Vesicle protrusion induced by antimicrobial peptides suggests common carpet mechanism for short antimicrobial peptides

Short-cationic alpha-helical antimicrobial peptides (SCHAMPs) are promising candidates to combat the growing global threat of antimicrobial resistance. They are short-sequenced, selective against bacteria, and have rapid action by destroying membranes. A full understanding of their mechanism of action will provide key information to design more potent and selective SCHAMPs. Molecular Dynamics (MD) simulations are invaluable tools that provide detailed insights into the peptide-membrane interaction at the atomic- and meso-scale level. We use atomistic and coarse-grained MD to look into the exact steps that four promising SCHAMPs-BP100, Decoralin, Neurokinin-1, and Temporin L-take when they interact with membranes. Following experimental set-ups, we explored the effects of SCHAMPs on anionic membranes and vesicles at multiple peptide concentrations. Our results showed all four peptides shared similar binding steps, initially binding to the membrane through electrostatic interactions and then flipping on their axes, dehydrating, and inserting their hydrophobic moieties into the membrane core. At higher concentrations, fully alpha-helical peptides induced membrane budding and protrusions. Our results suggest the carpet mode of action is fit for the description of SCHAMPs lysis activity and discuss the importance of large hydrophobic residues in SCHAMPs design and activity.

Effect of tryptophan position and lysine/arginine substitution in antimicrobial peptides on antifungal action

Every year, the overprescription, misuse, and improper disposal of antibiotics have led to the rampant development of drug-resistant pathogens and, in turn, a significant increase in the number of patients who die of drug-resistant fungal infections. Recently, researchers have begun investigating the use of antimicrobial peptides (AMPs) as next-generation antifungal agents to inhibit the growth of drug-resistant fungi. The antifungal activity of alpha-helical peptides designed using the cationic amino acids containing lysine and arginine and the hydrophobic amino acids containing isoleucine and tryptophan were evaluated using 10 yeast and mold fungi. Among these peptides, WIK-14, which is composed of a 14-mer with tryptophan sequences at the amino terminus, showed the best antifungal activity via transient pore formation and ROS generation. In addition, the in vivo antifungal effects of WIK-14 were investigated in a mouse model infected with drug-resistant Candida albicans. The results demonstrate the potential of AMPs as antifungal agents.

An Overview of Frog Skin-Derived Esc Peptides: Promising Multifunctional Weapons against Pseudomonas aeruginosa-Induced Pulmonary and Ocular Surface Infections

Antimicrobial resistance is a silent pandemic harming human health, and Pseudomonas aeruginosa is the most common bacterium responsible for chronic pulmonary and eye infections. Antimicrobial peptides (AMPs) represent promising alternatives to conventional antibiotics. In this review, the in vitro/in vivo activities of the frog skin-derived AMP Esc(1-21) are shown. Esc(1-21) rapidly kills both the planktonic and sessile forms of P. aeruginosa and stimulates migration of epithelial cells, likely favoring repair of damaged tissue. However, to undertake preclinical studies, some drawbacks of AMPs (cytotoxicity, poor biostability, and limited delivery to the target site) must be overcome. For this purpose, the stereochemistry of two amino acids of Esc(1-21) was changed to obtain the diastereomer Esc(1-21)-1c, which is more stable, less cytotoxic, and more efficient in treating P. aeruginosa-induced lung and cornea infections in mouse models. Incorporation of these peptides (Esc peptides) into nanoparticles or immobilization to a medical device (contact lens) was revealed to be an effective strategy to ameliorate and/or to prolong the peptides' antimicrobial efficacy. Overall, these data make Esc peptides encouraging candidates for novel multifunctional drugs to treat lung pathology especially in patients with cystic fibrosis and eye dysfunctions, characterized by both tissue injury and bacterial infection.

Combating Antimicrobial Resistance by Employing Antimicrobial Peptides: Immunomodulators and Therapeutic Agents against Infectious Diseases

The rising prevalence of multiple-drug-resistant pathogens poses a formidable challenge to conventional antimicrobial treatments. The inability of potent antibiotics to combat these "superbugs" underscores the pressing need for alternative therapeutic agents. Antimicrobial peptides (AMPs) represent an alternative class of antibiotics. AMPs are essential immunomodulatory molecules that are found in various organisms. They play a pivotal role in managing microbial ecosystems and bolstering innate immunity by targeting and eliminating invading microorganisms. AMPs also have applications in the agriculture sector by combating animal as well as plant pathogens. AMPs can be exploited for the targeted therapy of various diseases and can also be used in drug-delivery systems. They can be used in synergy with current treatments like antibiotics and can potentially lead to a lower required dosage. AMPs also have huge potential in wound healing and regenerative medicine. Developing AMP-based strategies with improved safety, specificity, and efficacy is crucial in the battle against alarming global microbial resistance. This review will explore AMPs' increasing applicability, their mode of antimicrobial activity, and various delivery systems enhancing their stability and efficacy.

