Nature-Inspired Stalactite Nanopores for Biosensing and Energy Harvesting.

Nature provides a wide range of self-assembled structures from the nanoscale to the macroscale. Under the right thermodynamic conditions and with the appropriate material supply, structures like stalactites, icicles, and corals can grow. However, the natural growth process is time-consuming. This work demonstrates a fast, nature-inspired method for growing stalactite nanopores using heterogeneous atomic deposition of hafnium dioxide at the orifice of templated silicon nitride apertures. The stalactite nanostructures combine the benefits of reduced sensing region typically for 2-dimensional material nanopores with the asymmetric geometry of capillaries, resulting in ionic selectivity, stability, and scalability. The proposed growing method provides an adaptable nanopore platform for basic and applied nanofluidic research, including biosensing, energy science, and filtration technologies.

Lead Halide Perovskite Quantum Dots To Enhance the Power Conversion Efficiency of Organic Solar Cells.

The facile synthesis, solution-processability, and outstanding optoelectronic properties of emerging colloidal lead halide perovskite quantum dots (LHP QDs) makes them ideal candidates for scalable and inexpensive optoelectronic applications, including photovoltaic (PV) devices. The first demonstration of integrating CsPbI3 QDs into a conventional organic solar cell (OSC) involves embedding the LHP QDs in a donor-acceptor (PTB7-Th:PC71 BM) bulk heterojunction. Optimizing the loading amount at 3 wt %, we demonstrate a power conversion efficiency of 10.8 %, which is a 35 % increase over control devices, and is a record amongst hybrid ternary OSCs. Detailed investigation into the mechanisms behind the performance enhancement shows that increased light absorption is not a factor, but that increased exciton separation in the acceptor phase and reduced recombination are responsible.

Derivatives of 3-Aminopyrazine-2-carboxamides: Synthesis, Antimicrobial Evaluation, and in Vitro Cytotoxicity.

We report the design, synthesis, and in vitro antimicrobial activity of a series of N-substituted 3-aminopyrazine-2-carboxamides with free amino groups in position 3 on the pyrazine ring. Based on various substituents on the carboxamidic moiety, the series is subdivided into benzyl, alkyl, and phenyl derivatives. The three-dimensional structures of the title compounds were predicted using energy minimization and low mode molecular dynamics under AMBER10:EHT forcefield. Compounds were evaluated for antimycobacterial, antibacterial, and antifungal activities in vitro. The most active compound against Mycobacterium tuberculosis H37Rv (Mtb) was 3-amino-N-(2,4-dimethoxyphenyl)pyrazine-2-carboxamide (17, MIC = 12.5 µg/mL, 46 µM). Antimycobacterial activity against Mtb and M. kansasii along with antibacterial activity increased among the alkyl derivatives with increasing the length of carbon side chain. Antibacterial activity was observed for phenyl and alkyl derivatives, but not for benzyl derivatives. Antifungal activity was observed in all structural subtypes, mainly against Trichophyton interdigitale and Candida albicans. The four most active compounds (compounds 10, 16, 17, 20) were evaluated for their in vitro cytotoxicity in HepG2 cancer cell line; only compound 20 was found to exert some level of cytotoxicity. Compounds belonging to the current series were compared to previously published, structurally related compounds in terms of antimicrobial activity to draw structure activity relationships conclusions.

Design, synthesis and antimycobacterial activity of hybrid molecules combining pyrazinamide with a 4-phenylthiazol-2-amine scaffold.

