Stohrer, Juergen; Groebner, Gerhard; Reimer, Dirk; Weisz, Klaus; Mayer, Christian; Kothe, Gerd:

Collective lipid motions in bilayer membranes studied by transverse deuteron spin relaxation.

In: Journal of Chemical Physics (J.Chem.Phys.), Jg. 95 (1991) ; Nr. 1, S. 672-678
ISSN: 0021-9606
Zeitschriftenaufsatz / Fach: Chemie
The anisotropy and pulse frequency dispersion of the spin-spin relaxation time T2ECP from Carr-Purcell-Meiboom-Gill pulse sequences is employed to evaluate the major contribution to transverse 2H spin relaxation in bilayer membranes. Anal. of the expts. is achieved in terms of a d. operator formalism, employing the stochastic Liouville approach. From a comparison of the obsd. angular and frequency dependences of T2ECP with those predicted for order director fluctuations, collective lipid motions constitute the dominant transverse relaxation process. Computer simulation provide the viscoelastic parameters of the lipid membranes. For 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayers at T = 318 K, an av. elastic const. of K = 2 * 10-11 N and an effective viscosity of h = 0.1 P were detd. Using the exptl. accessible value for the long wavelength cutoff of the elastic modes, one obtains the mean square amplitude of the director fluctuations {q02} = 0.04. This corresponds to an order parameter of SOF = 0.94. Apparently, the contributions of the collective motions to the measured order parameters are marginal.