American Chemical Society
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Comparison of Fully Optimized α- and 310-Helices with Extended β-Strands. An ONIOM Density Functional Theory Study

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journal contribution
posted on 2004-11-03, 00:00 authored by Robert Wieczorek, J. J. Dannenberg
We compare the structures and energies of β-strands, α-helices, and 310-helices for capped polyalanines, acetyl(ala)NNH2, for values of N from 2 to 18, using completely optimized mixed DFT/AM1 calculations. Non-pairwise additive cooperativity is manifest from the variation of the relative energies, helical strain, dipole moments, and H-bond lengths of both types of helices, but especially for the α-helices. While the gas-phase 310-helices are more stable for small polyalanines, largely due to the additional H-bond, the α-helices become relatively more stable as the polyalanines increase in size.