1-Naphthylacetic acid appended amino acids-based hydrogels: probing of the supramolecular catalysis of ester hydrolysis reaction.

A 1-naphthaleneacetic acid-appended phenylalanine-derivative (Nap-F) forms a stable hydrogel with a minimum gelation concentration (MGC) of 0.7% w/v (21 mM) in phosphate buffer of pH 7.4. Interestingly, Nap-F produces two-component [Nap-F + H = Nap-FH, Nap-F + K = Nap-FK and Nap-F + R = Nap-FR], three-component [Nap-F + H + K = Nap-FH-K, Nap-F + H + R = Nap-FH-R and Nap-F + K + R = Nap-FK-R] and four-component [Nap-F + H + K + R = Nap-FH-K-R] hydrogels in water with all three natural basic amino acids (H = histidine, K = lysine and R = arginine) at various combinations below its MGC. Nap-F-hydrogel forms a nice entangled nanofibrillar network structure as evidenced by field emission scanning electron microscopy (FE-SEM). Interestingly, lysine-based co-assembled two- (Nap-FK), three- (Nap-FH-K and Nap-FK-R) and four-component (Nap-FH-K-R) xerogels exhibit helical nanofibrillar morphology, which was confirmed by circular dichroism spectroscopy, FE-SEM and TEM imaging. However, histidine and arginine-based two-component (Nap-FH and Nap-FR) and three-component (Nap-FH-R) co-assembled xerogels exhibiting straight nanofibrillar morphology. In their co-assembled states, these two-, three- and four-component supramolecular hydrogels show promising esterase-like activity below their MGCs. The enhanced catalytic activity of helical fibers compared to obtained straight fibers (other than lysine-based assembled systems) suggests that the helical fibrillar nanostructure is involved in ordering the esterase-like although all supramolecular assemblies are chemically different from one another.

A promising antifungal lipopeptide from Bacillus subtilis: its characterization and insight into the mode of action.

Emerging resistance of fungal pathogens and challenges faced in drug development have prompted renewed investigations into novel antifungal lipopeptides. The antifungal lipopeptide AF3 reported here is a natural lipopeptide isolated and purified from Bacillus subtilis. The AF3 lipopeptide's secondary structure, functional groups, and the presence of amino acid residues typical of lipopeptides were determined by circular dichroism, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The lipopeptide's low minimum inhibitory concentrations (MICs) of 4-8 mg/L against several fungal strains demonstrate its strong antifungal activity. Biocompatibility assays showed that ~ 80% of mammalian cells remained viable at a 2 × MIC concentration of AF3. The treated Candida albicans cells examined by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy clearly showed ultrastructural alterations such as the loss of the cell shape and cell membrane integrity. The antifungal effect of AF3 resulted in membrane permeabilization facilitating the uptake of the fluorescent dyes-acridine orange (AO)/propidium iodide (PI) and FUN-1. Using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 4-(2-[6-(dioctylamino)-2-naphthalenyl] ethenyl)-1-(3-sulfopropyl) pyridinium inner salt (di-8-ANEPPS), we observed that the binding of AF3 to the membrane bilayer results in membrane disruption and depolarization. Flow cytometry analyses revealed a direct correlation between lipopeptide activity, membrane permeabilization (~ 75% PI uptake), and reduced cell viability. An increase in 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence demonstrates endogenous reactive oxygen species production. Lipopeptide treatment appears to induce late-stage apoptosis and alterations to nuclear morphology, suggesting that AF3-induced membrane damage may lead to a cellular stress response. Taken together, this study illustrates antifungal lipopeptide's potential as an antifungal drug candidate. KEY POINTS: • The studied lipopeptide variant AF3 displayed potent antifungal activity against C. albicans • Its biological activity was stable to proteolysis • Analytical studies demonstrated that the lipopeptide is essentially membranotropic and able to cause membrane dysfunction, elevated ROS levels, apoptosis, and DNA damage.

Myco-synthesis of multi-twinned silver nanoparticles as potential antibacterial and antimalarial agents.

