Contribution of the first twenty PCA eigenvectors to the overall closing motion of the PSI.

<p>The contribution of the first 20 PCA eigenvectors to the closing motion of the PSI at active (<b>A</b>) and inactive (<b>B</b>) pH are presented. The first eigenvectors contribute 78.8% and 74.2% of the overall motions for the pH 4.5 and pH 7.4 simulations, respectively, and correspond to the collapse of helices α1/α2 onto helices α3/α4.