  The synthetic actin network arouses great interest as bio-material due to its
soft and wet nature that mimics many biological scaffolding structures. Inside
the cell, the actin network is regulated by tens of actin-binding proteins
(ABP's), which make for a highly complex system with several emergent
behaviours. In particular, calponin is an ABP that was identified as an actin
stabiliser, but whose mechanism is still poorly understood. Recent experiments
using an in vitro model system of cross-linked actin with calponin and large
deformation bulk rheology, found that networks with basic calponin exhibited a
delayed onset and were able to withstand a higher maximal strain before
softening.
  In this work, we show that the difference between the two networks, with and
without calponin, not only provides bundle flexibility. But, also encodes
alterations in the pre-strain and the regulation of the crosslinks adhesion
energy to define the new yielding point. We verify these effects theoretically
using nonlinear continuum mechanics for the semiflexible and crosslinked
network. In addition, the alterations over the microstructure are described by
the definition of an interaction parameter $\Gamma$ according the formalism of
Landau. According to this simple model we demonstrates that the interaction
parameter can describe the experimental observations following an scaling
exponent as $\Gamma \sim \mid c-c_{cr} \mid^{1/2}$, where $c$ is the ratio
between concentration of calponin and actin. This result provides interesting
feedback to improve our understanding of several mechano-biological pathways.
