Functional groups matter: metabolomics analysis of Escherichia coli exposed to trans-cinnamic acid and its derivatives unveils common and unique targets.

Phenolic acids are derivatives of benzoic and cinnamic acids, which possess important biological activities at certain concentrations. Trans-cinnamic acid (t-CA) and its derivatives, such as p-coumaric acid (p-CA) and ferulic acid (FA) have been shown to have antibacterial activity against various Gram-positive and -negative bacteria. However, there is limited information available concerning the antibacterial mode of action of these phenolic acids. In this study, we aimed to ascertain metabolic alterations associated with exposure to t-CA, p-CA, and FA in Escherichia coli BW25113 using a nuclear magnetic resonance (NMR)-based metabolomics approach. The results showed that t-CA, p-CA, and FA treatments led to significant changes (p < 0.05) in the concentration of 42, 55, and 74% of the identified metabolites in E. coli, respectively. Partial least-squares discriminant analysis (PLS-DA) revealed a clear separation between control and phenolic acid groups with regard to metabolic response. Moreover, it was found that FA and p-CA treatment groups were clustered closely together but separated from the t-CA treatment group. Arginine, putrescine, cadaverine, galactose, and sucrose had the greatest impact on group differentiation. Quantitative pathway analysis demonstrated that arginine and proline, pyrimidine, glutathione, and galactose metabolisms, as well as aminoacyl-tRNA and arginine biosyntheses, were markedly affected by all phenolic acids. Finally, the H2O2 content of E. coli cells was significantly increased in response to t-CA and p-CA whereas all phenolic acids caused a dramatic increase in the number of apurinic/apyrimidinic sites. Overall, this study suggests that the metabolic response of E. coli cells to t-CA is relatively different from that to p-CA and FA. However, all phenolic acids had a certain impact on oxidative/antioxidant status, genomic stability, arginine-related pathways, and nucleic acid metabolism.

NMR metabolomics analysis of Escherichia coli cells treated with Turkish propolis water extract reveals nucleic acid metabolism as the major target.

AIMS: Propolis is a resinous bee product containing several hundred biologically active compounds. Although the antibacterial activity of propolis has been demonstrated in many in vitro studies, less is known about its mode of action. In this study, we aimed to shed some light on the antibacterial mechanism of action of propolis against Escherichia coli BW25113 using a nuclear magnetic resonance (NMR) based metabolomics approach. METHODS: E. coli BW25113 cells were subjected to different sub-lethal concentrations (0, 2, 4, and 6 mg/mL) of Turkish propolis water extract (PWE). The 500-MHz 1H NMR spectroscopy was then employed to ascertain the metabolic profiles of E. coli extracts. RESULTS: A total of 52 metabolites were identified from the NMR spectra, belonging to 17 main classes, such as amino acids and peptides, purines, and fatty acids. Twelve out of these 52 metabolites displayed remarkable changes at all tested PWE concentrations when compared to control conditions (P < .05). Levels of 28 more metabolites were significantly altered in at least one of the three PWE treatments. The results of partial least squares discriminant analysis showed that there was a clear separation between control and propolis-treated cells and that putrescine, adenine, adenosine, guanosine, glucose, N6-acetyllysine, and acetamide had the highest effect on group differentiation. Finally, quantitative pathway analysis revealed that purine metabolism was significantly affected by PWE treatments. CONCLUSIONS: Our results suggest that PWE inhibits the growth of E. coli BW25113 by affecting nucleic acid metabolism to a great extent. To the best of our knowledge, this is the first study to evaluate the global metabolic response of a bacterium to propolis.

Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells.

Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.

Conformal quantum dot-SnO2 layers as electron transporters for efficient perovskite solar cells.

Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous-titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid-stabilized tin(IV) oxide quantum dots (paa-QD-SnO2) on the compact-titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL-perovskite interface. The use of paa-QD-SnO2 as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively.

Development of an Autoinducible Plasmid for Recombinant Protein Production.