Hybrid compounds based on a combination of the first-line antitubercular pyrazinamide (PZA) and a formerly identified antimycobacterial scaffold of 4-arylthiazol-2-amine were designed. Eighteen compounds were prepared, characterized and tested for in vitro growth inhibition activity against M. tuberculosis H37Rv, M. kansasii, M. avium and M. smegmatis by Microplate Alamar Blue Assay at neutral pH. Active compounds were tested for in vitro cytotoxicity in the human hepatocellular carcinoma cell line (HepG2). The most active 6-chloro-N-[4-(4-fluorophenyl)thiazol-2-yl]pyrazine-2-carboxamide (9b) also had the broadest spectrum of activity and inhibited M. tuberculosis, M. kansasii, and M. avium with MIC = 0.78 µg mL-1 (2.3 µM) and a selectivity index related to HepG2 cells of SI > 20. Structure-activity relationships within the series are discussed. Based on its structural similarity to known inhibitors and the results of a molecular docking study, we suggest mycobacterial beta-ketoacyl-(acyl-carrier-protein) synthase III (FabH) as a potential target.

Correction to: Interaction of soy isoflavones and their main metabolites with hOATP2B1 transporter.

The published online version contains mistake in the caption of Figures 3, 4 and 5 for in front of the figure legends designations "a-g", "a-e", and "a-b" have been provided. Such data should be deleted.

Interaction of soy isoflavones and their main metabolites with hOATP2B1 transporter.

Membrane organic anion-transporting polypeptides (OATPs) are responsible for the drug transmembrane transport within the human body. The function of OATP2B1 transporter can be inhibited by various natural compounds. Despite increased research interest in soya as a part of human diet, the effect of its active components to interact with hOATP2B1 has not been elucidated in a complex extent. This in vitro study examined the inhibitory effect of main soy isoflavones (daidzin, daidzein, genistin, genistein, glycitin, glycitein, biochanin A, formononetin) and their metabolites formed in vivo (S-equol, O-desmethylangolensin) towards human OATP2B1 transporter. MDCKII cells overexpressing hOATP2B1 were employed to determine quantitative inhibitory parameters of the tested compounds and to analyze mechanism/s of the inhibitory interaction. The study showed that aglycones of soy isoflavones and the main biologically active metabolite S-equol were able to significantly inhibit hOATP2B1-mediated transport. The Ki values for most of aglycones range from 1 to 20 µM. In contrast, glucosides did not exhibit significant inhibitory effect. The kinetic analysis did not indicate a uniform type of inhibition towards the hOATP2B1 although predominant mechanism of inhibition seemed to be competitive. These findings may suggest that tested soy isoflavones and their metabolites might affect transport of xenobiotics including drugs across tissue barriers via hOATP2B1.

Honey flavonoids inhibit hOATP2B1 and hOATP1A2 transporters and hOATP-mediated rosuvastatin cell uptake in vitro.

1. Some flavonoids contained in the common diet have been shown to interact with important membrane uptake transporters, including organic anion transporting polypeptides (OATPs). OATP2B1 and OATP1A2 expressed in the apical membrane of human enterocytes may significantly contribute to the intestinal absorption of drugs, e.g. statins. This study is aimed at an evaluation of the inhibitory potency of selected food honey flavonoids (namely galangin, myricetin, pinocembrin, pinobanksin, chrysin and fisetin) toward hOATP2B1 and hOATP1A2 as well as at examining their effect on the cellular uptake of the known OATP substrate rosuvastatin. 2. Cell lines overexpressing the hOATP2B1 or hOATP1A2 transporter were employed as in vitro model to determine the inhibitory potency of the flavonoids toward the OATPs. 3. Chrysin, galangin and pinocembrin were found to inhibit both hOATP2B1 and hOATP1A2 in lower or comparable concentrations as the known flavonoid OATP inhibitor quercetin. Galangin, chrysin and pinocembrin effectively inhibited rosuvastatin uptake by hOATP2B1 with IC50 ∼1-10 µM. The inhibition of the hOATP1A2-mediated transport of rosuvastatin by these flavonoids was weaker. 4. The found data indicate that several of the tested natural compounds could potentially affect drug cellular uptake by hOATP2B1 and/or hOATP1A2 at relative low concentrations, a finding which suggests their potential for food-drug interactions.

Amphiphilic derivatives of (3ß,17ß)-3-hydroxyandrost-5-ene-17-carboxylic acid.

