TCO-PEG-ald(Ald-PEG-TCO) is a versatile chemical compound that has gained popularity in pharmaceutical research and development due to its unique functional groups. TCO stands for trans-cyclooctene, which is a strained cyclic alkene that readily reacts with tetrazines. PEG refers to polyethylene glycol, a polymer that is widely used in drug delivery due to its biocompatibility and ability to improve drug solubility. Ald refers to an aldehyde group, which is a reactive functional group that can be used for the conjugation of biomolecules. TCO-PEG-ald is typically used in bioconjugation reactions, where it can be used to attach drugs or other bioactive molecules to specific targets in the body. This makes it a valuable tool in the development of targeted therapies and imaging agents.