Abstract
Ion-solvent interactions play a very important role in the studies of stoichiometry, structure, and stability of complexes of cations with natural and synthetic ionophores. These compounds are extremely useful in study of the interaction of neutral salts with macromolecules and the mechanism of cation transport across biological membranes. Knowledge of the ionophore solvation properties enables one to choose a suitable solvent for complexation studies and to obtain detailed information on the solvent effect. We would like to present in this paper a very simple method of estimating the solvation properties of ionophores. We treat the ligand as an assembly of individual noninteracting binding sites. The solvation properties of solvents can be used to represent the solvation sites in natural and synthetic ligands. The solvation properties are represented by the Gutmann donor number (DN) of the model solvent. We can define the solvation ability of a ligand binding site be "donor number of binding site" (DN binding site), which in turn can be represented by the DN of the appropriate model solvent. The average DN of the ligand (DN average) is defined as [xi ni-1 (DN binding site)i]/n, where n is the number of the ligand binding sites. Comparison of the DN average with the DN solvent, together with the knowledge of the composition of the system, characterizes remarkably well the solvation properties of the ligand. This model explains (a) the stoichiometry of many alkali and alkaline earth cation complexes with natural and synthetic ligands in aprotic organic solvents, (b) the transport of alkali and alkaline earth cations across lipid bilayers, and (c) how polypeptides and proteins interact with neutral salts in solutions.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Baron D., Pease L. G., Blout E. R. Cyclic peptides. 19. Cation binding of a cyclic dodecapeptide cyclo-(L-Val-Gly-Gly-L-Pro)3 in an aprotic medium. J Am Chem Soc. 1977 Dec 7;99(25):8299–8366. doi: 10.1021/ja00467a030. [DOI] [PubMed] [Google Scholar]
- Bartman B., Deber C. M., Blout E. R. 13C NMR relaxation studies of complexes between cyclo(L-Pro-Gly)3 and amino acids. Conformational aspects of stepwise binding. J Am Chem Soc. 1977 Feb 16;99(4):1028–1033. doi: 10.1021/ja00446a009. [DOI] [PubMed] [Google Scholar]
- CHAPPELL J. B., CROFTS A. R. GRAMICIDIN AND ION TRANSPORT IN ISOLATED LIVER MITOCHONDRIA. Biochem J. 1965 May;95:393–402. doi: 10.1042/bj0950393. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Easwaran K. R., Pease L. G., Blout E. R. Conformations of an ion-binding cyclic peptide analogue of valinomycin, cyclo(L-Val-Gly-Gly-L-Pro)3. Biochemistry. 1979 Jan 9;18(1):61–67. doi: 10.1021/bi00568a010. [DOI] [PubMed] [Google Scholar]
- Ivanov V. T. "Sandwich" complexation in cyclopeptides and its implications in membrane processes. Ann N Y Acad Sci. 1975 Dec 30;264:221–243. doi: 10.1111/j.1749-6632.1975.tb31485.x. [DOI] [PubMed] [Google Scholar]
- Läuger P. Carrier-mediated ion transport. Science. 1972 Oct 6;178(4056):24–30. doi: 10.1126/science.178.4056.24. [DOI] [PubMed] [Google Scholar]
- Madison V., Atreyi M., Deber C. M., Blout E. R. Cyclic peptides. IX. Conformations of a synthetic ion-binding cyclic peptide, cyclo-(pro-gly)3, from circular dichroism and 1H and 13C nuclear magnetic resonance. J Am Chem Soc. 1974 Oct 16;96(21):6725–6734. doi: 10.1021/ja00828a031. [DOI] [PubMed] [Google Scholar]
- Madison V., Deber C. M., Blout E. R. Cyclic peptides. 17. Metal and amino acid complexes of cyclo(pro-gly)4 and analogues studied by nuclear magnetic resonance and circular dichroism. J Am Chem Soc. 1977 Jul 6;99(14):4788–4798. doi: 10.1021/ja00456a042. [DOI] [PubMed] [Google Scholar]
- Mueller P., Rudin D. O. Development of K+-Na+ discrimination in experimental bimolecular lipid membranes by macrocyclic antibiotics. Biochem Biophys Res Commun. 1967 Feb 21;26(4):398–404. doi: 10.1016/0006-291x(67)90559-1. [DOI] [PubMed] [Google Scholar]