Identification and characterization of a bactericidal and proapoptotic peptide from cycas revoluta seeds with DNA binding properties

Short Peptides as Powerful Arsenal for Smart Fighting Cancer

Short peptides have been coming around as a strong weapon in the fight against cancer on all fronts-in immuno-, chemo-, and radiotherapy, and also in combinatorial approaches. Moreover, short peptides have relevance in cancer imaging or 3D culture. Thanks to the natural 'smart' nature of short peptides, their unique structural features, as well as recent progress in biotechnological and bioinformatics development, short peptides are playing an enormous role in evolving cutting-edge strategies. Self-assembling short peptides may create excellent structures to stimulate cytotoxic immune responses, which is essential for cancer immunotherapy. Short peptides can help establish versatile strategies with high biosafety and effectiveness. Supramolecular short peptide-based cancer vaccines entered clinical trials. Peptide assemblies can be platforms for the delivery of antigens, adjuvants, immune cells, and/or drugs. Short peptides have been unappreciated, especially in the vaccine aspect. Meanwhile, they still hide the undiscovered unlimited potential. Here, we provide a timely update on this highly active and fast-evolving field.

Morphological Transformations of SARS-CoV-2 Nucleocapsid Protein Biocondensates Mediated by Antimicrobial Peptides

Recently, the discovery of antimicrobial peptides (AMPs) as excellent candidates for overcoming antibiotic resistance has attracted significant attention. AMPs are short peptides active against bacteria, cancer cells, and viruses. It has been shown that the SARS-CoV-2 nucleocapsid protein (N-P) undergoes liquid-liquid phase separation in the presence of RNA, resulting in biocondensate formation. These biocondensates are crucial for viral replication as they concentrate the viral RNA with the host cell's protein machinery required for viral protein expression. Thus, N-P biocondensates are promising targets to block or slow down viral RNA transcription and consequently virion assembly. We investigated the ability of three AMPs to interfere with N-P/RNA condensates. Using microscopy techniques, supported by biophysical characterization, we found that the AMP LL-III partitions into the condensate, leading to clustering. Instead, the AMP CrACP1 partitions into the droplets without affecting their morphology but reducing their dynamics. Conversely, GKY20 leads to the formation of fibrillar structures after partitioning. It can be expected that such morphological transformation severely impairs the normal functionality of the N-P droplets and thus virion assembly. These results could pave the way for the development of a new class of AMP-based antiviral agents targeting biocondensates.

Cycads: A comprehensive review of its botany, traditional uses, phytochemistry, pharmacology and toxicology

Cycads, which primarily consist of the families Cycadaceae and Zamiaceae, possess intrinsic therapeutic attributes that are prominently expressed across their morphological spectrum, including roots, leaves, flowers, and seeds. In Chinese traditional medicine, the leaves of cycads are particularly revered for their profound healing capabilities. This meticulous review engages with existing literature on cycads and presents insightful avenues for future research. Over 210 phytoconstituents have been isolated and identified from various cycad tissues, including flavonoids, azoxy metabolites, sterols, lignans, non-proteogenic amino acids, terpenoids, and other organic constituents. The contemporary pharmacological discourse highlights the antineoplastic, antimicrobial, and antidiabetic activities inherent in these ancient plants, which are of particular importance to the field of oncology. Despite the prevalent focus on crude extracts and total flavonoid content, our understanding of the nuanced pharmacodynamics of cycads lags considerably behind. The notoriety of cycads derived toxicity, notably within the context of Guam's neurological disease cluster, has precipitated an established emphasis on toxicological research within this field. As such, this critical review emphasizes nascent domains deserving of academic and clinical pursuit, whilst nested within the broader matrix of current scientific understanding. The systematic taxonomy, traditional applications, phytochemical composition, therapeutic potential, and safety profile of cycads are holistically interrogated, assimilating an indispensable repository for future scholarly inquiries. In conclusion, cycads stand as a veritable treasure trove of pharmacological virtue, displaying remarkable therapeutic prowess and holding vast promise for ongoing scientific discovery and clinical utilization.

