Objective: UPlanSApo 100x oil/1.40	Exposure: 250 ms
Microscope: Olympus DSU/IX81	Gain: 3
Camera: Hamamatsu ImagEM	Interval: 2 s

Microtubules are biopolymers that are composed of subunits made from an abundant globular cytoplasmic protein known as tubulin. Each subunit of the microtubule is made of two slightly different but closely related simpler units called alpha-tubulin and beta-tubulin that are bound very tightly together to form heterodimers. In a microtubule, the subunits are organized in such a way that they all point the same direction to form 13 parallel protofilaments. This organization gives the structure polarity, with only the alpha-tubulin proteins exposed at one end and only beta-tubulin proteins at the other. The digital video above illustrates the tracking of microtubule +TIPs (plus end tracking proteins) in Gray fox lung fibroblast cells labeled with a chimera of microtubule end-binding protein EB3 fused to monomeric Kusabira Orange fluorescent protein, which is pseudo colored red for optimum visualization.