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Updated: Feb 21, 2026

Delivery of Proteins, Peptides or Cell-impermeable Small Molecules into Live Cells by Incubation with the Endosomolytic Reagent dfTAT
Published on: September 2, 2015
Cytosolic Delivery of Proteins by Bioreversible Esterification
Kalie A Mix1, Jo E Lomax, Ronald T Raines1
1Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Abstract:
Cloaking its carboxyl groups with a hydrophobic moiety is shown to enable a protein to enter the cytosol of a mammalian cell. Diazo compounds derived from (p-methylphenyl)glycine were screened for the ability to esterify the green fluorescent protein (GFP) in an aqueous environment. Esterification of GFP with 2-diazo-2-(p-methylphenyl)-N,N-dimethylacetamide was efficient. The esterified protein entered the cytosol by traversing the plasma membrane directly, like a small-molecule prodrug. As with prodrugs, the nascent esters are substrates for endogenous esterases, which regenerate native protein. Thus, esterification could provide a general means to deliver native proteins to the cytosol.
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