Natural Peptides Inducing Cancer Cell Death: Mechanisms and Properties of Specific Candidates for Cancer Therapeutics

Nowadays, cancer has become the second highest leading cause of death, and it is expected to continue to affect the population in forthcoming years. Additionally, treatment options will become less accessible to the public as cases continue to grow and disease mechanisms expand. Hence, specific candidates with confirmed anticancer effects are required to develop new drugs. Among the novel therapeutic options, proteins are considered a relevant source, given that they have bioactive peptides encrypted within their sequences. These bioactive peptides, which are molecules consisting of 2–50 amino acids, have specific activities when administered, producing anticancer effects. Current databases report the effects of peptides. However, uncertainty is found when their molecular mechanisms are investigated. Furthermore, analyses addressing their interaction networks or their directly implicated mechanisms are needed to elucidate their effects on cancer cells entirely. Therefore, relevant peptides considered as candidates for cancer therapeutics with specific sequences and known anticancer mechanisms were accurately reviewed. Likewise, those features which turn certain peptides into candidates and the mechanisms by which peptides mediate tumor cell death were highlighted. This information will make robust the knowledge of these candidate peptides with recognized mechanisms and enhance their non-toxic capacity in relation to healthy cells and further avoid cell resistance.

Natural Peptides Inducing Cancer Cell Death: Mechanisms and Properties of Specific Candidates for Cancer Therapeutics

Nowadays, cancer has become the second highest leading cause of death, and it is expected to continue to affect the population in forthcoming years. Additionally, treatment options will become less accessible to the public as cases continue to grow and disease mechanisms expand. Hence, specific candidates with confirmed anticancer effects are required to develop new drugs. Among the novel therapeutic options, proteins are considered a relevant source, given that they have bioactive peptides encrypted within their sequences. These bioactive peptides, which are molecules consisting of 2–50 amino acids, have specific activities when administered, producing anticancer effects. Current databases report the effects of peptides. However, uncertainty is found when their molecular mechanisms are investigated. Furthermore, analyses addressing their interaction networks or their directly implicated mechanisms are needed to elucidate their effects on cancer cells entirely. Therefore, relevant peptides considered as candidates for cancer therapeutics with specific sequences and known anticancer mechanisms were accurately reviewed. Likewise, those features which turn certain peptides into candidates and the mechanisms by which peptides mediate tumor cell death were highlighted. This information will make robust the knowledge of these candidate peptides with recognized mechanisms and enhance their non-toxic capacity in relation to healthy cells and further avoid cell resistance.

Short Peptides Make a Big Difference: The Role of Botany-Derived AMPs in Disease Control and Protection of Human Health

Botany-derived antimicrobial peptides (BAMPs), a class of small, cysteine-rich peptides produced in plants, are an important component of the plant immune system. Both in vivo and in vitro experiments have demonstrated their powerful antimicrobial activity. Besides in plants, BAMPs have cross-kingdom applications in human health, with toxic and/or inhibitory effects against a variety of tumor cells and viruses. With their diverse molecular structures, broad-spectrum antimicrobial activity, multiple mechanisms of action, and low cytotoxicity, BAMPs provide ideal backbones for drug design, and are potential candidates for plant protection and disease treatment. Lots of original research has elucidated the properties and antimicrobial mechanisms of BAMPs, and characterized their surface receptors and in vivo targets in pathogens. In this paper, we review and introduce five kinds of representative BAMPs belonging to the pathogenesis-related protein family, dissect their antifungal, antiviral, and anticancer mechanisms, and forecast their prospects in agriculture and global human health. Through the deeper understanding of BAMPs, we provide novel insights for their applications in broad-spectrum and durable plant disease prevention and control, and an outlook on the use of BAMPs in anticancer and antiviral drug design.

Antimicrobial peptides against colorectal cancer-a focused review

Despite recent advances in the treatment of colorectal cancer (CRC), low patient survival rate due to emergence of drug resistant cancer cells, metastasis and multiple deleterious side effects of chemotherapy, is a cause of public concern globally. To negate these clinical conundrums, search for effective and harmless novel molecular entities for the treatment of CRC is an urgent necessity. Since antimicrobial peptides (AMPs) are part of innate immunity of living beings, it is quite imperative to look for essential attributes of these peptides which may contribute to their effectiveness against carcinogenesis. Once identified, those characteristics can be suitably modified using several synthetic and computational techniques to further enhance their selectivity and pharmacokinetic profiles. Hence, this review analyses scientific reports describing the antiproliferative action of AMPs derived from several sources, particularly focusing on various colon cancer in vitro/in vivo investigations. On perusal of the literature, it appears that AMPs based therapeutics would definitely find special place in CRC therapy in future either alone or as an adjunct to chemotherapy provided some necessary alterations are made in their natural structures to make them more compatible with modern clinical practice. In this context, further in-depth research is warranted in adequate in vivo models.

