(11-Mercaptoundecyl)tetra(ethylene glycol) (MUTEG) is a capping agent that is used in the surface modification of a variety of nanoparticles. It can be also be used as an effective protein repellent.MUTEG can be used to functionalize gold nanoparticles, which can potentially be used to signal peptides, as fluorescent probes and as electrocatalytic membranes. It can also facilitate the sensing of protein on polymeric substrates for biosensor based applications.