Post-translational modifications can dramatically impact protein activity, but identifying such structure:function relationships, as well as capitalizing on functionally enhanced variants, is a significant challenge. Here, affinity chromatography resins that contained immobilized FcRIII receptors were used to enrich nonfucosylated antibodies 6- to 9-fold, offering what may be a tractable method for both the identification of post-translational modifications that affect function, as well as a means to enrich variants with enhanced activity. (c) 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:825-828, 2013