Ecofriendly ruthenium-containing nanomaterials: synthesis, characterization, electrochemistry, bioactivity and catalysis

Among transition metals, ruthenium being an in-demand element along with its complexes with multidimensional applications in biology, catalysis (especially photocatalysis), and several other aspects of industrial materials, is lacking regards for the potential aspect of its nanoparticles. In the modern synthetic scenario, green synthesis of novel ruthenium nanoparticles for the development of novel materials with potential applications has become a focus. Ru-containing nanomaterials (Ru-cNMs) combined with metals like platinum and palladium or with non-metals like phosphorus and oxygen have shown applications as an anticancer, antimicrobial, and antioxidant agents along with wide-ranging catalytic applications. Reduction of Ru salts using biomaterials including plants etc. has emerged enabling the synthesis of Ru-cNMs. In this context, authors realize that poor availability of literature in this area of research seems to be one of the major handicaps that perhaps could be limiting its attractiveness to researchers. Therefore, it was thought worthwhile to present a review article to encourage, guide, and facilitate scientific researches in green ruthenium nanochemistry embodying synthesis, characterization and biological as well as catalytic applications.

Fluoroquinolone antibiotics show genotoxic effect through DNA-binding and oxidative damage

The fluoroquinolones (FQs) are one the most successful class of synthetic antibiotics that primarily target the type II topoisomerases. With a pursuit to evaluate their genotoxicity, the present work established moderate to good DNA-damaging properties of some of the well-known and clinically prescribed fluoroquinolone antibiotics (2^nd and 3^rd generation). Hypochromic shift in UV-Vis absorption titration, fluorescence quenching in competitive ethidium bromide displacement assay (with calf-thymus DNA) and in-silico studies established DNA-intercalation with binding constants of the order 10⁴. A basic Structure Activity Relationship (SAR) has been derived from the docking results. MTT assay has been also done to evaluate the effect of these antibiotics on cell viability. The expression level of specific DNA-glycosylase enzymes responsible for repairing the oxidized DNA bases are quantified through western blot analysis. The studies revealed that fluoroquinolone antibiotics initiate the genotoxic effect at a concentration of above 50 μg/mL. Recruitment of APE1 and NEIL1 was found to be significantly increased to remove the oxidized nucleobases.

Metabolite profiling and in-vitro colon cancer protective activity of Cycas revoluta cone extract

The methanolic extract of Cycas revoluta cone (MECR) was analyzed by GC-MS and UHPLC for metabolite profiling and was evaluated for anti-colon cancer property by using in vitro assays like Cell Viability Assay, Colony Formation Assay, ROS Determination, Flowcytometry, DAPI staining assay, Tunel assay. GC-MS and HPLC analysis confirmed the presence of different phytochemicals in the extract of Cycas revoluta cone. In-vitro studies showed MECR extract showed significant anti-colon cancer activity by reducing proliferation and inducing apoptosis in colon cancer cell (HCT-8) line, but no such activity was seen in normal colon cell (CCD-18Co) line. The investigation confirms that MECR may be a promising candidate in colon cancer protection.

A structural perspective of plant antimicrobial peptides

Among the numerous strategies plants have developed to fend off enemy attack, antimicrobial peptides (AMPs) stand out as one of the most prominent defensive barriers that grant direct and durable resistance against a wide range of pests and pathogens. These small proteins are characterized by a compact structure and an overall positive charge. AMPs have an ancient origin and widespread occurrence in the plant kingdom but show an unusually high degree of variation in their amino acid sequences. Interestingly, there is a strikingly conserved topology among the plant AMP families, suggesting that the defensive properties of these peptides are not determined by their primary sequences but rather by their tridimensional structure. To explore and expand this idea, we here discuss the role of AMPs for plant defense from a structural perspective. We show how specific structural properties, such as length, charge, hydrophobicity, polar angle and conformation, are essential for plant AMPs to act as a chemical shield that hinders enemy attack. Knowledge on the topology of these peptides is facilitating the isolation, classification and even structural redesign of AMPs, thus allowing scientists to develop new peptides with multiple agronomical and pharmacological potential.

Purification and MIC analysis of antimicrobial proteins from Cucumis sativus L. seeds

BACKGROUND

Cucumis sativus L. (cucumber), from the family Cucurbitaceae, is a therapeutic plant with various pharmacological benefits, broadly utilized as a part of complementary medicine (e.g., Unani, Ayurveda, Siddha, and Traditional Chinese). In light of past research discoveries, this plant had been chosen to consider its potential antibacterial action.

METHODS

Extracts were purified by dialysis and ion exchange chromatography strategy and then assayed for antibacterial activity against four standard pathogenic bacterial strains known to cause foodborne infections and spoilage of food and herbal drugs. Antimicrobial peptides were extracted from seeds using a sodium phosphate citrate (pH 7.2) - CTAB cradle (pH 6.0).

