Nuclear magnetic resonance line shapes in lipid bi-layer model membranes

NMR Studies of Membrane Structure and Dynamics

“…A third contribution to the linewidth arises from spinlattice relaxation, but, since (lffz) >> (1~) for anisotropie motion, it can be ignored. Note that in the absence of chain reorientation relative to the director, the PetersenChan linewidth expression reduces to 4 (3~h) which is identical to expressions commonly used to calculate linewidths in sonicated vesicles (54).…”

“…Finer and co-workers (64-66), Bloom et al (54), and more recently Wennerstr6m & Ulmius (67), and Stockton et al (24) have interpreted the linewidth reduction as an effect of the rapid overall isotropic tumbling of the vesicles. Bloom et al (54), and Wennerstr6m & Ulmius (67) have, in fact, derived theoretical expressions for vesicle lineshapes.…”

“…Finer and co-workers (64-66), Bloom et al (54), and more recently Wennerstr6m & Ulmius (67), and Stockton et al (24) have interpreted the linewidth reduction as an effect of the rapid overall isotropic tumbling of the vesicles. Bloom et al (54), and Wennerstr6m & Ulmius (67) have, in fact, derived theoretical expressions for vesicle lineshapes. On the other hand, Chan and co-workers (17,18,44,68,69), and Horowitz et al (70) have argued that overall www.annualreviews.org/aronline Annual Reviews tumbling is too slow to produce the narrow resonances observed in vesicle spectra, and that the narrow lines occur as a result of additional disruption in the bilayer order caused by the extreme surface curvature in the vesicles.…”

“…Chart et al (50) showed that these interpretations were incorrect and that the origin of the observed band shape is the incomplete averaging of static dipolar interactions present in the anisotropic phase. A number of attempts have been made to determine theoretical expressions for the complex lineshapes observed for amphiphilic molecules in the liquid crystalline state (14,18,(51)(52)(53)(54)(55). All of these treatments argue that, in addition to incomplete averaging of static dipolar interactions, effective axial symmetry about the bilayer normal is necessary for the observation of the super-Lorentzian band shape.…”

Lateral diffusion rates of phosphatidylcholine in vesicle membranes: Eeffects of cholesterol and hydrocarbon phase transitions

“…They are attractive systems for the application of 31P-NMR techniques as the rapid re-orientations of the phospholipid molecules in such systems give rise to high resolution spectra [8][9][10][11]. This isotropic motion arises from two sources, namely rapid rotation (tumbling) of the entire vesicle, or lateral diffusion of the lipids around the inner and outer monolayers of the vesicle [12]. In the case of 31P-NMR these mechanisms both modulate the two line broadening interactions ~xperienced by the phosphate phosphorus, which are the chemical shift anisotropy [9] and the dipolar interactions with the two nearest neighbour methylene groups.…”