Copper complexes of pyridine derivatives with superoxide scavenging and antimicrobial activities. Eur J Med Chem. 2009;44:3259-3265. [PMID: 19375194 DOI: 10.1016/j.ejmech.2009.03.033]

Antioxidant and Antibacterial Screening and Hg(II) Sensing, Activities of Cu(II)pyridine-2,6-dicarboxylate Complexes

In this study five different complexes of Cu(II) were synthesized for the purpose of environmentally notorious mercury sensing and preliminary biological screening. Pyridine-2,6-dicarboxylic acid (also known as dipicolinic acid, and abbreviated as H2DPA), 3-phenyl pyrazole (3-ppz), 4-iodo-1H-pyrazole (4-ipz), 4-nitropyrazole (4-npz), 4-bromopyrazole (4-bpz), and 4-chloropyrazole (4-cpz) were chosen as potential ligands. The synthesized complexes labelled as 1-5, namely [Cu(DPA)(3-ppz)], [Cu(DPA)(4-ipz)], [Cu(DPA)(4-npz)], [Cu(DPA)(4-bpz)], [Cu(DPA)(4-cpz)], were proposed based on spectroscopic data (FTIR, TGA, and UV-visible spectroscopy). These complexes feature C=O functionalities that are not involved in coordination and may be used for further applications. The isolated complexes were utilized for detecting Hg(II) ions in water samples. Various concentrations of Hg(II) ions were prepared for detection purposes, and changes in absorption concerning complexes 1-5 were determined using UV-Visible spectroscopy. It was found that complexes 3 and 4 exhibit efficient sensing abilities towards Hg(II) ions. The antibacterial activities of complexes 1-5 were assessed against S. typhi and E. coli. The complexes 1 and 3 displayed good antibacterial activities against S. typhi (13.67, and 13.56 mm, respectively) while complexes 1, 2 and 4 were found to be efficient against E. coli (11.6, 12.66, 11.31 mm, respectively). The absorption maxima of 2,2-diphenyl-1-picryhydrazyl (DPPH) at 517 nm, considerably shifted upon addition of complexes 1-5. The results reveal that the complexes possess potential free radical scavenging abilities.

Influence of Cu L-Histidinate Schiff Base Derivatives on Structural Features of Irradiated Rat's DNA

A study of rats liver DNA damages under the influence of X-ray radiation at a dose of 6.5 Gy(LD60) was carried out. The radioprotective properties of newly synthesized Cu(II) L-Schiff Histidinate complexes were also studied. The survival of rats was determined over a 30-day period after exposure to X-rays without pretreatment and also after preadministration of Cu(II) L-Histidinate-Schiff base complexes. The structural defects of rat's liver DNA were detected at 3, 7, 14, and 30 days post-irradiation extracted. The results obtained revealed that irradiation with a 6.5Gy dose in the control group degraded the characteristics of rat liver DNA in comparison to healthy DNA. On all investigated experimental days, a decrease in the melting temperature (Tm), a widening of the melting interval (ΔT), and a decrease in hypochromicity (Δh) were observed in the DNA samples of irradiated animals compared to the norm. The rat's pretreatment by Cu(II) L-Histidinate complexes 1 or 24 hours prior to irradiation improved DNA characteristics. Electrophoretic studies of DNA were in good agreement with the melting data. Based on the study results, it can be concluded that Cu(II) L-Histidinate complexes exhibit radioprotective properties under the studied conditions and can protect DNA from damage.

