Evaluating the effects of hydrophobic and cationic residues on antimicrobial peptide self-assembly

Triazole-Bridged Peptides with Enhanced Antimicrobial Activity and Potency against Pathogenic Bacteria

There are still no linear antimicrobial peptides (AMPs) available as a treatment option against bacterial infections. This is caused by several drawbacks that come with AMPs such as limited proteolytic stability and low selectivity against human cells. In this work, we screened a small library of rationally designed new peptides based on the cell-penetrating peptide sC18* toward their antimicrobial activity. We identified several effective novel AMPs and chose one out of this group to further increase its potency. Therefore, we introduced a triazole bridge at different positions to provide a preformed helical structure, assuming that this modification would improve (i) proteolytic stability and (ii) membrane activity. Indeed, placing the triazole bridge within the hydrophilic part of the linear analogue highly increased membrane activity as well as stability against enzymatic digestion. The new peptides, 8A and 8B, demonstrated high activity against several bacterial species tested including pathogenic N. gonorrhoeae and methicillin-resistant S. aureus. Since they exhibited significantly good tolerability against human fibroblast and blood cells, these novel peptides offer true alternatives for future clinical applications and are worth studying in more detail.

Effect of number of lysine motifs on the bactericidal and hemolytic activity of short cationic antimicrobial peptides

Antimicrobial peptides (AMPs) are vital components of the nonspecific immune system that represent a promising broad-spectrum alternative to conventional antibiotics. Several short cationic antimicrobial peptides show highly effective antibacterial activity and low hemolytic activity, which are based on the action of a few critical amino acids, such as phenylalanine (F) and lysine (K). Previous studies have reported that Fmoc-based phenylalanine peptides possess appreciable antibacterial potency against Gram-positive bacteria, but their ability to kill Gram-negative bacteria was suboptimal. In this study, we designed and prepared a series of Fmoc-K_nF peptide (n = 1-3) series by adding lysine motifs to strengthen their broad-spectrum antibacterial activity. The effect was investigated that the amount of lysine in Fmoc-F peptides on their antibacterial properties and hemolytic activities. Our results showed that the Fmoc-KKF peptide holds the strongest antimicrobial activity against both Gram-positive and negative bacteria among all designed peptides, as well as low hemolytic activity. These results provide support for the general strategy of enhancing the broad-spectrum antibacterial activity of AMPs through increased lysine content.

Study on the self-assembly of aromatic antimicrobial peptides based on different PAF26 peptide sequences

Antimicrobial peptide (AMP) self-assembly is an effective way to synthesis antimicrobial biomaterials. In previous studies, we found PAF26 AMP (Ac-RKKWFW-NH2) and its derivative K2–F2 peptide (Ac-KKRKKWFWFF-NH2) could both self-assemble into hydrogels, but they had distinct microscopic structures. Therefore, in this work five PAF26 peptide derivatives with different numbers of aromatic amino acids are designed to better understand the self-assembly mechanism of aromatic AMP. The transmission electron microscopy, infrared spectroscopy, circular dichroism, and fluorescence spectroscopy characterizations are carried out to study the microscope structure, secondary conformation, and molecular interactions. It is found that the five peptide derivatives have different microscopic structures, and the number of aromatic amino acids will affect the peptide hydrogen bonding and aromatic stacking interactions, causing significant differences in the secondary conformation and microscopic structure. This work will enhance the comprehension of aromatic AMP self-assembly.

Industrial application of antimicrobial peptides based on their biological activity and structure-activity relationship

Last several years, a rapid increase in drug resistance to traditional antibiotics has driven the emergence and development of antimicrobial peptides (AMPs). AMPs have also gained considerable attention from scientists due to their high potency in combatting infectious pathogens. A subset of analogues and their derivatives with specific targets have been successfully designed based on natural peptide patterns. In this review, scientific knowledge on the mechanisms of action related to biological activity and structure-activity relationship (SAR) of AMPs are summarized, and the biological applications in several important fields are critically discussed. SAR shows that the positive charge, secondary structure, special amino acid residues, hydrophobicity, and helicity of AMPs are closely related to their biological activities. The combination of nanotechnology, bioinformatics, and genetic engineering can accelerate to achieve the application of AMPs as effective, safe, economical, and nonresistant antimicrobial agents in medicine, the food and feed industries, and agriculture in coming years. Given the intense interest in AMPs, further investigations are needed in the future to evaluate the specific structure and function that make their use favorable in several industries. This review may provide a comprehensive reference for future studies on chemical modifications, mechanistic exploration, and applications of AMPs.