N^α‐Methylation of arginine: Implications for cell‐penetrating peptides

Abstract

The field of cell‐penetrating peptides is dominated by the use of oligomers of arginine residues. Octanol–water partitioning in the presence of an anionic lipid is a validated proxy for cell‐penetrative efficacy. Here, we add one, two, or three N‐methyl groups to Ac‐Arg‐NH2 and examine the effects on octanol–water partitioning. In the absence of an anionic lipid, none of these arginine derivatives can be detected in the octanol layer. In the presence of sodium dodecanoate, however, increasing N‐methylation correlates with increasing partitioning into octanol, which is predictive of higher cell‐penetrative ability. We then evaluated fully Nα‐methylated oligoarginine peptides and observed an increase in their cellular penetration compared with canonical oligoarginine peptides in some contexts. These findings indicate that a simple modification, Nα‐methylation, can enhance the performance of cell‐penetrating peptides.

Cell Penetrating Peptides: Classification, Mechanisms, Methods of Study, and Applications

“…To enhance cell permeability of CPPs and cargo transport efficiency, different strategies have been used such as the use of alternative side chains composed of cationic moieties different from the natural lysine-or arginine-like residues, [114] the synthesis of macrocyclic peptoids enriched with hydrophobic residues [115] or recently, by introducing arginine Nα-methylation, a modification demonstrated to enhance the performance of cell-penetrating peptides. [116] A generally accepted dogma regarding CPPs was that the cationic character was mandatory to exploit cell permeabilization. This aspect has been refuted by different studies in which anionic peptides perform as well as cationic counterparts, effectively broadening the landscape of molecules transportable by these peptides.…”