Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Growth and shortening of microtubules: a two-state model approach   In this study, a two-state mechanochemical model is presented to describe the
dynamic instability of microtubules (MTs) in cells. The MTs switches between
two states, assembly state and disassembly state. In assembly state, the growth
of MTs includes two processes: free GTP-tubulin binding to the tip of
protofilament (PF) and conformation change of PF, during which the first
tubulin unit which curls outwards is rearranged into MT surface using the
energy released from the hydrolysis of GTP in the penultimate tubulin unit. In
disassembly state, the shortening of MTs includes also two processes, the
release of GDP-tibulin from the tip of PF and one new tubulin unit curls out of
the MT surface. Switches between these two states, which are usually called
rescue and catastrophe, happen stochastically with external force dependent
rates. Using this two-state model with parameters obtained by fitting the
recent experimental data, detailed properties of MT growth are obtained, we
find that MT is mainly in assembly state, its mean growth velocity increases
with external force and GTP-tubulin concentration, MT will shorten in average
without external force. To know more about the external force and GTP-tubulin
concentration dependent properties of MT growth, and for the sake of the future
experimental verification of this two-state model, eleven {\it critical forces}
are defined and numerically discussed.

20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph