title: Proton NMR detection of porphyrins and cytochrome C in small unilamellar vesicles: role of the dissociation kinetic constant.
abstract: The molecular tumbling of small unilamellar vesicles is not fast enough to enable the detection of (1)H NMR signals of molecules associated with phospholipids. We show that relatively fast kinetic exchange of the interacting molecules is able to induce a strong decrease of the residual homonuclear dipolar coupling, allowing the acquisition of sharp signals. At low molecule/lipids molecular ratio, this can be lead to signal broadening due to exchange at intermediate rates on the NMR chemical timescale. However, proton resonances can be easily detected when sufficient lipids are added to prevent the occurrence of any free compounds in solution. This is demonstrated, using lipid signal suppression, in the case of paramagnetic porphyrin derivatives as well as diamagnetic hematoporphyrin. Since several peptides and proteins are expected to be associated with lipids having relatively fast dynamics, this study addresses, as a first example, the interaction of cytochrome c.
authors.affiliation: Resonance Magnetique Nucleaire-Interactions Lipids Proteines, Centre National de la Recherche Scientifique, UMR 6026, Institut Federatif de Recherche 140, Université de Rennes 1, Rennes, France.
authors.forename: Gregory
authors.initials: G
authors.lastname: Da Costa
authors.forename: Soizic
authors.initials: S
authors.lastname: Chevance
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Le Rumeur
authors.forename: Arnaud
authors.initials: A
authors.lastname: Bondon
mesh_terms: D045304:Cytochromes c / Q000032:analysis*; D007700:Kinetics; D008567:Membranes, Artificial; D019906:Nuclear Magnetic Resonance, Biomolecular; D011166:Porphyrins / Q000032:analysis*; D011522:Protons
chemical_list: D008567:Membranes, Artificial; D011166:Porphyrins; D011522:Protons; D045304:Cytochromes c