A biologically inactivated cell-specifically effective molecule for biologically inactive transfection into a target cell to inhibit expression of genes in the target cell after biological activation of the molecule, by bonding to mRNA and with the formation of a RISC complex, the biologically inactivated cell-specifically effective molecule comprising siRNA coupled with at least one peptide via a linker which remains at the siRNA after biological activation of the molecule, the linker comprising an amino Cn linker wherein n is an integer of 1-6. Kits include the molecule or the constituents thereof and transfection reagents in ampoules and injection equipment for injecting mixtures of the ampoule contents into a medium containing a target cell.
