Enzyme mimics (mimetics) include abzymes (catalytic antibodies), RNA molecules (ribozymes), and enzyme analogues synthesized upon a polypeptide backbone structure (synzymes). Also, there is a variety of model systems such as the zeolite-membrane systems containing metal complexes, which mimic cytochrome P-450. Enzymes are being subjected to redesign procedures to introduce desired features such as thermostability that could improve their industrial usefulness : but even such novel enzymes may not be able in the near future to out-perform the enzyme mimics in all circumstances, such as at temperatures above about 120 degrees C or under completely non-aqueous conditions.