Thiolreactive

Thiolreactive refers to reagents or chemical motifs that react specifically with thiol groups (-SH) present in molecules such as cysteine residues in proteins, glutathione, or other thiols. These reagents are used to label, modify, or detect thiols in biochemical and materials contexts. The reactivity stems from nucleophilicity of sulfur and the electrophilicity of the reagent's functional group.

Common thiol-reactive motifs include maleimides, vinyl sulfones, iodoacetamides, and disulfide-based reagents. Maleimides undergo a Michael-type addition with thiols to form stable thioether linkages, typically under near-neutral pH. Iodoacetamides alkylate thiols via SN2-like substitution, yielding thioether products. Disulfide-reagents can form or exchange disulfide bonds, enabling reversible labeling or quantification assays.

Applications include protein labeling and immobilization, detection and quantification of thiols, affinity capture, fluorescent tagging, and redox biology studies. In proteomics, thiol-reactive probes enable selective tagging of cysteine-containing peptides or proteins. In materials science, thiol-reactive compounds help attach dyes or cross-linkers to surface thiols.

Considerations include that reactivity is influenced by pH, steric accessibility, and competing nucleophiles such as amines. Some reagents form reversible adducts; others yield stable products. Off-target modification of non-thiol nucleophiles can occur, so selectivity, reaction time, and concentration must be managed. Safety and compatibility with aqueous buffers and biological systems are important.