m-PEG-Lys-NHS ester, MW 40K is a PEG linker containing a maleimide end group and a t-Boc protected lysine. The maleimide can react with thiol groups between a pH range of 6.5 to 7.5.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.