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. 
Francesco Pampaloni, Gianluca Lattanzi, Alexandr Jon\'a\v{s}, Thomas   Surrey, Erwin Frey and Ernst-Ludwig Florin