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

The ends of microtubules are always in dynamic formation: addition or removal of tubulin proteins alters the length of the biopolymer. The rate of depolymerization is different for each end according to its polarity, and the side that grows the fastest is considered the positive end while the other, more stable terminus, is negative. The dynamic, fast-growing portion of the microtubule is composed of beta-tubulin projected out towards the membrane of the cell. The alpha-tubulins stabilize their structure towards the nucleus at the centriole located in the centrosome of the cell. Tubulin is transported around the cell by the very microtubules they modify when and where restructuring is needed. 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.