Discovery of endosomalytic cell-penetrating peptides based on bacterial membrane-targeting sequences.

Cell-penetrating peptides (CPPs) are prominent scaffolds for drug developments and related research, particularly the endocytic delivery of biomacromolecules. Effective cargo release from endosomes prior to lysosomal degradation is a crucial step, where the rational design and selection of CPPs remains a challenge and calls for deeper mechanistic understandings. Here, we have investigated a strategy of designing CPPs that selectively disrupt endosomal membranes based on bacterial membrane targeting sequences (MTSs). Six synthesized MTS peptides all exhibit cell-penetrating abilities, among which two d-peptides (d-EcMTS and d-TpMTS) are able to escape from endosomes and localize at ER after entering the cell. The utility of this strategy has been demonstrated by the intracellular delivery of green fluorescent protein (GFP). Together, these results suggest that the large pool of bacterial MTSs may be a rich source for the development of novel CPPs.

α-Selective Lysine Ligation and Application in Chemical Synthesis of Interferon Gamma.

A traceless ß-mercaptan-assisted α-selective ligation of N-terminal lysine-containing peptides has been developed. In this ligation-desulfurization-based protocol, the ε-amine of lysine is free of protection, thus improving the overall synthetic efficiency and avoiding harsh reactions in preparing large peptides and proteins. The applicability of this methodology has been demonstrated in the synthesis of an acid-labile therapeutic protein, interferon gamma, and the anticancer activity of synthetic protein has also been evaluated.