Elastic properties of grafted microtubules

We use single-particle tracking to study the elastic properties of
single microtubules grafted to a substrate. Thermal fluctuations of
the free microtubule's end are recorded, in order to measure
position distribution functions from which we calculate the
persistence length of microtubules with contour lengths between 2.6
and 48 micrometers. We find the persistence length to vary by more
than a factor of 20 over the total range of contour lengths. Our
results support the hypothesis that shearing between protofilaments
contributes significantly to the mechanics of microtubules