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Natural and Synthetic Transmembrane Channels

Transmembrane channels represent a special type of multi-unit effector allowing the passage of ions or molecules through membranes by a flow or site-to-site hopping mechanism. They are the main effectors of biological ion transport. Natural and synthetic peptide channels (gramicidin A, alamethicin) allowing the transfer of cations have been studied [6.66-6.68]. [Pg.79]

Successful synthetic transmembrane channels must have three characteristics if they are to replicate the behaviour of natural systems. They must span the cell membrane, implying a single molecule or stable self-assembled complex over 4 nm in length. Ideally they should also be able to discriminate in favour of one chemical species, if they are to mimic the highly selective channels, and transport that species at rates in the region of 104 to 108 ions per second to match the efficacy of natural channels. [Pg.172]

During the past decade, numerous studies have been undertaken to develop synthetic ionophores that might permit cations or molecules to pass through a lipid bilayer [1]. Naturally-occurring gramicidin A is known to form transmembrane channels [2] and efforts to prepare a cation-conducting channel have been reported as well [3]. In our work, we have studied the selectivity of numerous crown ethers, lariat ethers [4, 5], and multi-armed versions of the latter [6]. Much has been learned about flexible ionophores and we have now attempted to utilize the concepts of flexibility and self-assembly to permit construction of a cation- or molecule-conducting channel. [Pg.73]

It is now recognised that a wide range of organic molecules, collectively termed ionophores 185,186) or complexones 187), are able to facilitate ion (usually cation) transport. Two major mechanisms have been revealed for this process, namely the involvement of transmembrane ion carriers and transmembrane pores or channels (see Fig. 19). The majority of ionophores studied to date are natural antibiotics and their synthetic analogues which are, on a biological scale, comparatively small molecules lending themselves to study outside the biological system. In contrast far less is known about the molecular structures involved in normal transport processes. Such molecules are likely to be more complex or present in small amounts and may require... [Pg.180]


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Channels transmembrane

Natural and synthetic

Synthetic natural

Transmembrane

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