Figure 2.

`Sphere' model for the internal motion of a variable-length vector in a macromolecular system. (a) Diagram depicting the DIS model in which atoms 1 and 2 are uniformly distributed in two separate spheres. On the left, atom 2 is distributed in a sphere of radius RN; on the right, the case with RN = 0 is shown. (b) Relationship between the order parameter S2 for the variable-length vector and the ratio RP/R for the `Sphere' model (solid line, RN = 0; dotted line, RN/RP = 0.4). (c) Impact of neglecting RN in the determination of RP. The ratio of the apparent RP (obtained from Eqs. [4], [7] and [8]) to the true value of RP as a function of RP/R and RN/RP is plotted.