Intrinsically disordered Prosystemin discloses biologically active repeat motifs

The in-depth studies over the years on the defence barriers by tomato plants have shown that the Systemin peptide controls the response to a wealth of environmental stress agents. This multifaceted stress reaction seems to be related to the intrinsic disorder of its precursor protein, Prosystemin (ProSys). Since latest findings show that ProSys has biological functions besides Systemin sequence, here we wanted to assess if this precursor includes peptide motifs able to trigger stress-related pathways. Candidate peptides were identified in silico and synthesized to test their capacity to trigger defence responses in tomato plants against different biotic stressors. Our results demonstrated that ProSys harbours several repeat motifs which triggered plant immune reactions against pathogens and pest insects. Three of these peptides were detected by mass spectrometry in plants expressing ProSys, demonstrating their effective presence in vivo. These experimental data shed light on unrecognized functions of ProSys, mediated by multiple biologically active sequences which may partly account for the capacity of ProSys to induce defense responses to different stress agents.

Tryptophan-PNA gc Conjugates Self-Assemble to Form Fibers

Peptide nucleic acids and their conjugates to peptides can self-assemble and generate complex architectures. In this work, we explored the self-assembly of PNA dimers conjugated to the dipeptide WW. Our studies suggest that the indole ring of tryptophan promotes aggregation of the conjugates. The onset of fluorescence is observed upon self-assembly. The structure of self-assembled WWgc is concentration-dependent, being spherical at low concentrations and fibrous at high concentrations. As suggested by molecular modeling studies, fibers are stabilized by stacking interactions between tryptophans and Watson-Crick hydrogen bonds between nucleobases.

Non-covalent strategies to functionalize polymeric nanoparticles with NGR peptides for targeting breast cancer

Surface functionalization of nanoparticles (NPs) with tumor-targeting peptides is an emerging approach with a huge potential to translate in the clinic and ameliorate the efficacy of nano-oncologicals. One major challenge is to find straightforward strategies for anchoring peptides on the surface of biodegradable NPs and ensuring their correct exposure and orientation to bind the target receptor. Here, we propose a non-covalent strategy to functionalize polyester aminic NPs based on the formation of either electrostatic or lipophilic interactions between NPs and the peptide modified with an anchoring moiety. We selected an iNGRt peptide containing a CendR motif (CRNGR) targeting neuropilin receptor 1 (NRP-1), which is upregulated in several cancers. iNGRt was linked with either a short poly(glutamic acid) chain (polyE) or a palmitoyl chain (Palm) and used to functionalize the surface of NPs made of a diamine poly(ε-caprolactone). iNGRt-PolyE was adsorbed on preformed cationic NPs through electrostatic interaction, whereas iNGRt-Palm was integrated into the forming NPs through interactions. In both cases, peptides were strongly associated with NPs of ∼100 nm, low polydispersity indexes, and positive zeta potential values. NPs entered MDA-MB231 breast cancer cells overexpressing NRP-1 via receptor-mediated endocytosis and showed a different cell localization depending on the mode of peptide anchoring. When loaded with the lipophilic anticancer drug docetaxel (DTX), NPs functionalized with the iNGRt-Palm variant exerted a time- and dose-dependent cytotoxicity similar to DTX in MDA-MB-231 cells but were less toxic than DTX toward control MRC-5 human fibroblasts, not expressing NRP-1. In a heterotopic mouse model of triple negative breast cancer, iNGRt-Palm NPs were tolerated better than free DTX and demonstrated superior anticancer activity and survival compared to both free DTX and NPs without peptide functionalization. We foresee that the functionalization strategy with palmitoylated peptides proposed here can be extended to other biodegradable NPs and peptide sequences designed for therapeutic or targeting purposes.

The Membrane Activity of the Amphibian Temporin B Peptide Analog TB_KKG6K Sheds Light on the Mechanism That Kills Candida albicans

Temporin B (TB) is a 13-amino-acid-long, cationic peptide secreted by the granular glands of the European frog Rana temporaria. We recently showed that the modified TB peptide analog TB_KKG6K rapidly killed planktonic and sessile Candida albicans at low micromolar concentrations and was neither hemolytic nor cytotoxic to mammalian cells in vitro. The present study aimed to shed light into its mechanism of action, with a focus on its fungal cell membrane activity. We utilized different fluorescent dyes to prove that it rapidly induces membrane depolarization and permeabilization. Studies on model membrane systems revealed that the TB analog undergoes hydrophobic and electrostatic membrane interactions, showing a preference for anionic lipids, and identified phosphatidylinositol and cardiolipin as possible peptide targets. Fluorescence microscopy using fluorescein isothiocyanate-labeled TB_KKG6K in the presence of the lipophilic dye FM4-64 indicated that the peptide compromises membrane integrity and rapidly enters C. albicans cells in an energy-independent manner. Peptide-treated cells analyzed by cryo-based electron microscopy exhibited no signs of cell lysis; however, subcellular structures had disintegrated, suggesting that intracellular activity may form part of the killing mechanism of the peptide. Taken together, this study proved that TB_KKG6K compromises C. albicans membrane function, which explains the previously observed rapid, fungicidal mode of action and supports its great potential as a future anti-Candida therapeutic. IMPORTANCE Fungal infections with the opportunistic human pathogen C. albicans are associated with high mortality rates in immunocompromised patients. This is partly due to the yeast's ability to rapidly develop resistance toward currently available antifungals. Small, cationic, membrane-active peptides are promising compounds to fight against resistance development, as many of them effectuate rapid fungal cell death. This fast killing is believed to hamper the development of resistance, as the fungi do not have sufficient time to adapt to the antifungal compound. We previously reported that the synthetic variant of the amphibian TB peptide, TB_KKG6K, rapidly kills C. albicans. In the current study, the mechanism of action of the TB analog was investigated. We show that this TB analog is membrane-active and impairs cell membrane function, highlighting its potential to be developed as an attractive alternative anti-C. albicans therapeutic that may hinder the development of resistance.