Characterization of Copper(II) and Zinc(II) Complexes of Peptides Mimicking the CuZnSOD Enzyme

Antimicrobial peptides are short cationic peptides that are present on biological surfaces susceptible to infection, and they play an important role in innate immunity. These peptides, like other compounds with antimicrobial activity, often have significant superoxide dismutase (SOD) activity. One direction of our research is the characterization of peptides modeling the CuZnSOD enzyme and the determination of their biological activity, and these results may contribute to the development of novel antimicrobial peptides. In the framework of this research, we have synthesized 10, 15, and 16-membered model peptides containing the amino acid sequence corresponding to the Cu(II) and Zn(II) binding sites of the CuZnSOD enzyme, namely the Zn(II)-binding HVGD sequence (80-83. fragments), the Cu(II)-binding sequence HVH (fragments 46-48), and the histidine (His63), which links the two metal ions as an imidazolate bridge: Ac-FHVHEGPHFN-NH2 (L1(10)), Ac-FHVHAGPHFNGGHVG-NH2 (L2(15)), and Ac-FHVHEGPHFNGGHVGD-NH2 (L3(16)). pH-potentiometric, UV-Vis-, and CD-spectroscopy studies of the Cu(II), Zn(II), and Cu(II)-Zn(II) mixed complexes of these peptides were performed, and the SOD activity of the complexes was determined. The binding sites preferred by Cu(II) and Zn(II) were identified by means of CD-spectroscopy. From the results obtained for these systems, it can be concluded that in equimolar solution, the -(NGG)HVGD- sequence of the peptides is the preferred binding site for copper(II) ion. However, in the presence of both metal ions, according to the native enzyme, the -HVGD- sequence offers the main binding site for Zn(II), while the majority of Cu(II) binds to the -FHVH- sequence. Based on the SOD activity assays, complexes of the 15- and 16-membered peptide have a significant SOD activity. Although this activity is smaller than that of the native CuZnSOD enzyme, the complexes showed better performance in the degradation of superoxide anion than other SOD mimics. Thus, the incorporation of specific amino acid sequences mimicking the CuZnSOD enzyme increases the efficiency of model systems in the catalytic decomposition of superoxide anion.

Changes in the Microbiome of Sugarcane (Saccharum spp. Hybrids.) Rhizosphere in Response to Manganese Toxicity

Manganese toxicity has limited sugarcane (Saccharum spp. hybrid.) growth and production in acidic soils in south China. The rhizosphere plays an irreplaceable role in plant adaptation to soil abiotic stress, but the responses of the sugarcane rhizosphere to manganese toxicity are still unknown. We designed pot experiments in Mn-rich acidic soil, collected the sugarcane rhizosphere and bulk soil samples, and then investigated the changes in Mn-related soil parameters and microbiome. The results indicated that the water-soluble and exchangeable manganese concentrations in the sugarcane rhizosphere were significantly lower than that in the bulk soil, which was not associated with soil pH changes. In contrast, the number of bacteria and the activity of peroxidase, sucrase, urease, and laccase in the rhizosphere were significantly higher. The 16S rDNA sequencing results showed that the bacterial diversity and quantity along with the abundance of Proteobacteria in the rhizosphere were significantly higher than in the bulk soil, while the abundance of Acidobacteria was lower than in the bulk soil. The soil laccase activity and the number of bacteria decreased significantly with the increase in the manganese toxicity stress. Finally, the relative abundance of proteins associated with manganese transportation and oxidation was significantly higher in the rhizosphere soil. In summary, the Mn-induced response of the rhizosphere is an important mechanism in sugarcane adaptation to manganese toxicity in acidic soil.

Effects of dandelion (Taraxacum sp.,) supplements on lactation performance, antioxidative activity, and plasma metabolome in primiparous dairy cows

OBJECTIVE

This study evaluated the effects of dandelion supplements on lactation performance, circulating antioxidative activity and plasma metabolomics in primiparous dairy cows.

METHODS

A total of 60 mid-lactation dairy cows (milk yield = 34.29±0.34 kg/d; days in milk = 151.72±2.36 days) were divided into 4 treatment groups randomly, comprising the addition of dandelion at 0, 100, 200, 400 g/d per head. The experiment lasted for 8 weeks with an extra 10 days' pre-feeding period. Milk and blood samples were collected, and plasma samples were selected to perform metabolomics analysis.

