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.
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