Measurement of the life time of attachments formed by a single microtubule (MT) with a single kinetochore (kt) {\it in-vitro} under force-clamp conditions  revealed a catch-bond-like behavior. In the past the physical origin of this apparently counter-intuitive phenomenon was traced to the nature of the force-dependence of the (de-)polymerization kinetics of the microtubules . Here first the same model kt-MT attachment is subjected to external tension that is ramped up till the attachment gets ruptured; the trend of variation of the rupture force distribution with increasing loading rate is consistent with that displayed by the catch bonds formed in some other ligand-receptor systems{\it  {\it   . We then extend the formalism to model an attachment of a bundle of multiple parallel microtubules with a single kt  under force-clamp and force-ramp conditions. From numerical studies of the model we predict the trends of variation of the mean life time and mean rupture force with the increasing number of MTs in the bundle. Both the mean life time and the mean rupture force display nontrivial nonlinear dependence on the maximum number of MTs that can attach simultaneously to the same kt.
Measurement of the life time of attachments formed by a single microtubule (MT) with a single kinetochore (kt) {\it in-vitro} under force-clamp conditions had earlier revealed a catch-bond-like behavior. In the past the physical origin of this apparently counter-intuitive phenomenon was traced to the nature of the force-dependence of the (de-)polymerization kinetics of the MTs . Here first the same model MT-kt attachment is subjected to external tension that increases linearly with time until rupture occurs. In our{\it force-ramp experiments{\it in-silico , the model displays the well known `mechanical signatures' of a catch-bond probed by molecular force spectroscopy. Exploiting this new evidence, we have further strengthened the analogy between MT-kt attachments and common ligand-receptor bonds in spite of the crucial differences in their underlying physical mechanisms . We then extend the formalism to model the stochastic kinetics of an attachment formed by a bundle of multiple parallel microtubules with a single kt considering the effect of rebinding under force-clamp and force-ramp conditions. From numerical studies of the model we predict the trends of variation of the mean life time and mean rupture force with the increasing number of MTs in the bundle. Both the mean life time and the mean rupture force display nontrivial nonlinear dependence on the maximum number of MTs that can attach simultaneously to the same kt.
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had earlier
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microtubules
MTs
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kt-MT
MT-kt
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is ramped up till the attachment gets ruptured; the trend of variation of the rupture force distribution with increasing loading rate is consistent with that displayed by the catch bonds formed in some other ligand-receptor systems
increases linearly with time until rupture occurs. In our
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force-ramp
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experiments
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in-silico
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, the model displays the well known `mechanical signatures' of a catch-bond probed by molecular force spectroscopy. Exploiting this new evidence, we have further strengthened the analogy between MT-kt attachments and common ligand-receptor bonds in spite of the crucial differences in their underlying physical mechanisms
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an attachment of
the stochastic kinetics of an attachment formed by
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considering the effect of rebinding