Photoexcitation of the methionine—iron bond in iron(III) cytochrome c: Bimolecular reaction with NADH

Ferri, Albertino; Patti, Daniele; Chiozzi, Paola; Cattozzo, Margherita; Bartocci, C.; Maldotti, Andrea

doi:10.1016/1011-1344(88)85053-x

Cited by 5 publications

(2 citation statements)

References 22 publications

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“…We next sought to explore whether Se-NH 2 has this capability. To our surprise, inspired by the studies of Ferri 48 and Sadler, 13 we were delighted to discover that Se-NH 2 -mediated photoredox catalysis between NADH and hemoprotein Cyt c (Fe 3+ ) could proceed readily without the requirement for O 2 as an electron acceptor, thereby enabling new possibilities for a NIR photon-initiated O 2independent photocatalytic cascade in living cells. As presented in Figure 3d, in comparison to the smoothly proceeding cyt c (Fe 3+ ) photoreduction under air-saturated PBS conditions (TOF = 41.2 min −1 , Figure 3c), when we sparged the reaction mixture with nitrogen (N 2 ), the overall photocatalytic performance of Se-NH 2 for cyt c (Fe 3+ ) was greatly promoted instead of being diminished, reaching a higher level with a TOF of up to 62.1 min −1 , highlighting that O 2 was not necessary for the above photoredox cascade to proceed.…”

Section: ■ Design Planmentioning

confidence: 99%

Conditionally Activatable Photoredox Catalysis in Living Systems

Gebremedhin

et al. 2021

J. Am. Chem. Soc.

100

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The transformational effect of photoredox catalytic chemistries has inspired new opportunities, enabling us to interrogate nature in ways that are not possible otherwise and to unveil new biotechnologies in therapy and diagnosis. However, the deployment of artificial photoredox catalysis in living systems remains challenging, mired by the off-target risk and safety concerns of photocatalyst toxicity. Here, we present an appealing approach, namely conditionally activatable photoredox catalysis (ConAPC), and as a proof of concept design the first ConAPC architecture (Se-NO 2 ) based upon classic self-immolative chemistry, in which the inherent photocatalytic properties can be temporarily caged while the species becomes active only at the tumor sites via sensing to specific biomarkers. Such a masking strategy allows a spatial–temporal control of photoresponsivity in vitro and in vivo. In particular, for ConAPC design, a new biologically benign metal-free photocatalyst (Se-NH 2 ), which is able to initiate NIR photoredox catalysis to manipulate the cellular electron pool in an O2-independent mechanism of action, is identified. With this unique strategy, potent tumor-specific targeting photocatalytic eradication (TGI: 95%) is obtained in a mouse model. Impressively, favorable features such as high-resolution tumor recognition (SBR: 33.6) and excellent biocompatibility and safety are also achieved. This work therefore offers a new possibility for chemists to leverage artificial photocatalytic reactions toward the development of facile and intelligent photocatalytic theranostics.

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Section: ■ Design Planmentioning

confidence: 99%

Conditionally Activatable Photoredox Catalysis in Living Systems

Gebremedhin

et al. 2021

J. Am. Chem. Soc.

100

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“…Many groups have studied the photoreduction of heme proteins and metalloporphyrins by monitoring the absorption spectrum of the sample via irradiation with broadband excitation. Some groups have used external electron donors (3–5), but photoreduction of Cyt c has also been reported in the absence of foreign donors (6–8).…”

Section: Introductionmentioning

confidence: 99%

Transient and Stationary Spectroscopy of Cytochrome c: Ultrafast Internal Conversion Controls Photoreduction

Löwenich

Kleinermanns

Karunakaran

et al. 2007

Photochem & Photobiology

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Photoreduction of cytochrome c (Cyt c) has been reinvestigated using femtosecond-to-nanosecond transient absorption and stationary spectroscopy. Femtosecond spectra of oxidized Cyt c, recorded in the probe range 270-1000 nm, demonstrate similar evolution upon 266 or 403 nm excitation: an ultrafast 0.3 ps internal conversion followed by a 4 ps vibrational cooling. Late transient spectra after 20 ps, from the cold ground-state chromophore, reveal a small but measurable signal from reduced Cyt c. The yield phi for Fe3+-->Fe2+ photoreduction is measured to be phi(403) = 0.016 and phi(266) = 0.08 for 403 and 266 nm excitation. These yields lead to a guess of the barrier E(f)(A) = 55 kJ mol(-1) for thermal ground-state electron transfer (ET). Nanosecond spectra initially show the typical absorption from reduced Cyt c and then exhibit temperature-dependent sub-microsecond decays (0.5 micros at 297 K), corresponding to a barrier E(A)(b) = 33 kJ mol(-1) for the back ET reaction and a reaction energy DeltaE = 22 kJ mol(-1). The nanosecond transients do not decay to zero on a second time scale, demonstrating the stability of some of the reduced Cyt c. The yields calculated from this stable reduced form agree with quasistationary reduction yields. Modest heating of Cyt c leads to its efficient thermal reduction as demonstrated by differential stationary absorption spectroscopy. In summary, our results point to ultrafast internal conversion of oxidized Cyt c upon UV or visible excitation, followed by Fe-porphyrin reduction due to thermal ground-state ET as the prevailing mechanism.

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