Role of the ammonium group in the diffusion of quaternary ammonium compounds in Streptococcus mutans biofilms
Bibliographic record
Abstract
OBJECTIVES: Cetylpyridinium chloride (CPC), a quaternary ammonium compound, was shown to interact irreversibly with Streptococcus mutans biofilms, leading to a slow diffusion compared with poly(ethylene glycol) (PEG) molecules of similar size. The objective of this work is to determine if the retardation of CPC diffusion and its strong binding to biofilms is caused by interactions between the ammonium group of CPC and the exopolysaccharide (EPS) matrix. METHODS: First, we characterized the diffusion of two analogues of CPC in S. mutans biofilms: dodecylpyridinium chloride (DPC), carrying a shorter alkyl chain than CPC, and tetramethylene bispyridinium chloride (TMBPC), a compound carrying two positively charged ammonium groups. Second, we cultured biofilms with different densities of EPS and examined the impact of this density on the transport properties of CPC. The diffusion of these compounds was probed using infrared spectroscopy with attenuated total reflectance sampling. RESULTS: The diffusion of CPC, DPC and TMBPC in S. mutans biofilm is slower than that of PEG10k. In addition, TMBPC and DPC, as PEG10k, could be readily washed out from the biofilms while CPC association was practically irreversible. The penetration of CPC through the EPS matrix was found to be not significantly affected by the increased EPS density, whereas the penetration of PEG with a molar mass of 10k was considerably reduced. CONCLUSIONS: These results suggest that the interactions between the quaternary ammonium groups and the EPS matrices are not the prime contribution of the strong CPC binding, and the alkyl chain length plays a role in this association, likely through hydrophobic interactions.
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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".