Propargyl-PEG4-CH2CO2H is a linker consisting of a propargyl group with a carboxylic acid group. The carboxylic acid can react with primary amine groups in the presence of activators such as HATU or EDC. The propargyl group can react with azide compounds in Click Chemistry; copper catalyst will be needed. The PEG units help the molecule to have better solubility in aqueous solution.
Propargyl-PEG3-CH2COOH is a PEG-based PROTAC linker can be used in the synthesis of PROTACs[1]. Propargyl-PEG3-CH2COOH is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.