RESULTS

The highest protein concentration was seen with elute fractions 1 and 3 (370 mg/mL) compared with elute fractions 2 and 4 (340 mg/mL). Among the bacteria utilized, E. coli was clearly the most sensitive out of selected four strains.

CONCLUSION

Our results suggest that Cucumis sativus L seeds extracts have significant potentials as new antimicrobial agents.

Chloramphenicol-borate/boronate complex for controlling infections by chloramphenicol-resistant bacteria

Increasing bacterial resistance to antibiotics is a pressing problem worldwide, with many health organisations prioritizing this issue. Whilst there is a desperate need for new effective antimicrobials, it is also important to understand the mechanisms and epidemiology of the resistant pathogens currently present in the community. Chloramphenicol is one such well known antibiotic which had lost its efficacy due to bacterial resistance. In this paper, we report the design, synthesis, and bio-studies of novel chloramphenicol-borate/boronate derivatives which showed the ability to control the infections caused by chloramphenicol-resistant bacteria. Activity profiling against P. aeruginosa strain EXR1 with catB gene indicated the inability of acetyl transferase to acetylate the chloramphenicol-borate/boronate complex, unlike chloramphenicol. Results obtained from the antimicrobial assays were further rationalized by molecular docking studies. The latter revealed that the probable reason for the enhanced antibacterial activity may be attributed to the change in the binding site of chloramphenicol-borate/boronate with chloramphenicol acetyl transferase (CAT) with respect to chloramphenicol itself. Hemolytic and genotoxic studies established the reduced toxicity of these synthetic derivatives with respect to chloramphenicol.

We report the design, synthesis, and bio-studies of novel chloramphenicol-borate/boronate derivatives which could control the infections caused by chloramphenicol-resistant bacteria.

A self-assembled clavanin A-coated amniotic membrane scaffold for the prevention of biofilm formation by ocular surface fungal pathogens

Amniotic membrane (AM) is frequently used in ophthalmologic surgery for rapid ocular surface reconstruction. Sometimes it may create a major problem with associated infections after biofilm formation over the membrane. To overcome this problem, AM was coated with the antimicrobial peptide clavanin A. The antifungal activity of clavanin A in the native and self-assembled form was determined against the common ocular surface pathogens Candida albicans, Aspergillus fumigatus, Alternaria sp. and Fusarium sp. Biofilm formation over the coated surface was significantly reduced in comparison with the uncoated membrane. The coated membrane revealed effectiveness in terms of biocompatibility, cell attachment colonization when tested in non-cancerous 3T3 and human embryonic kidney (HEK)-293 cell lines. Clavanin A-coated AM also exhibited excellent physical, morphological and antifungal characteristics, indicating potential applicability for ocular surface infection control.

Antibacterial coating on in-line suction respiratory catheter to inhibit the bacterial biofilm formation using renewable cardanyl methacrylate copolymer

Health-care materials associated with infections are very common in hospital admitted patients. There are generally infected by contact with the catheter or other multipurpose devices which are contacted with microbes. The respiratory infections associated with the pathogens having strong biofilm forming ability on catheter surface, causes life-threatening in every year. Therefore, a catheter coating material is of great interest which inhibits the biofilm formation of pathogens on a catheter to prevent respiratory infections. In this study, we synthesized cardanol containing copolymers as antimicrobial healthcare material via radical polymerization of cardanyl methacrylate (CMA) with styrene (St) monomer in presence of free radical initiator. The rate of polymerization was drastically reduced with the increase of feeding CMA monomer in copolymer. The thermal and mechanical properties were found to increase with incorporation of cardanol moiety in brittle and hard polystyrene. This soft copolymer was grafted onto polyvinyl chloride respiratory catheter which showed high antibacterial activity, inhibit the biofilm formation and also prevent bacterial adhesion. Therefore, the developed coating material on respiratory catheter surface is effective way to control the respiratory catheter-associated nosocomial infections.

π-Stacking assisted redox active peptide–gallol conjugate: synthesis of a new generation of low-toxicity antimicrobial silver nanoparticles

We have synthesized, via click-chemistry, a redox-active peptide–gallol conjugate which facilitates rapid formation of antimicrobial silver nanoparticles with prominent antifungal activity.

