| James W. Dawson1, Harry B. Gray1,
H. Eckhardt Hoenig2,
George R.
Rossman1, Jeffrey
M. Schredder1, Run-Han Wang2 1Arthur Amos Noyes Laboratory of Chemical Physics California Institute of Technology, Pasadena, CA 2The Alfred P. Sloan Laboratory of mathematics and Physics California Institute of Technology, Pasadena, CA |
The magnetic
susceptibilities of
oxy- and metaquohemerythrin in the range 3-200 K have been determined
using an
ultrasensitive superconducting quantum magnetometer, and for the first
time
their antiferromagnetic components have been conclusively resolved. The
exchange coupling constants, J, between the two high-spin iron(III)
atoms in each
subunit are -77 and -134 cm-1, respectively. The electronic
spectra
of these two proteins in deuterium oxide have been measured from 800 to
1200 nm
but no additional bands were obtained. After comparison to magnetic and
spectroscopic
data obtained previously for ferric dimer model complexes, it is
concluded that
the two iron(III) atoms in subunits of both oxy- and
metaquohemerythrin are oxo bridged.