m-PEG-Thiol, MW 1K (mPEG-SH) is a linear polyPEG with a thiol group with a free thiol group at one end, which can react with maleimide or disulfide. Increasing the number of PEG repeating units also improves the water solubility of the compounds.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.