The assignment of the 1H nuclear magnetic resonance (n.m.r.) spectrum of the trypsin inhibitor homologue K from the venom of Dendroaspis polylepis polylepis is described and documented. The assignments are based entirely on the amino acid sequence and on 2-dimensional n.m.r. experiments at 360 and 500 M Hz. Individual assignments were obtained for the backbone and C beta protons of all 57 residues of the inhibitor homologue K, with the exceptions of the N-terminal amino group, the amide protons of Arg16, Gly37 and Gly40 and the C beta protons of Arg16 and Pro19. The assignments for the non-labile protons of the amino acid side-chains are complete, with the exception of Gln29, Glu49 and all the proline, lysine and arginine residues. For Asn and Trp the labile side-chain protons have also been assigned. The chemical shifts for the assigned resonances are listed for an aqueous solution at 50 degrees C and pH 3.4.
The I3C-NMR. in Zn(I1) (Porphin), Fe(III)(Porphin)(CN,), Zn(II)(Tetraphenylporphin), and Fe(1II) (Tetraphenylporphin) (CN,) have been identified, and the lSC hyperfinc shifts in the iron complexes evaluated. It was found that dipole-dipole coupling with the electron spin localized in the n-orbitals of the aromatic carbon atoms makes an important contribution to the 13C hyperfine shifts. I n a preliminary analysis the experimental spin density distribution obtained from the combined IH-and W-NMR.-data is compared with theoretical models of the iron porphyrin complexes.
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