title: Water populations in restricted environments of lipid membrane interphases.
abstract: We employ molecular dynamics simulations to study the hydration properties of Dipalmitoylphosphatidylcholine (DPPC) bilayers, both in the gel and the liquid crystalline states. We show that while the tight hydration centers (PO and CO moieties) are significantly hydrated in both phases, the gel-fluid transition involves significant changes at the second hydration shell, particularly at the buried region between the hydrocarbon tails. Thus, while almost no buried water population exists in the gel state below the carbonyls, this hydrophobic region becomes partially water accesible in the liquid crystalline state. We shall also show that such water molecules present a lower H-bond coordination as compared to the molecules at the primary hydration shell. This means that, while the latter are arranged in relatively compact nanoclusters (as already proposed), the buried water molecules tend to organize themselves in less compact structures, typically strings or branched strings, with a scarce population of isolated molecules. This behavior is similar to that observed in other hydration contexts, like water penetrating carbon nanotubes or model hydrophobic channels or pores, and reflects the reluctance of water to sacrifice HB coordination.
authors.affiliation: Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina.
authors.forename: Laureano M
authors.initials: LM
authors.lastname: Alarcón
authors.affiliation: Laboratorio de Biointerfases y Sistemas Biomiméticos, Laboratorios Centrales, CITSE-UNSE, Santiago del Estero, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: de Los Angeles Frías
authors.affiliation: Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina.
authors.forename: Marcela A
authors.initials: MA
authors.lastname: Morini
authors.affiliation: Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Belén Sierra
authors.affiliation: Sección Fisicoquímica, INQUISUR-UNS-CONICET, Universidad Nacional del Sur, Av. Alem 1253, 8000-Bahía, Blanca, Argentina. appignan@criba.edu.ar.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Appignanesi
authors.affiliation: Laboratorio de Biointerfases y Sistemas Biomiméticos, Laboratorios Centrales, CITSE-UNSE, Santiago del Estero, Argentina.
authors.forename: E
authors.initials: E
authors.lastname: Anibal Disalvo
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine; D008051:Lipid Bilayers; D056004:Molecular Dynamics Simulation; D037742:Nanotubes, Carbon; D014867:Water
chemical_list: D008051:Lipid Bilayers; D037742:Nanotubes, Carbon; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine
keywords: Flowing Matter: Liquids and Complex Fluids