title: Synthesis, characterization and applications of a perdeuterated amphipol.
abstract: Amphipols are short amphipathic polymers that can substitute for detergents at the hydrophobic surface of membrane proteins (MPs), keeping them soluble in the absence of detergents while stabilizing them. The most widely used amphipol, known as A8-35, is comprised of a polyacrylic acid (PAA) main chain grafted with octylamine and isopropylamine. Among its many applications, A8-35 has proven particularly useful for solution-state NMR studies of MPs, for which it can be desirable to eliminate signals originating from the protons of the surfactant. In the present work, we describe the synthesis and properties of perdeuterated A8-35 (perDAPol). Perdeuterated PAA was obtained by radical polymerization of deuterated acrylic acid. It was subsequently grafted with deuterated amines, yielding perDAPol. The number-average molar mass of hydrogenated and perDAPol, ~4 and ~5 kDa, respectively, was deduced from that of their PAA precursors, determined by size exclusion chromatography in tetrahydrofuran following permethylation. Electrospray ionization-ion mobility spectrometry-mass spectrometry measurements show the molar mass and distribution of the two APols to be very similar. Upon neutron scattering, the contrast match point of perDAPol is found to be ~120% D2O. In (1)H-(1)H nuclear overhauser effect NMR spectra, its contribution is reduced to ~6% of that of hydrogenated A8-35, making it suitable for extended uses in NMR spectroscopy. PerDAPol ought to also be of use for inelastic neutron scattering studies of the dynamics of APol-trapped MPs, as well as small-angle neutron scattering and analytical ultracentrifugation.
authors.affiliation: Laboratoire de Physico-Chimie Moléculaire des Membranes Biologiques, UMR 7099, Institut de Biologie Physico-Chimique (FRC 550), Centre National de la Recherche Scientifique and Université Paris-7, 13 rue Pierre et Marie Curie, 75005, Paris, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Giusti
authors.forename: Jutta
authors.initials: J
authors.lastname: Rieger
authors.forename: Laurent J
authors.initials: LJ
authors.lastname: Catoire
authors.forename: Shuo
authors.initials: S
authors.lastname: Qian
authors.forename: Antonio N
authors.initials: AN
authors.lastname: Calabrese
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Watkinson
authors.forename: Marina
authors.initials: M
authors.lastname: Casiraghi
authors.forename: Sheena E
authors.initials: SE
authors.lastname: Radford
authors.forename: Alison E
authors.initials: AE
authors.lastname: Ashcroft
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Popot
mesh_terms: D003903:Deuterium / Q000737:chemistry*; D041961:Deuterium Exchange Measurement / Q000379:methods*; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008565:Membrane Proteins / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry*; D011437:Propylamines / Q000138:chemical synthesis* / Q000737:chemistry*; D012995:Solubility; D012996:Solutions; D013194:Staining and Labeling / Q000379:methods; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D008565:Membrane Proteins; D011108:Polymers; D011437:Propylamines; D012996:Solutions; D013501:Surface-Active Agents; C499017:amphipol A8-35; D014867:Water; D003903:Deuterium