Thiol-PEG3-acid is a PEG linker containing a thiol group and a terminal carboxylic acid. The hydrophilic PEG spacer increases solubility in aqueous media. The thiol group reacts with maleimide, OPSS, vinylsulfone and transition metal surfaces including gold, silver, etc. The terminal carboxylic acid can react with primary amine groups in the presence of activators (e.g. EDC, or HATU) to form a stable amide bond.
