Tos-PEG4-CH2CO2H linker contains a tosyl group and a terminal carboxylic acid. The tosyl group is a very good leaving group for nucleophilic substitution reactions. It readily reacts with thiol such as lysine residue of proteins. The terminal carboxylic acid can be used to conjugate with amine bearing molecules in the presence of amide coupling reagents such as EDC, DCC and HATU. The hydrophilic PEG linker increase the solubility of compounds in aqueous media.
Axispharm offers 3000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.