Small-angle neutron scattering study of the lipid bilayer thickness in unilamellar dioleoylphosphatidylcholine vesicles prepared by the cholate dilution method: n-decane effect.
Previous X-ray diffraction studies on fully hydrated fluid lamellar egg phosphatidylcholine phases indicated a approximately 10 A increase of bilayer thickness in the presence of excess n-decane [Biochim. Biophys. Acta 597 (1980) 455], while the small-angle neutron scattering (SANS) on unilamellar extruded dioleoylphosphatidylcholine (DOPC) vesicles detected substantially smaller 2.4+/-1.3 A bilayer thickness increase at n-decane/DOPC molar ratio of 1.2 [Biophys. Chem. 88 (2000) 165]. The purpose of the present study is to investigate the n-decane effect on the bilayer thickness in unilamellar DOPC vesicles prepared by the sodium cholate (NaChol) dilution method. Mixed DOPC+NaChol micelles at DOPC and NaChol concentrations of 0.1 mol/l were prepared in 2H(2)O containing 0.135 mol/l NaCl. This micellar solution was diluted in 0.135 mol/l NaCl in 2H(2)O to reach the final DOPC and NaChol concentrations of 0.008 mol/l. Thirty microliters of n-decane solution in methanol was added to 1 ml of this dispersion. After methanol evaporation, SANS was conducted on the dispersions. From the Kratky-Porod plot ln[I(Q)Q(2)] vs. Q(2) of SANS intensity I(Q) in the range of scattering vector values Q corresponding to interval 0.001 A(-2)<or=Q(2)<or=0.006 A(-2), the bilayer radius of gyration R(g) and the bilayer thickness parameter d(g)=12(0.5)R(g) were obtained. The values of d(g) indicate that the bilayer thickness increases by 2.4+/-0.9 A up to n-decane/DOPC molar ratio of 1.6. This result confirms the previous SANS findings obtained with extruded vesicles.
Uhríková
Daniela
D
Department of Physical Chemistry, Faculty of Pharmacy, J A Comenius University, Odbojárov 10, 83232 Bratislava, Slovakia.
Kucerka
Norbert
N
Islamov
Akhmed
A
Kuklin
Alexander
A
Gordeliy
Valentin
V
Balgavý
Pavol
P
D000473:Alkanes / Q000737:chemistry*; D017301:Ca(2+) Mg(2+)-ATPase / Q000737:chemistry; D017666:Deuterium Oxide; D008051:Lipid Bilayers / Q000737:chemistry*; D008433:Mathematics; D033363:Neutron Diffraction / Q000379:methods; D010713:Phosphatidylcholines / Q000737:chemistry*; D011865:Radioisotope Dilution Technique; D020358:Sodium Cholate
D000473:Alkanes; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D017301:Ca(2+) Mg(2+)-ATPase; C017251:1,2-oleoylphosphatidylcholine; D017666:Deuterium Oxide; C012867:decane; D020358:Sodium Cholate