title: The solvent polarity dependent conformational equilibrium of the carboxylic ionophore narasin: a proton NMR study.
abstract: Two dimensional homonuclear (1H-1H) chemical shift correlation, double resonance and nuclear Overhauser effect difference spectroscopy were used to determine spectral parameters of narasin acid in different solvents approximating the range of polarities encountered within a biological membrane. The observed chemical shift and coupling constant changes were consistent with a polarity mediated shift between two conformational states, with the major conformational adjustments occurring in two specific backbone regions of the molecule previously described as "hinges" (1,2). Evidence suggests that the conformational equilibrium is not only mediated by solvent polarity but may in part be determined by the intrinsic propensity of narasin to form inclusion complexes with H+.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D011522:Protons; D011714:Pyrans; D012997:Solvents
chemical_list: D011522:Protons; D011714:Pyrans; D012997:Solvents; C013612:narasin