Stability Of Antimicrobial Peptides Research Articles

Adsorption Process of Various Antimicrobial Peptides on Different Surfaces of Cellulose.

Current antimicrobial challenges in hospitals, pharmaceutical production units, and food packaging have motivated the development of antimicrobial agents, among them the antimicrobial compounds based on cellulose and peptides. Herein, we develop molecular dynamics (MD) models to dissect and characterize the adsorption process of antimicrobial peptides (AMPs) such as protegrin 1, magainin 2, and cyclic indolicidin on various surfaces of cellulose including [-1-10], [1-10], [-100], [100], [-110], and [110]. Our results suggest that the magainin 2 antimicrobial peptide loses most of its initial helix form, spreads on the cellulose surface, and makes the most rigid structure with [110] surface. The cyclic indolicidin peptide has the lowest affinity to adsorb on the cellulose surfaces, and the protegrin 1 peptide successfully adsorbs on all the proposed cellulose surfaces. Our MD simulations confirmed that cellulose can improve the corresponding peptides' structural stability and change their secondary structures during adsorption. The [-1-10] and [100] surfaces of cellulose show considerable affinity against the AMPs, exhibiting greater interactions with and adsorption to the peptides. Our data imply that the stronger adsorptions are caused by a set of H-bonds, van der Waals, and electrostatic interactions, where van der Waals interactions play a prominent role in the stability of the AMP-cellulose structures. Our energy analysis results suggest that glutamic acid and arginine amino acids have key roles in the stability of AMPs on cellulose surfaces due largely to stronger interactions with the cellulose surfaces as compared with other residues. Our results can provide useful insight at the molecular level that can help design better antimicrobial biomaterials based on cellulose.

The Metabolic Stability of Antimicrobial Peptides IK8 in Plasma and Liver S9

In the face of mounting global antibiotic resistance, which has become a critical clinical problem, antimicrobial peptides (AMPs) have received considerable interest as new therapeutics with the efficacy for the treatment of multidrug-resistant (MDR) infections due to their novel mechanism. However, certain inherent shortcomings such as instability seriously limit their systemic applications in the clinic. In this study, we intend to clarify the connection between three configurations of IK8 and their stability in plasma and liver S9 of various species by confirming the metabolites. The structural information of these metabolites was scanned and identified using HPLC and Q-TOF, respectively. The results found that IK8-D exhibits superior stability, compared with IK8-2D and IK8-L in plasma and liver S9 incubation, which indicated D- type amino acids could significantly increase the stability of antimicrobial peptides.

Tryptic Stability and Antimicrobial Activity of the Derivatives of Polybia-CP with Fine-Tuning Modification in the Side Chain of Lysine

Antimicrobial peptides (AMPs) were believed to be a class of promising antimicrobials to combat the increasing resistant microbes. However, AMPs could be easily degraded by endogenous proteases, which limited their clinic use. Considering that lysine is the only one cationic amino acid residue in polybia-CP which were related to the cleavage of trypsin like serine protease’s digestion, we introduced lysine’s mimics which kept the key function group side chain –NH2 and only varied the methylene chains in the sequence of polybia-CP to investigate the effect of the introduction of non-proteinogenic amino acids on the activity and stability of antimicrobial peptides. In addition, two analogs in which lysine were substituted by the other two proteinogenic cationic amino acids arginine and histidine also were synthesized to evaluate the effect of fine tuning the function group in lysine on its antimicrobial activity and stability. We found that the introduction of amino acids with shortened side chain length of lysine could enhance the trypsin resistance of the derivatives of polybia-CP, while maintain the same or comparable antimicrobial activity with the parent peptide. In addition, while lysine was substituted by histidine, His-CP demonstrated comparable antimicrobial activity and dramatically improved trypsin resistance. Although the analog exhibited excellent antimicrobial activity while lysine was substituted by Arginine residue (Arg-CP), its enzymatic stability was almost the same as its parent peptide. These results suggest that the fine-tuning of side chain of lysine may offer a promising strategy to improve the tryptic stability and retain the antimicrobial activity of antimicrobial peptide.