Antibacterial and Hemolytic Activity of Antimicrobial Hydrogels Utilizing Immobilized Antimicrobial Peptides

Antimicrobial peptides (AMPs) are viewed as potential compounds for the treatment of bacterial infections. Nevertheless, the successful translation of AMPs into clinical applications has been impeded primarily due to their low stability in biological environments and potential toxicological concerns at higher concentrations. The covalent attachment of AMPs to a material's surface has been sought to improve their stability. However, it is still an open question what is required to best perform such an attachment and the role of the support. In this work, six different AMPs were covalently attached to a long-ranged ordered amphiphilic hydrogel, with their antibacterial efficacy evaluated and compared to their performance when free in solution. Among the tested AMPs were four different versions of synthetic end-tagged AMPs where the sequence was altered to change the cationic residue as well as to vary the degree of hydrophobicity. Two previously well-studied AMPs, Piscidin 1 and Omiganan, were also included as comparisons. The antibacterial efficacy against Staphylococcus aureus remained largely consistent between free AMPs and those attached to surfaces. However, the activity pattern against Pseudomonas aeruginosa on hydrogel surfaces displayed a marked contrast to that observed in the solution. Additionally, all the AMPs showed varying degrees of hemolytic activity when in solution. This activity was entirely diminished, and all the AMPs were non-hemolytic when attached to the hydrogels.

Screening and Application of DNA Aptamers for Heparin-Binding Protein

Rapid detection of heparin-binding protein (HBP) is essential for timely intervention in sepsis cases. Current detection techniques are usually antibody-based immunological methods, which have certain problems, such as complexity and slow detection, and fall short in meeting the urgency of clinical needs. The application of an aptamer can address these concerns well. In this study, HBP-specific DNA aptamers were screened first. Among which, Apt-01, Apt-02, and Apt-13 had a high affinity for HBP, exhibiting impressive KD values of 3.42, 1.44, and 1.04 nmol/L, respectively. Then, the aptamer of HBP and its partially complementary primer probe were combined to form double-stranded DNA (dsDNA) and synthesize a circular DNA template. The template is complementary to the primer probe, but due to the presence of dsDNA, ExoIII cleaves C2-13 as an RCA primer probe, rendering the template unable to recognize the primer probe and preventing the RCA reaction from proceeding. When the target is present, it competes with the adapter for recognition and releases C2-13, exposing its 3' end. After initiating the RCA at room temperature and reacting with SYBR GreenII at 37 °C for 20 min, fluorescence changes can be observed and quantitatively analyzed at a 530 nm wavelength, achieving quantitative biological analysis. Apt-01 was used to develop a fluorescent biosensor for HBP detection, which exhibited a good linear range (0.01 nmol/L to 10 nmol/L) and detection limit (0.0056 nmol/L). This advancement holds the potential to lay a solid groundwork for pioneering sensitive and specific methods for HBP detection and to significantly enhance the diagnostic processes for sepsis.

Antibacterial activity of a short de novo designed peptide against fish bacterial pathogens

In the face of increasing antimicrobial resistance in aquaculture, researchers are exploring novel substitutes to customary antibiotics. One potential solution is the use of antimicrobial peptides (AMPs). We aimed to design and evaluate a novel, short, and compositionally simple AMP with potent activity against various bacterial pathogens in aquaculture. The resulting peptide, KK12YW, has an amphipathic nature and net charge of + 7. Molecular docking experiments disclosed that KK12YW has a strong affinity for aerolysin, a virulence protein produced by the bacterial pathogen Aeromonas sobria. KK12YW was synthesized using Fmoc chemistry and tested against a range of bacterial pathogens, including A. sobria, A. salmonicida, A. hydrophila, Edwardsiella tarda, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and methicillin-resistant S. aureus. The AMP showed promising antibacterial activity, with MIC and MBC values ranging from 0.89 to 917.1 µgmL-1 and 3.67 to 1100.52 µgmL-1, respectively. In addition, KK12YW exhibited resistance to high temperatures and remained effective even in the presence of serum and salt, indicating its stability. The peptide also demonstrated minimal hemolysis toward fish RBCs, even at higher concentrations. Taken together, these findings indicate that KK12YW could be a highly promising and viable substitute for conventional antibiotics to combat microbial infections in aquaculture.

