3,6,9,12,15,18,21,24,27,30,33-Undecaoxatetratriacontanoic acid

m-PEG11-CH2COOH is a PEG linker containing a terminal carboxylic acid. The terminal carboxylic acid can react with primary amine groups in the presence of activators (e.g. EDC, or HATU) to form a stable amide bond. The hydrophilic PEG spacer increases solubility in aqueous media.