Wobbling motion, chains

Rotational Motion of the Chains (Wobbling Motion of the Chains) and of the Headgroup... 

Figure 9.5 Schematic presentation of a wobbling motion of alkyl chain and the rotational...

Table 9.1 A comparison of dynamical properties of lipids. Relaxation times of the wobbling motion of the hydrophobic chain and the rotational motion of the headgroup (PN vector) and lateral diffusion coefficient, D.

A successful MOMD model for analyzing ESR line shapes for spin-labeled polymers was introduced by Meirovitch et al. This model, mentioned in Section 3.3, allows for constraints in the rotational diffusion. More precisely, the polymer chain segmental motion sensed by the tethered nitroxide, that is, the wobbling motion of the effective axis of internal rotation, was considered as constrained by an orienting potential, typically given by Eq. 3,... 

Two other possible segmental motions not depicted in Fig. 6 are in distinctly different time realms. At the slow end of the time scale (greater than milliseconds for reasonable amplitudes) are the Rouse-Zimm normal coordinate modes that result from the collective behavior of units of atoms (beads) along the chain pulling one another and acted on by Brownian forces, solvent frictional resistance, and other parts of the chain (Berne and Pecora, 1976). Librational motions, generally accorded to be of the order of 10 s , may also result from the thermally induced displacements of groups of atoms such wobbling motions have been proposed as important factors in the NMR relaxation of proteins (Howarth, 1979). 

In the membrane lipid alkyl chains of n-SASL and n-PC spin labels undergo rapid rotational motion about the long axis of the spin label and wobble within the confines of a cone imposed by the... 

The observation that r(t) decays to the finite value rro soon led to the recognition that the fluorophore DPH has an orientational motion which is restricted due to the surrounding lipid chains/35-37 From this the wobbling-in-cone model(37 43 44) was developed. In this model, DPH was assumed to wobble within a cone of half angle 6C (which relates to the degree of orientational constraint, order, or rm) with a wobbling diffusion constant D (which relates to the rate of motion) with... 

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