Azido-PEG-CH2COOH is a type of polyethylene glycol (PEG) that has been modified with an azide group and a carboxylic acid group attached to it. It is a water-soluble molecule used in bioconjugation chemistry, which involves linking two molecules together. It is used in the production of bioconjugates, which are molecules that are composed of two or more different components. These molecules are used in drug delivery, diagnostics, and other biomedical applications.