RESULTS

Supplementing 200 g/d of dandelion increased the yield of milk and lactose (p≤ 0.05). The milk somatic cell counts (p≤0.05) were lower in all dandelion groups than those in the control group. The activity of glutathione peroxidase (p≤0.05) and superoxide dismutase (p≤0.05) were increased and plasma malondialdehyde (p = 0.01) was decreased when cows were fed 200 g/d dandelion. Plasma metabolomics analysis showed that 23 hub differential metabolites were identified in the 200 g/d dandelion group. These metabolites such as ribose, glutamic acid, valine, and phenylalanine were enriched in D-glutamine and D-glutamate metabolism (p = 0.06, impact value = 1), phenylalanine, tyrosine, and tryptophan biosynthesis (p = 0.05, impact value = 0.5), and starch and sucrose metabolism (p = 0.21, impact value = 0.13). Moreover, correlation analysis showed that circulating ribose, mannose, and glutamic acid were positively related to milk yield.

CONCLUSION

Dandelion supplementation could improve lactation performance and elevate the plasma carbohydrate and amino acids metabolism and antioxidative activity. Supplementation of 200 g/d dandelion is recommended for lactating dairy cows.

Copper(ii) and silver(i) complexes with dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz): the influence of the metal ion on the antimicrobial potential of the complex

Dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz) was used as a ligand for the synthesis of new copper(ii) and silver(i) complexes, [CuCl2(py-2pz)]2 (1), [Cu(CF3SO3)(H2O)(py-2pz)2]CF3SO3·2H2O (2), [Ag(py-2pz)2]PF6 (3) and {[Ag(NO3)(py-2pz)]·0.5H2O} n (4). The complexes were characterized by spectroscopic and electrochemical methods, while their structures were determined by single crystal X-ray diffraction analysis. The X-ray analysis revealed the bidentate coordination mode of py-2pz to the corresponding metal ion via its pyridine and pyrazine nitrogen atoms in all complexes, while in polynuclear complex 4, the heterocyclic pyrazine ring of one py-2pz additionally behaves as a bridging ligand between two Ag(i) ions. DFT calculations were performed to elucidate the structures of the investigated complexes in solution. The antimicrobial potential of the complexes 1-4 was evaluated against two bacterial (Pseudomonas aeruginosa and Staphylococcus aureus) and two Candida (C. albicans and C. parapsilosis) species. Silver(i) complexes 3 and 4 have shown good antibacterial and antifungal properties with minimal inhibitory concentration (MIC) values ranging from 4.9 to 39.0 μM (3.9-31.2 μg mL-1). All complexes inhibited the filamentation of C. albicans and hyphae formation, while silver(i) complexes 3 and 4 had also the ability to inhibit the biofilm formation process of this fungus. The binding affinity of the complexes 1-4 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy to clarify the mode of their antimicrobial activity. Catechol oxidase biomimetic catalytic activity of copper(ii) complexes 1 and 2 was additionally investigated by using 3,5-di-tert-butylcatechol (3,5-DTBC) and o-aminophenol (OAP) as substrates.

PicR as a MarR Family Transcriptional Repressor Multiply Controls the Transcription of Picolinic Acid Degradation Gene Cluster pic in Alcaligenes faecalis JQ135

