Application io 0 n c h r to the amide group the

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Unformatted text preview: ibrous IZ of synthetic polypeptides. Moreover, ani.23 we have studied. A letter the The Nobel Prize in and globular proteins, as well as resonance Chemistry 1954 "for his nouncing their discovery was published last year. ' theory is now so well The problem that weCV/ have set ourselves is that and its experimental subgrounded of finding all hydrogenresearch into the nature of bonded structures for a single polypeptide chain, in so extensive that there 1o stantiation which the residues are H N 120° can be no doubt whatever about its the chemical bond and its 120O application to the elucidation of the structure of complex substances". application io 0 N C° H R to the amide group. The observed C-N distance, 1.32 iA, corresponds to nearly 50 per cent double-bond character, and we may conclude that rotation by as much as 100 from the planar configuration would result in instability by about 1 kcal. mole-'. The interatomic PepCde Bond: Cis ­Trans IsomerizaCon •  Cα carbons on same (cis) or opposite (trans) sides of “double” bond (pepCde bond) •  Trans configuraCon highly favored (steric) ≈ 99% R group Cα Cα Cα Cα R group •  ExcepCon: X ­Pro (pepCde bonds preceding Pro residues), some of which are cis… why? Berg et al., Fig. 2-24 94% 6% Backbone torsion/dihedral angles •  PolypepCde backbones can be described by their “torsion angles” or “dihedral angles” – ...
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