Characterization of the Pentacoordinate Sodium Cations in Hydrated Nucleoside 5‘-Phosphates by Solid-State <sup>23</sup>Na NMR and Quantum Mechanical Calculations
Bibliographic record
Abstract
We report a solid-state 23 Na NMR study for the sodium cations in four hydrated disodium salts of nucleoside 5‘-phosphates: 2‘-deoxycytidine 5‘-monophosphate (dCMP), 2‘-deoxyguanosine 5‘-monophosphate (dGMP), 2‘-deoxyuridine 5‘-monophosphate (dUMP), and adenosine 5‘-triphosphate (ATP). Using one- and two-dimensional solid-state NMR techniques, we were able to detect all crystallographically distinct Na + ions in each of the Na−nucleotide systems. A total of 12 Na sites were fully characterized, among which four exhibit unusual penta-coordination geometry. The present study provides the first reliable solid-state 23 Na NMR characterization for the pentacoordinate Na + ions in nucleoside 5‘-phosphates. Spectral assignment was achieved on the basis of quantum mechanical electric-field-gradient (EFG) calculations at the restricted Hartree−Fock level with a 6-31G(d) basis set. The pentacoordinate Na + ion found in [d(TG 4 T)] 4 by high-resolution X-ray crystallography was modeled by using an isolated guanine quartet together with a central Na + ion and an axial water molecule. Quantum mechanical calculations suggest that the 23 Na quadrupole coupling constant for this square-pyramidal Na site is large (ca. 3 MHz), providing a possible explanation for the previous failure in detecting this type of Na + ions by solid-state 23 Na NMR.
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 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 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".