The amphipathic design in helical antimicrobial peptides

Amphipathicity is a critical characteristic of helical antimicrobial peptides (AMPs). The hydrophilic region, primarily composed of cationic residues, plays a pivotal role in the initial binding to negatively charged components on bacterial membranes through electrostatic interactions. Subsequently, the hydrophobic region interacts with hydrophobic components, inducing membrane perturbation, ultimately leading to cell death, or inhibiting intracellular function. Due to the extensive diversity of natural and synthetic AMPs with regard to the design of amphipathicity, it is complicated to study the structure-activity relationships. Therefore, this work aims to categorize the common amphipathic design and investigate their impact on the biological properties of AMPs. Besides, the connection between current structural modification approaches and amphipathic styles was also discussed.

Combination of a pH-responsive peptide amphiphile and a conventional antibiotic in treating Gram-negative bacteria

BACKGROUND

Clinical treatments ofgastric infections using antibiotics suffer from the undesired killing of commensal bacteria and emergence of antibiotic resistance. It is desirable to develop pH-responsive antimicrobial peptides (AMPs) that kill pathogenic bacteria such as H. pyloriand resistant E. coli under acidic environment with minimal impact to commensal bacteria whilst not causing antibiotic resistance.

EXPERIMENTS

Using a combined approach of cell assays, molecular dynamics (MD) simulations and membrane models facilitating biophysical and biochemical measurements including small angle neutron scattering (SANS), we have characterized the pH-responsive physiochemical properties and antimicrobial performance of two amphiphilic AMPs, GIIKDIIKDIIKDI-NH2 and GIIKKIIDDIIKKI-NH2 (denoted as 3D and 2D, respectively), that were designed by selective substitutions of cationic residues of Lys (K) in the extensively studied AMP G(IIKK)3I-NH2 with anionic residue Asp (D).

FINDINGS

Whilst 2D kept non-ordered coils across the entire pH range studied, 3D displayed a range of secondary structures when pH was shifted from basic to acidic, with distinct self-assembly into nanofibers in aqueous environment. Further experimental and modeling studies revealed that the AMPs interacted differently with the inner and outer membranes of Gram-negative bacteria in a pH-responsive manner and that the structural features characterized by membrane leakage and intramembrane nanoaggregates revealed from fluorescence spectroscopy and SANS were well linked to antimicrobial actions. Different antimicrobial efficacies of 2D and 3D were underlined by the interplay between their ability to bind to the outer membrane lipid LPS (lipopolysaccharide), outer membrane permeability change and inner membrane depolarization and leakage. Furthermore, AMP's binding with the inner membrane under acidic condition caused both the dissipation of membrane potential (Δψ) and the continuous dissipation of transmembrane ΔpH, with Δψ and ΔpH being the key components of the proton motive force. Combinations of antibiotic (Minocycline) with the pH-responsive AMP generated the synergistic effects against Gram-negative bacteria only under acidic condition. These features are crucial to target applications to gastric infections, anti-acne and wound healing.

Recent advances in antimicrobial peptide-based therapy

Antimicrobial peptides (AMPs) are a group of polypeptide chains that have the property to target and kill a myriad of microbial organisms including viruses, bacteria, protists, etc. The first discovered AMP was named gramicidin, an extract of aerobic soil bacteria. Further studies discovered that these peptides are present not only in prokaryotes but in eukaryotes as well. They play a vital role in human innate immunity and wound repair. Consequently, they have maintained a high level of intrigue among scientists in the field of immunology, especially so with the rise of antibiotic-resistant pathogens decreasing the reliability of antibiotics in healthcare. While AMPs have promising potential to substitute for common antibiotics, their use as effective replacements is barred by certain limitations. First, they have the potential to be cytotoxic to human cells. Second, they are unstable in the blood due to action by various proteolytic agents and ions that cause their degradation. This review provides an overview of the mechanism of AMPs, their limitations, and developments in recent years that provide techniques to overcome those limitations. We also discuss the advantages and drawbacks of AMPs as a replacement for antibiotics as compared to other alternatives such as synthetically modified bacteriophages, traditional medicine, and probiotics.

