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Abstract Expanding renewable electricity (RE) use in global corporate supply chains can help to achieve global net-zero greenhouse gas emissions targets by mid-century, but efforts face several challenges. First, corporations and their suppliers may be subject to varying climate policy stringency, leading to a misalignment of incentives to act. Second, measuring true progress is difficult, because counterfactuals are unobserved, and measures of effort vary under policy. Third, relevant policy and broader stakeholder audiences differ in the standards of measurement they recognize. Transparent and broadly accepted, or at least interoperable, standards for assessing effort would help corporations and nations strengthen confidence in corporate claims that RE procurement efforts support international climate goals. 

Abstract Enzymes that oxidize aromatic substrates have shown utility in a range of cell-based technologies including live cell proximity labeling (PL) and electron microscopy (EM), but are associated with drawbacks such as the need for toxic H₂O₂. Here, we explore laccases as a novel enzyme class for PL and EM in mammalian cells. LaccID, generated via 11 rounds of directed evolution from an ancestral fungal laccase, catalyzes the one-electron oxidation of diverse aromatic substrates using O₂instead of toxic H₂O₂, and exhibits activity selective to the surface plasma membrane of both living and fixed cells. We show that LaccID can be used with mass spectrometry-based proteomics to map the changing surface composition of T cells that engage with tumor cells via antigen-specific T cell receptors. In addition, we use LaccID as a genetically-encodable tag for EM visualization of cell surface features in mammalian cell culture and in the fly brain. Our study paves the way for future cell-based applications of LaccID.