A series of amphiphilic derivatives of (3ß,17ß)-3-hydroxyandrost-5-ene-17-carboxylic acid (1) with the polyamine spermine and three other diamines, 1,2-diaminoethane, piperazine and cadaverine, were synthesized and their antimicrobial activity and cytotoxicity were investigated. Among the target compounds, several ones showed antimicrobial activity on Gram positive and Gram negative microorganisms. The most active compounds were 20 (Streptococcus mutans CCM 7409, 3.125 µM), 16 (Streptococcus mutans CCM 7409, 12.5 µM) and 10d (Escherichia coli CCM 3954, 12.5 µM). In addition, compounds 5d, 10d, 13 and 20 displayed cytotoxicity on CEM (12.1 ±â€¯2.1 µM, 7.6 ±â€¯1.0 µM, 19.0 ±â€¯0.4 µM and 5.9 ±â€¯0.7 µM, respectively). Two additional compounds displayed medium cytotoxicity on CEM, 5a (34.6 ±â€¯5.2 µM) and 5c (37.7 ±â€¯5.9 µM). The compound 13 and 20 displayed high toxicity also on normal fibroblasts.

Design, Synthesis, Antimycobacterial Evaluation, and In Silico Studies of 3-(Phenylcarbamoyl)-pyrazine-2-carboxylic Acids.

Pyrazinamide, the first-line antitubercular drug, has been regarded the basic component of tuberculosis treatment for over sixty years. Researchers have investigated its effect on Mycobacterium tuberculosis for this long time, and as a result, new potential targets of pyrazinamide or its active form, pyrazinoic acid, have been found. We have designed and prepared 3-(phenyl-carbamoyl)pyrazine-2-carboxylic acids as more lipophilic derivatives of pyrazinoic acid. We also prepared methyl and propyl derivatives as prodrugs with further increased lipophilicity. Antimycobacterial, antibacterial and antifungal growth inhibiting activity was investigated in all prepared compounds. 3-[(4-Nitrophenyl)carbamoyl]pyrazine-2-carboxylic acid (16) exerted high antimycobacterial activity against Mycobacterium tuberculosis H37Rv with MIC = 1.56 µg·mL-1 (5 µM). Propyl 3-{[4-(trifluoromethyl)phenyl]carbamoyl}pyrazine-2-carboxylate (18a) showed also high antimycobacterial activity against Mycobacterium tuberculosis H37Rv with MIC = 3.13 µg·mL-1. In vitro cytotoxicity of the active compounds was investigated and no significant cytotoxic effect was observed. Based to structural similarity to known inhibitors of decaprenylphosphoryl-ß-d-ribose oxidase, DprE1, we performed molecular docking of the prepared acids to DprE1. These in silico experiments indicate that modification of the linker connecting aromatic parts of molecule does not have any negative influence on the binding.

Synthesis of readily available fluorophenylalanine derivatives and investigation of their biological activity.

A series of thirty novel N-acetylated fluorophenylalanine-based aromatic amides and esters was synthesized using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide or phosphorus trichloride in pyridine. They were characterized by spectral methods and screened against various microbes (Mycobacterium tuberculosis, non-tuberculous mycobacteria, other bacteria, fungi), for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and cytotoxicity. All amino acids derivatives revealed a moderate inhibition of both cholinesterases with IC50 values for AChE and BChE of 57.88-130.75µM and 8.25-289.0µM, respectively. Some derivatives were comparable or superior to rivastigmine, an established drug. Phenyl 2-acetamido-3-(4-fluorophenyl)propanoate was identified as the selective and most potent inhibitor of BChE. The esterification and amidation of parent acids led to an improved BChE inhibition. The esters are better inhibitors of BChE than the amides. The introduction of NO2 and CH3 groups into aniline ring and CF3 moiety in phenol is translated into lower IC50 values. Seven compounds showed selectivity index higher than 10 for at least one cholinesterase. Especially the esters exhibited a mild activity against Gram-positive bacteria, mycobacteria and several fungal strains with minimum inhibitory concentrations starting from 125µM. The highest susceptibility was recorded for Trichophyton mentagrophytes fungus.

