Faculty Collaboration Database

EPR of Cu2+ prion protein constructs at 2 GHz using the g(perpendicular) region to characterize nitrogen ligation. Biophys J 2009 Apr 22;96(8):3354-62

Date

04/23/2009

Pubmed ID

19383478

Pubmed Central ID

PMC2718275

DOI

10.1016/j.bpj.2009.01.034

Scopus ID

2-s2.0-67649389968 (requires institutional sign-in at Scopus site)   14 Citations

Abstract

A double octarepeat prion protein construct, which has two histidines, mixed with copper sulfate in a 3:2 molar ratio provides at most three imidazole ligands to each copper ion to form a square-planar Cu(2+) complex. This work is concerned with identification of the fourth ligand. A new (to our knowledge) electron paramagnetic resonance method based on analysis of the intense features of the electron paramagnetic resonance spectrum in the g( perpendicular) region at 2 GHz is introduced to distinguish between three and four nitrogen ligands. The methodology was established by studies of a model system consisting of histidine imidazole ligation to Cu(2+). In this spectral region at 2 GHz (S-band), g-strain and broadening from the possible rhombic character of the Zeeman interaction are small. The most intense line is identified with the M(I) = +1/2 extra absorption peak. Spectral simulation demonstrated that this peak is insensitive to cupric A(x) and A(y) hyperfine interaction. The spectral region to the high-field side of this peak is uncluttered and suitable for analysis of nitrogen superhyperfine couplings to determine the number of nitrogens. The spectral region to the low-field side of the intense extra absorption peak in the g( perpendicular) part of the spectrum is sensitive to the rhombic distortion parameters A(x) and A(y). Application of the method to the prion protein system indicates that two species are present and that the dominant species contains four nitrogen ligands. A new loop-gap microwave resonator is described that contains approximately 1 mL of frozen sample.

Author List

Hyde JS, Bennett B, Walter ED, Millhauser GL, Sidabras JW, Antholine WE

Authors

Brian Bennett D.Phil. Professor and Chair in the Physics department at Marquette University
Jason W. Sidabras PhD Assistant Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Absorption
Computer Simulation
Copper
Copper Sulfate
Electron Spin Resonance Spectroscopy
Histidine
Nitrogen
Organometallic Compounds
Prions
Spectrum Analysis