Chiral Fibers Formation Upon Assembly of Tetraphenylalanine Peptide Conjugated to a PNA Dimer

Self‐assembly of biomolecules such as peptides, nucleic acids or their analogues affords supramolecular objects, exhibiting structures and physical properties dependent on the amino‐acid or nucleobase composition. Conjugation of the peptide diphenylalanine (FF) to peptide nucleic acids triggers formation of self‐assembled structures, mainly stabilized by interactions between FF. In this work we report formation of homogeneous chiral fibers upon self‐assembly of the hybrid composed of the tetraphenylalanine peptide (4F) conjugated to the PNA dimer adenine‐thymine (at). In this case nucleobases seem to play a key role in determining the morphology and chirality of the fibers. When the PNA “at” is replaced by guanine‐cytosine dimer “gc”, disordered structures are observed. Spectroscopic characterization of the self‐assembled hybrids, along with AFM and SEM studies is reported. Finally, a structural model consistent with the experimental evidence has also been obtained, showing how the building blocks of 4Fat arrange to give helical fibers.

Biodegradable nanoparticles combining cancer cell targeting and anti-angiogenic activity for synergistic chemotherapy in epithelial cancer

A biodegradable engineered nanoplatform combining anti-angiogenic activity and targeting of cancer cells to improve the anticancer activity of docetaxel (DTX) is here proposed. Indeed, we have developed biodegradable nanoparticles (NPs) of poly(ethylene glycol)-poly(ε-caprolactone), exposing on the surface both folate motifs (Fol) for recognition in cells overexpressing Folate receptor-α (FRα) and the anti-angiogenic hexapeptide aFLT1. NPs showed a size around 100 nm, the exposure of 60% of Fol moieties on the surface, and the ability to entrap DTX and sustain its release with time. NPs were stable in simulated biological fluids and slightly interacted with Fetal Bovine serum, especially in the formulation decorated with Fol and aFLT1. The presence of Fol on NPs did not impair the anti-angiogenic activity of aFLT1, as assessed by in vitro tube formation assay in HUVEC endothelial cells. In both 2D and 3D KB cell cultures in vitro, the cytotoxicity of DTX loaded in NPs was not significantly affected by Fol/aFLT1 double decoration compared to free DTX. Remarkably, NPs distributed differently in 3D multicellular spheroids of FRα-positive KB cancer cells depending on the type of ligand displayed on the surface. In particular, NPs unmodified on the surface were randomly distributed in the spheroid, whereas the presence of Fol promoted the accumulation in the outer rims of the spheroid. Finally, NPs with Fol and aFLT1 gave a uniform distribution throughout the spheroid structure. When tested in zebrafish embryos xenografted with KB cells, NPs displaying Fol/aFLT1 reduced DTX systemic toxicity and inhibited the growth of the tumor mass and associated vasculature synergistically. Overall, nanotechnology offers excellent ground for combining therapeutic concepts in cancer, paving the way to novel multifunctional nanopharmaceuticals decorated with bioactive elements that can significantly improve therapeutic outcomes.

Diphenylalanine Motif Drives Self-Assembling in Hybrid PNA-Peptide Conjugates

Peptides and nucleic acids can self-assemble to give supramolecular structures that find application in different fields, ranging from the delivery of drugs to the obtainment of materials endowed with optical properties. Forces that stabilize the "suprastructures" typically are hydrogen bonds or aromatic interactions; in case of nucleic acids, Watson-Crick pairing drives self-assembly while, in case of peptides, backbone hydrogen bonds and interactions between aromatic side chains trigger the formation of structures, such as nanotubes or ribbons. Molecules containing both aromatic peptides and nucleic acids could in principle exploit different forces to self-assemble. In this work we meant to investigate the self-assembly of mixed systems, with the aim to understand which forces play a major role and determine formation/structure of aggregates. We therefore synthesized conjugates of the peptide FF to the peptide nucleic acid dimer "gc" and characterized their aggregates by different spectroscopic techniques, including NMR, CD and fluorescence.

Probing the helical stability in a VEGF-mimetic peptide

The analysis of the forces governing helix formation and stability in peptides and proteins has attracted considerable interest in order to shed light on folding mechanism. We analyzed the role of hydrophobic interaction, steric hindrance and chain length on i, i + 3 position in QK peptide, a VEGF mimetic helical peptide. We focused on position 10 of QK, occupied by a leucine, as previous studies highlighted the key role of the Leu7-Leu10 interaction in modulating the helix formation and inducing an unusual thermodynamic stability. Leu10 has been replaced by hydrophobic amino acids with different side-chain length, hydrophobicity and steric hindrance. Ten peptides were, hence, synthesized and analyzed combining circular dichroism, calorimetry and NMR spectroscopy. We found that helical content and thermal stability of peptide QK changed when Leu10 was replaced. Interestingly, we observed that the changes in the helical content and thermal stability were not always correlated and they depend on the type of interaction (strength and geometry) that could be established between Leu7 and the residue in position 10.

