FIGURE 3.

Stability of the caging group in cell culture. (A) EGFP expression after different periods of proliferation. HeLa cells were transfected with caged siRNA IV and proliferated without irradiation for increasing time spans before fluorescence intensity was analyzed. While 24 h past transfection the caged siRNA is still inactive, after 28 h a reactivation with resulting decreasing fluorescence intensity of EGFP sets in, which further progresses with increasing time to reach an activation of ∼40% after 46 h past transfection. (B) In the siRNA IV the photolabile protection group is positioned at nucleotide # 9 of the antisense strand.