Front Cover: Engineering and Structural Elucidation of a Sac7d‐Derived IgG Fc‐Specific Affitin and Its Application for the Light‐Controlled Affinity Purification of Antibodies (ChemBioChem 11/2025)

Antibodies (mAbs) are isolated in one step, under physiological conditions, via light‐controlled affinity purification using an affitin derived from the Sac7d scaffold and the Azo‐tag, thus overcoming limitations of conventional protein A chromatography and acid‐triggered elution. X‐ray crystallographic analysis and affinity measurements revealed complex formation of the affitin with Fc at the C H 2/C H 3 junction, similar to protein A/G and FnRn, which is remote from the binding site, hence allowing direct application of the purified mAb for biochemical or cell culture assays. More details can be found in article 2500102 by Arne Skerra and co‐workers.