Influence of adding terminal tags on the structural and antimicrobial properties of the peptide caerin 1.1

Aquaculture is threatened by severe bacterial and viral outbreaks which can cause massive mortality and limit productivity. Antimicrobial peptides are a promising tool for the control of infectious diseases; however, their use in the aquaculture sector has been poorly explored. Recombinant production of peptides is an interesting alternative to their chemical synthesis, which has still important challenges to address. Although extra amino acid tags are usually added to the ends of recombinant proteins to enhance their stability and facilitate their purification or their translational processing, the effect of these tags on the function and the stability of antimicrobial peptides is completely unknown. This is particularly important in the case of the short cationic antimicrobial peptide caerin, originally isolated from frog skin secretions, and other peptides which bioactivity has been directly related with its ability to adopt an amphipathic alpha-helical structure upon interaction with the microbial membranes. Caerin has demonstrated bactericidal activity against several important human pathogens, however its antimicrobial activity over usual aquaculture pathogens remains practically unexplored. In the present work, we have studied the effect of adding the terminal tag polyhistidine (6xHis) and the 2A peptide from the foot and mouth disease virus (FMDV-2A) to the N- or the C- terminus of caerin on its activity against a collection of bacterial and viral pathogens common to aquaculture species. In addition, the antimicrobial activity of a peptide composed of two tandem consecutive caerin sequences has been investigated. We have concluded that the addition of terminal tags to caerin causes a drastic reduction of its antiviral activity against the studied viruses and that the effect of the added tags on the bactericidal activity of the peptide depends of the target bacterial species. However, caerin with a 6xHis extension at its N terminus maintains or increases its antimicrobial activity against most of the fish pathogenic bacteria tested. According to our data, there is only a moderate agreement between the theoretical predictions obtained from in silico models and the experimental observations. This information is essential for the rational design of strategies to aim the recombinant production of caerin and other antimicrobial peptides, which can be used as anti-infective agents in aquaculture.

Inhibition of bacterial adherence to biomaterials by coating antimicrobial peptides with anionic surfactant

Medical devices are widely used in modern medicine, but their utilities are often limited by the biofilm formation of bacteria that are tolerant to most antibiotics. In this report, antimicrobial peptides (AMPs) were coated onto biomaterials by the aid of surfactant through hydrophobic interactions. To increase the coating efficiency, stability of AMPs in body fluids and spectrum of antimicrobial activity, pairs of AMPs were coated simultaneously onto various substrates, such as silicone, polyurethane and titanium, which are commonly used components of biomedical devices. These coated AMPs exhibited very low cytotoxicity and hemolytic activities because they were gradually released into urine or serum. The AMP pairs, such as T9W + SAAP159 and T9W + RRIKA, coated onto the silicone discs were able to inhibit in vitro bacterial adherence in urine. Most importantly, AMP pairs coated onto the silicone tubing by surfactant SDBS could prevent bacterial adherence to mouse bladder and the silicone tubing implanted within it. These results provide a promising approach towards circumventing urinary catheter-associated infections caused by bacterial adherence.

Reverse micelle-lipid nanocapsules: a novel strategy for drug delivery of the plectasin derivate AP138 antimicrobial peptide.

IntroductionResistance to traditional antibiotics is an increasingly serious problem. Antimicrobial peptides (AMPs) have emerged as a new therapeutic class with great potential against infectious diseases, as they are less prone to induce resistance. Nanotechnology-based delivery strategies can improve the efficiency and stability of AMPs, particularly against proteolytic degradation. Lipid nanocapsules (LNCs) are a new generation of biomimetic nanocarriers and were used in this study to deliver peptides.MethodsAMP-loaded reverse micelles (RM) were developed and incorpo rated into LNCs by the phase inversion process and the antimicrobial activity of the AMPs-loaded LNC was evaluated by the minimum inhibitory concentration method. We studied the activity of AMP solutions and AMP-loaded LNCs against Gram-positive and Gram-negative bacterial strains and then evaluated the encapsulation of a new cationic AMP called AP138. Finally, we analyzed the effect of enzymatic attack on AP138 and AP138-RM-LNCs after incubation with trypsin.ResultsAP138 was efficiently encapsulated in the LNCs (encapsulation efficiency = 97.8% at a drug loading of 0.151%), resulting in protection against degradation by proteases and the preservation of antimicrobial activity against Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus.ConclusionThis study shows that RM-LNCs are an excellent candidate system to deliver AMPs.

