m-PEG-thiol, MW 5K is a linear monofunctional PEG with a free thiol group at one end that can react with maleimide or disulfide. The thiol groups on the cysteine side chains are PEGylated under mild reaction conditions.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.