Extended helical conformation newly observed in protein folding

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Science  12 Nov 1976:
Vol. 194, Issue 4266, pp. 720-722
DOI: 10.1126/science.982035


A new secondary structure, which shows regularity within the experimental error, is noticed in alpha-chymotrypsin, and considering its extended nature, the name epsilon-helix has been suggested for the same. The average observed values of phi and psi for this conformation are -93 degrees and +146 degrees, respectively. The helical parameters turn out to be n = 2.7 and h = 3.3 angstroms.