HS-PEG-COOH, MW 3.5K (SH-PEG-COOH, MW 3.5K) offered by Axispharm is a linear heterobifunctional PEG reagent with thiol and carboxyl groups. It is a useful crosslinker with a PEG spacer.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.