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