XB-IMG-117112
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Fig. 4. Single-step analysis and quantification of release force. a Example traces selected from independent experiments displaying stepwise displacements of the beads in the laser-trap driven by individual Eg5 motors [grey, unfiltered data; red, averaged (15-point) and median-filtered data (0.3 s sliding window, rank 10)]. The trap stiffnesses were: trace I: 0.014; II: 0.021; III, IV: 0.029; V: 0.042 pN/nm. b PDF of 10 traces including the ones shown in a to detect steps. Double Gaussian fit to this distribution yields a mean step size of 6.5 ± 0.2 nm (mean ± SEM). c Histogram analysis of detachment forces observed for single Kinesin-1- (black) and Eg5-motors (red). d Histograms of relative motor speeds directly preceding detachment: we scored the speeds of beads driven by Kinesin-1 (black) and Eg5 (red) in time interval before detachment (between arrows in a and Fig. 3 corresponding to about 10 motor steps in both cases) relative to the unloaded motors speeds. e Systematic variation of the trap stiffness revealed a hyperbolic relation to the obtained displacement (green circles). Error bars denote SEM, the number of evaluated events varied between 5 < N < 73. The resulting detachment forces (product of displacement and trap stiffness) are nearly constant (purple triangles) Image published in: Korneev MJ et al. (2007) Image downloaded from an Open Access article in PubMed Central. © EBSA 2007 Larger Image Printer Friendly View |