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Journal of the American Chemical Society
With the aim to establish optimal photocleavage conditions for
ASSOCIATED CONTENT
Supporting Information
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releasing doxorubicin within cells following immunoproteasome
β5i inhibition, we investigated the amount of doxorubicin formed
as a function of irradiation time (Figure 2B, S3-4). As much as 50%
doxorubicin was released when compound 1 was irradiated for 30
seconds at 375 nm (3 mW/cm2), whereas 50 seconds of irradiation
with 420 nm light (13 mW/cm2) was required to yield the same
percentage of the free anthracycline. Quantitative release was
observed after one minute irradiation of 1 at 375 nm and after two
minutes irradiation at 420 nm. Construct 2 showed insufficient
uncaging yields to warrant further investigation (Figure S5-6).
Phototoxicity studies on cells exposed to either of the two
wavelengths yielded a surprising result (Figure 2C, S7). Photolytic
cell death reached 50% after cells were exposed for 40 seconds to
irradiation at 420 nm, whilst no significant decrease in cell viability
was observed after 180 seconds of irradiating at the higher
energetic wavelength (375 nm). We therefore conducted further
experiments at 375 nm to exclude phototoxic effects.
The Supporting Information is available free of charge on the ACS
Publications website and includes supplementary schemes, figures
and all experimental procedures.
AUTHOR INFORMATION
Corresponding Author
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Author Contributions
‡These authors contributed equally.
ACKNOWLEDGMENT
We are thankful to Prof. Dr. Sylvestre Bonnet and Dr. Andrea
Pannwitz’s assistance in the photochemical characterization. HSO
was funded by the Nederland Genomics Initiative (Zenith). SIVK
was funded by the European Research Council (ERC-2014-StG-
639005).
We next explored the ability of conjugate 1 to induce apoptosis
in AMO-1 cells, both those with an acquired resistance for CFZ and
CFZ-sensitive cells (Figure 2D, S8). After incubation with
conjugate 1, the cells were washed and irradiated for 60 seconds at
375 nm. Three days later cell survival was determined. Although
CFZ-resistant AMO-1 cells displayed minor resistance towards
conjugate 1 when compared to non-resistant AMO-1 cells, 50% of
both cell variants were killed when exposed to 5 µM of the
compound after irradiation.
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proteolytic stress and poisoning topoisomerase II yielding DNA
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