Single crystals of tetra- and pentaglycines were grown from aqueous solutions and investigated with XRD analysis (see Figure for pentaglycine). The newly collected data together with those reported previously reveal general trends likely present throughout all glycine oligomers. An antiparallel, hydrogen bound, β-sheet-like structure exists throughout the whole series and is the most stable polymorphic form in higher oligomers. Further, the thermal reactivity of this series was studied using gas chromatography – mass spectrometry (GC-MS), thermal gravimetric analysis (TGA) coupled with IR spectroscopy, differential scanning calorimetry (DSC) and bulk oven heating regimes. Finally 1H and 13C NMR and XRD analysis were used to identify key components of the thermal decomposition pathways as well as new products discovered during the thermal treatment. The results from all these studies suggest that the thermal stability of the oligomers increases with the chain length, but the decomposition pathways for the series are similar. In all cases, 2,5-diketopiperazine was formed through either condensation reactions (glycine and diglycine[1]) or depolymerisation of the peptide chain[2] in parallel with competing decomposition mechanisms. 2,5-Diketopiperazine and its derivatives are important biologically active molecules, and if this trend holds for other peptide oligomers, this solid state reaction could form a new, widely applicable synthetic method.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".