title: Ion binding properties in acetonitrile of cyclopeptides built up from proline and glycine residues.
abstract: Ion binding properties of antamanide-like cyclopeptides cyclo-(Pro2-Glyn-Pro2-Gly m) (n,m=1-3) have been studies by CD spectroscopy and by conductivity measurements. Cyclo-(Pro2-Gly-Pro2-Gly) forming complexes of different stoichiometry can be characterized by a strong preference of selectivity for Mg++ and Ca++ ions over alkali ions whereas the other members of the series bind selectively alkali and alkaline earth cations with ion radius of about 1 A. Three main types of CD spectra of cyclic peptides and their complexes can be differentiated. Type I showing two negative Cotton effects at around 220 nm and 200 nm (Ib, Fig. 3), type II showing a positive band around 220 nm and a strong negative one below 190 nm (e.g. Ic in acetonitrile, Fig. 4), and type III showing a strong negative band in the 205 nm region (e.g. mental complexes of Id, Fig. 6).
mesh_terms: D000097:Acetonitriles / Q000032:analysis*; D000468:Alkalies; D055598:Chemical Phenomena; D002621:Chemistry; D004553:Electric Conductivity; D005998:Glycine; D007477:Ions; D010456:Peptides, Cyclic; D011392:Proline; D013057:Spectrum Analysis
chemical_list: D000097:Acetonitriles; D000468:Alkalies; D007477:Ions; D010456:Peptides, Cyclic; D011392:Proline; D005998:Glycine