title: Extraction of radio-labelled xanthine derivatives by artificial receptors: deep insight into the association behaviour.
abstract: Association constants for the interaction of almost insoluble substrates with triphenylene ketal-based receptors in toluene have been determined by means of an extraction method employing the corresponding radio-labelled substrates. Flexible and more polar receptors tend to aggregate and exhibit inferior extraction qualities. Binding constants in toluene were found to be in the range 10(5)-10(7) m(-1), which is significantly higher than in dichloromethane. X-ray analyses indicate the direct participation of a water molecule in the binding process, which may account for the surprisingly small effect of moisture in the solvent on the stability of the complexes.
authors.affiliation: Rheinische Friedrich-Wilhelms-Universität Bonn Kekulé-Institut für Organische Chemie und Biochemie, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bomkamp
authors.forename: Carsten
authors.initials: C
authors.lastname: Siering
authors.forename: Karin
authors.initials: K
authors.lastname: Landrock
authors.forename: Holger
authors.initials: H
authors.lastname: Stephan
authors.forename: Roland
authors.initials: R
authors.lastname: Fröhlich
authors.forename: Siegfried R
authors.initials: SR
authors.lastname: Waldvogel
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002110:Caffeine / Q000737:chemistry; D018360:Crystallography, X-Ray; D008752:Methylene Chloride / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D011868:Radioisotopes / Q000737:chemistry; D018000:Receptors, Peptide / Q000737:chemistry* / Q000187:drug effects; D012997:Solvents; D013806:Theophylline / Q000737:chemistry; D014050:Toluene / Q000737:chemistry; D014970:Xanthines / Q000737:chemistry*
chemical_list: D011868:Radioisotopes; D018000:Receptors, Peptide; D012997:Solvents; D014970:Xanthines; D014050:Toluene; D002110:Caffeine; D008752:Methylene Chloride; D013806:Theophylline