m-PEG4-(CH2)3-methyl ester contains a methyl ester end group. Methyl ester can be hydrolyzed under strong basic condition to form a free acid. The PEG spacer increases the solubility of the compound in aqueous media.
AxisPharm offers 4000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.