Interaction of Cecropin A (1-7) Analogs with DNA Analyzed by Multi-spectroscopic Methods

Cecropin A (1-7) is a cationic antimicrobial peptide which contain lots of basic amino acids. To understand the effect of basic amino acids on cecropin A (1-7), analogues CA2, CA3 and CA4 which have more arginine or lysine at the N-terminal or C-terminal were designed and synthesized. The interaction of cecropin A (1-7) and its analogs with DNA was studied using ultraviolet-visible spectroscopy, fluorescence spectroscopy and circular dichroism spectroscopy. Multispectral analysis showed that basic amino acids improved the interaction between the analogues and DNA. The interaction between CA4 and DNA is most pronounced. Fluorescence spectrum indicated that Ksv value of CA4 is 1.19 × 105  L mol-1 compared to original peptide cecropin A (1-7) of 3.73 × 104  L mol-1. The results of antimicrobial experiments with cecropin A (1-7) and its analogues showed that basic amino acids enhanced the antimicrobial effect of the analogues. The antimicrobial activity of CA4 against E. coli was eightfold higher than that of cecropin A (1-7). The importance of basic amino acid in peptides is revealed and provides useful information for subsequent studies of antimicrobial peptides.

Hydrocarbon stapled temporin-L analogue as potential antibacterial and antiendotoxin agents with enhanced protease stability

Antimicrobial resistance (AMR) is a serious global concern and a huge burden on the healthcare system. Antimicrobial peptides (AMPs) are considered as a solution of AMR due to their membrane-lytic and intracellular mode of action and therefore resistance development against AMPs is less frequent. One such AMPs, temporin-L (TL) is a 13-mer peptide reported as a potent and broad-spectrum antibacterial agent with significant immunomodulatory activity. However, TL is toxic to human erythrocytes at their antibacterial concentrations and therefore various analogues were synthesized with potent antimicrobial activity and lower hemolytic activity. In this work, we have selected a non-toxic engineered analogue of TL (eTL) and performed hydrocarbon stapling of amino acid residues at i to i + 4 positions at different part of sequence. The synthesized peptides were investigated against both the gram-positive and gram-negative bacteria as well as methicillin resistant S. aureus, its MIC was measured in the concentrations range of 0.9-15.2 µM. All analogues were found equal or better antibacterial as compared to parent peptide. Interestingly one analogue eTL [5-9] was found to be non-cytotoxic and stable in presence of the human serum. Mode of action studies revealed membrane depolarizing and disruptive mode of action with live MRSA. Further in vivo studies of antimicrobial against MRSA infection and anti-endotoxin activities in mice model revealed potential activity of the stapled peptide analogue. Overall, this reports on stapled analogue of the AMPs highlights an important strategy for the development of new antibacterial therapeutics against AMR.

NMR techniques for investigating antimicrobial peptides in model membranes and bacterial cells

AMPs are short, mainly cationic membrane-active peptides found in all living organism. They perform diverse roles including signaling and acting as a line of defense against bacterial infections. AMPs have been extensively investigated as templates to facilitate the development of novel antimicrobial therapeutics. Understanding the interplay between these membrane-active peptides and the lipid membranes is considered to be a significant step in elucidating the specific mechanism of action of AMPs against prokaryotic and eukaryotic cells to aid the development of new therapeutics. In this review, we have provided a brief overview of various NMR techniques commonly used for studying AMP structure and AMP-membrane interactions in model membranes and whole cells.

A Comprehensive Review of Patented Antimicrobial Peptides from Amphibian Anurans

Since the 1980s, studies of antimicrobial peptides (AMPs) derived from anuran skin secretions have unveiled remarkable structural diversity and a wide range of activities. This study explores the potential of these peptides for drug development by examining granted patents, amino acid modifications related to patented peptides, and recent amphibians' taxonomic updates influencing AMP names. A total of 188 granted patents related to different anuran peptides were found, with Asia and North America being the predominant regions, contributing 65.4% and 15.4%, respectively. Conversely, although the Neotropical region is the world's most diversified region for amphibians, it holds only 3.7% of the identified patents. The antimicrobial activities of the peptides are claimed in 118 of these 188 patents. Additionally, for 160 of these peptides, 66 patents were registered for the natural sequence, 69 for both natural and derivative sequences, and 20 exclusively for sequence derivatives. Notably, common modifications include alterations in the side chains of amino acids and modifications to the peptides' N- and C-termini. This review underscores the biomedical potential of anuran-derived AMPs, emphasizing the need to bridge the gap between AMP description and practical drug development while highlighting the urgency of biodiversity conservation to facilitate biomedical discoveries.

