Hydrophobic pathways

Hille B Local anesthetics Hydrophilic and hydrophobic pathways for the drug-receptor reactions. J Gen Physiol 1977 69 497. [PMID 300786]... 

The Hydrophilic and the Hydrophobic Pathways through the Skin Barrier. 12... 

THE HYDROPHILIC AND THE HYDROPHOBIC PATHWAYS THROUGH THE SKIN BARRIER... 

Hille, B. 1977. Local anesthetics hydrophilic and hydrophobic pathways for the drug-receptor reaction. J. Gen. Physiol. 69, 497-515. 

The lipid-soluble anesthetic molecules, on the other hand, diffuse across the neuronal membrane in their un-ionized forms. They can interact with the same receptors from either the hydrophilic pathway (pathway b in Fig. 16.7) on reprotonation to their onium ions [BH + ] or via the hydrophobic pathway (pathway a in Fig. 16.7) in their un-ionized forms [B]. Benzocaine and other nonbasic local anesthetic molecules use this hydrophobic pathway and, thus, bind to the same receptor, although at the hydrophobic site of the receptor, to produce their actions. Again, this... 

Fig. 16.7. Model of a sodium channel, as suggested by Hille (34), depicting a hydrophilic pathway (denoted by b and b ) and a hydrophobic pathway (denoted by a) by which local anesthetics may reach their receptor sites.

Figure 6 9 Schematic of different liquid water imbibitions and transport behavior in hydrophilic and hydrophobic pores. The catalyst layer and diffusion media are typically mixed wettability media thus hydrophilic and hydrophobic pathways exist for transport of hquid and gas phases.

The alternating polymer shows large hydrophobic and hydrophilic domains with a poor continuity between the hydrophilic domains. The random copolymer exhibits a disordered morphology with some connectivity between the hydrophilic regions, but no well-defined ionic pathways for the proton or water transport. On the other hand, the multiblock copolymer shows a well-defined fingerprint-type structure with continuous hydrophilic and hydrophobic pathways. The authors concluded that this microstructure was probably responsible for the fast proton transport even at a low humidity, as well as the faster water transport than those of the alternating and random polymers. 

Contaminant transfer to bed sediments represents another significant transfer mechanism, especially in cases where contaminants are in the form of suspended solids or are dissolved hydrophobic substances that can become adsorbed by organic matter in bed sediments. For the purposes of this chapter, sediments and water are considered part of a single system because of their complex interassociation. Surface water-bed sediment transfer is reversible bed sediments often act as temporary repositories for contaminants and gradually rerelease contaminants to surface waters. Sorbed or settled contaminants are frequently transported with bed sediment migration or flow. Transfer of sorbed contaminants to bottomdwelling, edible biota represents a fate pathway potentially resulting in human exposure. Where this transfer mechanism appears likely, the biotic fate of contaminants should be assessed. 

The most important removal pathways of PhACs during wastewater treatment are biotransformation/biodegradation and abiotic removal by adsorption to the sludge. The efficiency of their removal at WWTP depends on their physico-chemical properties, especially hydrophobicity and biodegradability, and process operating parameters (i.e., HRT, SRT, and temperature). For certain NSAIDs (e.g., ibuprofen, acetaminophen), high removals (>90%) are consistently reported in literature... 

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