title: NMR evidence of a valinomycin-proton complex.
abstract: In addition to the well-known complexes of valinomycin with alkali metal cations, an equimolar complex of the same compound with proton was found to be formed in nitrobenzene. Hydrogen bis(1,2-dicarbollylide) cobaltate (HDCC) was used as a proton source. According to NMR spectra, the complex formation is quantitative at proton/valinomycin molar ratios up to 1:1 but there is fast exchange of protons between coordinated and uncoordinated valinomycin molecules at lower ratios. 1H and 13C NMR spectra show a dramatic change in the valinomycin conformation during its coordination with protons, probably from a propeller-like to a bracelet-like form. As valinomycin is one of the well-known ion-carrying ionophores facilitating especially the K+ ion transport across a biological membrane, the existence of the valinomycin-proton complex could be important in biochemistry and biology.
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Kríz
authors.forename: Emanuel
authors.initials: E
authors.lastname: Makrlík
authors.forename: Petr
authors.initials: P
authors.lastname: Vanura
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009578:Nitrobenzenes / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D011522:Protons; D014634:Valinomycin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009578:Nitrobenzenes; D009942:Organometallic Compounds; D011522:Protons; D014634:Valinomycin