Embracing the era of antimicrobial peptides with marine organisms

Covering: 2018 to Jun of 2023The efficiency of traditional antibiotics has been undermined by the proliferation of antibiotic-resistant pathogenic microorganisms, necessitating the pursuit of innovative therapeutic agents. Antimicrobial peptides (AMPs), which are part of host defence peptides found ubiquitously in nature, exhibiting a wide range of activity towards bacteria, fungi, and viruses, offer a highly promising candidate solution. The efficacy of AMPs can frequently be augmented via alterations to their amino acid sequences or structural adjustments. Given the vast reservoir of marine life forms and their distinctive ecosystems, marine AMPs stand as a burgeoning focal point in the quest for alternative peptide templates extracted from natural sources. Advances in identification and characterization techniques have accelerated the discoveries of marine AMPs, thereby stimulating AMP customization, optimization, and synthesis research endeavours. This review presents an overview of recent discoveries related to the intriguing qualities of marine AMPs. Emphasis will be placed upon post-translational modifications (PTMs) of marine AMPs and how they may impact functionality and potency. Additionally, this review considers ways in which marine PTM might support larger-scale, heterologous AMP manufacturing initiatives, providing insights into translational applications of these important biomolecules.

The antibacterial properties of branched peptides based on poly(l-arginine): In vitro antibacterial evaluation and molecular dynamic simulations

The emergence of bacterial strains resistant to antibiotics is a major issue in the medical field. Antimicrobial peptides are widely studied as they do not generate as much resistant bacterial strains as conventional antibiotics and present a broad range of activity. Among them, the homopolypeptide poly(l-arginine) presents promising antibacterial properties, especially in the perspective of its use in biomaterials. Linear poly(l-arginine) has been extensively studied but the impact of its 3D structure remains unknown. In this study, the antibacterial properties of newly synthesized branched poly(l-arginine) peptides, belonging to the family of multiple antigenic peptides, are evaluated. First, in vitro activities of the peptides shows that branched poly(l-arginine) is more efficient than linear poly(l-arginine) containing the same number of arginine residues. Surprisingly, peptides with more arms and more residues are not the most effective. To better understand these unexpected results, interactions between these peptides and the membranes of Gram positive and Gram negative bacteria are simulated thanks to molecular dynamic. It is observed that the bacterial membrane is more distorted by the branched structure than by the linear one and by peptides containing smaller arms. This mechanism of action is in full agreement with in vitro results and suggest that our simulations form a robust model to evaluate peptide efficiency towards pathogenic bacteria.

Antimicrobial peptides designed by computational analysis of proteomes

Antimicrobial peptides (AMPs) are promising cationic and amphipathic molecules to fight antibiotic resistance. To search for novel AMPs, we applied a computational strategy to identify peptide sequences within the organisms' proteome, including in-house developed software and artificial intelligence tools. After analyzing 150.450 proteins from eight proteomes of bacteria, plants, a protist, and a nematode, nine peptides were selected and modified to increase their antimicrobial potential. The 18 resulting peptides were validated by bioassays with four pathogenic bacterial species, one yeast species, and two cancer cell-lines. Fourteen of the 18 tested peptides were antimicrobial, with minimum inhibitory concentrations (MICs) values under 10 µM against at least three bacterial species; seven were active against Candida albicans with MICs values under 10 µM; six had a therapeutic index above 20; two peptides were active against A549 cells, and eight were active against MCF-7 cells under 30 µM. This study's most active antimicrobial peptides damage the bacterial cell membrane, including grooves, dents, membrane wrinkling, cell destruction, and leakage of cytoplasmic material. The results confirm that the proposed approach, which uses bioinformatic tools and rational modifications, is highly efficient and allows the discovery, with high accuracy, of potent AMPs encrypted in proteins.

