title: Exploring 3D structural influences of aliphatic and aromatic chemicals on α-cyclodextrin binding.
abstract: Binding of solutes to macromolecules is often influenced by steric effects caused by the 3D structures of both binding partners. In this study, the 1:1 α-cyclodextrin (αCD) binding constants (Ka1) for 70 organic chemicals were determined to explore the solute-structural effects on the αCD binding. Ka1 was measured using a three-part partitioning system with either a headspace or a passive sampler serving as the reference phase. The Ka1 values ranged from 1.08 to 4.97 log units. The results show that longer linear aliphatic chemicals form more stable complexes than shorter ones, and that the position of the functional group has a strong influence on Ka1, even stronger than the type of the functional group. Comparison of linear and variously branched aliphatic chemicals indicates that having a sterically unhindered alkyl chain is favorable for binding. These results suggest that only one alkyl chain can enter the binding cavity. Relatively small aromatic chemicals such as 1,3-dichlorobenzene bind to αCD well, while larger ones like tetrachlorobenzene and 3-ring aromatic chemicals show only a weak interaction with αCD, which can be explained by cavity exclusion. The findings of this study help interpret cyclodextrin binding data and facilitate the understanding of binding processes to macromolecules.
authors.affiliation: Helmholtz Centre for Environmental Research UFZ, Permoserstr. 15, D-04318 Leipzig, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Linden
authors.affiliation: Helmholtz Centre for Environmental Research UFZ, Permoserstr. 15, D-04318 Leipzig, Germany; University of Halle-Wittenberg, Institute of Chemistry, Kurt Mothes Str. 2, D-06120 Halle, Germany.
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Goss
authors.affiliation: Helmholtz Centre for Environmental Research UFZ, Permoserstr. 15, D-04318 Leipzig, Germany; Osaka City University, Urban Research Plaza & Graduate School of Engineering, Sugimoto 3-3-138, Sumiyoshi-ku, 558-8585 Osaka, Japan. Electronic address: satoshi.endo@urban.eng.osaka-cu.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Endo
mesh_terms: D001665:Binding Sites; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D047391:alpha-Cyclodextrins / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D047391:alpha-Cyclodextrins; C032613:alpha-cyclodextrin
keywords: Binding constant; Cyclodextrin water partitioning; Inclusion complex; Solute 3D structure; Steric effect; α-Cyclodextrin (CD)