Sterols stabilize the ripple phase structure in dihexadecylphosphatidylcholine.
The presence of various sterols in mixtures with dihexadecylphosphatidylcholine (DHPC) was studied using static X-ray diffraction of temperature equilibrated samples, and real-time X-ray diffraction of samples undergoing temperature scans. It was found that these sterols eliminate the interdigitation of the alkyl chains in the DHPC sub-gel and gel-state bilayers while stabilizing the ripple gel-state at the expense of the gel-state bilayer phase. The ripple-ripple phase transition previously observed for dipalmitoylphosphatidylcholine in the presence of low molar concentrations of sterols (Wolfe et al. (1992) Phys. Rev. Lett. 68, 1085-1088) was also observed for similar DHPC-sterol mixtures. In addition, we show the first evidence that the presence of 5 alpha-cholestane-3 beta,5,6 beta-triol will cause the lipid mixtures to continue to adopt a ripple mesophase structure even after the DHPC alkyl chain becomes disordered.
Department of Physics, Bucknell University, Lewisburg, PA 17837.
B A
BA
Cunningham
L
L
Midmore
O
O
Kucuk
L J
LJ
Lis
M P
MP
Westerman
W
W
Bras
D H
DH
Wolfe
P J
PJ
Quinn
S B
SB
Qadri
D002777:Cholestanols / Q000737:chemistry; D008051:Lipid Bilayers; D008968:Molecular Conformation; D010742:Phospholipid Ethers / Q000737:chemistry*; D013261:Sterols / Q000494:pharmacology*; D014961:X-Ray Diffraction
C052298:1,2-dihexadecyl-sn-glycero-3-phosphocholine; D002777:Cholestanols; D008051:Lipid Bilayers; D010742:Phospholipid Ethers; D013261:Sterols; C000474:cholestane-3,5,6-triol