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Find answers to frequently asked questions on chemotaxis assays.

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Chemotaxis Parameters

To quantify chemotaxis and migration, several values can be generated by using the Chemotaxis and Migration Software Tool. One value is the center of mass. A second is the x and y Forward Migration Indices. Both of these values are a measure of directed cell migration. A third value is directness, but this may not necessarily indicate a chemotaxis effect.

i is the index of the different single cells. The first cell has the index 1, the last one n.
index of the cells

Center of Mass (Mend)

The center of mass represents the averaged point of all cell endpoints. Its x and y values indicate the direction in which the group of cells primarily traveled.

x and y Forward Migration Indices
(xFMI, yFMI)

The xFMI and yFMI represent the efficiency of the forward migration of cells, in relation to the x- or y- axis. The larger the index on an axis, the stronger the chemotactic effect is on this axis. For simplification, it is assumed that either the x-axis or the y-axis is parallel to the direction of the chemotactic gradient.

For simplification, one can also define a direction parallel to the gradient (║) and a direction perpendicular to the gradient (┴). By this, one value for the FMI ┴ , and one for the FMI║, is created.

directionality of one single cell
averaged directionality of all cells

Directness (D) 

The directionality is calculated by comparing euclidean and accumulated distance. It is a measure of the directness of the cell trajectories. A directionality of D --> 1 equals a straight-line migration from start to endpoint.