Improving the Activity of Trp-Rich Antimicrobial Peptides by Arg/Lys Substitutions and Changing the Length of Cationic Residues.

Antimicrobial peptides (AMPs) constitute a promising alternative for the development of new antibiotics that could potentially counteract the growing number of antibiotic-resistant bacteria. However, the AMP structure–function relationships remain unclear and detailed studies are still necessary. The positively charged amino acid residues (Arg and Lys) play a crucial role in the activity of most AMPs due to the promotion of electrostatic interactions between the peptides and bacterial membranes. In this work we have analyzed the antimicrobial and structural properties of several Trp-rich AMPs containing exclusively either Arg or Lys as the positively charged residues. Their antimicrobial activity and mechanism of action were investigated, showing that Lys residues give rise to a reduced antimicrobial potency for most peptides, which was correlated, in turn, with a decrease in their ability to permeabilize the cytoplasmic membrane of Escherichia coli. Additionally, the presence of Arg and Lys renders the peptides susceptible to degradation by proteases, such as trypsin, limiting their therapeutic use. Therefore, modifications of the side chain length of Arg and Lys were investigated in an attempt to improve the protease resistance of AMPs. This approach resulted in enhanced stability to trypsin digestion, and in several cases, shorter sidechains conserved or even improved the antimicrobial activity. All together, these results suggest that Arg-to-Lys substitutions, coupled with side chain length modifications, can be extremely useful for improving the activity and stability of AMPs.

Computational Investigation of Cation-<I>π</I> Interactions in the Structural Stability of Antimicrobial Peptides

Computational Investigation of Cation-<I>π</I> Interactions in the Structural Stability of Antimicrobial Peptides

Contribution of unconventional C-H…O bonds to the structural stability of Antimicrobial peptides

The native structure of Antimicrobial peptides is stabilized by a large number of individually weak forces; a complete understanding of folding implies the need to evaluate the contribution of each of these, including nonconventional hydrogen bonds. In this work, we have analyzed the influence of C-H...O interactions in the structural stability of Antimicrobial peptides by comparison with conventional hydrogen bond. There are a number of amino acid residues that can form hydrogen bonds via their side chains in addition to their peptide group. Perhaps highest contribution in this category is polar residue (Cys) and charged residues such as Lys and Arg. A total of 2513 C-H...O interactions were found in a data set of 53 Antimicrobial peptides. Among the 2513 nonconventional interactions observed in the data set, 40% of interactions are bonded to alpha carbon. This is consistent with the fact that the hydrogens are more acidic than others. Most prominent were side-chain to main-chain C-H...O interactions (SM-C-H...O). 92% of the stabilizing centers in the Antimicrobial peptides were found to be involved in C-H...O interactions. These interactions are mainly formed by short range contacts. Moreover, the study shows that, there is an average of more than one C-H...O interactions observed for every single residue in the Antimicrobial peptides data set. It is concluded that the C-H...O interaction can, indeed, be categorized as a true stabilizing force like hydrogen bond in Antimicrobial peptides.

EXPLORING THE ROLE OF C–H … π INTERACTIONS ON THE STRUCTURAL STABILITY OF ANTIMICROBIAL PEPTIDES

A computational analysis on the C – H … π interactions in a group of 53 antimicrobial peptides was investigated. A total of 162 C – H … π interactions were observed. Side-chain to side-chain C – H … π interactions are the predominant type of interactions in antimicrobial peptides data set. There was an average of one significant C – H … π interaction for every 7 residues in the antimicrobial peptides investigated. Long-range C – H … π interactions are the predominant type of interactions. The secondary structure preference, solvent accessibility and stabilization centers of these of C – H … π interacting residues were estimated. It is likely that the C – H … π interactions contribute significantly to the overall stability of antimicrobial peptides. These interactions were observed after a molecular dynamics study on these set of antimicrobial peptides using CHARMM force field.