Mechanistic aspects of peptide-membrane interactions determined by optical, dielectric and piezoelectric techniques: an overview.

Antimicrobial peptides (AMPs) have been isolated from a wide variety of organisms that include microorganisms, plants, insects, frogs and mammals. As part of the innate immune system expressed in many tissues, AMPs are able to provide protection against invasion of foreign microorganisms and exhibit a broad spectrum of activity against bacteria, fungi and/or virus. Non-AMPs cell-penetrating peptides have been used as carriers for overcoming the membrane barrier and helping in the delivery of various molecules into the cell. Physicochemical peptide-lipid interactions studies can provide us with reliable molecular information about microbe defense response, including the elucidation of the prevailing mechanisms of its action, such as the barrel-stave, toroidal pore, carpet and detergent-like models. In this paper, we present an overview of the peptide-lipid mechanisms of interaction as well as discuss alternative techniques that could help to elucidate the peptides functionality. Quartz crystal microbalance (QCM), surface plasmon resonance (SPR) spectroscopy and electrochemical impedance spectroscopy (EIS) are useful techniques to investigate in details of the peptide-membrane interaction. The techniques here discussed could also offer specific and low-cost methods that can to shed some light over the different modes of action of AMPs, contributing to the development of drugs against infectious diseases.