Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cavity Waters Govern Insulin Association and Release: Inferences from
  Experimental Data and Molecular Dynamics Simulations   While a monomer of the ubiquitous hormone insulin is the biologically active
form in the human body, its hexameric assembly acts as an efficient storage
unit. However, the role of water molecules in the structure, stability and
dynamics of the insulin hexamer is poorly understood. Here we combine
experimental data with molecular dynamics simulations to investigate the shape,
structure and stability of an insulin hexamer focusing on the role of water
molecules. Both X-Ray analysis and computer simulations show that the core of
the hexamer cavity is barrel-shaped, holding, on an average, sixteen water
molecules. These encapsulated and constrained molecules impart structural
stability to the hexamer. Apart from the electrostatic interactions with Zn2+
ions, an intricate hydrogen bond network amongst cavity water and neighboring
protein residues stabilizes the hexameric association. These water molecules
solvate six glutamate residues inside the cavity decreasing electrostatic
repulsions amongst the negatively charged carboxylate groups. They also prevent
association between glutamate residues and Zn2+ ions and maintain the integrity
of the cavity. Simulations reveal that removal of these waters results in a
collapse of the cavity. Subsequent analyses also show that the hydrogen bond
network among these water molecules and protein residues that face the inner
side of the cavity is more rigid with a slower relaxation as compared to that
of the bulk solvent. Dynamics of cavity water reveal certain slow water
molecules which form the back bone of the stable hydrogen bond network. The
analysis presented here suggests a dominant role of structurally conserved
water molecules in maintaining the integrity of the hexameric assembly and
potentially modulating the dissociation of this assembly into the functional
monomeric form.

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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph