Structural Changes and Antibacterial Activity of Epsilon-poly-l-lysine in Response to pH and Phase Transition and Their Mechanisms

Abstract

ε-Poly-l-lysine (ε-PL) consists of 25–35 lysine residues which are linked by an isopeptide bond formed by dehydration condensation of α-carboxyl and ε-amino groups and has good antibacterial activity and broad-spectrum inhibition range. However, there is no clear conclusion about the structure and antibacterial mechanism of ε-PL in aqueous solution. Herein, a high purity of ε-PL was prepared using Amberlite IRC-50 ion-exchange resin. Membrane filtration and dynamic light scattering were used to study the variations of ε-PL aggregation in aqueous solution with pH value. The conformational changes and antibacterial activities of ε-PL and carbamoylated ε-PL in different water environments were studied with circular dichroism (CD) and inhibition zone. The structural changes during the spray-drying process were determined by Fourier transform infrared spectroscopy. The results indicated that the side chain amino charge played a decisive role in the ε-PL conformation and aggregation. ε-PL exhibited the properties of a β-sheet during spray drying from acidic liquids to solids. The cation enhanced the antibacterial activity of ε-PL but did not play a key role. Instead, the backbone of ε-PL might determine the mechanism of ε-PL antibacterial.

Epsilon-poly-L-lysine: Recent Advances in Biomanufacturing and Applications

“…In addition, ε-PL and its complexes, such as pluronic grafted dendritic α, ε-PLs (DPL-PF127) and ε-PL-sodium alginate nanoparticles, have been used as novel carriers for delivery of non-viral genes and vaccines (Dung et al, 2016;Yuan et al, 2018). Another recent report described a magnetic mesoporous silica/ε-PL nanomotor-based complex with strong potential for application in treatment of heavy metal poisoning due to its high capacity for removal of excessive lead ions from blood (Liu J. N. et al, 2020). Shima et al (1984).…”

Sequence-Controlled Secondary Structures and Stimuli Responsiveness of Bioinspired Polyampholytes

“…It is expected to deviate from electroneutral (satisfied when f + = f – ) to mostly positive ( f ≈ f + ) or negative ( f ≈ f – ) depending on the proximity of the solution pH to the theoretical p K a values of any of the constituent amino acids. Therefore, it is also of great relevance to determine how the secondary structures of polyampholytes consisting of the oppositely charged amino acids (e.g., Lys and Glu) are compared to the secondary structures of uniformly charged polypeptideshomo-polypeptides (e.g., poly- l -lysine and poly- l -glutamic acid) which have already been recognized for their stimuli responsiveness. − …”

A Wound-Friendly Antibacterial Hyaluronic Acid Dressing with On-Demand Removability for Infected Wound Healing

“…We prepared a new kind of wound dressing with HA and EPL through electrostatic self-assembly. Typically, HA is an acidic polysaccharide and is negatively charged because of the ionized carboxyl groups in the aqueous solution, while EPL is positively charged [42,43]. Bene ting from the strong electrostatic interactions, HA and EPL aggregated rapidly to form HA-EPL coacervates when they were mixed.…”