Exploiting Protein N-Terminus for Site-Specific Bioconjugation

Although a plethora of chemistries have been developed to selectively decorate protein molecules, novel strategies continue to be reported with the final aim of improving selectivity and mildness of the reaction conditions, preserve protein integrity, and fulfill all the increasing requirements of the modern applications of protein conjugates. The targeting of the protein N-terminal alpha-amine group appears a convenient solution to the issue, emerging as a useful and unique reactive site universally present in each protein molecule. Herein, we provide an updated overview of the methodologies developed until today to afford the selective modification of proteins through the targeting of the N-terminal alpha-amine. Chemical and enzymatic strategies enabling the selective labeling of the protein N-terminal alpha-amine group are described.

New Perspectives in the Antimicrobial Activity of the Amphibian Temporin B: Peptide Analogs Are Effective Inhibitors of Candida albicans Growth

Temporin B (TB) is a short, positively charged peptide secreted by the granular glands of the European frog Rana temporaria. While the antibacterial and antiviral efficacy of TB and some of its improved analogs are well documented, nothing is known about their antifungal potency so far. We dedicated this study to characterize the antifungal potential of the TB analog TB_KKG6K and the newly designed D-Lys_TB_KKG6K, the latter having the L-lysines replaced by the chiral counterpart D-lysines to improve its proteolytic stability. Both peptides inhibited the growth of opportunistic human pathogenic yeasts and killed planktonic and sessile cells of the most prevalent human pathogen, Candida albicans. The anti-yeast efficacy of the peptides coincided with the induction of intracellular reactive oxygen species. Their thermal, cation, pH and serum tolerance were similar, while the proteolytic stability of D-Lys_TB_KKG6K was superior to that of its template peptide. Importantly, both peptides lacked hemolytic activity and showed minimal in vitro cytotoxicity in primary human keratinocytes. The tolerance of both peptides in a reconstructed human epidermis model further supports their potential for topical application. Our results open up an exciting field of research for new anti-Candida therapeutic options based on amphibian TB analogs.

Peptide grafting strategies before and after electrospinning of nanofibers

Nanofiber films produced by electrospinning currently provide a promising platform for different applications. Although nonfunctionalized nanofiber films from natural or synthetic polymers are extensively used, electrospun materials combined with peptides are gaining more interest. In fact, the selection of specific peptides improves the performance of the material for biological applications and mainly for tissue engineering, mostly by maintaining similar mechanical properties with respect to the simple polymer. The main drawback in using peptides blended with a polymer is the quick release of the peptides. To avoid this problem, covalent linking of the peptide is more beneficial. Here, we reviewed synthetic protocols that enable covalent grafting of peptides to polymers before or after the electrospinning procedures to obtain more robust electrospun materials. Applications and the performance of the new material compared to that of the starting polymer are discussed.

Morpholino-based peptide oligomers: Synthesis and DNA binding properties

The chemical structure of oligonucleotide analogues dictates the conformation of oligonucleotide analogue oligomers, their ability to hybridize complementary DNA and RNA, their stability to degradation and their pharmacokinetic properties. In a study aimed at investigating new analogues featuring a neutral backbone, we explored the ability of oligomers containing a morpholino-peptide backbone to bind oligonucleotides. Circular Dichroism studies revealed the ability of our oligomers to interact with DNA, molecular modelling studies revealed the interaction responsible for complex stabilization.

Application of Biophysical Techniques to Investigate the Interaction of Antimicrobial Peptides With Bacterial Cells

Gaining new understanding on the mechanism of action of antimicrobial peptides is the basis for the design of new and more efficient antibiotics. To this aim, it is important to detect modifications occurring to both the peptide and the bacterial cell upon interaction; this will help to understand the peptide structural requirement, if any, at the base of the interaction as well as the pathways triggered by peptides ending in cell death. A limited number of papers have described the interaction of peptides with bacterial cells, although most of the studies published so far have been focused on model membrane-peptides interactions. Investigations carried out with bacterial cells highlighted the limitations connected to the use of oversimplified model membranes and, more importantly, helped to identify molecular targets of antimicrobial peptides and changes occurring to the bacterial membrane. In this review, details on the mechanism of action of antimicrobial peptides, as determined by the application of spectroscopic techniques, as well as scattering, microscopy, and calorimetry techniques, to complex systems such as peptide/bacteria mixtures are discussed.

