화학공학소재연구정보센터
Journal of the American Chemical Society, Vol.133, No.42, 17072-17086, 2011
Structural Dynamics of Free Proteins in Diffraction
Among the macromolecular patterns of biological significance, right-handed alpha-helices are perhaps the most abundant structural motifs. Here, guided by experimental findings, we discuss both ultrafast initial steps and longer-time-scale structural dynamics of helix-coil transitions induced by a range of temperature jumps in large, isolated macromolecular ensembles of an alpha-helical protein segment thymosin beta(9) (T beta(9)), and elucidate the comprehensive picture of (un)folding. In continuation of an earlier theoretical work from this laboratory that utilized a simplistic structure-scrambling algorithm combined with a variety of self-avoidance thresholds to approximately model helix-coil transitions in T beta(9), in the present contribution we focus on the actual dynamics of unfolding as obtained from massively distributed ensemble-convergent MD simulations which provide an unprecedented scope of information on the nature of transient macromolecular structures, and with atomic-scale spatiotemporal resolution. In addition to the use of radial distribution functions of ultrafast electron diffraction (UED) simulations in gaining an insight into the elementary steps of conformational interconversions, we also investigate the structural dynamics of the protein via the native (alpha-helical) hydrogen bonding contact metric which is an intuitive coarse graining approach. Importantly, the decay of alpha-helical motifs and the (globular) conformational annealing in T beta(9) occur consecutively or competitively, depending on the magnitude of temperature jump.