Antimicrobial Peptides from Plants

Plant antimicrobial peptides (AMPs) have evolved differently from AMPs from other life forms. They are generally rich in cysteine residues which form multiple disulfides. In turn, the disulfides cross-braced plant AMPs as cystine-rich peptides to confer them with extraordinary high chemical, thermal and proteolytic stability. The cystine-rich or commonly known as cysteine-rich peptides (CRPs) of plant AMPs are classified into families based on their sequence similarity, cysteine motifs that determine their distinctive disulfide bond patterns and tertiary structure fold. Cystine-rich plant AMP families include thionins, defensins, hevein-like peptides, knottin-type peptides (linear and cyclic), lipid transfer proteins, α-hairpinin and snakins family. In addition, there are AMPs which are rich in other amino acids. The ability of plant AMPs to organize into specific families with conserved structural folds that enable sequence variation of non-Cys residues encased in the same scaffold within a particular family to play multiple functions. Furthermore, the ability of plant AMPs to tolerate hypervariable sequences using a conserved scaffold provides diversity to recognize different targets by varying the sequence of the non-cysteine residues. These properties bode well for developing plant AMPs as potential therapeutics and for protection of crops through transgenic methods. This review provides an overview of the major families of plant AMPs, including their structures, functions, and putative mechanisms.

Amphotericin B and anidulafungin directly interact with DNA and induce oxidative damage in the mammalian genome

Amphotericin B and anidulafungin are widely used antifungal drugs for the treatment of systemic and serious mycoses. Amphotericin B is a relatively toxic drug which has long been established. This study is first of its kind to systematically investigate the nature of binding to DNA, and to evaluate intercalation of AMP-B or ANIDULA with the aid of UV-Vis, ITC, and CD spectroscopy. The binding affinity of AMP-B with exclusion sites of 4.68 base pairs (1.2 × 10(5) M(-1)) was found to be higher than that of ANIDULA with exclusion sites of 6.67 base pairs (3.78 × 10(4) M(-1)); consistent with the binding affinity values obtained for AMP-B (10(5) M(-1)) and ANIDULA (10(4) M(-1)). The binding of two drugs with double-stranded DNA was favoured by negative enthalpy as well as negative entropy changes. The intercalation of drugs to duplex polynucleotide induced changes in the intrinsic CD spectra and revealed comparatively higher affinity towards AMP-B than ANIDULA. Molecular docking studies revealed that the negative binding energy was higher in the case of AMP-B reflecting more affinity towards single-stranded DNA. The results of the cytotoxicity, immunoblotting, and gene specific LA-QPCR assay have indicated that ANIDULA is less genotoxic than AMP-B. Hence, the superiority of ANIDULA over AMP-B as a systemic antifungal drug has been established beyond doubt.

Plant antimicrobial peptides as potential anticancer agents

Antimicrobial peptides (AMPs) are part of the innate immune defense mechanism of many organisms and are promising candidates to treat infections caused by pathogenic bacteria to animals and humans. AMPs also display anticancer activities because of their ability to inactivate a wide range of cancer cells. Cancer remains a cause of high morbidity and mortality worldwide. Therefore, the development of methods for its control is desirable. Attractive alternatives include plant AMP thionins, defensins, and cyclotides, which have anticancer activities. Here, we provide an overview of plant AMPs anticancer activities, with an emphasis on their mode of action, their selectivity, and their efficacy.

Structural insights into Cn-AMP1, a short disulfide-free multifunctional peptide from green coconut water

Multifunctional and promiscuous antimicrobial peptides (AMPs) can be used as an efficient strategy to control pathogens. However, little is known about the structural properties of plant promiscuous AMPs without disulfide bonds. CD and NMR were used to elucidate the structure of the promiscuous peptide Cn-AMP1, a disulfide-free peptide isolated from green coconut water. Data here reported shows that peptide structure is transitory and could be different according to the micro-environment. In this regard, Cn-AMP1 showed a random coil in a water environment and an α-helical structure in the presence of SDS-d25 micelles. Moreover, deuterium exchange experiments showed that Gly4, Arg5 and Met9 residues are less accessible to solvent, suggesting that flexibility and cationic charges seem to be essential for Cn-AMP1 multiple activities.

Antiproliferative effect of Dendrobium catenatum Lindley polypeptides against human liver, gastric and breast cancer cell lines

Ten sub-peptides from Dendrobium catenatum Lindley contained in fraction A3 were separated. Fraction A3 exhibited anti-proliferative activity against cancer cells.

