Lipid carbonyl groups terminate the hydrogen bond network of membrane-bound water.
We present a combined experimental sum-frequency generation (SFG) spectroscopy and ab initio molecular dynamics simulations study to clarify the structure and orientation of water at zwitterionic phosphatidylcholine (PC) lipid and amine N-oxide (AO) surfactant monolayers. Simulated O-H stretch SFG spectra of water show good agreement with the experimental data. The SFG response at the PC interface exhibits positive peaks, whereas both negative and positive bands are present for the similar zwitterionic AO interface. The positive peaks at the water/PC interface are attributed to water interacting with the lipid carbonyl groups, which act as efficient hydrogen bond acceptors. This allows the water hydrogen bond network to reach, with its (up-oriented) O-H groups, into the headgroup of the lipid, a mechanism not available for water underneath the AO surfactant. This highlights the role of the lipid carbonyl group in the interfacial water structure at the membrane interface, namely, stabilizing the water hydrogen bond network.
Max-Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.|Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
Tatsuhiko
T
Ohto
Max-Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
Ellen H G
EH
Backus
Max-Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
Cho-Shuen
CS
Hsieh
Department of Physics, Johannes-Gutenberg University , Staudinger Weg 7, 55099 Mainz, Germany.
Marialore
M
Sulpizi
Max-Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
Mischa
M
Bonn
Max-Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
Yuki
Y
Nagata
D006860:Hydrogen Bonding; D008055:Lipids / Q000737:chemistry*; D008566:Membranes / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D010713:Phosphatidylcholines / Q000737:chemistry; D014867:Water / Q000737:chemistry*
D008055:Lipids; D010713:Phosphatidylcholines; D014867:Water
amine N-oxide; hydrogen bond network; interfacial water; phosphatidylcholine; sum-frequency generation spectroscopy