Behavior of the Antibacterial Peptide Cyclo[RRRWFW], Explored Using a 3-Hydroxychromone-Derived Fluorescent Amino Acid.

Labeling biomolecules with fluorescent labels is an established tool for structural, biochemical, and biophysical studies; however, it remains underused for small peptides. In this work, an amino acid bearing a 3-hydroxychromone fluorophore, 2-amino-3-(2-(furan-2-yl)-3-hydroxy-4-oxo-4H-chromen-6-yl)propanoic acid (FHC), was incorporated in a known hexameric antimicrobial peptide, cyclo[RRRWFW] (cWFW), in place of aromatic residues. Circular dichroism spectropolarimetry and antibacterial activity measurements demonstrated that the FHC residue perturbs the peptide structure depending on labeling position but does not modify the activity of cWFW significantly.

Development of a pathogenesis-based therapy for peeling skin syndrome type 1.

Background: Peeling skin syndrome type 1 (PSS1) is a rare and severe autosomal recessive form of congenital ichthyosis. Patients are affected by pronounced erythroderma accompanied by pruritus and superficial generalized peeling of the skin. The disease is caused by nonsense mutations or complete deletion of the CDSN gene encoding for corneodesmosin (CDSN).

Bacterial Aggregation Triggered by Fibril Forming Tryptophan-Rich Sequences: Effects of Peptide Side Chain and Membrane Phospholipids.

The influence of side chain residue and phospholipid characteristics of the cytoplasmic membrane upon the fibrillation and bacterial aggregation of arginine (Arg) and tryptophan (Trp) rich antimicrobial peptides (AMPs) has not been well described to date. Here, we utilized the structural advantages of HHC-10 and HHC-10 (Har, l-homoarginine) that are highly active Trp-rich AMPs and investigated their fibril formation and activity behavior against bacteria. The peptides revealed time-dependent self-assembly of polyproline II (PPII) α-helices, but by comparison, HHC-10 tended to form higher ordered fibrils due to relatively strong cation-π stacking of Trp with Har residue.

Functionalized Lipopeptide Micelles as Highly Efficient NMR Depolarization Seed Points for Targeted Cell Labelling in Xenon MRI.

Improving diagnostic imaging and therapy by targeted compound delivery to pathological areas and across biological barriers is of urgent need. A lipopeptide, P-CrA-A2, composed of a highly cationic peptide sequence (A2), an N-terminally attached palmitoyl chain (P) and cryptophane molecule (CrA) for preferred uptake into blood-brain barrier (BBB) capillary endothelial cells, was generated. CrA allows reversible binding of Xe for NMR detection with hyperpolarized nuclei.

The impact of non-ideality of lipid mixing on peptide induced lipid clustering.

The influence of several antimicrobial trivalent cyclic hexapeptides on the mixing behavior of bilayer lipid membranes containing phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) with varying composition was studied using DSC and ITC. The peptides contained three arginines and three aromatic amino acids and had different sequences. All of them induce clustering of PG-rich clusters with bound peptides after binding.

Arginine/Tryptophan-Rich Cyclic α/β-Antimicrobial Peptides: The Roles of Hydrogen Bonding and Hydrophobic/Hydrophilic Solvent-Accessible Surface Areas upon Activity and Membrane Selectivity.

The bacterial selectivity of an amphiphilic library of small cyclic α/β-tetra-, α/β-penta-, and α/β-hexapeptides rich in arginine/tryptophan (Arg/Trp) residues, which contains asymmetric backbone configurations and differ in hydrophobicity and alternating d,l-amino acids, was investigated against Bacillus subtilis and Escherichia coli. The structural analyses showed that the peptides tend to form assemblies of different shapes. All-l-peptides, especially the most hydrophobic pentamers, were more strongly anti-B.

Characterization of Aptamer BC 007 Substance and Product Using Circular Dichroism and Nuclear Magnetic Resonance Spectroscopy.

Possible unwanted folding of biopharmaceuticals during manufacturing and storage has resulted in analysis schemes compared to small molecules that include bioanalytical characterization besides chemical characterization. Whether bioanalytical characterization is required for nucleotide-based drugs, may be decided on a case-by-case basis. Nucleotide-based pharmaceuticals, if chemically synthesized, occupy an intermediate position between small-molecule drugs and biologics.

Antimicrobial peptide cWFW kills by combining lipid phase separation with autolysis.

