Figure 2 - Schematic molecules with different persistence lengths.
From the following article
Polymer Physics: DNA off the Hooke
Rudolf Podgornik
Nature Nanotechnology 1, 100 - 101 (2006)
doi:10.1038/nnano.2006.114
The more flexible molecule (a) changes direction over relatively short distances and so coils up on itself. The stiffer molecule (b) has a much longer persistence length, and therefore remains straighter.