Practical oxygen therapy for newborn piglets

Aims: To evaluate the effect of a novel method of practical oxygen therapy on physiological parameters related to survival, weaning weight and preweaning mortality of neonatal piglets under commercial farm conditions. Methods: Piglets from hyperprolific sows born with signs of asphyxia, (n = 109; <6 on a score of respiration, meconium staining and activity) or very low birth weight (VLBW; n = 112; <1.05 kg) were selected for the study. Approximately half of each group (n = 55 VLBW piglets and n = 57 piglets with asphyxia) received 100% oxygen immediately after birth using a specially designed facemask for 45 seconds (VLBW) or 1 minute (asphyxiated). Physiological parameters (peripheral blood oxygen saturation (SpO₂) blood glucose concentration and rectal temperature) were measured before oxygen treatment 5 minutes after birth (SpO₂) and 24 hours later (SpO₂, blood glucose concentration, temperature). Weight at birth, at 24 hours and at 21 days of age, preweaning mortality, and estimated colostrum intake were also recorded. Results: A significant treatment effect on SpO₂ was observed (p = 0.013 and p < 0.001 for VLBW and asphyxiated piglets respectively). VLBW and asphyxiated piglets that received oxygen treatment had higher SpO₂ after treatment (measured 5 minutes after birth, 97.7 and 97.8% respectively) compared to immediately after birth (93.3 and 86.8% respectively) while untreated piglets showed no variation. Blood glucose concentrations increased in all piglets between birth and 24 hours of age (p = 0.003 and p < 0.001 for asphyxiated and VLBW piglets respectively) and this was higher in asphyxiated piglets that received oxygen than those that did not (5.6 (SE 0.2) mmol/L; p < 0.05). Estimated colostrum intake was higher in asphyxiated (401.6 (SD 24.4) g/kg) and VLBW (374.9 (SE 23.4 g/kg) piglets that received oxygen than those that did not (273.2 (SE 24.1) g/kg; p < 0.001 and 249.0 (SE 22.5) g/kg; p < 0.001 respectively). Similarly weight at weaning was higher in asphyxiated (5.8 (SE 0.2) kg) and VLBW (4.9 (SE 0.2) kg) piglets that received oxygen therapy than control animals (4.9 (SE 0.2) kg; = 0.005 and 4.1 (SE 0.2) kg; p = 0.008 respectively). Furthermore, oxygen treatment markedly reduced preweaning mortality from 9/52 (17%) untreated to 1/57 (1.7%) oxygen-treated piglets suffering asphyxia at birth (p = 0.006). Conclusions: Oxygen therapy improves physiological and productive parameters in piglets born with signs of asphyxia or VLBW. The incorporation of this strategy as part of the farrowing routine enhances the advantages of rearing hyperprolific sows.

Thanatin Impairs Lipopolysaccharide Transport Complex Assembly by Targeting LptC-LptA Interaction and Decreasing LptA Stability

The outer membrane (OM) of Gram-negative bacteria is a highly selective permeability barrier due to its asymmetric structure with lipopolysaccharide (LPS) in the outer leaflet. In Escherichia coli, LPS is transported to the cell surface by the LPS transport (Lpt) system composed of seven essential proteins forming a transenvelope bridge. Transport is powered by the ABC transporter LptB₂FGC, which extracts LPS from the inner membrane (IM) and transfers it, through LptC protein, to the periplasmic protein LptA. Then, LptA delivers LPS to the OM LptDE translocon for final assembly at the cell surface. The Lpt protein machinery operates as a single device, since depletion of any component leads to the accumulation of a modified LPS decorated with repeating units of colanic acid at the IM outer leaflet. Moreover, correct machine assembly is essential for LPS transit and disruption of the Lpt complex results in LptA degradation. Due to its vital role in cell physiology, the Lpt system represents a good target for antimicrobial drugs. Thanatin is a naturally occurring antimicrobial peptide reported to cause defects in membrane assembly and demonstrated in vitro to bind to the N-terminal β-strand of LptA. Since this region is involved in both LptA dimerization and interaction with LptC, we wanted to elucidate the mechanism of inhibition of thanatin and discriminate whether its antibacterial effect is exerted by the disruption of the interaction of LptA with itself or with LptC. For this purpose, we here implemented the Bacterial Adenylate Cyclase Two-Hybrid (BACTH) system to probe in vivo the Lpt interactome in the periplasm. With this system, we found that thanatin targets both LptC–LptA and LptA–LptA interactions, with a greater inhibitory effect on the former. We confirmed in vitro the disruption of LptC–LptA interaction using two different biophysical techniques. Finally, we observed that in cells treated with thanatin, LptA undergoes degradation and LPS decorated with colanic acid accumulates. These data further support inhibition or disruption of Lpt complex assembly as the main killing mechanism of thanatin against Gram-negative bacteria.

The antimicrobial peptide Temporin L impairs E. coli cell division by interacting with FtsZ and the divisome complex

BACKGROUND

The comprehension of the mechanism of action of antimicrobial peptides is fundamental for the design of new antibiotics. Studies performed looking at the interaction of peptides with bacterial cells offer a faithful picture of what really happens in nature.

METHODS

In this work we focused on the interaction of the peptide Temporin L with E. coli cells, using a variety of biochemical and biophysical techniques that include: functional proteomics, docking, optical microscopy, TEM, DLS, SANS, fluorescence.

RESULTS

We identified bacterial proteins specifically interacting with the peptides that belong to the divisome machinery; our data suggest that the GTPase FtsZ is the specific peptide target. Docking experiments supported the FtsZ-TL interaction; binding and enzymatic assays using recombinant FtsZ confirmed this hypothesis and revealed a competitive inhibition mechanism. Optical microscopy and TEM measurements demonstrated that, upon incubation with the peptide, bacterial cells are unable to divide forming long necklace-like cell filaments. Dynamic light scattering studies and Small Angle Neutron Scattering experiments performed on treated and untreated bacterial cells, indicated a change at the nanoscale level of the bacterial membrane.

CONCLUSIONS

The peptide temporin L acts by a non-membrane-lytic mechanism of action, inhibiting the divisome machinery.

GENERAL SIGNIFICANCE

Identification of targets of antimicrobial peptides is pivotal to the tailored design of new antimicrobials.

Monoacylglycerides from the Diatom Skeletonema marinoi Induce Selective Cell Death in Cancer Cells

Microalgae are an excellent source of valuable compounds for nutraceutical and cosmeceutical applications. These photosynthesizing microorganisms are amenable for large-scale production, thus overcoming the bottleneck of biomass supply for chemical and activity characterization of bioactive compounds. This characteristic has recently also prompted the screening of microalgae for potential pharmaceutical applications. Here, we show that monoacylglycerides (MAGs) purified from the marine diatom Skeletonema marinoi have selective cytotoxic activity against the haematological cancer cell line U-937 and colon cancer cell line HCT-116 compared to normal MePR-2B cells. LC-MS analysis of the raw extract revealed that in their natural form, MAGs occur as 2-monoacyl derivatives and include mainly C16 and C20 analogues, but they are converted into the corresponding 1-isomers during purification processes. Pure compounds along with the synthetic 1-monoarachidonoylglycerol tested on HCT-116 and U-937 tumor cell lines induced cell death via apoptosis. The mechanism of action was investigated, and we show that it involves the induction of apoptosis through caspase 3/7 activation. These findings pave the way for the possible use of these molecules as potential anticancer agents or as precursors for the generation of new and more potent and selective compounds against tumor cells.