The synthetic cyclic hexapeptide cWFW (cyclo(RRRWFW)) has a rapid bactericidal activity against both Gram-positive and Gram-negative bacteria. Its detailed mode of action has, however, remained elusive. In contrast to most antimicrobial peptides, cWFW neither permeabilizes the membrane nor translocates to the cytoplasm.

Antifungal membranolytic activity of the tyrocidines against filamentous plant fungi.

The tyrocidines and analogues are cyclic decapeptides produced by Brevibacillus parabrevis with a conserved sequence of cyclo(D-Phe-Pro-X-x-Asn-Gln-X-Val-X-Leu) with Trp/Phe in the aromatic dipeptide unit, Lys/Orn as their cationic residue and Tyr (tyrocidines), Trp (tryptocidines) or Phe (phenicidines) in position 7. Previous studies indicated they have a broad antifungal spectrum with the peptides containing a Tyr residue in position 7 being more active than those with a Phe or Trp residue in this position. Detailed analysis of antifungal inhibition parameters revealed that Phe-D-Phe in the aromatic dipeptide unit lead to more consistent activity against the three filamentous fungi in this study.

Lipopeptide-based micellar and liposomal carriers: Influence of surface charge and particle size on cellular uptake into blood brain barrier cells.

Lipopeptide-based micelles and liposomes were found to differ in cell recognition and uptake mode into blood brain barrier (BBB) endothelial cells. Here we analyse the role of size and surface charge of micelles and liposomes composed of different lipopeptide sequences with respect to uptake into human brain capillary (HBMEC) and aortic (HAoEC) endothelial cells. Comparable to the dipalmitoylated apolipoprotein E-derived P2A2, lipopeptides of cationic poly-arginine (P2Rn), poly-lysine (P2Kn) and an anionic glutamic-acid sequence (P2En) self assemble into micelles (12-14nm in diameter) with high surface charge density, and bind to small (SUVs, about 24nm in diameter) and large (LUV, about 100nm in diameter) liposomes at variable lipid to peptide ratios.

The efficacy of trivalent cyclic hexapeptides to induce lipid clustering in PG/PE membranes correlates with their antimicrobial activity.

Various models have been proposed for the sequence of events occurring after binding of specific antimicrobial peptides to lipid membranes. The lipid clustering model arose by the finding that antimicrobial peptides can induce a segregation of certain negatively charged lipids in lipid model membranes. Anionic lipid segregation by cationic peptides is initially an effect of charge interaction where the ratio of peptide and lipid charges is thought to be the decisive parameter in the peptide induced lipid demixing.

Liquid storage of boar semen: Current and future perspectives on the use of cationic antimicrobial peptides to replace antibiotics in semen extenders.

Antibiotics are of great importance in boar semen extenders to ensure long shelf life of spermatozoa and to reduce transmission of pathogens into the female tract. However, the use of antibiotics carries a risk of developing resistant bacterial strains in artificial insemination laboratories and their spread via artificial insemination. Development of multiresistant bacteria is a major concern if mixtures of antibiotics are used in semen extenders.

Challenges and Limits Using Antimicrobial Peptides in Boar Semen Preservation.

Antibiotics are of great importance for the preservation of ejaculates for livestock breading. The use of antibiotics, however, is not an appropriate compensation for a lack of hygiene standards in artificial insemination (AI) centres. Sophisticated hygiene management and the proper identification of hygienic critical control points (HCCPs) at AI centres provide the basis for counteracting the development of antibiotic resistance in contaminant bacteria and their settlement in AI centres.

Evidence for a novel mechanism of antimicrobial action of a cyclic R-,W-rich hexapeptide.

The development of antimicrobial peptides as new class of antibiotic agents requires structural characterisation and understanding of their diverse mechanisms of action. As the cyclic hexapeptide cWFW (cyclo(RRRWFW)) does not exert its rapid cell killing activity by membrane permeabilisation, in this study we investigated alternative mechanisms of action, such as peptide translocation into the cytoplasm and peptide interaction with components of the phospholipid matrix of the bacterial membrane. Using fluorescence microscopy and an HPLC-based strategy to analyse peptide uptake into the cells we could confirm the cytoplasmic membrane as the major peptide target.

Anchoring dipalmitoyl phosphoethanolamine to nanoparticles boosts cellular uptake and fluorine-19 magnetic resonance signal.

