K562 cells were lipofected using DMRIE-C as described in “Materials and methods.” Cells were analyzed 24 hours after lipofection by flow cytometric analysis for enhanced green fluorescent protein (EGFP) expression to estimate transfection efficiency (= % EGFP⁺ cells) as well as by ethidium bromide exclusion for cell viability. Results are the mean of 4 independent experiments each with a different in vitro–transcribed mRNA batch (standard error of the mean < 2.5%).