BACKGROUND: The production of recombinant proteins in E. coli involves such factors as host strains, expression vectors, culture media, and induction methods. The typical procedure to produce heterologous proteins consists of the following: (1) insertion of the target gene into a suitable vector to construct an overexpression plasmid, (2) transformation of a strain specialized for protein production with the constructed plasmid DNA, (3) growth of the host in a suitable medium and induction of the protein production at a right moment, and (4) further growth to get the maximum yield. There are hurdles involved in each of these steps, and researchers have developed many materials or methods, which often require special recipes or procedures. OBJECTIVE: To eliminate the special requirements for recombinant protein production by using readily available materials. Also to save time and effort in the routine protein production work. METHODS: We started with a vector capable of producing a target protein fused to the C-terminus of the maltose-binding protein (MBP). The mCherry (red fluorescent protein) gene was fused to MBP. It acted as a reporter in the initial screening procedure. The original lethal gene (barnase) was replaced with sacB. We chose 3 stationary phase promoters and made hybrids of them by mixing halves from each one. The T5 promoter was replaced with these stationary phase promoters or their hybrids. The best plasmid was selected by the color intensity of the cell pellet. MBP and GST genes were inserted in the place of sacB, and their production yields were compared with the original plasmid in the conventional way of expression. RESULTS: We constructed an expression plasmid with an autoinducible promoter working in a host that was not specially designed for protein production and in a TB medium that did not contain any secret ingredient, nor was it difficult to prepare unlike Studier's defined medium. This plasmid also contains a color indicator that turns red when protein production is successful. We tested our system with the maltose-binding protein (MBP) and the glutathione S-transferase (GST), and showed that both proteins were produced to a level comparable to what the commercial medium and/or the specialized strain yielded. CONCLUSION: We developed a plasmid equipped with an autoinducible promoter, a hybrid of the two promoters which were activated at the stationary phase. This plasmid does not need a special E. coli strain nor a sophisticated nor an expensive medium. It produces an intense red (or pink) color, which can be used as an indicator of a successful production of the target protein and as a predictive measure of the amount of the produced target protein. We speculate that this plasmid will have its greatest advantage when growing cells at low temperatures, which would inevitably take a long time.

A simple and sensitive detection of the binding ligands by using the receptor aggregation and NMR spectroscopy: a test case of the maltose binding protein.

Protein-ligand interaction is one of the highlights of molecular recognition. The most popular application of this type of interaction is drug development which requires a high throughput screening of a ligand that binds to the target protein. Our goal was to find a binding ligand with a simple detection, and once this type of ligand was found, other methods could then be used to measure the detailed kinetic or thermodynamic parameters. We started with the idea that the ligand NMR signal would disappear if it was bound to the non-tumbling mass. In order to create the non-tumbling mass, we tried the aggregates of a target protein, which was fused to the elastin-like polypeptide. We chose the maltose binding proteinas a test case, and we tried it with several sugars, which included maltose, glucose, sucrose, lactose, galactose, maltotriose, and ß-cyclodextrin. The maltose signal in the H-1 NMR spectrum disappeared completely as hoped around the protein to ligand ratio of 1:3 at 298 K where the proteins aggregated. The protein signals also disappeared upon aggregation except for the fast-moving part, which resulted in a cleaner background than the monomeric form. Since we only needed to look for a disappearing signal amongst those from the mixture, it should be useful in high throughput screening. Other types of sugars except for the maltotriose and ß-cyclodextrin, which are siblings of the maltose, did not seem to bind at all. We believe that our system would be especially more effective when dealing with a smaller target protein, so both the protein and the bound ligand would lose their signals only when the aggregates formed. We hope that our proposed method would contribute to accelerating the development of the potent drug candidates by simultaneously identifying several binders directly from a mixture.

Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells.

Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT: PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT: PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells.

An organic surface modifier to produce a high work function transparent electrode for high performance polymer solar cells.