Fluorescence and Morphology of Self-Assembled Nucleobases and Their Diphenylalanine Hybrid Aggregates

Studies carried out in recent decades have revealed that the ability to self-assemble is a widespread property among biomolecules. Small nucleic acid moieties or very short peptides are able to generate intricate assemblies endowed with remarkable structural and spectroscopic properties. Herein, the structural/spectroscopic characterization of aggregates formed by nucleobases and peptide nucleic acid (PNA)-peptide conjugates are reported. At high concentration, all studied nucleobases form aggregates characterized by previously unreported fluorescence properties. The conjugation of these bases, as PNA derivatives, to the dipeptide Phe-Phe leads to the formation of novel hybrid assemblies, which are characterized by an amyloid-like association of the monomers. Although these compounds share the same basic cross-β motif, the nature and number of PNA units have an important impact on both the level of structural order and the intrinsic fluorescence of the self-assembled nanostructure.

Tomato Plants Treated with Systemin Peptide Show Enhanced Levels of Direct and Indirect Defense Associated with Increased Expression of Defense-Related Genes

Plant defense peptides represent an important class of compounds active against pathogens and insects. These molecules controlling immune barriers can potentially be used as novel tools for plant protection, which mimic natural defense mechanisms against invaders. The constitutive expression in tomato plants of the precursor of the defense peptide systemin was previously demonstrated to increase tolerance against moth larvae and aphids and to hamper the colonization by phytopathogenic fungi, through the expression of a wealth of defense-related genes. In this work we studied the impact of the exogenous supply of systemin to tomato plants on pests to evaluate the use of the peptide as a tool for crop protection in non-transgenic approaches. By combining gene expression studies and bioassays with different pests we demonstrate that the exogenous supply of systemin to tomato plants enhances both direct and indirect defense barriers. Experimental plants, exposed to this peptide by foliar spotting or root uptake through hydroponic culture, impaired larval growth and development of the noctuid moth Spodoptera littoralis, even across generations, reduced the leaf colonization by the fungal pathogen Botrytis cinerea and were more attractive towards natural herbivore antagonists. The induction of these defense responses was found to be associated with molecular and biochemical changes under control of the systemin signalling cascade. Our results indicate that the direct delivery of systemin, likely characterized by a null effect on non-target organisms, represents an interesting tool for the sustainable protection of tomato plants.

Coordination of a bis-histidine-oligopeptide to Re(i) and Ga(iii) in aqueous solution

We have spectroscopically analyzed the chemistry in aqueous solution and the properties of the histidine-based chelator pHis2 complexed to the fac-[Re(H₂O)₃(CO)₃]⁺ and Ga(iii) to unveil the molecular determinants of their coordination.

Effect of Acylation on the Antimicrobial Activity of Temporin B Analogues

New peptides derived from the natural antimicrobial temporin B were obtained. The design, antimicrobial activity, and characterization of the secondary structure of peptides in the presence of bacterial cells is described herein. TB_KKG6K (KKLLPIVKNLLKSLL) has been identified as the most active analogue against Gram-positive and -negative bacteria, compared with natural temporin B (LLPIVGNLLKSLL) and TB_KKG6A (KKLLPIVANLLKSLL). Acylation with hydrophobic moieties generally led to reduced activity; however, acylation at the 6-position of TB_KKG6K led to retained sub-micromolar activity against Staphylococcus epidermidis.

An anti-PDGFRβ aptamer for selective delivery of small therapeutic peptide to cardiac cells

Small therapeutic peptides represent a promising field for the treatment of pathologies such as cardiac diseases. However, the lack of proper target-selective carriers hampers their translation towards a potential clinical application. Aptamers are cell-specific carriers that bind with high affinity to their specific target. However, some limitations on their conjugation to small peptides and the functionality of the resulting aptamer-peptide chimera exist. Here, we generated a novel aptamer-peptide chimera through conjugation of the PDGFRβ-targeting Gint4.T aptamer to MP, a small mimetic peptide that via targeting of the Cavβ2 subunit of the L-type calcium channel (LTCC) can recover myocardial function in pathological heart conditions associated with defective LTCC function. The conjugation reaction was performed by click chemistry in the presence of N,N,N',N',N"-pentamethyldiethylenetriamine as a Cu (I) stabilizing agent in a DMSO-free aqueous buffer. When administered to cardiac cells, the Gint4.T-MP aptamer-peptide chimera was successfully internalized in cells, allowing the functional targeting of MP to LTCC. This approach represents the first example of the use of an internalizing aptamer for selective delivery of a small therapeutic peptide to cardiac cells.

