Protein-Associated Cation
Clusters in Aqueous Arginine
Solutions and Their Effects on Protein Stability and Size
Vincent Vagenende
Alvin X. Han
Monika Mueller
Bernhardt
L. Trout
10.1021/cb300440x.s001
https://acs.figshare.com/articles/journal_contribution/Protein_Associated_Cation_Clusters_in_Aqueous_Arginine_Solutions_and_Their_Effects_on_Protein_Stability_and_Size/2442652
Arginine is one of the most prominent residues in protein
interactions,
and arginine hydrochloride is widely used as an additive in protein
solutions because of its exceptional effects on protein association
and folding. The molecular origins of arginine effects on protein
processes remain, however, controversial, and little is known about
the molecular interactions between arginine cations and protein surfaces
in aqueous arginine solutions. In this study, we report a unique biochemical
phenomenon whereby clusters of arginine cations (Arg<sup>+</sup>)
are associated with a protein surface. The formation of protein-associated
Arg<sup>+</sup> clusters is initiated by Arg<sup>+</sup> ions that
associate with specific protein surface loci through cooperative interactions
with protein guanidinium and carboxyl groups. Molecular dynamics simulations
indicate that protein-associated Arg<sup>+</sup> ions subsequently
attract other Arg<sup>+</sup> ions and form dynamic cation clusters
that extend further than 10 Å from the protein surface. The effects
of arginine on the thermal stability and size of lysozyme and ovalbumin
are measured over a wide concentration range (0 to 2 M), and we find
that the formation of protein-associated Arg<sup>+</sup> clusters
consistently explains the complex effects of arginine on protein stability
and size. This study elucidates the molecular mechanisms and implications
of cluster formation of Arg<sup>+</sup> ions at a protein surface,
and the findings of this study may be used to manipulate synthetic
and biological systems through arginine-derived groups.
2013-02-15 00:00:00
cluster
Molecular dynamics simulations
arginine cations
protein surface
protein surface loci
Aqueous Arginine Solutions