title: A limiting law for the electrostatics of the binding of polypeptides to phospholipid bilayers.
abstract: Two cysteine-substituted variants of a peptide derived from the first 25 residues of the presequence for subunit IV of cytochrome c oxidase were synthesized and modified with a nitroxide spin label. The equilibrium partitioning of these spin-labeled peptides into negatively charged phospholipid vesicles was studied with electron paramagnetic resonance (EPR) to investigate the binding energetics. It is found that the binding equilibrium constant is an explicit function of a unique variable, the membrane surface potential psi in the Gouy-Chapman-Stern theory. Moreover, at low psi (< 0.5RT/F) the binding equilibrium is described by the linear dependence of the transfer free energy delta G(el) on psi with a slope equal to the full formal charge of the peptides. However, the partition constant levels off at higher psi, suggesting departure from the ideal limiting behavior.
authors.affiliation: Department of Chemistry, University of California, Berkeley 94720, USA.
authors.forename: T E
authors.initials: TE
authors.lastname: Thorgeirsson
authors.forename: Y G
authors.initials: YG
authors.lastname: Yu
authors.forename: Y K
authors.initials: YK
authors.lastname: Shin
mesh_terms: D000595:Amino Acid Sequence; D003553:Cystine; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011485:Protein Binding; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010455:Peptides; D003553:Cystine; D003576:Electron Transport Complex IV