Simple enrichment of thiol‐containing biomolecules by using zinc(II)–cyclen‐functionalized magnetic beads

A simple and efficient method based on magnetic‐bead technology has been developed for the enrichment of thiol‐containing biomolecules, such as l‐glutathione and cysteine‐containing peptides. The thiol‐binding site on the bead is a mononuclear complex of zinc(II) with 1,4,7,10‐tetraazacyclododecane (cyclen); this is linked to a hydrophilic cross‐linked agarose coating on a particle that has a magnetic core. All steps for the thiol‐affinity separation are conducted in aqueous buffers with 0.10 mL of the magnetic beads in a 1.5 mL microtube. The entire separation protocol for thiol‐containing compounds, from addition to elution, requires less than one hour per sample, provided the buffers and the zinc(II)–cyclen‐functionalized magnetic beads have been prepared in advance. The thiol‐affinity magnetic beads are reusable at least 15 times without a decrease in their thiol‐binding ability, and they are stable for six months at room temperature.