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

  • Liu, Jia-Ning
  • Chang, Sen-Lin
  • Xu, Peng-Wei
  • Tan, Ming-Hui
  • Zhao, Bing
  • Wang, Xiao-Dong
  • Zhao, Qing-Sheng
Publication Date
Jan 29, 2020
Institutional Repository of Institute of Process Engineering, CAS (IPE-IR)
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epsilon-Poly-L-lysine (epsilon-PL) consists of 25-35 lysine residues which are linked by an isopeptide bond formed by dehydration condensation of alpha-carboxyl and epsilon-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 epsilon-PL in aqueous solution. Herein, a high purity of epsilon-PL was prepared using Amberlite IRC-50 ion-exchange resin. Membrane filtration and dynamic light scattering were used to study the variations of epsilon-PL aggregation in aqueous solution with pH value. The conformational changes and antibacterial activities of epsilon-PL and carbamoylated epsilon-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 epsilon-PL conformation and aggregation. epsilon-PL exhibited the properties of a beta-sheet during spray drying from acidic liquids to solids. The cation enhanced the antibacterial activity of epsilon-PL but did not play a key role. Instead, the backbone of epsilon-PL might determine the mechanism of epsilon-PL antibacterial.

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