Picolinic acid (PA) is a natural toxic pyridine derivative as well as an important intermediate used in the chemical industry. In a previous study, we identified a gene cluster, pic, that responsible for the catabolism of PA in Alcaligenes faecalis JQ135. However, the transcriptional regulation of the pic cluster remains known. This study showed that the entire pic cluster was composed of 17 genes and transcribed as four operons: picR, picCDEF, picB4B3B2B1, and picT1A1A2A3T2T3MN. Deletion of picR, encoding a putative MarR-type regulator, greatly shortened the lag phase of PA degradation. An electrophoretic mobility shift assay and DNase I footprinting showed that PicR has one binding site in the picR-picC intergenic region and two binding sites in the picB-picT1 intergenic region. The DNA sequences of the three binding sites have the palindromic characteristics of TCAG-N4-CTNN: the space consists of four nonspecific bases, and the four palindromic bases on the left and the first two palindromic bases on the right are strictly conserved, while the last two bases on the right vary among the three binding sites. An in vivo β-galactosidase activity reporter assay indicated that 6-hydroxypicolinic acid but not PA acted as a ligand of PicR, preventing PicR from binding to promoter regions and thus derepressing the transcription of the pic cluster. This study revealed the negative transcriptional regulation mechanism of PA degradation by PicR in A. faecalis JQ135 and provides new insights into the structure and function of the MarR-type regulator. IMPORTANCE The pic gene cluster was found to be responsible for PA degradation and widely distributed in Alpha-, Beta-, and Gammaproteobacteria. Thus, it is very necessary to understand the regulation mechanism of the pic cluster in these strains. This study revealed that PicR binds to three sites of the promoter regions of the pic cluster to multiply regulate the transcription of the pic cluster, which enables A. faecalis JQ135 to efficiently utilize PA. Furthermore, the study also found a unique palindrome sequence for binding of the MarR-type regulator. This study enhanced our understanding of microbial catabolism of environmental toxic pyridine derivatives.

Pyridine: the scaffolds with significant clinical diversity

The nitrogen-bearing heterocycle pyridine in its several analogous forms occupies an important position as a precious source of clinically useful agents in the field of medicinal chemistry research. This privileged scaffold has been consistently incorporated in a diverse range of drug candidates approved by the FDA (Food and Drug Administration). This moiety has attracted increasing attention from several disease states owing to its ease of parallelization and testing potential pertaining to the chemical space. In the next few years, a larger share of novel pyridine-based drug candidates is expected. This review unifies the current advances in novel pyridine-based molecular frameworks and their unique clinical relevance as reported over the last two decades. It highlights an inclination to the use of pyridine-based molecules in drug crafting and the subsequent emergence of several potent and eligible candidates against a range of diversified diseases.

The nitrogen-bearing heterocycle pyridine in its several analogous forms occupies an important position as a precious source of clinically useful agents in the field of medicinal chemistry research.

Promising Antifungal and Antibacterial Agents Based on 5-Aryl-2,2'-bipyridines and Their Heteroligand Salicylate Metal Complexes: Synthesis, Bioevaluation, Molecular Docking

A series of new 5-aryl-2,2'-bipyridines and their (polyfluoro)salicylate complexes of Cu(II), Co(II) and Mn(II) were synthesized. Their antimicrobial activity was evaluated in vitro against six strains of Trichophytons, E. floccosum, M. canis, C. ablicans and Gram-negative bacteria N. gonorrhoeae. Among azo-ligands, Ph-bipy and Tol-bipy showed promising antifungal activity (minimum inhibitory concentration (MIC)<0.8-27 μM). Their antifungal action was found can be realized via binding Fe(III) ions. Tol-bipy suppressed growth of Gram-positive bacteria S. aureus, S. aureus MRSA and their monospecies biofilms (MIC 6-16 μM). Using molecular docking, the anti-staphylococcal action mechanism based on the inhibition of S. aureus DNA gyrase GyrB was proposed for the lead compounds. Among metal complexes, Cu(II) and Mn(II) complexes based on tetrafluorosalicylic acid and Tol-bipy or Ph-bipy had the high antifungal activity (MIC<0.24-32 μM). Mn(SalF₄ -2H)₂ (Tol-bipy)₂ ] suppressed the growth of seven Candida strains at MIC 12-24 μM. [Cu(Sal-2H)(Ph-bipy)] and [Cu(SalF₃ -2H)(Ph-bipy)₂ ] showed the promising anti-gonorrhoeae activity (MIC 4.2-5.2 μM). (Cu(SalF_n -2H)(Tol-bipy)₂ ], [Cu(SalF₄ -2H)(Ph-bipy)₂ ] and [Cu(SalF₃ -2H)(Ph-bipy)₂ ]) were found active against the bacteria of S. aureus, S. aureus MRSA and their biofilms (MIC 2.4-41.4 μM). The most active compounds were tested for toxicity in vitro against human embryonic kidney (HEK-293) cells and in vivo experiments with CD-1 mice.

