The order-disorder transitions in grains and glasses, two widely different materials, occurring upon increasing temperature and external load, respectively, have common features. They lead to a universal jamming phase diagram conjecture, but unified theories are lacking, mainly because of the disparate nature of the particle interactions. In my talk I will discuss how the order-disorder transition in proteins exhibits signatures common to both glassiness and jamming by using molecular dynamics simulations. Ordered protein regions develop a peak in the interatomic force distributions that falls on a universal curve with experimentally measured forces on jammed grains and droplets. Dynamical signatures are found as a dramatic slowdown of stress relaxation upon folding, and a picture of the role of internal interactions emerges. Secondly, in my talk I will also discuss how NMR order parameters which measure motional disorder at the bond level, are affected by order-disorder transitions and I will link their motional change to a sea-to-lakes transition of the underlying free energy surface. Results have implications for designing stable polymers and can open avenues to unify protein folding and jamming theories.
Time-permitting, I will also discuss a trajectory reweighting method for Langevin dynamics based on Wiener stochastic path integrals yielding a formalism to obtain equilibrium entropy and enthalpy form non-equilibrium trajectories. In effect, this allows estimating temperature derivatives of Jarzynski-like (fluctuation theorem-based) free energies.
(1) P. P. Jose and I. Andricioaei, Nature Communications 3, 1161-1168 (2012)
(2) D. Jeong and I. Andricioaei, “Reconstructing equilibrium entropy and enthalpy profiles from non-equilibrium pulling,” J. Chem. Phys. 138, 114110 (2013)
Ioan Andricioaei was born in Romania. After finishing his bachelor’s studies in physics and biophysics from the A. I. Cuza University of Iasi, he pursued graduate studies at Boston University and completed his Ph.D. in 1999 under the supervision of Professor John Straub. He then worked as a postdoctoral fellow at Harvard with Nobel Laureate Martin Karplus. Andricioaei was then on the faculty at the University of Michigan, before moving to the University of California, Irvine in 2008, where is Professor of Chemistry and, by courtesy, of Physics. His research explores theoretical topics at the interface between molecular biophysics and physical chemistry.
Bi-Weekly Seminar Series by the NYU-ECNU Center for Computational Chemistry at NYU Shanghai