title: Water Structure at the Lipid Multibilayer Surface: Anionic Versus Cationic Head Group Effects.
abstract: Membrane water interface is a potential reaction site for many biochemical reactions. Therefore, a molecular level understanding of water structure and dynamics that strongly depend on the chemical structure of lipid is prerequisite for elucidating the role of water in biological reactions on membrane surface. Recently, we carried out femtosecond infrared pump-probe studies of water structure and dynamics at multibilayer surfaces of zwitterionic phosphatidylcholine-analogue lipid ( J. Phys. Chem. Lett. 2016 , 7 , 741 ). Here, to further elucidate the anionic and cationic headgroup effects on water, we study vibrational dynamics of water on lipid multibilayers formed by anionic phospho-glycerol lipid molecules as well as by cationic choline-derivatized lipid molecules. We observed two significantly different vibrational lifetime components (very fast 0.5 ps and slow 1.9 ps) of the OD stretch mode of HOD molecules at the negatively charged phospho-lipid multibilayer whereas only one vibrational lifetime component (1.6 ps) was observed at the positively charged choline-derivatized lipid multibilayer. From the detailed analyses about the vibrational energy and rotational relaxations of HOD molecules in lipid multibilayers composed of anionic lipid with phosphate and cationic lipid without phosphate, the role of phosphate group in structuring water molecules at phospholipid membrane interface is revealed.
authors.affiliation: Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Korea University , Seoul 02841, Republic of Korea.|Department of Chemistry, Korea University , Seoul 02841, Republic of Korea.
authors.forename: Achintya
authors.initials: A
authors.lastname: Kundu
authors.affiliation: Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Korea University , Seoul 02841, Republic of Korea.|Department of Chemistry, Korea University , Seoul 02841, Republic of Korea.
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Kwak
authors.affiliation: Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Korea University , Seoul 02841, Republic of Korea.|Department of Chemistry, Korea University , Seoul 02841, Republic of Korea.
authors.forename: Minhaeng
authors.initials: M
authors.lastname: Cho
mesh_terms: D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D000838:Anions; D002412:Cations; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D014867:Water