Chemistry Reference
In-Depth Information
Figure 3.11 MALDI-TOF MS spectrum of degradation products ob-
tained by incubation of myoglobin (1.2
10
-5
M
) with 22 (C
o
= 2.3
10
-3
M
) at pH 9.0 and 50
8
C for 4 h. Peaks with m/z of 6868 and 10 086
originate from cleavage of myoglobin (m/z 16 953; the heme group
dissociates during measurement of MALDI-TOF MS) at Gln(91)-
Ser(92), and m/z 6577 and 10 382 arose from cleavage of myoglobin at
Ala(94)-Thr(95).
A molecular modeling study, based on the X-ray crystallographic structure of myo-
globin, suggested that the site-selectivity was due to anchorage of one Cu(
II
)Cyc unit of
the catalytic module to a heme carboxylate of myoglobin (Figure 3.12). The myoglobin
Figure 3.12 Schematic of the structure of the complex formed be-
tween 22 and myoglobin leading to cleavage of myoglobin at Gln(91)-
Ser(92). The picture was obtained through optimization of the structure
of the active site of 22 by molecular modeling programs with the
structure of myoglobin frozen as that in the crystal.