Structure modification of anoplin for fighting resistant bacteria

The emergence of bacterial resistance has posed a significant challenge to clinical antimicrobial treatment, rendering commonly used antibiotics ineffective. The development of novel antimicrobial agents and strategies is imperative for the treatment of resistant bacterial infections. Antimicrobial peptides (AMPs) are considered a promising class of antimicrobial agents due to their low propensity for resistance and broad-spectrum activity. Anoplin is a small linear α-helical natural antimicrobial peptide that was isolated from the venom of the solitary wasp Anplius samariensis. It exhibits rich biological activity, particularly broad-spectrum antimicrobial activity and low hemolytic activity. Over the past three decades, more than 40 research publications on anoplin have been made available online. This review focuses on the advancements of anoplin in antimicrobial research, encompassing its sources, characterization, antimicrobial activity, influencing factors and structural modifications. The aim is to provide assistances for the development of new antimicrobial agents that can combat bacterial resistance.

Unlocking Antibacterial Potential: Key-Site-Based Regulation of Antibacterial Spectrum of Peptides

In the pursuit of combating multidrug-resistant bacteria, antimicrobial peptides (AMPs) have emerged as promising agents; however, their application in clinical settings still presents challenges. Specifically, the exploration of crucial structural parameters that influence the antibacterial spectrum of AMPs and the subsequent development of tailored variants with either broad- or narrow-spectrum characteristics to address diverse clinical therapeutic needs has been overlooked. This study focused on investigating the effects of amino acid sites and hydrophobicity on the peptide's antibacterial spectrum through Ala scanning and fixed-point hydrophobic amino acid substitution techniques. The findings revealed that specific amino acid sites played a pivotal role in determining the antibacterial spectrum of AMPs and confirmed that broadening the spectrum could be achieved only by increasing hydrophobicity at certain positions. In conclusion, this research provided a theoretical basis for future precise regulation of an antimicrobial peptide's spectrum by emphasizing the intricate balance between amino acid sites and hydrophobicity.

Rational Design of a Potent Antimicrobial Peptide Based on the Active Region of a Gecko Cathelicidin

The emergence of multidrug-resistant (MDR) bacteria presents a significant challenge to public health, increasing the risk of infections that are resistant to current antibiotic treatment. Antimicrobial peptides (AMPs) offer a promising alternative to conventional antibiotics in the prevention of MDR bacterial infections. In the present study, we identified a novel cathelicidin AMP from Gekko japonicus, which exhibited broad-spectrum antibacterial activity against both Gram-negative and Gram-positive bacteria, with minimal inhibitory concentrations ranging from 2.34 to 4.69 μg/mL. To improve its potential therapeutic application, a series of peptides was synthesized based on the active region of the gecko-derived cathelicidin. The lead peptide (RH-16) showed an antimicrobial activity comparable to that of the parent peptide. Structural characterization revealed that RH-16 adopted an amphipathic α-helical conformation. Furthermore, RH-16 demonstrated neither hemolytic nor cytotoxic activity but effectively killed a wide range of clinically isolated, drug-resistant bacteria. The antimicrobial activity of RH-16 was attributed to the nonspecific targeting of bacterial membranes, leading to rapid bacterial membrane permeabilization and rupture. RH-16 also retained its antibacterial activity in plasma and exhibited mild toxicity in vivo. Notably, RH-16 offered robust protection against skin infection in a murine model. Therefore, this newly identified cathelicidin AMP may be a strong candidate for future pharmacological development targeting multidrug resistance. The use of a rational design approach for isolating the minimal antimicrobial unit may accelerate the transition of natural AMPs to clinically applicable antibacterial agents.

Recombinant production of antimicrobial peptides in plants

Classical plant breeding methods are limited in their ability to confer disease resistance on plants. However, in recent years, advancements in molecular breeding and biotechnological have provided new approaches to overcome these limitations and protect plants from disease. Antimicrobial peptides (AMPs) constitute promising agents that may be able to protect against infectious agents. Recently, peptides have been recombinantly produced in plants at scale and low cost. Because AMPs are less likely than conventional antimicrobials to elicit resistance of pathogenic bacteria, they open up exciting new avenues for agricultural applications. Here, we review recent advances in the design and production of bioactive recombinant AMPs that can effectively protect crop plants from diseases.

