Dilute only the needed amount of Profectin™ Transfection Reagent 1:10 in sterile deionized water 0 to 1 hour prior to co-transfection. For example, if you are performing one co-transfection, add 5μl of Profectin™ to a sterile 1.5 ml Eppendorf tube, add 45 μl of water and mix gently by pipetting up and down 2-3 times. Similarly, mix 10 μl of Profectin™ with 90 μl of water, 15 μl with 135 μl, or 20 μl with 180 μl for 2, 3 or 4 co-transfections, respectively. It is also important to avoid creating bubbles in the diluted transfection reagent when mixing. No special tubes are required for diluting the reagent, and any remaining diluted Profectin™ should not be stored or used for future transfections.