Low molecular weight disulfide cross-linking peptides as nonviral gene delivery carriers

Cross-linking peptides have been developed by inserting multiple Cys residu es into a 20 amino acid condensing peptide that polymerizes through disulfi de bond formation when bound to DNA resulting in small, highly stable DNA c ondensates that mediate efficient in vitro gene transfer [McKenzie et al. ( 2000) J. Biol. Chem. 275, 9970-9977]. In the present study, a minimal pepti de of four Lys and two terminal Cys residues was found to substitute for Cy s-Trp-(Lys)(17)-Cys resulting in DNA condensates with similar particle size and gene expression in HepG2 cells. Substitution of His for Lys residues r esulted in an optimal peptide of Cys-His-(Lys)(6)-His-Cys that, in addition to the attributes described above, also provided buffering capacity to enh ance in vitro gene expression in the absence of chloroquine. The reported s tructure-activity relationships systematically explore peptides with combin ations of Lys, Cys, and His residues resulting in low molecular weight pept ides with improved gene transfer properties.