Because supplementation of liquid culture with 40mM sodium selenite creates a condition where GRLMR expressing cells proliferate whereas inactivated GRLMR cells do not, we attempted selections of the EP-PCR library at 50mM sodium selenite concentration (10 mM higher than in the proof-of-concept experiments), under the hypothesis that GRLMR mutants with improved activity will out-compete WT-GRLMR in these conditions in the same way that WT-GRLMR outcompeted Ala-GRLMR.