1 \subsection{Wormlike chains}
2 \label{sec:tension:wlc}
4 The unfolded forms of many domains can be modeled as Worm-Like Chains
5 (WLCs)\citep{marko95,bustamante94}
6 \index{WLC}\nomenclature{WLC}{Wormlike Chain}, which treats the
7 unfolded polymer as an elastic rod of persistence length $p$ and
8 contour length $L$. The relationship between tension $F$ and
9 extension (end-to-end distance) $x$ is given to within XX\% by
10 Bustamante's interpolation formula\citep{marko95,bustamante94}.
12 F_\text{WLC}(x,p,L) = \frac{k_B T}{p_u}
13 \p[{ \frac{1}{4}\p({ \frac{1}{(1-x/L)^2} - 1 })
17 where $p$ is the persistence length.
19 For chain with $N_u$ unfolded domains sharing a persistence length
20 $p_u$ and per-domain contour lengths $L_{u1}$, the tension of the WLC
21 is determine by summing the contour lengths
23 F(x, p_u, L_u, N_u) = F_\text{WLC}(x, p_u, N_uL_{u1})