Shielding tensors alanines

Figure 7. 13CP alanine shielding tensor results. A, 11 Tesla 13C CP-MAS NMR spectrum of crystalline ala-[l3C]ala-ala,vr =1.2 kHz. B, graph showing experimental shift tensor elements versus computed shieldings slope = 1.07, R2 = 0.99. 

Figure 4. (A) A tensor plot of the C shielding in alanine with sheet dihedral angles ( - -60°, ij/ = -60°). (Reproduced with permission from ref. 18. Copyright 1997 American Chemical Society.)...

Fig. 4. Orientation of the shielding tensor elements in the molecular frame on alanyl-alanine, cTn lies essentially in the plane of the peptide linkage as do the N-H, N-Ca,...

According to recent work by Oas et a/.36,37 the alignment of the 15N shielding tensors of L-[l-13C]-alanyl-L-[15N]-alanine has been determined from the... 

While the Ur — 2uj DQ-HORROR condition selectively recouples dipolar interactions, the homonuclear rotary resonance condition = leads to single-quantum and double-quantum recoupling, including recoupling of CSA. Accordingly, the homonuclear n = I condition with Wr = has also been called MSD-HORROR (mixed single- and double quantum HORROR) " and has been employed to determine the orientation of the two C chemical shielding tensors in 2,3- C2-labelled L-alanine. However, the homonuclear resonance condition simultaneously represents a heteronuclear n = 1... 

Fig. 6, Dependence of the chemical shielding on the dihedral angles (, for C" carbons of L-alanine in peptides. The chemical shieldings are calculated with the Gl AO-CHE method using a 4-3IG basis set. The geometry of TV-acetyl-TV -methyl L-alanine amide was optimized on the 4-31G HE level. The different panels show (a) the isotropic value, as well as the tensor components, (b) cth, (c) 022, and (d) 0 33 (adapted from Asakawa et al. with permission of the authors).

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