Sortase A LPETGG Research Peptide

IRDye 700DX is not simply a second colour. Alongside its use as a 700 nm fluorophore it is the photosensitiser employed in near-infrared photoimmunotherapy, where illuminating the bound conjugate kills the cell carrying it. A substrate built on this dye therefore carries a capability the 800CW version does not.

That cuts both ways and is worth deciding about before use. Where controlled ablation is the aim, site-specific attachment through sortase A places the photosensitiser at one defined position rather than scattered across surface lysines, giving a homogeneous conjugate with predictable stoichiometry. Where only imaging is intended, excitation should be limited, since prolonged strong illumination may reduce viability and confound the very measurement being made.

Sortase A recognises the LPXTG motif and exchanges the residues after the threonine for a glycine-bearing nucleophile, which is what allows single-site installation. Because 700DX and 800CW are read on separate channels of standard near-infrared imagers, the two substrates support two-colour experiments in which distinct labelling events are resolved in one sample.

• Second-channel label for two-colour sortase experiments
• Near-infrared photoimmunotherapy and light-triggered cell ablation
• Photosensitiser delivery to a defined position on a target protein
• Imaging in the 700 nm channel alongside an 800 nm counter-label
• Controlled phototoxicity studies requiring site-specific attachment

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2. Nakandakari-Higa S, Walker S, Canesso MCC, et al. Universal recording of immune cell interactions in vivo. Nature (2024) 627:399. doi:10.1038/s41586-024-07134-4