Microtubule polarity and (+) end vs. (-) end tracking
Microtubules have an intrinsic polarity with a slow growing (-) and a faster growing (+) end. Usually, (+) end dynamics are reported and this option allows for (+) end selection. If the first frames do not allow for unambiguous determination of polarity, the user can use Option 2 to move to a frame where growth is visible. The default setting is that all recognized ends will be tracked over the complete length of the movie. Clicking “Confirm dynamic seeds” will show which seeds are going to be tracked. In the final track files the plus and minus ends will be determined by the program by comparing the growth velocity of the two ends it is tracking and plus end would be the one which has on average a higher growth velocity than the other end.
If the user deselects certain ends that end would be labelled as zero end, same is true for the ends that the user selects, each track file will also contain the seed label which is a unique label assigned to every seed and helps in distinguishing between different seeds.