Self-Assembling of Fmoc-GC Peptide Nucleic Acid Dimers into Highly Fluorescent Aggregates

The study of molecules that self-assemble through noncovalent interactions is one of the most attractive topics in supramolecular chemistry. The use of short peptides or modified nucleotides as building blocks for the aggregates is particularly intriguing because these are very easy to synthesize; moreover, subtle changes in the chemical structure of such building blocks may drastically affect the properties of the aggregates. The ability of peptide nucleic acids (PNA) to aggregate has been very little explored, despite its practical applications. In this work we investigated the self-assembling properties of a PNA dimer, conjugated at the N-terminus to a fluorenylmethoxycarbonyl group. This PNA dimer forms nano-aggregates at low concentration in CHCl₃ /CH₃ OH mixtures. The aggregates retain very interesting fluorescent properties (high quantum yield in the visible region with lifetimes on the nanosecond scale), which make them promising materials for applications in optoelectronics.

Conformational stabilization of a β-hairpin through a triazole–tryptophan interaction

Triazole and indole rings stabilize a β-hairpin conformation through an aromatic–aromatic interaction.

Plant-to-plant communication triggered by systemin primes anti-herbivore resistance in tomato

Plants actively respond to herbivory by inducing various defense mechanisms in both damaged (locally) and non-damaged tissues (systemically). In addition, it is currently widely accepted that plant-to-plant communication allows specific neighbors to be warned of likely incoming stress (defense priming). Systemin is a plant peptide hormone promoting the systemic response to herbivory in tomato. This 18-aa peptide is also able to induce the release of bioactive Volatile Organic Compounds, thus also promoting the interaction between the tomato and the third trophic level (e.g. predators and parasitoids of insect pests). In this work, using a combination of gene expression (RNA-Seq and qRT-PCR), behavioral and chemical approaches, we demonstrate that systemin triggers metabolic changes of the plant that are capable of inducing a primed state in neighboring unchallenged plants. At the molecular level, the primed state is mainly associated with an elevated transcription of pattern -recognition receptors, signaling enzymes and transcription factors. Compared to naïve plants, systemin-primed plants were significantly more resistant to herbivorous pests, more attractive to parasitoids and showed an increased response to wounding. Small peptides are nowadays considered fundamental signaling molecules in many plant processes and this work extends the range of downstream effects of this class of molecules to intraspecific plant-to-plant communication.

Detection of oligonucleotides by PNA-peptide conjugates recognizing the biarsenical fluorescein complex FlAsH-EDT2

We report the application of the arsenical complex FlAsH-EDT₂ for the identification of oligonucleotide sequences. We designed PNA sequences conjugated to either a tetracysteine motif and to split tetracysteine sequences, that are recognized by FlAsH. The effect of conjugation of the PNA to the tetracysteine peptide and RNA hybridization on the fluorescence of the arsenical complex has been investigated. The reconstitution of the tetracysteine motif, starting from 15-mer PNAs conjugated to split tetracysteine sequences and hybridized to a complementary oligonucleotide was also explored.

Highly efficient DNA-free gene disruption in the agricultural pest Ceratitis capitata by CRISPR-Cas9 ribonucleoprotein complexes

The Mediterranean fruitfly Ceratitis capitata (medfly) is an invasive agricultural pest of high economic impact and has become an emerging model for developing new genetic control strategies as an alternative to insecticides. Here, we report the successful adaptation of CRISPR-Cas9-based gene disruption in the medfly by injecting in vitro pre-assembled, solubilized Cas9 ribonucleoprotein complexes (RNPs) loaded with gene-specific single guide RNAs (sgRNA) into early embryos. When targeting the eye pigmentation gene white eye (we), a high rate of somatic mosaicism in surviving G0 adults was observed. Germline transmission rate of mutated we alleles by G0 animals was on average above 52%, with individual cases achieving nearly 100%. We further recovered large deletions in the we gene when two sites were simultaneously targeted by two sgRNAs. CRISPR-Cas9 targeting of the Ceratitis ortholog of the Drosophila segmentation paired gene (Ccprd) caused segmental malformations in late embryos and in hatched larvae. Mutant phenotypes correlate with repair by non-homologous end-joining (NHEJ) lesions in the two targeted genes. This simple and highly effective Cas9 RNP-based gene editing to introduce mutations in C. capitata will significantly advance the design and development of new effective strategies for pest control management.

Studying the Interaction of Magainin 2 and Cecropin A with E. coli Bacterial Cells Using Circular Dichroism

The potential of antimicrobial peptides (AMPs) as an effective therapeutic alternative to classic and current antibiotics has encouraged studies to understand how they interact with the bacterial membrane. Here we describe how to detect, by circular dichroism (CD), the secondary structures of two antimicrobial peptides, magainin 2 and cecropin A, in the presence of E. coli bacterial cells.

New Cross-Talk Layer between Ultraconserved Non-Coding RNAs, MicroRNAs and Polycomb Protein YY1 in Bladder Cancer

MicroRNAs (miRNAs) are highly conserved elements in mammals, and exert key regulatory functions. Growing evidence shows that miRNAs can interact with another class of non-coding RNAs, so-called transcribed ultraconserved regions (T-UCRs), which take part in transcriptional, post-transcriptional and epigenetic regulation processes. We report here the interaction of miRNAs and T-UCRs as a network modulating the availability of these non-coding RNAs in bladder cancer cells. In our cell system, antagomiR-596 increased the expression of T-UCR 201+. Moreover, T-UCR 8+ silencing increased miR-596 expression, which in turn reduced total T-UCR 283+, showing that the perturbation of one element in this network changes the expression of other interactors. In addition, we identify the polycomb protein Yin Yang 1 (YY1) as mediator of binding between miR-596 and T-UCR 8+. These new findings describe for the first time a network between T-UCRs, miRNAs and YY1 protein, highlighting the existence of an additional layer of gene expression regulation.

