Methionine enkephalin, rotational

Rotational correlation times obtained from the observed C Ti values of the glycyl residues in methionine enkephalin as a function of "pH" are given in Figure 6. The 3-glycyl residue... 

Bleich HE, Day AR, Ereer RJ, Glasel JA (1979) NMR rotating frame relaxation studies of intramolecular motion in peptides. Tyrosine ring motion in methionine-enkephalin. Biochem Biophys Res Commun 87 1146-1153... 

The optimal correlation times for overall molecular reorlenta-tlon (t i) of methionine-enkephalin were determined for rotational diffusion about the principal axes (A, B, C In Figure 2) of the moment of Inertia tensor t = 3.2 x 10" >, t = 1.7 x 10 and t = 9.9 x 10 sec rad. They are Independent of any physically reasonable starting values for Xy or x, and Insensitive to the molecular conformation chosen for trie least-squares fitting (Tancrbde et al. 1978). The optimal values of the correlation times for Internal motion (xj t) which will reproduce the observed Ti values of the side chains are shown In Table 2. The least-squares fit was performed using a folded conformation of enkephalin with optimal correlation times for overall molecular motion of % = x = 2.4 x 10" , x = 9.9 x 10 sec rad. The former two values are averaged because the computer program used In these calculations assumes that the overall motion of the molecule has at least cylindrical symmetry (Deslaurlers and Somorjal, 1976). 

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