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Computer modeling of adsorption on an activated charcoal surface
D E Wurster1, W M Kolling, B M Knosp
1Division of Pharmaceutics, College of Pharmacy, University of Iowa, Iowa City 52242-1112.
Journal of Pharmaceutical Sciences
|December 1, 1994
Summary
Molecular modeling simulated barbiturate adsorption on activated charcoal. The hydroxylated surface (C-OH) showed stronger adsorption than the carbonyl surface (C=O), aligning with experimental data for these drug molecules.
Area of Science:
- Computational Chemistry
- Materials Science
- Pharmacology
Background:
- Activated charcoal is widely used for drug adsorption, but the specific interactions with barbiturates require detailed understanding.
- Surface functional groups, particularly oxygen-containing ones like hydroxyl (C-OH) and carbonyl (C=O), significantly influence adsorption properties.
- Previous experimental studies indicated the importance of the C-O functional state for barbiturate adsorption.
Purpose of the Study:
- To simulate the adsorption of various barbiturates (barbituric acid, barbital, phenobarbital, mephobarbital, primidone) onto an activated charcoal surface using molecular modeling.
- To investigate the influence of different surface functional groups (none, C-OH, C=O) on the adsorption process.
- To compare simulated adsorption energies with experimental calorimetric data.
Main Methods:
- Utilized the SYBYL molecular modeling program for simulations.
- Energetically minimized structures of barbiturates and modeled activated charcoal surfaces as graphitic crystallites with varying functional groups.
- Employed docking simulations to predict conformational changes and calculated heats of adsorption and displacement.
Main Results:
- Conformational changes were observed in barbiturates upon adsorption.
- Simulated heats of adsorption ranged from -62.3 kJ/mol (barbituric acid) to -91.1 kJ/mol (mephobarbital) on the hydroxylated surface.
- Calculated heat of displacement values closely matched experimental data, with the C-OH surface showing greater adsorption affinity than the C=O surface.
Conclusions:
- Molecular modeling effectively predicts barbiturate adsorption behavior on activated charcoal.
- The hydroxyl functional group (C-OH) on activated charcoal plays a more critical role in barbiturate adsorption than the carbonyl group (C=O).
- The simulation results validate previous experimental findings regarding the importance of surface chemistry in drug adsorption.