In recent days, biogenic and green approaches for synthesizing nanostructures have gained much attention in biological and biomedical applications. Endophytic fungi have been recognized to produce several important biomolecules for use in various fields. The present work describes the use of endophytic fungi isolated from Berberis aristata for the synthesis of multi-twinned silver nanoparticles (MT-AgNPs) and their successful applications in antimicrobial and antimalarial studies. TEM images reveal the formation of multi-twined structures in the synthesized silver nanoparticles. The synthesized MT-AgNPs have shown excellent antibacterial activities against five opportunistic bacteria, viz. Bacillus subtilis (MTCC 441), Pseudomonas aeruginosa (MTCC 424), Escherichia coli (MTCC 443), Klebsiella pneumonia (MTCC 3384), and Aeromonas salmonicida (MTCC 1522). The synthesized MT-AgNPs also exhibit interesting antimalarial activities against Plasmodium falciparum parasites (3D7 strain) by displaying 100% inhibition at a concentration of 1 µg mL-1 against the malaria parasite P. falciparum 3D7. Overall, the results describe a green method for the production of twinned-structured nanoparticles and their potential to be applied in the biomedical, pharmaceutical, food preservation, and packaging industries.

Simple high-precision diode laser system with digital control.

A simple wavelength tunable diode laser system has been designed and fabricated for laboratory use. Both the current and temperature controllers are based on an AVR microcontroller, and the experimental controls have been implemented with the help of daemon programs running in a message passing interface environment, which allows the users to run the control server and client programs on separate computers. The stability of the controllers has been tested using a distributed feedback (DFB) diode laser with a central wavelength of 852.3 nm. A noise spectral analysis of the current controller with and without the use of the diode laser as the active load has been demonstrated. The absorption spectra of 6S 1/2→6P 3/2 transition of 133 C s, as recorded by using the DFB laser system developed, are also presented.

Expedient Ni-catalyzed C-H/C-H cross-dehydrogenative coupling of aryl amides with azoles.

A nickel-catalyzed C-H heteroarylation of arenes has been described using a removable oxazoline-aniline derived directing group. Utilization of an inexpensive nickel(II)-catalyst, substrate scope, functional group diversity and late-stage functionalization of xanthine-derived commercial drugs are the important practical features.

Mechanism of Side Chain-Controlled Proton Conductivity in Bioinspired Peptidic Nanostructures.

Bioinspired peptide assemblies are promising candidates for use as proton-conducting materials in electrochemical devices and other advanced technologies. Progress toward applications requires establishing foundational structure-function relationships for transport in these materials. This experimental-theoretical study sheds light on how the molecular structure and proton conduction are linked in three synthetic cyclic peptide nanotube assemblies that comprise the three canonical basic amino acids (lysine, arginine, and histidine). Experiments find an order of magnitude higher proton conductivity for lysine-containing peptide assemblies compared to histidine and arginine containing assemblies. The simulations indicate that, upon peptide assembly, the basic amino acid side chains are close enough to enable direct proton transfer. The proton transfer kinetics is determined in the simulations to be governed by the structure and flexibility of the side chains. Together, experiments and theory indicate that the proton mobility is the main determinant of proton conductivity, critical for the performance of peptide-based devices.

Pd-catalyzed bidentate auxiliary assisted remote C(sp3)-H functionalization.

Pd-catalyzed C-H functionalisation affords effective synthetic tools to construct C-C and C-X bonds. Despite the challenges, the distal functionalization of C(sp3)-H bonds has witnessed significant developments and the use of bidentate auxiliaries has garnished this area by providing an opportunity to control reactivity as well as selectivity beyond proximal sites. This article covers the recent developments on the Pd-catalyzed bidentate auxiliary-assisted distal C(sp3)-H functionalization and is categorized based on the nature of functionalizations.

Optimization of the performance of a voltage measuring station using genetic algorithm.

This article describes the use of the genetic algorithm (GA) for the optimization of the performance of a voltage measuring station. This procedure can be used for the instruments for which regular and systematic calibration is required for better performance. Here, a GA-based correction module has been used to internally store a few previous measured-value and measured-time pairs and to use these values to correct the current readings. Sanity-checking runs against zero and standard voltages from time to time and auto-calibrates itself. The genetic algorithm libraries have been developed along with the correction module. This system can also be considered as a test bed for the study of self-calibration algorithms.

Evaluation of nested PCR and loop mediated isothermal amplification assay (LAMP) targeting 47 ​kDa gene of Orientia tsutsugamushi for diagnosis of scrub typhus.

