title: Water and membrane dynamics in suspensions of lipid vesicles functionalized with poly(ethylene glycol)s.
abstract: The present work was aimed at studying the molecular dynamics at different levels of model membranes having a simulated glycoclix, with focus on the molecular crowding conditions at the lipid-water interfacial region. Thus, binary mixtures of dipalmitoylphosphatidylcholine (dpPC) and a poly(ethylene glycol) (PEG(n)) derivative of dipalmitoylphosphatidylethanolamine (PE) (where n = 350, 1000, and 5000, respectively, refer to PEG molecular masses) were submitted to (1)H spin-lattice relaxation time (T1) and (31)P NMR spectra analysis. (1)H NMR relaxation times revealed two contributing components in each proton system (PEG, phospholipids, and water), for all the mixtures studied, exhibiting values of T1 with very different orders of magnitude. This allowed identifying confined and bulk water populations as well as PEG moieties becoming more disordered and independent from the phospholipid moiety as n increased. (31)P spectra showed a typical broad bilayer signal for n = 350 and 1000, and an isotropic signal characteristic of micelles for n = 5000. Surface pressure (π)-molecular area isotherms and compressional modulus measurements provided further structural information. Moreover, epifluorescence microscopy data from monolayers at π ∼ 30 mN/m, the expected equilibrium π in lipid bilayers, allowed us to postulate that both (1)H populations resolved through NMR in phospholipids and lipopolymers corresponded to different phase domains.
authors.affiliation: IIByT (CONICET-UNC), Cátedra de Química Biológica, Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de Córdoba , Av. Vélez Sarsfield 1611, X5016GCA Córdoba, Argentina.
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Clop
authors.forename: Ana K
authors.initials: AK
authors.lastname: Chattah
authors.forename: María A
authors.initials: MA
authors.lastname: Perillo
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D046169:Dermoscopy; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D015394:Molecular Structure; D010714:Phosphatidylethanolamines; D010759:Phosphorus Isotopes; D011092:Polyethylene Glycols / Q000737:chemistry*; D011312:Pressure; D011522:Protons; D013499:Surface Properties; D013535:Suspensions; D014867:Water / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008823:Micelles; D010714:Phosphatidylethanolamines; D010759:Phosphorus Isotopes; D011522:Protons; D013535:Suspensions; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C007510:1,2-dipalmitoyl-3-phosphatidylethanolamine; D011092:Polyethylene Glycols