Described herein are small peptide domains and consensus sequences that bind small target molecules of industrial importance, e.g., metals such as nickel, β carotene, and isoflavones such as genistein. Also described are fusion proteins containing such binding domains fused to proteins or to peptide domains like GST or CBD that bind other ligands and can be used to immobilize the target binding domain on a support. One class of fusion proteins that is useful in industrial settings are fusions that contain concatemers of target binding domains, which increases the binding equivalents per molecule.