3-Substituted N-Benzylpyrazine-2-carboxamide Derivatives: Synthesis, Antimycobacterial and Antibacterial Evaluation.

A series of substituted N-benzyl-3-chloropyrazine-2-carboxamides were prepared as positional isomers of 5-chloro and 6-chloro derivatives, prepared previously. During the aminolysis of the acyl chloride, the simultaneous substitution of chlorine with benzylamino moiety gave rise to N-benzyl-3-(benzylamino)pyrazine-2-carboxamides as side products, in some cases. Although not initially planned, the reaction conditions were modified to populate this double substituted series. The final compounds were tested against four mycobacterial strains. N-(2-methylbenzyl)-3-((2-methylbenzyl)amino)pyrazine-2-carboxamide (1a) and N-(3,4-dichlorobenzyl)-3-((3,4-dichlorobenzyl)amino)pyrazine-2-carboxamide (9a) proved to be the most effective against Mycobacterium tuberculosis H37Rv, with MIC = 12.5 µg·mL-1. Compounds were screened for antibacterial activity. The most active compound was 3-chloro-N-(2-chlorobenzyl)pyrazine-2-carboxamide (5) against Staphylococcus aureus with MIC = 7.81 µM, and Staphylococcus epidermidis with MIC = 15.62 µM. HepG2 in vitro cytotoxicity was evaluated for the most active compounds; however, no significant toxicity was detected. Compound 9a was docked to several conformations of the enoyl-ACP-reductase of Mycobacterium tuberculosis. In some cases, it was capable of H-bond interactions, typical for most of the known inhibitors.

Synthesis of Novel Pyrazinamide Derivatives Based on 3-Chloropyrazine-2-carboxamide and Their Antimicrobial Evaluation.

Aminodehalogenation of 3-chloropyrazine-2-carboxamide with variously substituted benzylamines yielded a series of fifteen 3-benzylaminopyrazine-2-carboxamides. Four compounds possessed in vitro whole cell activity against Mycobacterium tuberculosis H37Rv that was at least equivalent to that of the standard pyrazinamide. MIC values ranged from 6 to 42 µM. The best MIC (6 µM) was displayed by 3-[(4-methylbenzyl)amino]pyrazine-2-carboxamide (8) that also showed low cytotoxicity in the HepG2 cell line (IC50 ≥ 250 µM). Only moderate activity against Enterococcus faecalis and Staphylococcus aureus was observed. No activity was detected against any of tested fungal strains. Molecular docking with mycobacterial enoyl-ACP reductase (InhA) was performed to investigate the possible target of the prepared compounds. Active compounds shared common binding interactions of known InhAinhibitors. Antimycobacterial activity of the title compounds was compared to the previously published benzylamino-substituted pyrazines with differing substitution on the pyrazine core (carbonitrile moiety). The title series possessed comparable activity and lower cytotoxicity than molecules containing a carbonitrile group on the pyrazine ring.

Novel salicylanilides from 4,5-dihalogenated salicylic acids: Synthesis, antimicrobial activity and cytotoxicity.

Salicylanilides have proved their activity against tuberculosis (TB). One weak electron-withdrawing substituent is favored at the salicylic part, specially Cl or Br atoms at positions 4 or 5. On the other hand, the antimycobacterial activity of salicylanilides is negatively affected when a strong electron-withdrawing substituent (NO2) is present at the same positions. Herein we describe the synthesis and characterization of novel salicylanilides possessing two weak electron-withdrawing groups (halogen atoms) at their salicylic part and compare their antitubercular activity with their monohalogenated analogues. All dihalogenated derivatives proved to possess antitubercular activity at a very narrow micromolar range (MIC=1-4µM), similar with their most active monohalogenated analogues. More importantly, the most active final molecules were further screened against multidrug resistant strains and found to inhibit their growth at the range of 0.5-4µM.

NAS agar is more suitable than McKay agar for primary culture of Streptococcus milleri group (SMG) fastidious bacteria, S. intermedius in particular.

