cantilever/theory.tex: Cite Walton 2008 as motivation

diff --git a/src/cantilever/theory.tex b/src/cantilever/theory.tex
index 386e2c7d5f16b75f1402426d4dcc09a3311f35bb..a4a9a6c89c96b28e1d8d63e33b62373b3c71f140 100644 (file)
--- a/src/cantilever/theory.tex
+++ b/src/cantilever/theory.tex
@@ -1,4 +1,21 @@
-\section{Theory}
+\section{Theoretical background}
+\label{sec:cantilever:theory}
+
+Understanding a protein's free energy landscape is important to
+effectively model protein folding and unfolding behavior.  Force
+spectroscopy has been a useful technique for exploring these free
+energy landscapes and those of the related field of ligand-receptor
+kinetics.  In force spectroscopy with the atomic force microscope
+(AFM), it is common practice to use spring constants in the range of
+$50\U{pN/nm}$, but the effect of the cantilever itself on the free
+energy landscape is generally ignored.  However, in AFM
+biotin-streptavidin unbinding experiments, \citet{walton08}
+demonstrated a surprisingly strong effect on unbinding force due to
+cantilever stiffness.  The unbinding force approximately doubled due
+to a change from a $35\U{pN/nm}$ cantilever to a $58\U{pN/nm}$
+cantilever.  Alarmed by the magnitude of the shift, we repeated their
+experiment on octomeric I27 to determine the magnitude for our
+mechanical protein unfolding experiments.
 
 \begin{figure}
   \asyinclude{figures/schematic/landscape-cant}