FIG. 7. Guided translocation of phage along a grooved flagellar filament. The phage, shown in green, has a capsid head of size 2ah, a tail of length Lt and fibres of cross-sectional radius rfib. The flagellar filament (light blue) has helical grooves of helix angle α and is rotating at a rate ωfl. The phage slides along the grooves with speed V in the frame of the flagellar filament. As shown in the inset, the force acting on the fibre sliding along the grooves consists of two parts: (i) a drag resisting the sliding motion of magnitude µ̃V in the −tfib direction and (ii) a restoring force acting to keep the fibre in the centre of the groove of magnitude kδ in the hbfib direction, where δ is the local offset of the centre of the fibre cross-section from the centre of the groove and bfib is the local binormal to the fibre centreline that lies in the local tangent plane of the surface of the flagellar filament and is perpendicular to the tangent of the fibre centreline.
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