Radiolabeled or biologically functional DNA molecules were introduced into cells by electroporation in a variety of forms: double stranded circles, linearized double stranded fragments and single stranded circular molecules. Molecules rapidly entered cells after exposure to a high field-strength electric pulse and then redistributed between the cytoplasm and the nucleus. Maximal intranuclear levels approximated 104 molecules per cell. Introduced DNA persisted in a biologically active form with a half-life of 15–24 h. There was no evidence for biologically significant alteration of two double stranded gene sequences. Single stranded DNA molecules also retained biological activity.
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