ct6b01251_si_001.pdf (3.27 MB)
Computing the Diamagnetic Susceptibility and Diamagnetic Anisotropy of Membrane Proteins from Structural Subunits
journal contribution
posted on 2017-04-18, 00:00 authored by Mahnoush Babaei, Isaac C. Jones, Kaushik Dayal, Meagan S. MauterThe
behavior of large, complex molecules in the presence of magnetic
fields is experimentally challenging to measure and computationally
intensive to predict. This work proposes a novel, mixed-methods approach
for efficiently computing the principal magnetic susceptibilities
and diamagnetic anisotropy of membrane proteins. The hierarchical
primary (amino acid), secondary (α helical and β sheet),
and tertiary (α helix and β barrel) structure of transmembrane
proteins enables analysis of a complex molecule using discrete subunits
of varying size and resolution. The proposed method converts the magnetic
susceptibility tensor for all protein subunits to a unit coordinate
system and sums them to build the magnetic susceptibility tensor for
the membrane protein. Using this approach, we calculate the diamagnetic
anisotropy for all transmembrane proteins of known structure and investigate
the effect of different subunit resolutions on the resulting predictions
of diamagnetic anisotropy. We demonstrate that amino acid residues
with aromatic side groups exhibit higher diamagnetic anisotropies.
On average, high percentages of aromatic amino acid subunits, a β
barrel tertiary structure, and a small volume are correlated with
high volumetric diamagnetic anisotropy. Finally, we demonstrate that
accounting for the spatial position of the residues with respect to
one another is critical to accurately computing the magnetic properties
of the complex protein molecule.