A synchrotron small angle x-ray diffraction (SAXRD) study of microtubule (MT), subjected to osmotic stress and depletion attraction due to added poly-(ethylene-oxide) (PEO) was discussed. It was found that the solutions of MT undergo two transitions. SAXRD of microtubules shows the transition to rectangular bundles with noncircular buckled cross sections, followed by hexagonally packed bundles, under increasing osmotic stress. The new technique probes the strength of interprotofilament bonds, by which the chemotherapy drug taxol and associated proteins stabilize microtubules.
Bibliographical noteFunding Information:
We acknowledge insightful discussions with Bob McMeeking and Robijn Bruinsma. Supported by NIH GM-59288 and NS-13560, NSF DMR-0203755, CTS-0103516, and CTS-0404444. DOE supports SSRL. NSF-DMR-0080034 supports the UCSB MRL.