Local conformational dynamics in α-helices measured by fast triplet transfer

• DOI: 10.1073/pnas.0808581106
• Publication Date: 2009-01-09T02:10:29Z
• Authors: Beat Fierz; Andreas Reiner; Thomas Kiefhaber
• Keywords: Helix (gastropod); Microsecond; Nanosecond

Coupling fast triplet-triplet energy transfer (TTET) between xanthone and naphthylalanine to the helix-coil equilibrium in alanine-based peptides allowed observation of local fluctuations alpha-helices on nanoseconds microseconds time scale. The experiments revealed faster helix unfolding terminal regions compared with central parts constants varying from 250 ns 1.4 micros at 5 degrees C. Local formation occurs a constant approximately 400 ns, independent position helix. Comparing experimental data simulations using kinetic Ising model showed that experimentally observed dynamics can be explained by 1-dimensional boundary diffusion position-independent elementary 50 for addition 65 removal an alpha-helical segment. growth agrees well previously measured short loops unfolded polypeptide chains, suggesting elongation is mainly limited conformational search.