m-PEG-Succinimidyl Valerate(m-PEG-SVA), MW 20K is an amino (-NH2) reactive PEG derivative, the hydrolysis of the NHS-ester competes with the reaction in aqueous solution and increases with increasing pH.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.