Modification of an ITO electrode with small-molecule organic surface modifier, 4-chloro-benzoic acid (CBA), via a simple spin-coating method produces a high-work-function electrode with high transparency and a hydrophobic surface. As an alternative to PEDOT:PSS, CBA modification achieves efficiency enhancement up to 8.5%, which is attributed to enhanced light absorption within the active layer and smooth hole transport from the active layer to the anode.

Boosting the power conversion efficiency of perovskite solar cells using self-organized polymeric hole extraction layers with high work function.

A self-organized hole extraction layer (SOHEL) with high work function (WF) is designed for energy level alignment with the ionization potential level of CH3 NH3 PbI3 . The SOHEL increases the built-in potential, photocurrent, and power conversion efficiency (PCE) of CH3 NH3 PbI3 perovskite solar cells. Thus, interface engineering of the positive electrode of solution-processed planar heterojunction solar cells using a high-WF SOHEL is a very effective way to achieve high device efficiency (PCE = 11.7% on glass).

Mixed solvents for the optimization of morphology in solution-processed, inverted-type perovskite/fullerene hybrid solar cells.

We investigate mixed solvents of N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) to produce the smooth surface of a perovskite film and uniform crystal domains. This ideal morphology from mixed solvents enhances the power conversion efficiency to over 6% by improving the exciton dissociation efficiency and reducing the recombination loss at both interfaces of PEDOT:PSS/perovskite and perovskite/PCBM.

Vapor coating method using small-molecule organic surface modifiers to replace N-type metal oxide layers in inverted polymer solar cells.

We investigate a simple fabrication method for vapor coating small-molecule organic interlayers as replacements for metal oxide films. The interfacial layers, which serve both as both surface modifiers to reduce the substrate work function and electron selective layers, maximize light absorption within the active layer while improving electron transport and compatibility between the active layer and cathode, leading to a ∼22% enhancement in power conversion efficiency and similar air stability compared to devices using a ZnO layer.

Inverted colloidal quantum dot solar cells.

An inverted architecture of quantum dot solar cells is demonstrated by introducing a novel ZnO method on top of the PbS CQD film. Improvements in device characteristics stem from constructive optical interference from the ZnO layer that enhances absorption in the PbS CQD layer. Outstanding diode characteristics arising from a superior PbS/ZnO junction provide a further electronic advantage.

Effects of ionic liquid molecules in hybrid PbS quantum dot-organic solar cells.

We investigated the effect of ionic liquid molecules (ILMs) in hybrid quantum dot-organic solar cells (HyQD-OSCs). The insertion of an ILM layer between PbS and phenyl-C61-butyric acid methyl ester (PCBM) can shift the band edge of PCBM closer to the vacuum level of PbS due to spontaneous dipole polarization. Because of this new architecture, improvements in device performance were achieved, including increases in open-circuit voltage (VOC, from 0.41 V to 0.49 V), fill factor (FF, from 0.48 to 0.59), and power conversion efficiency (PCE, from 1.62% to 2.21%), compared to reference devices under AM 1.5G illumination at 100 mW cm(-2). We observed that treatment of the PbS layer with ILMs causes a significant increase in work function from 3.58 eV to 3.93 eV. Furthermore, the ILMs layer minimizes the contact resistance between PbS and PCBM due to the improved compatibility between the two layers, confirmed as a decrease in charge transfer resistance, as measured by electrical impedance spectroscopy.

Gold(I)-catalyzed intramolecular hydroamination of alkyne with trichloroacetimidates.

[reaction: see text] A study on the gold (I)-catalyzed intramolecular hydroamination of trichloroacetimidates derived from propargyl and homopropargyl alcohols is described. In the presence of 2-5 mol % of cationic Au(I) complex, a variety of trichloroacetimidates undergo efficient hydroamination under an exceptionally mild condition. An orthogonality of the current catalytic protocol with those using a stoichiometric electrophile as well as a preliminary synthetic application as a stable precursor of 2-acylamino-1,3-diene has been demonstrated.