Studies on the structure and composition of the outer membrane of Caulobacter crescentus
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Classically, outer membranes are half lipid, half protein, and the outmost layers of Gram- negative bacteria. For Caulobacter crescentus the outer membrane is the penultimate layer beneath a protein surface layer (S-layer). The S-layer of the caulobacter cell envelope is an exciting platform for high density peptide display and biotechnology development. We focused on elucidating the structure of the outer membrane by crystallizing the S-layer protein, RsaA; solving the structure of the the lipopolysaccharide; and characterizing a newly discovered porin, OmpW. S-layer proteins are highly resistant to crystallization, because wo-dimensional S-layer formation out competes three-dimensional crystal formation. To achieve a crystallisable form of RsaA, a C-terminal truncation version was constructed and expressed in the native host, C. crescentus. The secreted protein was prone to aggregation, so low agitation and slow concentration protocols had to be developed. The RsaA truncate produced large crystals that diffracted to <2.5 Å. Solving the phases proved to be a serious hurdle and the final protein structure remains unsolved. The lipopolysaccharide of C. crescentus is the anchor that supports the S-layer. The structure of the lipid A portion was solved previously but structures for the core oligosaccharide and the O-polysaccharide had not been deduced. In collaboration with Dr. Evgeny Vinogradov, these remaining structures were solved. The core oligosaccharide has a branched heptasaccharide structure. The O-polysaccharide is a heptasaccharide containing the dideoxy sugar N-acetylperosamine. Additionally, a rhamnan polysaccharide was discovered and its structure was determined. Porins, non-specific passive protein channels, are significant components of classical Gram-negative outer membranes. Despite this, no porin had ever been identified in C. crescentus. We report the identification and characterization of the porin OmpW in C. crescentus. OmpW has low conductance of 125 pSv in 1 M KCl. That is interesting because homologous porins in other bacteria have no detectable pore-forming activity. The cell envelopes of bacteria are remarkable structures; the work here illuminates the unique structures present in the caulobacter envelope.
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.
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 it