HOOC-PEG-COOH (MW 2000) has two active carboxyl groups at both ends, which can selectively react with the amino groups in peptide coupling agents. HOOC-PEG-COOH (MW 2000) is a good cross-linking agent for PEGylation of proteins and peptides, nanoparticles and surface modification[1].
References:
[1].Bian Y, et al. Carboxyl PEGylation of magnetic nanoparticles as antithrombotic and thrombolytic agents by calcium binding. J Colloid Interface Sci. 2023 May 15;638:672-685.