A 50 kD anti-actin antibody fragment labeled with Texas Red was delivered to HeLa cells and labeled the cytoskeleton of the live cells with bright fluorescence using Endo-Porter from Gene Tools. Endo-Porter is a peptide which acts as an endosomal release agent. When a large molecule (such as an antibody or, better, an antibody fragement) is co-endocytosed with Endo-Porter, the large molecule is released from the endosome to the cytosol as endosomal acidification protonates Endo-Porter, making Endo-Porter membrane-active.

Endo-Porter delivers weakly charged or uncharged cargos into live cells effectively and is commonly used to deliver uncharged Morpholino antisense to cultured cells. Endo-Porter does not work well with nucleic acid cargos, as in its cationic form the Endo-Porter complexes with the anionic nucleic acids and loses membrane activity. Antibody fragments are good cargos for Endo-Porter.

Summerton JE. Endo-porter: a novel reagent for safe, effective delivery of substances into cells. Ann N Y Acad Sci. 2005 Nov;1058:62-75.

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