Chemistry Reference
In-Depth Information
FIGURE 6.6
Ferroxidase site in reduced Bacterioferritin from Desulfovibrio desulfuricans with iron
e
ligand distances in ˚ngstr¨ms: (a) as
determined by crystallography, (b) adjusted to give agreement with the EXAFS. Grey, carbon;
red, oxygen; blue, nitrogen; orange, iron;
hydrogens are omitted for clarity. Green and blue distance values refer to Fe
A
(left
iron ion) and Fe
B
(right), respectively.
(From
Toussaint
et al., 2009
.
Copyright 2009 with permission from Springer.)
give agreement with the EXAFS data (
Toussaint et al., 2009
)
. The iron
ligand distances are shorter than in the
crystallographic study, and the iron ion in the reduced state has an ionic radius which is significantly larger that
that measured in the oxidized state, consistent with reduction from Fe(III) to Fe(II).
e
X-RAY DIFFRACTION
Protein crystallography had its beginnings in 1934, when J.D. Bernal and Dorothy Crowfoot (Hodgkin) showed
that crystals of pepsin gave an X-ray diffraction pattern, made up of sharp reflections which showed that the
protein had an ordered structure, with most of its 5000 atoms occupying clearly defined positions. Since then,
protein crystallography has advanced to become one of the most important techniques for structure determination
of macromolecules, with thousands of structures being determined every year. The principal reasons for this
explosion of X-ray crystallographic prowess are: (i) more coherent protocols for protein crystallisation; (ii) cryo-
crystallography; (iii) the use of brighter and tunable synchrotron-generated X-ray beams (which can enable