Magnetic resonance (MR) methods to detect and quantify fluorine ((19)F) nuclei provide the opportunity to study the fate of cellular transplants in vivo. Cells are typically labeled with (19)F nanoparticles, introduced into living organisms and tracked by (19)F MR methods. Background-free imaging and quantification of cell numbers are amongst the strengths of (19)F MR-based cell tracking but challenges pertaining to signal sensitivity and cell detection exist.

Cationic synthetic peptides: assessment of their antimicrobial potency in liquid preserved boar semen.

Various semen extender formulas are in use to maintain sperm longevity and quality whilst acting against bacterial contamination in liquid sperm preservation. Aminoglycosides are commonly supplemented to aid in the control of bacteria. As bacterial resistance is increasing worldwide, antimicrobial peptides (AMPs) received lively interest as alternatives to overcome multi-drug resistant bacteria.

Brain endothelial cell targeting via a peptide-functionalized liposomal carrier for xenon hyper-CEST MRI.

A nanoparticulate carrier system is used to efficiently deliver a contrast agent for highly sensitive xenon Hyper-CEST MRI. The carrier system not only improves the biocompatibility and solubility of the contrast agent, it also allows selective cell targeting as demonstrated by the discrimination of human brain capillary and aortic endothelial cells.

Effects of cationic antimicrobial peptides on liquid-preserved boar spermatozoa.

Antibiotics are mandatory additives in semen extenders to control bacterial contamination. The worldwide increase in resistance to conventional antibiotics requires the search for alternatives not only for animal artificial insemination industries, but also for veterinary and human medicine. Cationic antimicrobial peptides are of interest as a novel class of antimicrobial additives for boar semen preservation.

Kinetics and efficiency of a methyl-carboxylated 5-Fluorouracil-bovine serum albumin adduct for targeted delivery.

5-Fluorouracil (5-FU) is a clinically well-established anti-cancer drug effectively applied in chemotherapy, mainly for the treatment of breast and colorectal cancer. Substantial disadvantages are adverse effects, arising from serious damage of healthy tissues, and shortcoming pharmacokinetics due to its low molecular weight. A promising approach for improvement of such drugs is their coupling to suitable carriers.

Synergistic activity of the tyrocidines, antimicrobial cyclodecapeptides from Bacillus aneurinolyticus, with amphotericin B and caspofungin against Candida albicans biofilms.

Tyrocidines are cationic cyclodecapeptides from Bacillus aneurinolyticus that are characterized by potent antibacterial and antimalarial activities. In this study, we show that various tyrocidines have significant activity against planktonic Candida albicans in the low-micromolar range. These tyrocidines also prevented C.

What Goes around Comes around-A Comparative Study of the Influence of Chemical Modifications on the Antimicrobial Properties of Small Cyclic Peptides.

Tryptophan and arginine-rich cyclic hexapeptides of the type cyclo-RRRWFW combine high antibacterial activity with rapid cell killing kinetics, but show low toxicity in human cell lines. The peptides fulfil the structural requirements for membrane interaction such as high amphipathicity and cationic charge, but membrane permeabilisation, which is the most common mode of action of antimicrobial peptides (AMPs), could not be observed. Our current studies focus on elucidating a putative membrane translocation mechanism whereupon the peptides might interfere with intracellular processes.

Characterization of cell-penetrating lipopeptide micelles by spectroscopic methods.

The transport of bioactive compounds to the site of action is a great challenge. A promising approach to overcome application-related problems is the development of targeting colloidal transport systems, such as micelles which are equipped with uptake mediating moieties. Here, we investigated a set of novel lipopeptides which exhibit a surfactant-like structure due to attachment of two palmitoyl chains to the N-terminus of cationic or anionic amino acid sequences.

Effects of charge and charge distribution on the cellular uptake of multivalent arginine-containing peptide-polymer conjugates.

Copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-methacryloyl-β-alaninyl-S-benzyl thioester were prepared by employing free radical or RAFT conditions and denominated as "NCL polymers". The copolymer with a polydispersity index of 1.2-1.

Topical enzyme-replacement therapy restores transglutaminase 1 activity and corrects architecture of transglutaminase-1-deficient skin grafts.

Transglutaminase-1 (TG1)-deficient autosomal-recessive congenital ichthyosis (ARCI) is a rare and severe genetic skin disease caused by mutations in TGM1. It is characterized by collodion babies at birth, dramatically increased transepidermal water loss (TEWL), and lifelong pronounced scaling. The disease has a tremendous burden, including the problem of stigmatization.