Smart Poly(imidazoyl-l-lysine): Synthesis and Reversible Helix-to-Coil Transition at Neutral pH

Abstract

Polypeptide polymers can adopt natural protein secondary structures such as α-helices or β-sheets, and this unique feature is at the origin of some intriguing physico-chemical properties.In this work, we present how side chain imidazoylation of a poly(L-lysine) scaffold affords the preparation of poly(histidine) counterparts exhibiting α-helix conformation. This structuring behavior is reversible and can be controlled by means of pH and or temperature changes.

Stimuli-Responsive Polypeptides for Biomedical Applications

“…These findings show the possibility for developing pH-sensitive collagen-based materials which can selectively release cargo molecules at low pH [26]. A similar concept was reported by imidazoylated poly- l -lysine (PLL) [27]. PLL is endowed with a random-coiled conformation because of dominant electrostatic repulsion.…”

“…PLL is endowed with a random-coiled conformation because of dominant electrostatic repulsion. To form a pH-sensitive helical structure, the imidazole moieties were attached to the primary amines of the PLL by the formation of amide bonds [27]. It was observed that imidazoylated PLL underwent a pH-triggered conformational transition from an alpha helix to a random coil structure with a decreasing pH level [27].…”

“…To form a pH-sensitive helical structure, the imidazole moieties were attached to the primary amines of the PLL by the formation of amide bonds [27]. It was observed that imidazoylated PLL underwent a pH-triggered conformational transition from an alpha helix to a random coil structure with a decreasing pH level [27]. The reason for the pH-triggered random coil formation was that the imidazole rings were protonated at acidic pH [27].…”

“…It was observed that imidazoylated PLL underwent a pH-triggered conformational transition from an alpha helix to a random coil structure with a decreasing pH level [27]. The reason for the pH-triggered random coil formation was that the imidazole rings were protonated at acidic pH [27]. This concept of a conformation-transformable characteristic by pH was used in a pH-triggered drug release system at a specific target site [27].…”

“…The reason for the pH-triggered random coil formation was that the imidazole rings were protonated at acidic pH [27]. This concept of a conformation-transformable characteristic by pH was used in a pH-triggered drug release system at a specific target site [27].…”