Influence of the curvature on the water structure in the headgroup region of phospholipid bilayer studied by the solvent relaxation technique.
Solvent relaxation (SR) in 1,2-dioleoyl-palmitoyl-sn-glycero-3-phosphocholine (DOPC) unilamellar vesicles of different size was probed by 6-hexadecanoyl-2-(((2-(trimethylammonium)ethyl)methyl)amino)naphthalene chloride (Patman), 6-propionyl-2-dimethylaminonaphthalene (Prodan) and 4-[(n-dodecylthio)methyl]-7-(N,N-dimethylamino)-coumarin (DTMAC). Patman probes the amount and mobility of the bound water molecules located at the carbonyl region of the bilayer. Membrane curvature significantly accelerates the solvent relaxation process, but does not influence the total Stokes shift, showing that membrane curvature increases the mobility, without affecting the amount of water molecules present in the headgroup region. This pattern was also verified for other phosphatidylcholines. Prodan is located in the phosphate region of the bilayer and probes a more polar, mobile and heterogeneous environment than Patman. The influence of membrane curvature on SR probed by Prodan is similar, however, less pronounced compared to Patman. DTMAC (first time used in SR) shows a broad distribution of locations along the z-axis. A substantial amount of the coumarin chromophores face bulk water. No effect of curvature on SR probed by DTMAC is detectable.
Sýkora
Jan
J
J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 3, CZ-18223 Prague 8, Czech Republic.
Jurkiewicz
Piotr
P
Epand
Richard M
RM
Kraayenhof
Ruud
R
Langner
Marek
M
Hof
Martin
M
D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D015335:Molecular Probes; D010713:Phosphatidylcholines; D010743:Phospholipids / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry*
D008051:Lipid Bilayers; D008081:Liposomes; D015335:Molecular Probes; D010713:Phosphatidylcholines; D010743:Phospholipids; D014867:Water; C017251:1,2-oleoylphosphatidylcholine