Binding of ciprofloxacin by humic substances: A molecular dynamics study

摘要: A comprehensive assessment of the potential impacts antimicrobials released into environment requires an understanding their sequestration by natural particles. Of particular interest are strong interactions with organic matter (NOM), which believed to reduce bioavailability, retard abiotic and biotic degradation, facilitate persistence in soils aquatic sediments. Molecular dynamics (MD) relaxation studies a widely used fluoroquinolone antibiotic, ciprofloxacin (Cipro), interacting model humic substance (HS) hydrated environment, were performed elucidate mechanisms these interactions. Specifically, zwitterionic Cipro molecule, predominant species at circumneutral pH, was reacted either protonated HS or deprotonated bearing Ca, Mg, Fe(II) cations. The underwent conformational changes through rearrangements its hydrophobic hydrophilic regions disruption intramolecular H-bonds favorable intermolecular H-bonding Cipro. Complexation metal cations carboxylates appeared impede binding positively charged amino group negatively complexation sites. On other hand, outer-sphere complex between HS-bound cation led ternary Cipro-metal-HS complexes case Mg-HS Fe(II)-HS, but no such bridging interaction occurred Ca-HS. results suggested that ionic (valence/ionic radius) divalent may be determining factor formation complex, high favoring interaction. Environ. Toxicol. Chem. 2010;29:90-98. (c) 2009 SETAC.