Determination of membrane immersion depth with O-2: A high-pressure F-19 NMR study
Biophysics; cholesterol; conformational-changes; dynamics; lipid bilayers; micelles; nuclear magnetic-resonance; phospholipid-bilayers; protein-structure; solid-state nmr; x-ray-diffraction
Oxygen is known to partition with an increasing concentration gradient toward the hydrophobic membrane interior. At partial pressures (P-O2) of 100 Atm or more, this concentration gradient is sufficient to induce paramagnetic effects that depend sensitively on membrane immersion depth. This effect is demonstrated for the fluorine nucleus by depth-dependent: paramagnetic shifts and spin-lattice relaxation rates, using a fluorinated detergent, CF3(CF2)(5)C2H4-O-maltose (TFOM), reconstituted into a lipid bilayer model membrane system, To interpret the spin-lattice relaxation rates (R-1(P)) in terms of a precise immersion depth, two specifically fluorinated cholesterol species (6-fluorocholesterol and 25-fluorocholesterol), whose membrane immersion depths were independently estimated, were studied by F-19 NMR. The paramagnetic relaxation rates, R-1(P), of the cholesterol species were then used to parameterize a Gaussian profile that directly relates R-1(P) to immersion depth z.: This same Gaussian curve could then be used to determine the membrane immersion depth of all six fluorinated chain positions of TFOM and of two adjacent residues of specifically fluorinated analogs of the antibacterial peptide indolicidin. The potential of this method for determination of immersion depth and topology of membrane proteins is discussed.
Prosser R S; Luchette P A; Westerman P W; Rozek A; Hancock R E W
Biophysical Journal
2001
2001-03
Journal Article
<a href="http://doi.org/10.1016/s0006-3495(01)76113-9" target="_blank" rel="noreferrer noopener">10.1016/s0006-3495(01)76113-9</a>
On the stability of the ripple phase in the DPPC/PLPC/water ternary system
Biophysics; Biochemistry & Molecular Biology; gel; cholesterol; lysolecithin; membranes; nuclear-magnetic-resonance; water; transition; lipid bilayers; phospholipid-bilayers; Lipids; differential scanning calorimetry (DSC); lecithin; phosphatidylcholine; phosphatidylcholine bilayers; pretransition; scanning dilatometry (SD)
The effect of incorporation of 1-palmitoyl-sn-glycero-3-phosphocholine (PLPC) on the structure of the P-beta' ripple mesophase in aqueous dispersions of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) has been studied by differential scanning calorimetry (DSC) and scanning dilatometry (SD). For samples containing 34 wt. % (H2O)-H-2 and 0-15 wt. % PLPC, a pretransition was observed by DSC. The pretransition disappears at 15 wt. % PLPC. The behavior of thermodynamic functions at the pretransition and main transition gives new insights on the structural changes produced by PLPC on bilayers of DPPC. (C) 1997 Elsevier Science Ireland Ltd.
Checchetti A; Chidichimo G; Golemme A; Grasso D; Imbardelli D; LaRosa C; Nicoletta F P; Westerman P W
Chemistry and Physics of Lipids
1997
1997-11
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1016/s0009-3084(97)00086-8" target="_blank" rel="noreferrer noopener">10.1016/s0009-3084(97)00086-8</a>