Hydroxyl PEG Acetic Acid(HO-PEG-CH2COOH) is a heterobifunctional hydroxy PEG acetic acid product with COOH that reacts with primary amines and activators such as EDC or HATU to form stable amide bonds. Hydroxyl groups can be further derivatized. It is often used as a crosslinker or as a spacer between two different chemical entities. Suitable for antibody drug conjugate (ADC) development.