Deuterium NMR relaxation studies of peptide-lipid interactions

Abstract

A unique model membrane system composed of a synthetic amphiphilic peptide (Lys2-Gly-Leu16-Lys2-Ala-amide) and a specifically labeled phospholipid (1,2-[7,7-2H2]dipalmitoyl-sn-glycero-3-phosphocholine) has been studied by 2H NMR, using inversion recovery, quadrupolar echo, and modified Jeener-Broekaert sequences, from 213 to 333 K, at molar peptide concentrations of 0, 2, 4, and 6%. Analysis of the experiments, employing a density matrix treatment based on the stochastic Liouville equation, revealed information about the dynamic organization of the lipid in the model membrane system, whose phase behavior has been determined previously [Huschilt et al. (1985) Biochemistry 24, 1377-1386]. The dynamic organization is described in terms of segmental and molecular order parameters and in terms of correlation times corresponding to both internal and overall lipid motions. In the liquid crystalline phase, the molecular order parameter, SZZ, was observed to decrease slightly upon addition of peptide while the conformational order parameter corresponding to the seventh segment, SZ'Z', did not change for any concentration of peptide. In general, the gauche-trans isomerization rate in the middle of the chain was not observed to change upon peptide addition, whereas the whole body reorientational correlation times (tau R parallel and tau R perpendicular) increased by nearly an order of magnitude. The anisotropy ratio (tau R perpendicular/tau R parallel) decreased with peptide added. An additional motion which involves a jump about the axis of the sn-2 chain is also observed to be slowed down significantly in the presence of peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Order Parameters of a Transmembrane Helix in a Fluid Bilayer: Case Study of a WALP Peptide

“…For the uniform distribution, the values t 0 ¼ 20.8 and Dt ¼ 12.2 translate into S helix angle ¼ 0.81, S helix order ¼ 0.97, and S helix ¼ 0.78. This value of S helix order is significantly higher than the molecular order parameter S zz of a DPPC (53) or DMPC (54) lipid in the fluid phase, which is around 0.6. This is not surprising considering that the peptide is anchored on both sides of the bilayer, whereas the lipid molecules extend over only half of the bilayer.…”

Effects of amantadine on the dynamics of membrane-bound influenza A M2 transmembrane peptide studied by NMR relaxation

“…Membrane proteins can also undergo such rotational diffusion, because the same principle that underlies the phospholipid motion, which is Brownian diffusion in a two-dimensional fluid (Saffman and Delbruck, 1975), also applies to membrane proteins. A number of examples of this uniaxial diffusion have now been reported for membrane peptides and proteins (Hong, 2007, Hong and Doherty, 2006, Lewis et al, 1985, Macdonald and Seelig, 1988, Pauls et al, 1985, Prosser et al, 1992, Tian et al, 1998, Yamaguchi et al, 2001). Their NMR fingerprints include powder lineshapes with reduced anisotropy and an asymmetry parameter (η) of 0, vanishing intensity at the isotropic chemical shift of non-spinning cross polarization (CP) spectra, and narrow lines in macroscopically aligned samples whose alignment axis deviates from the static magnetic field (Aisenbrey and Bechinger, 2004, Glaser et al, 2004, Park et al, 2006).…”

Magic angle spinning and static oriented sample NMR studies of the relaxation in the rotating frame of membrane peptides

“…[25][26][27][28][29][30] They are further subjected to slower scale off-axis reorientational motions on the order of microseconds to milliseconds due to single molecule "wobble" or collective membrane undulations. Unlike species in solution, components of these phases are unable to reorient isotropically.…”