Structural changes and antibacterial activity of ε-PL in response to pH and phase transition and their mechanisms

e-poly-L-lysine (e-PL) consists of 25-35 lysine residues which are linked by an isopeptide bond formed by dehydration condensation of α-carboxyl and e-amino groups, has good antibacterial activity and broad-spectrum inhibition range. However, there is no clear conclusion about the structure and antibacterial mechanism of e-PL in aqueous solution. Herein, a high purity of e-PL was prepared using Amberlite IRC-50 ion-exchange resin. Membrane filtration and dynamic light scattering (DLS) were used to study the variations of e-PL aggregation in aqueous solution with pH value. The conformational changes and antibacterial activities of e-PL and carbamoylated e-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 (FT-IR). The results indicated that the side chain amino charge played a decisive role in the e-PL conformation and aggregation. e-PL exhibited t...