Self-assembled cardanol azo derivatives as antifungal agent with chitin-binding ability

Cardanol is a non-isoprenoic phenolic lipid-mixture of distilled cashew nut shell liquid obtained from Anacardium occidentale. Herein, cardanol is purified from cashew nut shell liquid (CNSL) and synthesized to new compounds with different azo amphiphiles. These synthesized compounds are allowed to self-assembled in hydrophobic environment and checked antifungal activity against Candida albicans. Self-assembled structure of CABA showed higher antifungal activity (16μg/mL) and chitin-binding ability in comparison to CAP and CANB. Furthermore, the self-assembled azo amphiphiles are immobilized with silver ions to prepare hydrogel which showed eight folds enhanced antifungal activity. Toxicity is reduced by several folds of self-assembled or hydrogel structure in comparison to pure compounds. Thus, the self-assembled structure of amphiphiles and their hydrogels have been found to be new macromolecules of interest with potential use as antifungal drugs.

Native and recombinant Pg-AMP1 show different antibacterial activity spectrum but similar folding behavior

Glycine-rich proteins (GRPs) derived from plants compose a family of proteins and peptides that share a glycine repeat domain and they can perform diverse functions. Two structural conformations have been proposed for GRPs: glycine loops arranged as a Velcro and an anti-parallel β-sheet with several β-strands. The antimicrobial peptide Pg-AMP1 is the only plant GRP with antibacterial activity reported so far and its structure remains unclear. Recently, its recombinant expression was reported, where the recombinant peptide had an additional methionine residue at the N-terminal and a histidine tag at the C-terminal (His6-tag). These changes seem to change the peptide's activity, generating a broader spectrum of antibacterial activity. In this report, through ab initio molecular modelling and molecular dynamics, it was observed that both native and recombinant peptide structures were composed of an N-terminal α-helix and a dynamic loop that represents two-thirds of the protein. In contrast to previous reports, it was observed that there is a tendency to adopt a globular fold instead of an extended one, which could be in both, glycine loops or anti-parallel β-sheet conformation. The recombinant peptide showed a slightly higher solvated potential energy compared to the native form, which could be related to the His6-tag exposition. In fact, the His6-tag could be mainly responsible for the broader spectrum of activity, but it does not seem to cause great structural changes. However, novel studies are needed for a better characterization of its pharmacological properties so that in the future novel drugs may be produced based on this peptide.

Screening of serine protease inhibitors with antimicrobial activity using iron oxide nanoparticles functionalized with dextran conjugated trypsin and in silico analyses of bacterial serine protease inhibition

Plants produce a variety of proteins and peptides which are involved in their defense against pathogens. Serine protease inhibitors are a well-established class of inhibitors correlated with plant defense. Increased levels of protease inhibitors delay cell damage and expand the cell's life-span. Recently, the rapid emergence of antibiotic-resistant microbial pathogens has prompted immense interest in purifying novel antimicrobial proteins or peptides from plant sources. Usually, the purification of protease inhibitors is accomplished by salt-extraction, ultrafiltration and affinity chromatography. Here, we developed a novel approach based on iron oxide nanoparticles conjugated to dextran functionalized with trypsin beads that accelerate the quick screening and purification of antimicrobial peptides with serine protease inhibitor activity. The method described here also works for screening other inhibitors using particular protein kinases, and it is therefore a novel tool for use as the leading method in the development of novel antimicrobial agents with protease inhibitory activity. Finally, and no less important, molecular modelling and dynamics studies of a homologous inhibitor studied here with Escherichia coli trypsin and chymotrypsin are provided in order to shed some light on inhibitor-enzyme interactions.

Current scenario of peptide-based drugs: the key roles of cationic antitumor and antiviral peptides

Cationic antimicrobial peptides (AMPs) and host defense peptides (HDPs) show vast potential as peptide-based drugs. Great effort has been made in order to exploit their mechanisms of action, aiming to identify their targets as well as to enhance their activity and bioavailability. In this review, we will focus on both naturally occurring and designed antiviral and antitumor cationic peptides, including those here called promiscuous, in which multiple targets are associated with a single peptide structure. Emphasis will be given to their biochemical features, selectivity against extra targets, and molecular mechanisms. Peptides which possess antitumor activity against different cancer cell lines will be discussed, as well as peptides which inhibit virus replication, focusing on their applications for human health, animal health and agriculture, and their potential as new therapeutic drugs. Moreover, the current scenario for production and the use of nanotechnology as delivery tool for both classes of cationic peptides, as well as the perspectives on improving them is considered.

