might bind negative residues on cargoes more weakly than
guanidinium-rich D9, which might explain the need for voltage or
lipid charge asymmetry when using Pep-1. So far, the DIB experiments
have revealed that these two pore-forming carriers work very differently
under well-defined conditions and that further investigation is needed
to understand these differences.
Here, we have shown that the guanidinium-rich D9-NBD polymer
can facilitate transport of a protein cargo across a lipid bilayer without
the requirement of negative charge or voltage. In addition, its ability
to transport this protein is enhanced when the carrier-cargo is not
pre-mixed demonstrating that pre-formed complexes are not required
for transport. The DIB system is ideally suited for probing the mechanistic
details of various carriers and enables well-defined, independent
variables to be studied in isolation which are more difficult to accomplish
in many bulk studies. Given the complex landscape of CPP related
transport, or internalization, we are motivated to continue studying
these systems as broadly as possible. The growing use of CPPs and related
molecules in molecular delivery applications highlights the need for
more fundamental studies of the delivery mechanism. Learning how to
develop more effective carriers is vital to researchers in many different
fields.