TTD, Cys-Interactome Capture Probe

TTD (Thianthrenium Dication) is a cell-permeable, bench-stable precursor that redefines live-cell PPI mapping by generating the reactive alkenyl thianthrenium species in situ. TTD’s mechanism operates via a rapid, stepwise chemical cascade: immediate deprotonation (t1/2 ≈ 3 s) facilitates cysteine-selective Michael addition (86% intracellular site-selectivity), followed by intramolecular thianthrene displacement to yield a highly reactive episulfonium intermediate. This intermediate undergoes nucleophilic ring-opening by proximal amino acids to secure stable ethylene-linked inter- and intra-protein cross-links. A critical design innovation is the integration of a bioorthogonal alkyne handle that enables affinity enrichment of low-abundance targets without elongating the inter-residue bridge, thereby preserving precise short-distance restraints (4–23 Å) essential for high-resolution modeling. Fully compatible with live-cell protocols (1 hour labeling) and exhibiting no acute cytotoxicity, TTD enables high-fidelity structural characterization of complex interaction interfaces in their native environment, revealing previously unreported protein−protein interactions (PPIs).

Hygroscopic, Store with desiccant