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. 2016 Aug 23;5:e17505. doi: 10.7554/eLife.17505

Figure 2. Free energy landscape of the L99A variant of T4L.

In the upper panel, we show the projection of the free energy along Spath, representing the Boltzmann distribution of the force field employed along the reference path. Differently colored lines represent the free energy profiles obtained at different stages of the simulation, whose total length was 667ns. As the simulation progressed, we rapidly found two distinct free energy basins, and the free energy profile was essentially constant during the last 100 ns of the simulation. Free energy basins around Spath=0.2 and Spath=0.75 correspond to the previously determined structures of the G- and E-state, respectively (labelled by red and blue dots, respectively). As discussed further below, the E-state is relatively broad and is here indicated by the thick, dark line with Spath ranging from 0.55 to 0.83. In the lower panel, we show the three-dimensional negative free energy landscape, -F(Spath, Zpath), that reveals a more complex and rough landscape with multiple free energy minima, corresponding to mountains in the negative free energy landscape. An intermediate-state basin around Spath=0.36 and Zpath=0.05 nm2, which we denote I0.36, is labeled by a yellow dot.

DOI: http://dx.doi.org/10.7554/eLife.17505.004

Figure 2.

Figure 2—figure supplement 1. Approximately equidistant frames along the reference path.

Figure 2—figure supplement 1.

The plot reveals a ‘gullwing’ shape of the matrix of pairwise RMSDs of the frames of the reference path, indicating that frames along the reference path are approximately equidistant. We used 31 structures to discretize the path.
Figure 2—figure supplement 2. One and two dimensional free energy landscape of L99A and the triple mutant.

Figure 2—figure supplement 2.

(A) The two-dimensional free energy surface F(Spath,Zpath) of L99A sampled by a 667 ns PathMetaD simulation. (B) The two-dimensional free energy surface F(Spath,Zpath) of the triple mutant sampled by a 961 ns PathMetaD simulation. (C) The free energy profiles as a function of Spath of both L99A (black) and the triple mutant (blue).