Binding Properties of DNA and Antimicrobial Peptide Chensinin-1b Containing Lipophilic Alkyl Tails

Multidrug-resistant bacteria present an important threat to human health. In this study, due to the weak antimicrobial activity of chensinin-1b against multidrug-resistant (MDR) bacteria, three lipo-chensinin-1b peptides, including OA-C1b, LA-C1b and PA-C1b, were designed and their activities against MDR bacteria were examined. Both the OA-C1b and LA-C1b peptides exhibited potent antimicrobial activity against selected multidrug-resistant bacterial strains. In addition to the direct disruption of bacterial membranes by antimicrobial peptides, it has also been proposed that DNA is a superior intracellular target for antimicrobial peptides. ctDNA was used as a model to investigate the binding properties of DNA and lipo-chensinin-1b peptides using a variety of biophysical methods. The kinetics results of both UV-Vis and CD spectroscopy suggested that the interaction between lipo-chensinin-1b peptides and ctDNA was concentration-dependent and resulted in an increase in polynucleotide helicity. Viscosity measurements, Trp fluorescence and iodide quenching experiments indicated that nonclassical groove binding and electrostatic binding interaction modes were utilized when the peptides interacted with the ctDNA. In addition, the formation of peptide-ctDNA complexes was monitored using dynamic light scattering experiments, during which the peptide exhibited the ability to neutralize the negative charges on the surface of the ctDNA. These results promote the possibility of designing peptide-based antibiotics targeted to DNA.