Streptococcus milleri group (SMG) is a group of three streptococcal species (S. anginosus, intermedius and constellatus) that act as opportunist pathogens, among others in cystic fibrosis. Due to their fastidious character, they are both difficult to cultivate and to differentiate from less pathogenic streptococcal species, therefore being most probably underdiagnosed. Semi-selective McKay agar and NAS agar were developed to facilitate SMG recovery from clinical samples; however, direct comparison of recovery rates has not been published yet. We tested the performance of both media on 123 patient samples and demonstrated general superiority of NAS agar for SMG recovery during primary cultivation convincingly. This observation was also confirmed by quantitative drop tests during subculture. Despite the undisputed overall superiority of NAS agar over McKay agar, a smaller fraction of strains grew better on McKay agar. Inter-strain differences were the most probable explanation. Therefore, when economic conditions are not limiting and maximum recovery rate is desirable, both plates are advised to be used in parallel for primary cultivation of clinical samples.

Alterations in Outer Membrane Permeability Favor Drug-Resistant Phenotype of Klebsiella pneumoniae.

The increasing number of infections caused by multidrug-resistant and pandrug-resistant bacteria represents a serious worlwide problem. Drug resistance limits available antimicrobials and can lead to suboptimal treatment of bacterial infections. It can be predicted that resistance to more antimicrobial drugs will be acquired by even more bacteria in the future. Among the distinct resistance strategies, preventing drug entrance to intracellular compartment through modification of membrane permeability (bacterial influx) and active export of compounds to the external environment (bacterial efflux) are of particular importance as they limit the interaction of the drug with its intracellular targets and, consequently, its deleterious effects on the cell. Several current studies have extended our understanding of drug resistance mechanisms associated with altered membrane permeability in gram-negative bacteria. In this study, we propose a summary of resistance mechanisms associated with transport of drugs across bacterial cell envelope exploited by Klebsiella pneumoniae, one of the most common nosocomial infection-causing pathogens. The better understanding of molecular bases of drug transport in/out of the single cell may have consequence for success in antimicrobial therapy of infection caused by drug-resistant Klebsiella.

p53 Specifically Binds Triplex DNA In Vitro and in Cells.

Triplex DNA is implicated in a wide range of biological activities, including regulation of gene expression and genomic instability leading to cancer. The tumor suppressor p53 is a central regulator of cell fate in response to different type of insults. Sequence and structure specific modes of DNA recognition are core attributes of the p53 protein. The focus of this work is the structure-specific binding of p53 to DNA containing triplex-forming sequences in vitro and in cells and the effect on p53-driven transcription. This is the first DNA binding study of full-length p53 and its deletion variants to both intermolecular and intramolecular T.A.T triplexes. We demonstrate that the interaction of p53 with intermolecular T.A.T triplex is comparable to the recognition of CTG-hairpin non-B DNA structure. Using deletion mutants we determined the C-terminal DNA binding domain of p53 to be crucial for triplex recognition. Furthermore, strong p53 recognition of intramolecular T.A.T triplexes (H-DNA), stabilized by negative superhelicity in plasmid DNA, was detected by competition and immunoprecipitation experiments, and visualized by AFM. Moreover, chromatin immunoprecipitation revealed p53 binding T.A.T forming sequence in vivo. Enhanced reporter transactivation by p53 on insertion of triplex forming sequence into plasmid with p53 consensus sequence was observed by luciferase reporter assays. In-silico scan of human regulatory regions for the simultaneous presence of both consensus sequence and T.A.T motifs identified a set of candidate p53 target genes and p53-dependent activation of several of them (ABCG5, ENOX1, INSR, MCC, NFAT5) was confirmed by RT-qPCR. Our results show that T.A.T triplex comprises a new class of p53 binding sites targeted by p53 in a DNA structure-dependent mode in vitro and in cells. The contribution of p53 DNA structure-dependent binding to the regulation of transcription is discussed.

McRAPD unlike MALDI-TOF MS is a suitable candidate for routine discrimination of new Haemophilus influenzae strain acquisition in chronic obstructive pulmonary disease (COPD) and cystic fibrosis.

