Interaction of tryptophan-arginine rich peptide with model membranes: Mechanistic insights into the outer-membrane disruption

Tyrica S Foster, Tennessee State University


There is a dramatic and continued evolution of drug resistant strains of bacteria. The response of the worldwide research scientific community is an intensive effort to develop new classes of antibiotics with novel mechanisms of antibacterial activity. One of the answers is to focus on antimicrobial peptides (AMP) that have the potential to be developed into new therapeutic agents. Their mode of action involves some type of membrane disruption which, by its very nature, decreases the ability of bacteria to develop resistance to them. Very few studies have investigated the interaction of (RW)4 with zwitterionic and anionic model membranes. The main objective is to investigate the mechanism of interaction of (RW)4 with the model membranes 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC, zwitterionic) and 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG, anionic). A secondary objective is to investigate the interaction of (RW)4 with membranes in a medium loaded with trivalent metal ions (Eu3+, Al3+, Fe3+). Infrared (IR) spectroscopy is used to report on secondary structures. Dynamic Light Scattering (DLS) is used to report on aggregation size of membrane/peptide complex. Fluorescence and UV-Visible spectroscopes are used to report on tertiary structure. Proton NMR is used to assess the involvement of N-H group. Infrared curve-fitting data indicate that (RW)4 adopts a mixture of secondary structures in water including some helix structures. (RW) 4 mainly adopts turn structures in the presence of DPPG and DPPC. Metal ions induced some helix structures in the structure of (RW)4. DLS experiments revealed that DPPC and DPPG form stable aggregates in water. The peptide/lipid molar ration of 1 or less is recommended. Fluorescence emission and absorption spectra showed a stronger interaction between (RW)4 and DPPG than DPPC, as evidenced by the quenching of the fluorescence of (RW) 4. UV-Visible results confirm fluorescence results of peptide lipid interaction. NMR results verify the binding of the N-atom. Based off the collaborative results obtained using the various spectroscopic techniques, we have determined that their killing mechanism occurs through a conformational change, using turn structure and through the disruption of the membranes. The presence of metal ions decreases the effect of the antimicrobial peptide (RW)4.

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Recommended Citation

Tyrica S Foster, "Interaction of tryptophan-arginine rich peptide with model membranes: Mechanistic insights into the outer-membrane disruption" (2012). ETD Collection for Tennessee State University. Paper AAI1533495.