Molecular motors and cytoskeletal filaments mostly work collectively under opposing forces. This opposing force may be due to cargo carried by motors , or resistance coming from  cell membrane pressing against the cytoskeletal filaments. Certain recent studies have shown that the collective maximum force (stall force) generated by multiple cytoskeletal filaments or molecular motors may not always be just a simple sum of stall force for individual filaments or motors. To understand this phenomena of excess or deficit collective force generation , we study a broad class of models of both cytoskeletal filaments and molecular motors. We argue that the stall force generated by a group of filaments or motors is additive, i.e. , the stall force of N  filaments (motors) is N times the stall force of one filament (motor), when the system is in equilibrium at stall. Consequently , we show that this additivity typically does not hold  when the system departs from equilibrium at stall. We thus present a novel and unified understanding of  existing models exhibiting such non- addivity, and generalize our arguments by developing new models that demonstrate this phenomena. We also propose a quantity similar to thermodynamic efficiency to provide a simple understanding of deviation from stall-force additivity for filament and motor collectives.
Molecular motors and cytoskeletal filaments work collectively most of the time under opposing forces. This opposing force may be due to cargo carried by motors or resistance coming from the cell membrane pressing against the cytoskeletal filaments. Some recent studies have shown that the collective maximum force (stall force) generated by multiple cytoskeletal filaments or molecular motors may not always be just a simple sum of the stall forces of the individual filaments or motors. To understand this excess or deficit in the collective force , we study a broad class of models of both cytoskeletal filaments and molecular motors. We argue that the stall force generated by a group of filaments or motors is additive, that is , the stall force of N number of filaments (motors) is N times the stall force of one filament (motor), when the system is in equilibrium at stall. Conversely , we show that this additive property typically does not hold true when the system is not at equilibrium at stall. We thus present a novel and unified understanding of the existing models exhibiting such non-addivity, and generalise our arguments by developing new models that demonstrate this phenomena. We also propose a quantity similar to thermodynamic efficiency to easily predict this deviation from stall-force additivity for filament and motor collectives.
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