g † = 2.078 A ‖ = 130 G, until r = 2 or r = 5 for the two concentrations of Cu-Zn
SOD. Then (r = 10) it appears a new species which can be associated with Cu
doxorubicin complex (Fig. 5.16). This means that the antitumor drug is able to
extract copper from the enzyme, as easier as lower the enzyme concentration.
5.21 Chemical Message
The ability of the antitumor drug to sequestrate Cu(II) suggests that, at least for the
part of the metal ion involved in the coordination, the enzyme becomes less active
in playing its role. This allows that a number of superoxide anions higher than in
the absence of drug survive and enhance the formation of oxygen-centered radicals.
(a)
(b)
Fig. 5.15 ESR spectra of Cu-Zn SOD doxorubicin at pH 6.5 for a Cu-Zn SOD 0.125 mmol dm
−3
and b Cu-Zn SOD 0.675 mmol dm
−3 both for the drug/enzyme molar ratios right-hand-indicated
[14]
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5 The Symmetry Properties Describe the Electronic Structure …