PURPOSE: Diagnostic testing, in particular early detection, is critical for scrub typhus, as most infected individuals have nonspecific symptoms that are easily confused with dengue and malaria. PCR and LAMP offer an alternative DNA amplification method for detection of Orientia tsutsugamushi. Detection of Orientia tsutsugamushi DNA by targeting the 47-kDa gene using nested PCR and LAMP for diagnosis of scrub typhus. METHODS: A cross-sectional study in a tertiary care hospital in central India. The present study was done on a total of 274 patients with fever of five days or more and negative for other causes of fever viz. malaria, dengue and enteric fever. From each patient 5 â€‹ml of blood samples was collected in EDTA vial for molecular tests (PCR and LAMP) and in plain vial for serological tests (IgM IFA). The data was entered in Excel sheet and 2 â€‹× â€‹2 tables were created to find sensitivity, specificity, positive and negative likelihood ratios, disease prevalence, positive and negative predictive values and accuracy. RESULTS: PCR showed a sensitivity of 29.73% while the sensitivity of LAMP was 16.22%. The specificity of nested PCR and LAMP was very high, 99.58% and 99.16% respectively. The diagnostic accuracy of nested PCR (90.15%) was found to be marginally better than LAMP (87.96%). CONCLUSIONS: For the treatment of scrub typhus, a gene-based diagnostic test would enable earlier and more accurate detection of the causative agents of the disease than serology in admission samples of patients with acute febrile illness in endemic areas.

Supramolecular Antiparallel ß-Sheet Formation by Tetrapeptides Based on Amyloid Sequence.

Self-assembly of short peptides has emerged as an interesting research field for a wide range of applications. Recently, several truncated fragments of long-chain peptides or proteins responsible for different neurodegenerative diseases were studied to understand whether they can mimic the property and function of native peptides or not. It was reported that such a kind of peptide adopts a ß-sheet structure in the disease state. It was observed that aromatic amino acid-rich peptide fragments possess a high tendency to adopt a ß-sheet conformation. In this article, we are first time reporting the crystal structure of two tetrapeptides: Boc-GAII-OMe (Peptide 1) and Boc-GGVV-OMe (Peptide 2), composed of aliphatic amino acids, and the sequences are similar to the Aß-peptide fragments Aß29-32 and Aß37-40 , respectively. In the solid-state, they are self-assembled in an antiparallel ß-sheet fashion. The peptide units are connected by the strong amide hydrogen-bonding (N-H···O) interactions. Apart from that, other noncovalent interactions are also present, which help to stabilize the cross-ß-sheet arrangement. Interestingly, in the crystal structure of Peptide 1, noncovalent C···C interaction between the electron-deficient carbonyl carbon, and the electron-rich sp3-carbon atom is observed, which is quite rare in the literature. The calculated torsion angles for these peptides are lying in the ß-sheet region of the Ramachandran plot. FT-IR studies also indicate the formation of an antiparallel ß-sheet structure in the solid-state. Circular dichroism of the peptides in the aqueous solution also suggests the presence of predominantly ß-sheet-like conformation in the aqueous solution. Under cross-polarized light, Congo Red stained both peptides showed green-gold color due to birefringence indicating their amyloidogenic nature. This result indicates that the short peptide composed of aliphatic amino acid is capable of forming a ß-sheet structure in the absence of aromatic amino acid and also can mimic the function of the native amyloid peptide.

Pd-Catalyzed sp3 C-H alkoxycarbonylation of 8-methylquinolines using Mo(CO)6 as a CO surrogate.

A Pd(ii)-catalyzed three-component sp3 C-H alkoxycarbonylation of 8-methylquinonlines (8-MQs) with alcohols is accomplished using the colorless crystalline Mo(CO)6 as a CO source. The protocol is compatible with a wide range of 8-MQs and alcohols, furnishing the carbonylated adducts in moderate to good yields. The substrate scope, functional group tolerance and natural product mutation are the important practical features.

Oxidative C-H/N-H Annulation of Aromatic Amides with Dialkyl Malonates: Access to Isoindolinones and Dihydrobenzoindoles.

A copper-mediated oxidative C-H/N-H annulation of aromatic amides with dialkyl malonates has been presented to afford synthetically valuable dihydrobenzoindoles and isoindolinones. The reaction proceeds through direct oxidative C(sp2)-H/C(sp3)-H coupling followed by an intramolecular N-H/C(sp3)-H dehydrogenative coupling to deliver the target motifs with broad scope and functional group tolerance.

Expedient iron-catalyzed stereospecific synthesis of triazines via cycloaddition of aziridines with diaziridines.

Iron-catalyzed stereospecific [3+3]-annulation of aziridines with diaziridines is described to furnish [1,2,4]-triazines in high yield at room temperature. The use of an inexpensive iron salt catalyst, substrate scope and enantiomeric purity are the important practical features.

Direct cyanidation of silver sulfide by heterolytic C-CN bond cleavage of acetonitrile.