Miniaturizing VEGF: Peptides mimicking the discontinuous VEGF receptor-binding site modulate the angiogenic response

The angiogenic properties of VEGF are mediated through the binding of VEGF to its receptor VEGFR2. The VEGF/VEGFR interface is constituted by a discontinuous binding region distributed on both VEGF monomers. We attempted to reproduce this discontinuous binding site by covalently linking into a single molecular entity two VEGF segments involved in receptor recognition. We designed and synthesized by chemical ligation a set of peptides differing in length and flexibility of the molecular linker joining the two VEGF segments. The biological activity of the peptides was characterized in vitro and in vivo showing a VEGF-like activity. The most biologically active mini-VEGF was further analyzed by NMR to determine the atomic details of its interaction with the receptor.

Binding studies of antimicrobial peptides to Escherichia coli cells

Understanding the mechanism of action of antimicrobial peptides is pivotal to the design of new and more active peptides. In the last few years it has become clear that the behavior of antimicrobial peptides on membrane model systems does not always translate to cells; therefore the need to develop methods aimed at capturing details of the interactions of peptides with bacterial cells is compelling. In this work we analyzed binding of two peptides, namely temporin B and TB_KKG6A, to Escherichia coli cells and to Escherichia coli LPS. Temporin B is a natural peptide active against Gram positive bacteria but inactive against Gram negative bacteria, TB_KKG6A is an analogue of temporin B showing activity against both Gram positive and Gram negative bacteria. We found that binding to cells occurs only for the active peptide TB_KKG6A; stoichiometry and affinity constant of this peptide toward Escherichia coli cells were determined.

A Case of Smith-Lemli-Opitz Syndrome, Defect of Cholesterol Biosynthesis

We report the case of a child with Smith-Lemli-Opitz Syndrome. The pregnancy was complicated by prenatal growth retardation. The baby was admitted to the Neonatal Intensive Care Unit of Chieti when she was five months old. She showed postnatal growth retardation, trouble sucking and swallowing, microcefaly and multiple major and minor malformations, including characteristic facial features and 2–3 syndactyly of the toes. We found correlations between multiple congenital malformations, failure to thrive and low plasmatic cholesterol measurement.

The influence of liposomal formulation on the incorporation and retention of PNA oligomers

Liposomal formulations composed of phospholipids with different unsaturation degrees, head groups and at different cholesterol content have been tested for the encapsulation of Peptide Nucleic Acid (PNA) oligomers. The best loading capability (177μg, ER%=87.2) was obtained for pure liposomes of phosphatidylglycerol (DOPG) with negatively charged head group. The insertion of a 10-20% of cholesterol in DOPG based liposomes provides a slight decrease (∼160μg) of the PNA loading. On the other hand, the cholesterol addition (20-30%) slows down the PNA's release (∼27%) in fetal bovine serum from the liposomal formulation. Based on the encapsulation and the release properties, PEGylated DOPG liposomes with a percentage of cholesterol of 10-20% are the optimal formulation for the loading of PNA-a210.

Determination of the secondary structure of peptides in the presence of Gram positive bacterium S. epidermidis cells

Temporin L folds into α helix upon incubation with S. epidermidis cells.

III Italian Consensus Conference on Malignant Mesothelioma of the Pleura. Epidemiology, Public Health and Occupational Medicine related issues

The III Italian Consensus Conference on Pleural Mesothelioma (MM) convened on January 29th 2015. This report presents the conclusions of the 'Epidemiology, Public Health and Occupational Medicine' section. MM incidence in 2011 in Italy was 3.64 per 100,000 person/years in men and 1.32 in women. Incidence trends are starting to level off. Ten percent of cases are due to non-occupational exposure. Incidence among women is very high in Italy, because of both non-occupational and occupational exposure. The removal of asbestos in place is proceeding slowly, with remaining exposure. Recent literature confirms the causal role of chrysotile. Fibrous fluoro-edenite was classified as carcinogenic by IARC (Group 1) on the basis of MM data. A specific type (MWCNT-7) of Carbon Nanotubes was classified 2B. For pleural MM, after about 45 years since first exposure, the incidence trend slowed down; with more studies needed. Cumulative exposure is a proxy of the relevant exposure, but does not allow to distinguish if duration or intensity may possibly play a prominent role, neither to evaluate the temporal sequence of exposures. Studies showed that duration and intensity are independent determinants of MM. Blood related MM are less than 2.5%. The role of BAP1 germline mutations is limited to the BAP1 cancer syndrome, but negligible for sporadic cases. Correct MM diagnosis is baseline; guidelines agree on the importance of the tumor gross appearance and of the hematoxylin-eosin-based histology. Immunohistochemical markers contribute to diagnostic confirmation: the selection depends on morphology, location, and differential diagnosis. The WG suggested that 1) General Cancer Registries and ReNaM Regional Operational Centres (COR) interact and systematically compare MM cases; 2) ReNaM should report results presenting the diagnostic certainty codes and the diagnostic basis, separately; 3) General Cancer Registries and COR should interact with pathologists to assure the up-to-date methodology; 4) Necroscopy should be practiced for validation. Expert referral centres could contribute to the definition of uncertain cases. Health surveillance should aim to all asbestos effects. No diagnostic test is recommended for MM screening. Health surveillance should provide information on risks, medical perspective, and smoking cessation. The economic burden associated to MM was estimated in 250,000 Euro per case.

