Investigation of peptide-lipid interaction by fluorescence correlation spectroscopy

Abstract

In this study a series of antimicrobial peptides (AMPs) called modified V4 (MV4s), was designed to have better solubility compared to original V4, which originated from a LPS-binding motif. The interaction between MV4s and different lipid model membranes was investigated using fluorescence correlation spectroscopy (FCS) and laser scanning confocal imaging. A similar mechanism of MV4s was observed as compared to V4. MV4s induced lipid aggregation before they disrupted the lipid membranes. By comparing between different MV4s, we found that a) highly positively charged peptides preferentially bound to negatively charged lipid, b) higher hydrophobicity gave rise to a higher activity against both negatively charged and zwitterionic lipid, and c) two binding motifs in V4 were crucial to maintain its activity. The study of AMPs on living E. coli suggested that peptides with medium hydrophobicity showed the highest antimicrobial activity. In order to further investigate AMPs mechanism of disrupting membrane, a new modality of FCS, imaging total internal reflection fluorescence correlation spectroscopy (ITIR-FCS), was developed to measure the molecular dynamics on membrane. Results obtained by ITIR-FCS could possibly indicate the aggregation of peptides on lipid membranes.