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Bernard Testa

Publications and source records attributed to Bernard Testa.

40 records · Page 3Linked to original sources
PubMed2002

Quantitative structure-permeation relationships for solute transport across silicone membranes.

PURPOSE: The purpose of this work was to assess the molecular properties that influence solute permeation across siliconemembranes and to compare the results with transport across human skin. METHODS: The permeability coefficients (log Kp) of a series of model solutes across silicone membranes were determined from the analysis of simple transport experiments using a pseudosteady-state mathematical model of the diffusion process. Subsequently, structure permeation relationships were constructed and examined, focusing in particular on the difference between solute octanol/water and 1,2 dichloroethane/water partition coefficients (deltalog P(oct-dce)), which re ported upon H-bond donor activity, and the computationally derived molecular hydrogen-bonding potential. RESULTS: The hydrogen-bond donor acidity and the lipophilicity of the compounds examined greatly influenced their permeation across sil cone membranes. Furthermore, for a limited dataset, a significant correlation was identified between solute permeation across silicone membranes and that through human epidermis. CONCLUSION: The key molecular properties that control solute perme ation across silicone membranes have been identified. For the set of substituted phenols and other unrelated compounds examined here a similar structure-permeation relationship has been derived for their transport through human epidermis, suggesting application of the results to the prediction of flux across biological barriers.

Biological Transport↗
PubMedDate not supplied

A cellular automata model of water structuring by a chiral solute.

The organization of water around a solute molecule with surface features of varying hydropathic states is studied. A stationary solute molecule and mobile water solvent molecules are modeled using cellular automata dynamics. It is shown that varying hydropathic states of solute molecule surface features influence the relative affinities of water for these features. In the case of a simulated chiral solute, a chiral pattern of associated water molecules binding to the surface is produced. This finding is in agreement with published simulations and circular dichroism measurements. A pattern of water molecules at locations beyond the surface of the solute molecules is detected, evidence of an emergent property in this solvent-solute system.

Journal Article↗
PubMedDate not supplied

Studies of ligand diffusion pathways over a protein surface.

Studies were conducted on the behavior of simulated molecules diffusing within organized water, postulated to form from the hydropathic states of protein surface amino acid side chains. This organization is postulated to facilitate the diffusion of ligands across the protein surface to their effector. These studies reveal that the organized water can be disrupted in their diffusion facilitating function by the presence of some other solute in high concentration. It was also found from cellular automata simulations that chiral isomers behaved in a slightly different manner when in an asymmetric enclosure simulating a fragment of the organized water pathway. These findings have relevance to observations about the mechanism of action of nonspecific anesthetic agents.

Amino Acids↗