Poly-L-arginine (P-Arg)

Poly-L-arginine is a synthetic, cationic polypeptide comprised exclusively of L-arginine amino acids linked together by peptide bonds. It is not a naturally occurring protein or receptor, but a laboratory-produced polymer notable for its high positive charge. This property enables strong electrostatic interactions with negatively charged molecules and cellular surfaces. Poly-L-arginine is often used in research as a mimic for cell-penetrating peptides (CPPs), in gene/drug delivery applications, and as a model for studying polyelectrolyte behavior. In aqueous solution, it generally adopts a random coil or extended conformation under physiological pH, but can adopt α-helical structures at high pH. Poly-L-arginine's cationic nature can promote membrane translocation of attached cargo, but also introduces cytotoxicity at elevated concentrations by destabilizing cellular membranes. It is not itself a receptor, enzyme, or classical biological drug target, but is important as an experimental reagent in both biomedical and material science contexts.

Other names

Poly(L-arginine)P-ArgPoly-L-Arginine hydrochloridepolyarginine

When used as a cell-penetrating peptide: enables cargo (e.g., nucleic acids, proteins, nanoparticles) to enter cells by destabilizing membranes and facilitating translocation. Acts through strong electrostatic interaction with negatively charged cell components, such as glycosaminoglycans in the extracellular matrix or plasma membrane.