Figure 3.

Effects of ionic strength on persistence length. (A) AFM images of rat type I collagen deposited from solutions covering a range of KCl concentration, for both neutral and acidic (∼3) pH. Scale bars, 250 nm. As salt concentration increases, the collagen chains appear to straighten. (B) Persistence lengths in these conditions. The reported values are the average of p extracted from fits to $\langle R^2\left(s\right)\rangle$ and to $\langle \cos \theta \left(s\right)\rangle$, and errors are the larger of the propagated error in this mean or half the separation between the two values of p. For the purposes of graphical representation, water was assumed to have an ionic strength of 10⁻⁷ M. Increasing the ionic strength causes a large increase in the apparent persistence length, an effect that is reduced slightly in the acidic condition for the same ionic strengths. To view this figure in color, go online.