Physical Properties of Microbial Polythioesters: Characterization of Poly(3-mercaptoalkanoates) Synthesized by Engineered <i>Escherichia coli</i>
Bibliographic record
Abstract
Physical properties of chiral poly(thioesters), PTEs, prepared by engineered Escherichia coli, were examined by GPC, 13C CP/MAS solid-state NMR, X-ray diffraction, and thermal analysis. Microbial homopolymers of PTEs, poly(3-mercaptopropionate), PMP, and poly(3-mercaptovalerate), PMV, showed different solubility characteristics compared to poly(hydroxyalkanoates), PHAs. Generally, PTEs required higher temperatures for dissolution. Poly(3-mercaptobutyrate), PMB, and PMV dissolve in chloroform, and the molecular weight values were revealed by GPC as 176,000 and 165,000, respectively. The density values for PMP and PMB were 1.42 and 1.27 g/cm3, respectively. These values are similar to those for oxygen analogues. The NMR spectra for PTEs showed that carbonyl carbons are greatly shifted downfield by the sulfur atoms in the chain backbone compared to the PHA family. X-ray powder diffraction data indicated that PTEs are crystalline materials, but they do not crystallize as well as in the PHA family. The melting point, Tm, for PMP was 170 degrees C, which is about 100 degrees C higher than the equivalent oxygen analogue, poly(3-hydroxypropionate), PHP, and almost the same as that of bacterial poly(3-hydroxybutyrate), PHB. According to thermal analysis, only the PMP sample had enhanced heat stability, e.g., the decomposition temperature for PMP was 277 degrees C at 5% weight loss, whereas the values for PHP and PHB were 233 and 260 degrees C at the same weight loss, respectively.
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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) | 0.001 | 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".