Nuclear magnetic resonance line-shape analysis of fluorine-19-labeled phospholipids

Abstract

The application of a fluorine-19 probe to the problem of motions present in the hydrophobic region of phospholipid dispersions and biological membranes has been extended to the study of phospholipids labeled with fluorine-19 in the 8 position and with deuterium in the 2, 7, and 9 positions of the 2-acyl chain. 1-Myristoyl-2-(8,8-difluoro[2,2,7,7,9,9-2H6]myristoyl)-sn-glycero-3- phosphocholine and its nondeuterated analogue have been investigated by 19F nuclear magnetic resonance at 282.4 MHz. Spectra obtained from macroscopically oriented bilayers exhibit Pake doublets from which order parameters can be obtained. The spectra obtained from nonoriented liposomes of the phospholipids can be explained in a satisfactory manner as a random superposition of doublets broadened by heteronuclear magnetic dipole-dipole interactions. From an analysis of the data, several conclusions about the motional state of the hydrocarbon chains in the liquid-crystalline phase can be drawn. The present results show that appropriate fluorine-19 probes in the acyl chains of phospholipids can be used to investigate the structure and dynamics of model and biological membranes.

Structural Parameters from19F Homonuclear Dipolar Couplings, Obtained by Multipulse Solid-State NMR on Static and Oriented Systems

“…The splitting of ⌬ FF ϭ 3.1 kHz at the high-field edge compares well (within 7%) with the dipolar coupling reported by Ho et al on the same compound and at the same temperature (8). In these earlier studies, which were performed at 282 MHz without 1 H-decoupling, the 19 F- 19 F coupling had to be extracted from the unresolved spectrum by lineshape deconvolution (25).…”

“…A CF 2 -group that is rigid on the NMR time scale would give rise to a splitting of ⌬ 0 ϭ 15.4 kHz in the powder spectrum (8,25). The reduced value of 3.1 kHz measured here is due to the long-axial rotation and further chain fluctuations of the lipid molecule, which are described by an order parameter S FF ϭ ⌬ FF /⌬ 0 .…”

“…, which carries two geminal fluorine labels in one chain, was a gift from Chien Ho, Carnegie Mellon University of Pittsburgh (8,25,26). The doubly fluorinated sterol diflucortolon-21-valerate (DFC) was a gift from Schering AG, Berlin.…”

“…The technique used in this study to measure the dipolar coupling is based on the CPMG sequence (32,33), which has already been successfully applied to determine internuclear distances and to evaluate motionally averaged order parameters (23,24,26,34,35). Oriented samples of fluorinated lipid bilayers have also been used previously for solid-state NMR investigations (25). However, to our knowledge measurements of homonuclear dipolar couplings have not yet been combined with oriented systems.…”

Orientation of the antimicrobial peptide PGLa in lipid membranes determined from 19F-NMR dipolar couplings of 4-CF3-phenylglycine labels

“…Whether the CF 3 -group rotates or undergoes 120°j umps or anything in between, does not make a difference. We had previously measured the maximum splitting D 0 CF 3 within a related aromatic CF 3 -group to be about 16 kHz [11], and the corresponding dipolar splitting within a CF 2 -segment was reported as 15.5 kHz [17,18].…”