  Simulations of protein folding and protein association happen on timescales
that are orders of magnitude larger than what can typically be covered in
all-atom molecular dynamics simulations. Use of low-resolution models
alleviates this problem but may reduce the accuracy of the simulations. We
introduce a replica-exchange-based multiscale sampling technique that combines
the faster sampling in coarse-grained simulations with the potentially higher
accuracy of all-atom simulations. After testing the efficiency of our
Resolution Exchange with Tunneling (ResET) in simulations of the Trp-cage
protein, an often used model to evaluate sampling techniques in protein
simulations, we use our approach to compare the landscape of wild type and A2T
mutant Abeta 1-42 peptides. Our results suggest a mechanism by that the
mutation of a small hydrophobic Alanine (A) into a bulky polar Threonine (T)
may interfere with the self-assembly of Abeta - fibrils.
