Vibrational Analysis of Methylcobalamin
Bibliographic record
Abstract
This work represents the first theoretical attempt to assign vibrational modes for methylcobalamin (MeCbl), the biologically active form of a vitamin B 12 derivative. Full vibrational analysis of MeCbl is currently beyond computational resources; thus, a simplified model, including the actual corrin ring, Im−[Co III (corrin)]−CH 3, was employed in the analysis. The scaled quantum mechanical (SQM) method has been used to refine density functional theory (DFT) based force constants calculated at the B3LYP level of theory. Normal-coordinate analysis based on a six-coordinate MeCbl model permitted assignment of the most important interligand modes. Direct comparison with experimental data showed that the DFT-SQM force field accurately predicts isotope shifts for interligand vibrations corresponding to CH 3 → CD 3 and 12 CH 3 → 13 CH 3 isotope labeling. The DFT-SQM force field for Im−[Co III (corrin)]−CH 3 gives a semiquantitative description of the corrin modes when compared to the Raman spectrum of MeCbl. The analysis of Raman data, together with DFT-computed frequencies, permitted assignment of certain modes located in the 1300−1600 cm -1 range. The calculated modes in this spectral range are mainly composed of single/double CC and CN stretch vibrations. These modes more closely resemble vibrations of connected short linear polyenes rather than modes delocalized over the corrin ring as observed in porphyrins. This localized character most likely is responsible for lack of structure-sensitive modes such as the “core size” marker.
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) | 0.003 | 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".