Extraction of silver as silver cyanide from silver sulfide was made possible using acetonitrile as the source of cyanide. The process of cyanidation took place through the oxidation of sulfide to sulfur oxides and cleavage of the C-CN bond of acetonitrile. The reaction was found to be catalyzed by vanadium pentoxide and hydrogen peroxide. The different species involved in the cyanidation process were duly characterized using FTIR, ESI-MS, HRMS, XPS and UV-vis spectroscopic analysis. The mechanism of the cyanidation process was confirmed through in situ FTIR analysis.

Self-Assembled Peptide Nanotube Films with High Proton Conductivity.

Design flexibility and modularity have emerged as powerful tools in the development of functional self-assembled peptide nanostructures. In particular, the tendency of peptides to form fibrils and nanotubes has motivated the investigation of electron and, more recently, proton transport in their fibrous films. In this study, we present a detailed characterization by impedance spectroscopy of films of self-assembled cyclic octa-d,l-α-peptide self-assembled nanotubes with amine side chains that promote proton transport. We show that the conductivity of the peptide nanotube film, which is in the range of 0.3 mS cm-1, is within the same order of magnitude as that of ultrathin films of Nafion, a benchmark proton conducting polymer. In addition, we show that while slow diffusion processes at the interface are present for both films, additional interface effects occur in the peptide nanotube films at the same rate as their bulk proton transport effects, further limiting charge transport at the interface. Overall, our studies demonstrate the great potential of using peptides as building blocks for the preparation of bioinspired supramolecular proton conducting polymers with improved conductivity with respect to that of natural systems.

Iron-Catalyzed Regioselective Remote C(sp2)-H Carboxylation of Naphthyl and Quinoline Amides.

Iron(III)-catalyzed regioselective direct remote C-H carboxylation of naphthyl and quinoline amides was developed using CBr4 and alcohol. The reaction involves a radical pathway using a coordination activation strategy and single electron transfer process. The use of sustainable iron catalysis, selectivity, and the substrate scope are the important practical features.

Rh-Catalyzed tandem C-C/C-N bond formation of quinoxalines with alkynes leading to heterocyclic ammonium salts.

An efficient Rh-catalyzed oxidative C-H activation/annulation of 2-arylquinoxalines with internal alkynes is described using Cu(OAc)2·H2O and AgBF4 to afford a diverse variety of substituted quarternary ammonium salts at room temperature. The mechanism of the protocol is established on the basis of isolation of the 5-membered rhodacycle intermediate and kinetic isotope studies. The mild reaction conditions, substrate scope and functional group diversity are the salient practical features.

Supramolecular Hydrogel from an Oxidized Byproduct of Tyrosine.

Herein we report for the first time the supramolecular hydrogelation of a derivative of 3-nitrotyrosine (3-NT), which is an oxidized byproduct of tyrosine, produced in the presence of reactive nitrogen species in the cell. The 9-fluorenylmethyloxycarbonyl (Fmoc) derivative of 3-NT, FNT, can form self-supported hydrogels at a wide range of pH values (4.5-8.5) in 50 mM phosphate buffer solutions. Hydrogels prepared at pH 7.0 are yellow, transparent, and thixotropic in nature. A yellow hydrogel was obtained by changing the pH from 4.5 to 8.5. Moreover, the gelation efficiency of the FNT gelator was enhanced by lowering the pH of the buffer solution. pH-Dependent self-assembly properties of the gelator were studied by using UV-vis, fluorescence, and circular dichroism spectroscopy and wide-angle X-ray diffraction techniques. Field-emission-scanning electron microscopy and transmission electron microscopy studies of the self-assembled FNT hydrogel showed a nanofibrillar network structure. Interestingly, the hydrogel showed injectable behavior at physiological pH. The low cytotoxicity value and high antimicrobial properties of the hydrogel indicated that it is a potential material for biomedical applications.

Copper-mediated regioselective C-H etherification of naphthylamides with arylboronic acids using water as an oxygen source.

The copper-mediated regioselective C-H activation and C-O bond formation of naphthylamides with arylboronic acids has been developed using water as an oxygen source. The kinetic isotope study suggests that C-H bond activation is the rate-determining step. The H2O18 labelling experiment reveals the incorporation of oxygen from water. The substrate scope, functional group diversity and post synthetic utilities are the important practical features.

Correction: Copper-mediated regioselective C-H etherification of naphthylamides with arylboronic acids using water as an oxygen source.

Correction for 'Copper-mediated regioselective C-H etherification of naphthylamides with arylboronic acids using water as an oxygen source' by Subhasish Roy et al., Chem. Commun., 2018, DOI: 10.1039/c8cc02158a.