Figure 4: Force field choice has a significant impact on the level of agreement between simulations and experiments on IDPs even when accounting for time averaging.

A) FRET efficiencies for Aβ40 labeled at positions 1 and 40 with Alexa 488 and Alexa 647 in different force fields. In each trace, the black line represents the experimental smFRET result, individual force field and water combinations indicated in the legend below the column. B) FRET efficiency distributions for T4-lysozyme residues 44 and 150 in amber03 with TIP3P water (purple) or charmm36m with TIP3P water (orange) or the experimental result (black). Experimental donor only counts (E < 0.25) have been removed for ease of comparison.