The attack of the phytopathogens and the trumpet solo: Identification of a novel plant antifungal peptide with distinct fold and disulfide bond pattern

Phytopathogens cause economic losses in agribusiness. Plant-derived compounds have been proposed to overcome this problem, including the antimicrobial peptides (AMPs). This paper reports the identification of Ps-AFP1, a novel AMP isolated from the Pisum sativum radicle. Ps-AFP1 was purified and evaluated against phytopathogenic fungi, showing clear effectiveness. In silico analyses were performed, suggesting an unusual fold and disulfide bond pattern. A novel fold and a novel AMP class were here proposed, the αβ-trumpet fold and αβ-trumpet peptides, respectively. The name αβ-trumpet was created due to the peptide's fold, which resembles the musical instrument. The Ps-AFP1 mechanism of action was also proposed. Microscopic analyses revealed that Ps-AFP1 could affect the fungus during the hyphal elongation from spore germination. Furthermore, confocal microscopy performed with Ps-AFP1 labeled with FITC shows that the peptide was localized at high concentration along the fungal cell surface. Due to low cellular disruption rates, it seems that the main target is the fungal cell wall. The binding thermogram and isothermal titration, molecular dynamics and docking analyses were also performed, showing that Ps-AFP1 could bind to chitin producing a stable complex. Data here reported provided novel structural-functional insights into the αβ-trumpet peptide fold.

IbACP, a sixteen-amino-acid peptide isolated from Ipomoea batatas leaves, induces carcinoma cell apoptosis

A 16-amino-acid peptide was isolated from the leaves of sweet potato. The peptide caused a rapid alkalinization response in tomato suspension culture media, a characteristic of defense peptides in plants. No post-translational modification was observed on the peptide according to MALDI-MS analysis. We have named the peptide Ipomoea batatas anti-cancer peptide (IbACP). IbACP also was shown with the ability to dose-dependently inhibit Panc-1, a pancreatic cancer line, cell proliferation. The morphological observations of the Panc-1 cells by phase contrast microscopy showed significant changes after treatment with IbACP. Moreover, caspase-3 and PARP [poly(ADP-ribose) polymerase] were activated by IbACP treatment, followed by cell death. An increase in the levels of cleaved caspase-3 and -9 was also detected by an immunoblot assay after treatment with IbACP. In addition, genomic DNA fragmentation and decreased cellular proliferation were induced when IbACP was supplied to the Panc-1 cells, further demonstrating its biological relevance. The combined data indicates that IbACP peptide may have an important role in the regulation of cellular proliferation by inducing and promoting apoptosis through the mitochondrial apoptotic pathway. This report also showed that IbACP peptide contains potent anti-cancer effects and may play an important role in herbal medicine development.

Theoretical structural insights into the snakin/GASA family

Among the main classes of cysteine-stabilized antimicrobial peptides, the snakin/GASA family has not yet had any structural characterization. Through the combination of ab initio and comparative modeling with a disulfide bond predictor, the three-dimensional structure prediction of snakin-1 is reported here. The structure was composed of two long α-helices with a disulfide pattern of Cys(I)-Cys(IX), Cys(II)-Cys(VII), Cys(III)-Cys(IV), Cys(V)-Cys(XI), Cys(VI)-Cys(XII) and Cys(VIII)-Cys(X). The overall structure was maintained throughout molecular dynamics simulation. Snakin-1 showed a small degree of structural similarity with thionins and α-helical hairpins. This is the first report of snakin-1 structural characterization, shedding some light on the snakin/GASA family.

N, N'-Olefin functionalized bis-imidazolium gold(I) salt is an efficient candidate to control keratitis-associated eye infection

Keratitis treatment has become more complicated due to the emergence of bacterial or fungal pathogens with enhanced antibiotic resistance. The pharmaceutical applications of N-heterocyclic carbene complexes have received remarkable attention due to their antimicrobial properties. In this paper, the new precursor, 3,3′-(p-phenylenedimethylene) bis{1-(2- methyl-allyl)imidazolium} bromide (1a) and its analogous PF₆ salt (1b) were synthesized. Furthermore, silver(I) and gold(I) -N-heterocyclic carbene (NHC) complexes [Ag₂LBr₂/Au₂LBr₂; 2a/3a], [(Ag₂L₂)(PF₆)₂/(Au₂L₂)(PF₆)₂; 2b/3b] were developed from their corresponding ligands. All compounds were screened for their antimicrobial activities against multiple keratitis-associated human eye pathogens, including bacteria and fungi. Complexes 2a and 3a showed highest activity, and the effectiveness of 3a was also studied, focusing eradication of pathogen biofilm. Furthermore, the structures of 1a, 2a and 3b were determined using single crystal X-ray analysis, 2b and 3a were optimized theoretically. The mechanism of action of 3a was evaluated by scanning electron microscopy and docking experiments, suggesting that its target is the cell membrane. In summary, 3a may be helpful in developing antimicrobial therapies in patients suffering from keratitis-associated eye infections caused by multidrug-resistant pathogens.

