Figure 1 : STM images of single tubulin self-assembly into protofilaments:

From: Live visualizations of single isolated tubulin protein self-assembly via tunneling current: effect of electromagnetic pumping during spontaneous growth of microtubule

Figure 1

(a). Tubulin molecule (left most). Series of STM images (2 V tip bias 10 pA current) of three protein molecules, they form a perfect linear assembly and stabilize. Scale bar for first four images 3.8 nm, for the last two images (one above another), scale bar is 5 nm. Protofilaments connected (extreme right), scale bar 8 nm. (b). STM images at 2.1 V tip bias 30 pA current, left to right frequencies are noted in Hz, M means mega 106 Hz, G means Giga 109 Hz, scale bar for all images 4 nm. (c). SEM image of a typical artificial cell environment (scale bar top left 1 mm). A circular region is expanded in its right, one electrode associated region is highlighted below (scale bar 4 μm), small hair like structures are microtubule like cylinders, one cylinder like structure is zoomed in its left (scale bar 150 nm). (d). Experimental (red) and theoretical46,47,48,49,50 (blue, see supporting online text) average length of microtubules (standard deviation ~200 nm) as a function of a.c. signal frequency (top left). AFM images of microtubules (right, top-to-bottom) grown at 500 kHz (scale bar is 7 μm), 5 MHz (scale bar is 5 μm) and 15 MHz (scale bar is 7 μm) on SiO2/Si substrate.