t-Butoxycarbonyl-PEG2-NHS ester features a t-Boc protecting group along with an NHS ester segment. The tert-butyl group can be deprotected under acidic conditions. The NHS ester reacts specifically and efficiently with primary amines, such as lysine residue side chains or amino-silane coated surfaces, under neutral or weakly basic conditions, forming covalent bonds. The hydrophilic PEG linker enhances the compound's solubility in aqueous media.