Fig. 4.

The probability of loop closure as a function of the arc length. The probability of loop closure was plotted as a function of protofibril length, based on theory of semiflexible polymers. The y-axis reports the ratio of the opening and closing rates. Blue data points are experimental ratios of open:closed for the in vitro protofibrils. The blue line is a fit from Eq. 4. As the arc length increases, so does the likelihood of finding a protofibril in a closed-loop conformation. Above a certain length, the likelihood decreases again as the probability of two open-chain ends finding each other decreases.