BACKGROUND AND AIMS: Haemophilus influenzae new strain acquisition has been demonstrated to increase the relative risk of acute exacerbation fourfold in contrast to colonisation or chronic infection by the same strain in chronic obstructive pulmonary disease (COPD). Unfortunately, molecular typing techniques are not suitable for routine use due to cost, labour-intensity and need for special expertise. We tested two techniques potentially useful for routine typing, namely the newly available MALDI-TOF MS and the modified McRAPD compared to MLST as the gold standard. METHODS: In 10 patients (10.8%) suffering from COPD or cystic fibrosis, H. influenzae isolates were recovered repeatedly at different timepoints from the same patient during the study period. This allowed for thirteen pairwise comparisons of typing results in isolates recovered consecutively from the same patient to test the ability of the techniques to uncover new strain acquisition. RESULTS: MLST detected 9 cases of new strain acquisition among the 13 pairwise comparisons. However, MALDI-TOF MS reported all 13 pairs as different and thus new. In contrast, McRAPD was able to differentiate all the new strain acquisitions from pre-existing ones, both by visual inspection of melting profiles and by Relative Significant Difference values. CONCLUSIONS: Unlike MALDI-TOF MS, McRAPD appears to be a suitable candidate for routine discrimination of new strain acquisitions because of its accuracy and, rapid, easy and economic performance.

Wild-type p53 binds to MYC promoter G-quadruplex.

G-quadruplexes are four-stranded nucleic acid structures that are implicated in the regulation of transcription, translation and replication. Genome regions enriched in putative G-quadruplex motifs include telomeres and gene promoters. Tumour suppressor p53 plays a critical role in regulatory pathways leading to cell cycle arrest, DNA repair and apoptosis. In addition to transcriptional regulation mediated via sequence-specific DNA binding, p53 can selectively bind various non-B DNA structures. In the present study, wild-type p53 (wtp53) binding to G-quadruplex formed by MYC promoter nuclease hypersensitive element (NHE) III1 region was investigated. Wtp53 binding to MYC G-quadruplex is comparable to interaction with specific p53 consensus sequence (p53CON). Apart from the full-length wtp53, its isolated C-terminal region (aa 320-393) as well, is capable of high-affinity MYC G-quadruplex binding, suggesting its critical role in this type of interaction. Moreover, wtp53 binds to MYC promoter region containing putative G-quadruplex motif in two wtp53-expressing cell lines. The results suggest that wtp53 binding to G-quadruplexes can take part in transcriptional regulation of its target genes.

[Prolonged culture in a humid chamber increases the yields of pathogenic bacteria from the respiratory tract samples of patients suffering from cystic fibrosis].

Current standards of care for cystic fibrosis (CF) patients lack unequivocal recommendations concerning the duration of primary culture of bacteriological samples. With the exception of Burkholderia cepacia (5 days), the minimum recommended duration of primary culture varies between 48 and 72 hours. Our aim was to evaluate the effect of an extended 10-day period of primary culture in a humid chamber in samples acquired from the respiratory tract of patients suffering from CF. Compared to standard culture, prolonged culture in a humid chamber yielded 1.85 times more isolates of pathogenic species in pharyngeal swabs (76 versus 41 isolates) and 1.4 times more isolates in sputum samples (116 versus 82), but only 1.14 times more isolates in nasal swabs (25 versus 22). Prolonged culture was most beneficial for Achromobacter spp. (6 versus 0), Stenotrophomonas maltophilia (16 versus 5) and Pseudomonas aeruginosa (69 versus 49), whereas there was little or no benefit at all for Staphylococcus aureus (87 versus 73) and Moraxella catarrhalis (10 versus 10). Therefore, prolonged culture in a humid chamber may definitely be recommended for pharyngeal swabs and sputum samples obtained from patients suffering from CF to achieve the maximum recovery rate of pathogenic bacteria, in particular non-fermenting Gram-negative rods.