Harvard's David Liu has created a GFP mutant with an approximate charge of 36+. The supercharged protein doesnŐt aggregate and binds to negatively macromolecules such as siRNA and DNA. This is incredibly useful as the mega-positive GFP penetrates mammalian cells with ease. By complexing the GFP36+ with nucleic acids the researchers were able to deliver into four different mammalian cell lines. "ItŐs too early to know if supercharged proteins will provide a general solution to a major delivery problem, but we are excited to explore that possibility."
Calculated electrostatic surface potentials of GFP variants used in this work, colored from -25 kT/e (dark red) to +25 kT/e (dark blue).
Flow cytometry analysis showing amounts of internalized GFP in HeLa cells treated with 200 nM each superpositive GFP variant and washed three times with PBS containing heparin to remove cell surface-bound GFP