Imaging microtubules and kinesin decorated microtubules using tapping modeatomic force microscopy in fluids

The atomic force microscope has been used to investigate microtubules and k inesin decorated microtubules in aqueous solution adsorbed onto a solid sub strate. The netto negatively charged microtubules did not adsorb to negativ ely charged solid surfaces but to glass covalently coated with the highly p ositively charged silane trimethoxysilylpropyldiethylenetriamine (DETA) or a lipid bilayer of 1,2-dipalmitoyl-3-dimethylammoniumpropane. Using electro n beam deposited tips for microtubules adsorbed on DETA, single protofilame nts could be observed showing that the resolution is up to 5 nm. Under cond itions where the silane coated surfaces are hydrophobic, microtubules opene d, presumably at the seam, whose stability is lower than that of the bonds between the other protofilaments. This led to a "sheet" with a width of abo ut 100 nm firmly attached to the surface. Microtubules decorated with a sto ichiometric low amount of kinesin molecules in the presence of the non-hydr olyzable ATP-analog 5'-adenylylimidodiphosphate could also be adsorbed onto silane-coated glass. Imaging was very stable and the molecules did not sho w any scan-induced deformation even after hundreds of scans with a scan fre quency of 100 Hz.