Water populations in restricted environments of lipid membrane interphases

ALARCON, L; FRIAS, M. DE LOS ANGELES; MORINI, M.; SIERRA, M.B.; APPIGNANESI, G.; DISALVO, EDGARDO ANIBAL

European Physical Journal E

Springer Berlin Heilderger

Año: 2017 vol. 39

1292-8941

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 thatwhile the tight hydration centers (PO and CO moieties) are significantly hydrated in both phases, thegel-fluid transition involves significant changes at the second hydration shell, particularly at the buriedregion between the hydrocarbon tails. Thus, while almost no buried water population exists in the gel statebelow the carbonyls, this hydrophobic region becomes partially water accesible in the liquid crystallinestate. We shall also show that such water molecules present a lower H-bond coordination as comparedto the molecules at the primary hydration shell. This means that, while the latter are arranged in relativelycompact nanoclusters (as already proposed), the buried water molecules tend to organize themselvesin less compact structures, typically strings or branched strings, with a scarce population of isolatedmolecules. This behavior is similar to that observed in other hydration contexts, like water penetratingcarbon nanotubes or model hydrophobic channels or pores, and reflects the reluctance of water to sacrificeHB coordination.