HO-PEG-amine, MW1K is PEG derivative with hydroxyl and amine end group. The hydroxyl can be reacted to further derivatize the compound. The amine group can react with carboxylic acids, activated NHS esters and other carbonyl groups. The hydrophilic PEG chain increases the water solubility of the compound in aqueous media. The water solubility properties of the PEG linker are enhanced with longer PEG chains.