Incorporation of Naked Peptide Nucleic Acids into Liposomes Leads to Fast and Efficient Delivery

The delivery of peptide nucleic acids (PNAs) to cells is a very challenging task. We report here that a liposomal formulation composed of egg PC/cholesterol/DSPE-PEG2000 can be loaded, according to different encapsulation techniques, with PNA or fluorescent PNA oligomers. PNA loaded liposomes efficiently and quickly promote the uptake of a PNA targeting the microRNA miR-210 in human erythroleukemic K562 cells. By using this innovative delivery system for PNA, down-regulation of miR-210 is achieved at a low PNA concentration.

Structural basis of a temporin 1b analogue antimicrobial activity against Gram negative bacteria determined by CD and NMR techniques in cellular environment

We here report an original approach to elucidate mechanisms of action of antimicrobial peptides and derive crucial structural requirements for the design of novel therapeutic agents. The high resolution structure of TB_KKG6A, an antimicrobial peptide designed to amplify the spectrum of action of Temporin B, bound to E. coli is here determined by means of CD and NMR methodologies. We have also defined, through STD analysis, the residues in closer proximity to the bacterial membrane.

Functional binding surface of a β-hairpin VEGF receptor targeting peptide determined by NMR spectroscopy in living cells

In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast (15)N-edited NMR spectroscopic experiments. To this aim, (15)N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope-edited NMR spectroscopic experiments, including (15)N relaxation measurements, allowed a precise characterization of the in-cell HPLW epitope recognized by VEGFR2.

Oligonucleotide analogues as modulators of the expression and function of noncoding RNAs (ncRNAs): emerging therapeutics applications

ncRNAs are emerging as key regulators of physiological and pathological processes and therefore have been identified as pharmacological targets and as markers for some diseases. Oligonucleotide analogues represent so far the most widely employed tool for the modulation of the expression of ncRNAs. In this perspective we briefly describe most of the known classes of ncRNAs and then we discuss the design and the applications of oligonucleotide analogues for their targeting. The effects of modifications of the chemical structure of the oligonucleotides on properties such as the binding affinity toward targets and off targets, and the stability to degradation and their biological effects (when known) are discussed. Examples of molecules currently used in clinical trials are also reported.

Antibacterial and anti-inflammatory activity of a temporin B peptide analogue on an in vitro model of cystic fibrosis

Natural peptides with antimicrobial properties are deeply investigated as tools to fight bacteria resistant to common antibiotics. Small peptides, as those belonging to the temporin family, are very attractive because their activity can easily be tuned after small modification to their primary sequence. Structure-activity studies previously reported by us allowed the identification of one peptide, analogue of temporin B, TB_KKG6A, showing, unlike temporin B, antimicrobial activity against both Gram-positive and Gram-negative bacteria. In this paper, we investigated the antimicrobial and anti-inflammatory activity of the peptide TB_KKG6A against Pseudomonas aeruginosa. Interestingly, we found that the peptide exhibits antimicrobial activity at low concentrations, being able to downregulate the pro-inflammatory chemokines and cytokines interleukin (IL)-8, IL-1β, IL-6 and tumor necrosis factor-α produced downstream infected human bronchial epithelial cells. Experiments were carried out also with temporin B, which was found to show pro-inflammatory activity. Details on the interaction between TB_KKG6A and the P. aeruginosa LPS were obtained by circular dichroism and fluorescence studies.

Inhibition of miRNA maturation by peptide nucleic acids

Molecules able to interfere in miRNA genesis and function are potent tools to unravel maturation and processing pathways. Antisense oligonucleotides or analogs are actually employed for the inhibition of miRNA function. Here we illustrate how Peptide Nucleic Acids oligomers targeting pre-miRNA are exploited to inhibit miRNA maturation.

Circular Dichroism studies on the interactions of antimicrobial peptides with bacterial cells

Studying how antimicrobial peptides interact with bacterial cells is pivotal to understand their mechanism of action. In this paper we explored the use of Circular Dichroism to detect the secondary structure of two antimicrobial peptides, magainin 2 and cecropin A, with E. coli bacterial cells. The results of our studies allow us to gain two important information in the context of antimicrobial peptides- bacterial cells interactions: peptides fold mainly due to interaction with LPS, which is the main component of the Gram negative bacteria outer membrane and the time required for the folding on the bacterial cells depends on the peptide analyzed.

GIS-based pollution hazard mapping and assessment framework of shallow lakes: southeastern Pampean lakes (Argentina) as a case study

The assessment of water vulnerability and pollution hazard traditionally places particular emphasis on the study on groundwaters more than on surface waters. Consequently, a GIS-based Lake Pollution Hazard Index (LPHI) was proposed for assessing and mapping the potential pollution hazard for shallow lakes due to the interaction between the Potential Pollutant Load and the Lake Vulnerability. It includes easily measurable and commonly used parameters: land cover, terrain slope and direction, and soil media. Three shallow lake ecosystems of the southeastern Pampa Plain (Argentina) were chosen to test the usefulness and applicability of this suggested index. Moreover, anthropogenic and natural medium influence on biophysical parameters in these three ecosystems was examined. The evaluation of the LPHI map shows for La Brava and Los Padres lakes the highest pollution hazard (≈30 % with high to very high category) while Nahuel Rucá Lake seems to be the less hazardous water body (just 9.33 % with high LPHI). The increase in LPHI value is attributed to a different loading of pollutants governed by land cover category and/or the exposure to high slopes and influence of slope direction. Dissolved oxygen and biochemical oxygen demand values indicate a moderately polluted and eutrophized condition of shallow lake waters, mainly related to moderate agricultural activities and/or cattle production. Obtained information by means of LPHI calculation result useful to perform a local diagnosis of the potential pollution hazard to a freshwater ecosystem in order to implement basic guidelines to improve lake sustainability.