Crunching the numbers. Responsibly.
Our top design, LUCI-tag, is a 19 kDa, monomeric, thermostable SLP that rapidly and covalently reacts with commercially available K-Ras(G12C) inhibitors bearing diverse payloads.
SEC, thermal analysis, mass spectrometry, and kinetic assays directly support the stated biochemical properties
LUCI-tag enabled rapid, wash-free, live-cell imaging and simultaneous three-color multiplexed experiments with HaloTag7 and SNAP-tag.
live-cell experiments directly demonstrate wash-free nuclear labeling and orthogonal three-color imaging
X-ray crystal structures of drug-bound and drug-free LUCI-tag showed the design was structurally accurate and contained a preorganized inhibitor-binding pocket that could explain its rapid labeling kinetics.
three structures directly support structural accuracy, while the kinetic interpretation is appropriately qualified
Unlike existing SLPs, LUCI-tag exhibited payload-agnostic labeling kinetics, outperforming HaloTag7 and SNAP-tag for a negatively charged payload.
AF488 results support the scoped comparison, though comparator rates partly come from a prior study
Proteomics and cell-signaling experiments confirmed LUCI-tag is biologically inert.
IP-MS and signaling assays support inactivity in tested settings, but do not establish universal biological inertness
Derived from the full evaluation — not a separate score.
Strengths
Biochemical kinetics, intact mass spectrometry, three crystal structures, IP-MS, signaling assays, and live-cell microscopy address complementary aspects of activity, structure, orthogonality, and use.
↳ Figures 2–5; Table S7
Simultaneous staining of LUCI-tag, HaloTag7, and SNAP-tag produced spatially exclusive signals without observed cross-reactivity in HEK293T cells.
↳ Figure 5c
Model parameters, filtering thresholds, sequences, plasmids, buffers, structural coordinates, proteomics records, and design code are identified in the supplement and availability statements.
↳ Tables S2–S13; Data Availability; Code Availability
Limitations
Figure 2f draws HaloTag7 and SNAP-tag rate constants from reference 25 rather than measuring every comparator contemporaneously under a fully matched protocol.
↳ Figure 2f caption; Table S4
The absolute “biologically inert” wording rests principally on IP-MS in Molt4 lysate and a Ras-pathway signaling assay in transfected HEK293T cells, limiting its generality.
↳ Abstract; Figure 4a–b
Functional cellular demonstrations cover several fusions and probes but remain concentrated in transformed mammalian cell lines, without primary-cell, tissue, organismal, or in vivo validation.
↳ Figures 5, S40, and S42
The strongest basis for the score is the end-to-end validation spanning the 20,000-design computational pipeline, characterization of 48 candidates, structural analysis, proteomics, signaling, and live-cell imaging. Figure 5c directly establishes the central three-color capability, while Figures 2 and 4 support rapid labeling and biological disengagement in the tested systems. The score remains below the airtight tier because Figure 2f partly relies on literature-derived comparator kinetics, the many redesign choices are not fully isolated experimentally, and cellular generality remains limited. The crystallographic resolution wording also requires clarification: the Results state 2.2 Å, Table S7 reports 2.94 Å overall, and Figure 3a identifies 2.2 Å as the anisotropic ellipsoidal limit.
Nabu’s assessment, alongside the field’s view.
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Strong4.1
Confidence mediumThe score reflects a substantial tool-development advance: a radically redesigned K-Ras(G12C) scaffold functions as an orthogonal third self-labeling tag and enables three-color imaging. Claims that the approach establishes a broadly applicable platform extend beyond the single redesigned target system demonstrated here.
“LUCI-tag enabled rapid, wash-free, live-cell imaging and simultaneous three-color multiplexed experiments with HaloTag7 and SNAP-tag.”
The design pipeline, filtering of 20,000 candidates, characterization of 48 selected proteins, structural analysis, proteomics, signaling assays, and microscopy form a well-aligned validation chain. The kinetic comparison with HaloTag7 and SNAP-tag partly uses literature values, and broader redesign components are not experimentally isolated one by one.
“Halo- and SNAP-tag values are taken from ref. 25.”
The presentation moves coherently from the multiplexing problem through design, biochemical and structural validation, biological orthogonality, and live-cell use. The abstract’s unqualified description of biological inertness is broader than the Molt4 IP-MS and HEK293T signaling settings directly tested.
“Proteomics and cell-signaling experiments confirmed LUCI-tag is biologically inert.”
The paper engages established tags, recent alternatives, and KRAS inhibitor chemistry while tracing practical limitations involving permeability, fluorogenicity, and cofactor dependence. External-validity limits across cell types and organisms receive less explicit treatment than probe-engineering limitations.
“Fit-for-purpose, non-clickable AG probes with optimized linkers could be synthesized to maximize cell permeability.”
Caveats4 of 4 checks
Core numerical and experimental claims are coherent, but the crystallographic resolution is reported using two conventions without the distinction being made in the main Results text. Some abstract wording also compresses findings obtained in specific payload and cellular settings into broader formulations.
Competing interests and funding are disclosed, and the paper names PDB, PRIDE, and Zenodo deposits. No human- or animal-subject ethics declaration is required for the reported protein, lysate, and established cell-line experiments.
Flags: 3 declared / 5 total
11 of 32 checkable references verified
32 references in manuscript
No retraction notice found in Retraction Watch.
Sources: Retraction Watch ✓
Where this paper’s evidence sits on the path from initial observation to real-world use.
LUCI-tag is tested in purified-protein assays, mammalian live-cell microscopy, intracellular and extracellular fusions, and a three-color workflow. Broader external validation and optimized probe distribution remain necessary for routine deployment across laboratories.
“We developed a ‘direct to biology’ protocol that does not require purification.”
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