Targeted activation in localized protein environments via deep red photoredox catalysis

Abstract

State-of-the art photoactivation strategies in chemical biology provide spatiotemporal control and visualization of biological processes. However, using high energy light (l < 500 nm) for substrate or photocatalyst sensitization can lead to background activation of photoactive small molecule probes and reduce its efficacy in complex biological environments. Here we describe the development of targeted aryl azide activation via deep red light (l = 660 nm) photoredox catalysis and its use in photocatalyzed proximity labeling. We demonstrate that aryl azides are converted to triplet nitrenes via a novel redox-centric mechanism and show that its spatially localized-formation requires both red light and a photocatalyst-targeting modality. This technology was applied in different colon cancer cell systems for targeted protein environment labeling of epithelial cell adhesion molecule (EpCAM). We identified a small subset of proteins with previously known and unknown association to EpCAM, including CDH3, a clinically relevant protein that shares high tumor selective expression with EpCAM.

Photochemical Identification of Auxiliary Severe Acute Respiratory Syndrome Coronavirus 2 Host Entry Factors Using μMap

“…We hypothesize that these interactions are potentially resulting from internalized spike-Ir conjugates, and future efforts will validate and functionally investigate these potentially critical interactions. Moreover, we and the Rovis group have also recently reported red light-based strategies for photocatalyic proximity labeling, 36,37 and future efforts will deploy these platforms for studying host−virus interactions in complex in vivo environments. Together, this work demonstrates a powerful and generalizable methodology…”

Visible-light-induced protein labeling in live cells with aryl azides

“…4b). 21 The photoexcited catalyst Os* reduced perfluorinated azides by electron transfer to generate the reduced azide and the oxidized Os + . The reduced azide released molecular nitrogen to yield the nitrene, which was further oxidized by Os + to afford triplet nitrenes.…”

μMap-Red: Proximity Labeling by Red Light Photocatalysis

“…In nature, porphyrin and chlorin scaffolds are ubiquitous photocatalysts that absorb longer-wavelength light (>600 nm) and deploy this energy via photoinduced electron transfer. Based upon sporadic reports of azide activation photocatalysts, we reasoned that red-light absorbing catalysts might be used to generate reactive proximity labeling intermediatesnitrenes or aminyl radicalsfrom aryl azide precursors . We call this red-light-mediated strategy μMap-Red.…”