The temperature and hydration dependences of lipid lateral diffusion in model membrane-D20 multilayers of dipalmitoyl (DPL), dimyristoyl (DML), dilauryl (DLL), and egg yolk (EYPC) lecithins were measured by using pulsed gradient proton NMR spin-echo techniques. Oriented samples were used to minimize anisotropic dipolar interactions and permit formation of a spin-echo. A general discussion of the technique and of the possible errors is included. Significantly lipid lateral diffusion is hydration dependent over the range studied (1 5-40% D20, w/w), varying in DPL over this range, for example, by a factor of 2. For the saturated lipids at the same hydration and temperature, diffusion decreases monotonically as the chain length increases. At a constant hydration of 200h D 2 0 (w/w), the activation energies (kcal/mol)

Constant gradient and pulsed gradient NMR spin echo methods have been used to measure the diffusion constant of potassium oleate in the lamellar phase. Oriented samples were employed and yielded a mean value of ?1×10−6 cm2/sec at 29 °C for the diffusion constant parallel to the lamellar surface.

Jones. M. 0.: Zanianchi. M. A. /bid. 1979. 56. 215. 1540. Harada, I.; Takeuchi, H.; Sakakibara, M.: Matsuura, H.; Shimanouchi, T.Abstract: Combined N M R multiple pulse homonuclear decoupling and multiple pulse gradient techniques have been used to determine the self-diffusion coefficients at 25 "C of the phospholipids in the Lg'(gel) phase of L-a-dipalmitoylphosphatidylcholine in a 15% (w/w) D20 model membrane and of potassium oleate in a 30% (w/w) D2O lamellar phase (above the phase transition). The values found, 1.6 X cm2 s-I, respectively, are considered in reasonable agreement with values obtained by other investigators using fluorescence photobleaching recovery. The technique has the advantage that it monitors lipid protons and hence avoids possible complications of added probes. The use and limitations of the method are discussed, and the values found for diffusion are compared with those determined or estimated by other methods. and 1.3 X

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Proton spin–lattice relaxation times (T1) have been measured in methyl deuterated para-azoxyanisole (PAA-d6) and in ring deuterated para-azoxyanisole (PAA-d8) samples as functions of frequency and temperature. When compared with recent order fluctuation theory, the agreement between theory and experiment is not as satisfactory for the intermolecular contribution to the spin–lattice relaxation as for the intramolecular contribution. Deuteron spin–lattice relaxation times (T1Q) have also been measured in a ring deuterated p-methoxybenzylidene p-n-butylaniline (MBBA-d8) sample. The above order fluctuation theory fails to predict the observed temperature dependence and the observed frequency independence of T1Q if the correlation time τc for local motions is taken to be one-third the dielectric relaxation time τD. However, a fair agreement is obtained if one uses τc= (1/100) τD, a value consistent with Ref. 6.