Design, biological characteristics, and antibacterial mechanism of high therapeutic index antimicrobial peptides with PRRP as central axis

As the important components of biological innate immunity, antimicrobial peptides (AMPs) were found in a variety of organisms including insects, plants, animals, bacteria, fungi, etc. However, high hemolytic activity, high toxicity, and poor stability of natural AMPs hinder serious their application as therapeutic agents. To overcome these problems, in this study we use PRRP as a central axis, and peptides were designed based on the sequence template XRRXXRXPRRPXRXXRRX-NH2, where X represents a hydrophobic amino acid like Phe (F), Ile (I), Val (V), and Leu (L). The designed peptides LR18, FR18, and IR18 showed effective antimicrobial activity against some Gram-positive bacteria and Gram-negative bacteria, low cytotoxicity to mammalian cells, and had a tendency to form α-helical structures in membrane-mimetic environments. Among them, peptide LR18 (X: L) showed the highest geometric mean average treatment index (GMTI = 42.7) against Gram-negative bacteria, and FR18 (X: L) showed the highest GMTI (22.86) against Gram-positive bacteria. LR18 and FR18 also showed better salt, temperature, pH, and trypsin stability. LR18 and FR18 exert their antimicrobial effects mainly through destroying bacteria cell membrane. Briefly, peptide LR18 and FR18 have the potential to serve as a therapeutic agent to reduce antibiotic resistance owing to its high therapeutic index and great stability.

Computational modelling of the antimicrobial peptides Cruzioseptin-4 extracted from the frog Cruziohyla calcarifer and Pictuseptin-1 extracted from the frog Boana picturata

A computational study of the peptides Cruzioseptin-4 and Pictuseptin-1, identified in Cruziohyla calcarifer and Boana picturata respectively, has been carried out. The studies on Cruzioseptin-4 show that it is a cationic peptide with a chain of 23 amino acids that possess 52.17% of hydrophobic amino acids and a charge of + 1.2 at pH 7. Similarly, Pictuseptin-1 is a 22 amino acids peptide with a charge of + 3 at pH 7 and 45.45% of hydrophobic amino acids. Furthermore, the predominant secondary structure for both peptides is alpha-helical. The physicochemical properties were predicted using PepCalc and Bio-Synthesis; secondary structures using Jpred4 and PredictProtein; while molecular docking was performed using Autodock Vina. Geometry optimization of the peptides was done using the ONIOM hybrid method with the HF/6-31G basis set implemented in the Gaussian 09 program. Finally, the molecular docking study indicates that the viable mechanism of action for both peptides is through a targeted attack on the cell membrane of pathogens via electrostatic interactions with different membrane components, leading to cell lysis.

Physical-Chemical Approach to Designing Drugs with Multiple Targets

Many people simultaneously exhibit multiple diseases, which complicates efficient medical treatments. For example, patients with cancer are frequently susceptible to infections. However, developing drugs that could simultaneously target several diseases is challenging. We present a novel theoretical method to assist in selecting compounds with multiple therapeutic targets. The idea is to find correlations between the physical and chemical properties of drug molecules and their abilities to work against multiple targets. As a first step, we investigated potential drugs against cancer and viral infections. Specifically, we investigated antimicrobial peptides (AMPs), which are short positively charged biomolecules produced by living systems as a part of their immune defense. AMPs show anticancer and antiviral activity. We use chemoinformatics and correlation analysis as a part of the machine-learning method to identify the specific properties that distinguish AMPs with dual anticancer and antiviral activities. Physical-chemical arguments to explain these observations are presented.

Differences in Relevant Physicochemical Properties Correlate with Synergistic Activity of Antimicrobial Peptides

With the urgent need for new medical approaches due to increased bacterial resistance to antibiotics, antimicrobial peptides (AMPs) have been considered as potential treatments for infections. Experiments indicate that combinations of several types of AMPs might be even more effective at inhibiting bacterial growth with reduced toxicity and a lower likelihood of inducing bacterial resistance. The molecular mechanisms of AMP-AMP synergistic antimicrobial activity, however, remain not well understood. Here, we present a theoretical approach that allows us to relate the physicochemical properties of AMPs and their antimicrobial cooperativity. It utilizes correlation and bioinformatics analysis. A concept of physicochemical similarity is introduced, and it is found that less similar AMPs with respect to certain physicochemical properties lead to greater synergy because of their complementary antibacterial actions. The analysis of correlations between the similarity and the antimicrobial properties allows us to effectively separate synergistic from nonsynergistic AMP pairs. Our theoretical approach can be used for the rational design of more effective AMP combinations for specific bacterial targets, for clarifying the mechanisms of bacterial elimination, and for a better understanding of cooperativity phenomena in biological systems.