title: SCRF-DFT and NMR comparison of tetracycline and 5a,6-anhydrotetracycline in solution.
abstract: A combination of structures, energies, and spectral data calculated using density functional theory (DFT) with experimental NMR data has been used to assign conformational equilibria for tetracycline and 5a,6-anhydrotetracycline in water at pH 1, 7, and 10 and in chloroform (5a,6-anhydrotetracycline) and methanol (tetracycline). The results suggest that tetracycline always prefers the extended conformation but that 5a,6-anhydrotetracycline exists in water as a mixture of the two conformers and in chloroform exclusively in the twisted conformation. The conformational equilibria are also shown to be pH dependent.
authors.affiliation: Computer-Chemie-Centrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstrasse 25, 91052 Erlangen, Germany.
authors.forename: Olaf G
authors.initials: OG
authors.lastname: Othersen
authors.forename: Reiner
authors.initials: R
authors.lastname: Waibel
authors.forename: Harald
authors.initials: H
authors.lastname: Lanig
authors.forename: Peter
authors.initials: P
authors.lastname: Gmeiner
authors.forename: Timothy
authors.initials: T
authors.lastname: Clark
mesh_terms: D003198:Computer Simulation; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons; D012996:Solutions / Q000737:chemistry; D012997:Solvents; D013754:Tetracyclines / Q000737:chemistry*
chemical_list: D011522:Protons; D012996:Solutions; D012997:Solvents; D013754:Tetracyclines