Cn-AMP1: a new promiscuous peptide with potential for microbial infections treatment

The antimicrobial peptides (AMPs) are evolutionarily ancient molecules that act as components of the innate immune system. Recently, it was demonstrated that a single AMP can perform various functions; this ability is known as "peptide promiscuity." However, little is known about promiscuity in plant AMPs without disulfide bonds. This study was carried out to evaluate the promiscuity of Cn-AMP1: a promising disulfide-free plant peptide with reduced size and cationic and hydrophobic properties. Its activity against human pathogenic bacteria and fungal pathogens, as well as its in vitro immunostimulatory activity and effects on cancerous and healthy mammalian cell proliferation were studied here. Cn-AMP1 exerts antimicrobial effects against Gram-positive bacteria, Gram-negative bacteria, and fungi. Moreover, tumor cell viability activity in Caco-2 cells, as well as immunostimulatory activity by evaluating upregulated inflammatory-cytokine secretion by monocytes was also positively observed. Cn-AMP1 does not exhibit a well-defined conformation in aqueous solution and probably undergoes a 3(10)-helix transition in hydrophobic environments. The experimental results support the promiscuous activity of Cn-AMP1, presenting a wide range of activities, including antibacterial, antifungal, and immunostimulatory activity. In the future, Cn-AMP1 should be used in the development of novel biopharmaceuticals, mainly due to its reduced size and broad spectrum of activity.

CS-AMPPred: an updated SVM model for antimicrobial activity prediction in cysteine-stabilized peptides

The antimicrobial peptides (AMP) have been proposed as an alternative to control resistant pathogens. However, due to multifunctional properties of several AMP classes, until now there has been no way to perform efficient AMP identification, except through in vitro and in vivo tests. Nevertheless, an indication of activity can be provided by prediction methods. In order to contribute to the AMP prediction field, the CS-AMPPred (Cysteine-Stabilized Antimicrobial Peptides Predictor) is presented here, consisting of an updated version of the Support Vector Machine (SVM) model for antimicrobial activity prediction in cysteine-stabilized peptides. The CS-AMPPred is based on five sequence descriptors: indexes of (i) α-helix and (ii) loop formation; and averages of (iii) net charge, (iv) hydrophobicity and (v) flexibility. CS-AMPPred was based on 310 cysteine-stabilized AMPs and 310 sequences extracted from PDB. The polynomial kernel achieves the best accuracy on 5-fold cross validation (85.81%), while the radial and linear kernels achieve 84.19%. Testing in a blind data set, the polynomial and radial kernels achieve an accuracy of 90.00%, while the linear model achieves 89.33%. The three models reach higher accuracies than previously described methods. A standalone version of CS-AMPPred is available for download at <http://sourceforge.net/projects/csamppred/> and runs on any Linux machine.

Structural and functional characterization of a multifunctional alanine-rich peptide analogue from Pleuronectes americanus

Recently, defense peptides that are able to act against several targets have been characterized. The present work focuses on structural and functional evaluation of the peptide analogue Pa-MAP, previously isolated as an antifreeze peptide from Pleuronectes americanus. Pa-MAP showed activities against different targets such as tumoral cells in culture (CACO-2, MCF-7 and HCT-116), bacteria (Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 25923), viruses (HSV-1 and HSV-2) and fungi (Candida parapsilosis ATCC 22019, Trichophyton mentagrophytes (28d&E) and T. rubrum (327)). This peptide did not show toxicity against mammalian cells such as erythrocytes, Vero and RAW 264.7 cells. Molecular mechanism of action was related to hydrophobic residues, since only the terminal amino group is charged at pH 7 as confirmed by potentiometric titration. In order to shed some light on its structure-function relations, in vitro and in silico assays were carried out using circular dichroism and molecular dynamics. Furthermore, Pa-MAP showed partial unfolding of the peptide changes in a wide pH (3 to 11) and temperature (25 to 95°C) ranges, although it might not reach complete unfolding at 95°C, suggesting a high conformational stability. This peptide also showed a conformational transition with a partial α-helical fold in water and a full α-helical core in SDS and TFE environments. These results were corroborated by spectral data measured at 222 nm and by 50 ns dynamic simulation. In conclusion, data reported here show that Pa-MAP is a potential candidate for drug design against pathogenic microorganisms due to its structural stability and wide activity against a range of targets.