(577i) Tensile Mechanics of Helical Polypeptides

Torabi, K., Northwestern University
Schatz, G. C., Northwestern University

Helices are amongst the most abundant secondary structures found in proteins. Here we report a thermodynamical model for helix-coil transition of polypeptides under mechanical tension. The proposed algorithm incorporates the empirical-based helix-coil algorithm of AGADIR [Viguera et al. J. Mol. Biol. 284, 173-191 (1998)] with the “partially freely rotating chain model” of random coil peptides [Hanke et al. EPL 92, 53001 (2010)]. Our model estimates the equilibrium value of overall and residue based helicity of a given polypeptide sequence under a given tensile force. Due to good agreement of the helix-coil algorithm AGADIR with numerous experimental data, this model is capable of making quantitative predictions of single molecule manipulations of helical peptides. The potential of mean force generated by the model elucidates the highly elastic characteristic of helical polypeptides as opposed to energy dissipative forced-unfolding of the tertiary structure of the proteins. We explains why nature chooses helical structures in certain domains of biological molecular machines where highly elastic feature of these structures avoids a large amount of energy dissipations and lead to higher energy efficiencies.