C O M M U N I C A T I O N S
Figure 4. Effect of chelator concentration on deoxyribose degradation by
OH•. A and Ao are the absorbance at 532 nm in the presence and absence
of chelator, respectively. Values below A/Ao ) 1 indicate protection of
deoxyribose. Conditions: 200 µM H2O2, 10 µM FeCl3, 2 mM ascorbic
acid, 15 mM deoxyribose in pH 7.4 NaHPO4 buffer.
Figure 2. UV-vis spectra of 60 µM BSIH in MeOH in the absence and
presence of 30 µM Fe(NO3)3. Addition of 0.6 mM H2O2 results in a
spectrum (open red circles) matching that of [Fe(SIH)2]+ (blue triangles).
The expanded view in the inset compares the mono and bis species,
[Fe(SIH)Cl2(CH3OH)] and [Fe(SIH)2]NO3, respectively, at 60 µM.
deoxyribose assay, as shown by the nearly constant A/Ao values
near unity in Figure 4. Whereas DFO and SIH protect deoxyribose
when OH• are generated in the absence of added H2O2, BSIH has
little effect under these conditions (Supporting Information). Taken
together, these data indicate that the protective effect of BSIH
against deoxyribose degradation derives from its H2O2-dependent
conversion to SIH, which in turn provides the right coordination
environment around Fe to prevent iron-promoted OH• generation.
Acknowledgment. We thank Duke University and the Parkin-
son’s Disease Foundation for support.
Supporting Information Available: Complete refs 9 and 10,
experimental details, and X-ray crystallographic data, including CIF
files. This material is available free of charge via the Internet at http://
pubs.acs.org.
Figure 3. UV-vis spectra showing the formation of [Fe(SIH)]2+ and
[Fe(SIH)2]+ upon addition of 100 mM H2O2 to a solution of 1.5 mM
Fe(NO3)3 and 3.0 mM BSIH in MeOH.
expression to give kobs ) 1.6 × 10-3 s-1. This value is consistent
with preliminary kinetic data for the conversion of BSIH to SIH
in the absence of iron (not shown), indicating that the rate-limiting
step for iron sequestration is oxidation of BSIH to SIH, followed
by rapid metal complexation.
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To test the effectiveness of BSIH for inhibiting OH• formation,
we used an in vitro deoxyribose assay in which hydroxyl radicals
that are generated via typical Fenton conditions of Fe3+, ascorbic
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Figure 4 displays the effect of increasing chelator concentration
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of A/Ao above 1 indicate that the additive promotes OH• formation,
whereas values below 1 indicate that the additive either scavenges
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catalyzed OH• formation via effective iron chelation. EDTA, a
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