Middle and peripheral sister KT pairs at the metaphase plate display significant differences in dynamics. (A) Diagram illustrating how middle and peripheral KT pairs were defined with respect to the metaphase plate and the spindle long axis. In each cell analyzed, quantifications/measurements were performed for the two peripheral KT pairs (one on each side) and for two middle KT pairs, as illustrated in the diagram. (B and C) Representative examples of dynamics of middle (B) and peripheral (C) sister KT pairs in live metaphase PtK1 cells. (D) Distribution of the standard deviations of the distances from the pole for middle (blue) and peripheral (red) KTs. (E and F) Kinetic profiles of normalized P (F) and AP (E) movement for oscillating (middle) KTs. The solid lines through the kinetic data in E and F were obtained by fourth-degree polynomial fitting. The insets in E and F represent the normalized AP and P velocity kinetics obtained from the derivatives of the polynomial curves of AP and P movement, respectively. The data presented in this figure were obtained by analyzing 24 middle KT pairs and 16 peripheral KT pairs.