Bromo-PEG-methyl ester is a PEG derivative with a terminal bromine group at one end and a methyl ester functional group at the other end. Methyl esters are hydrolyzable under strongly basic conditions, and bromide (Br) is a very good leaving group for nucleophilic substitution reactions. AxisPharm offers a range of high-purity bromo-PEG reagents with different linker lengths. Customer-specific PEG reagents are available through custom synthesis. Fast shipping.