Metabolomics combined with physiology and transcriptomics reveals how Citrus grandis leaves cope with copper-toxicity

Limited data are available on metabolic responses of plants to copper (Cu)-toxicity. Firstly, we investigated Cu-toxic effects on metabolomics, the levels of free amino acids, NH₄⁺-N, NO₃^--N, total nitrogen, total soluble proteins, total phenolics, lignin, reduced glutathione (GSH) and malondialdehyde, and the activities of nitrogen-assimilatory enzymes in 'Shatian' pummelo (Citrus grandis) leaves. Then, a conjoint analysis of metabolomics, physiology and transcriptomics was performed. Herein, 59 upregulated [30 primary metabolites (PMs) and 29 secondary metabolites (SMs)] and 52 downregulated (31 PMs and 21 SMs) metabolites were identified in Cu-toxic leaves. The toxicity of Cu to leaves was related to the Cu-induced accumulation of NH₄⁺ and decrease of nitrogen assimilation. Metabolomics combined with physiology and transcriptomics revealed some adaptive responses of C. grandis leaves to Cu-toxicity, including (a) enhancing tryptophan metabolism and the levels of some amino acids and derivatives (tryptophan, phenylalanine, 5-hydroxy-l-tryptophan, 5-oxoproline and GSH); (b) increasing the accumulation of carbohydrates and alcohols and upregulating tricarboxylic acid cycle and the levels of some organic acids and derivatives (chlorogenic acid, quinic acid, d-tartaric acid and gallic acid o-hexoside); (c) reducing phospholipid (lysophosphatidylcholine and lysophosphatidylethanolamine) levels, increasing non-phosphate containing lipid [monoacylglycerol ester (acyl 18:2) isomer 1] levels, and inducing low-phosphate-responsive gene expression; and (d) triggering the biosynthesis of some chelators (total phenolics, lignin, l-trytamine, indole, eriodictyol C-hexoside, quercetin 5-O-malonylhexosyl-hexoside, N-caffeoyl agmatine, N'-p-coumaroyl agmatine, hydroxy-methoxycinnamate and protocatechuic acid o-glucoside) and vitamins and derivatives (nicotinic acid-hexoside, B₁ and methyl nicotinate). Cu-induced upregulation of many antioxidants could not protect Cu-toxic leaves from oxidative damage. To conclude, our findings corroborated the hypothesis that extensive reprogramming of metabolites was carried out in Cu-toxic C. grandis leaves in order to cope with Cu-toxicity.

Synthesis, molecular docking, DFT study, and in vitro antimicrobial activity of some 4-(biphenyl-4-yl)-1,4-dihydropyridine and 4-(biphenyl-4-yl)pyridine derivatives

The evolution of microbial resistance necessitates the development of new antimicrobial drugs that are more effective than those currently on the market. To address this problem, we have prepared a series of novel 4-(biphenyl-4-yl)-1,4-dihydropyridine and 4-(biphenyl-4-yl)pyridine derivatives via Hantzsch reaction using nine different compounds containing active methylene group. IR, NMR, and mass spectra were used to determine the structures. Using ampicillin and griseofulvin as standards, the titled compounds were investigated for their antibacterial activity against different bacteria and fungi. Compounds 1f, 1g, 2f, and 2g have the best antibacterial activity against Gram-negative bacteria (minimum inhibitory concentration = 50 μg/ml), while 1f, 1h, 2g, and 2h have high antifungal activity against Candida albicans (minimum inhibitory concentration = 100 μg/ml). To gain a better understanding of the binding process and affinity for the bacterial Staphylococcus epidermidis protein, researchers used molecular docking and molecular mechanics, as well as the generalized Born model and solvent accessibility-based binding free energy. The active compounds 1g, 1h, and 2f have good docking scores of -5.575, -5.949, and -5.234, respectively, whereas compound 2c has the greatest docking score (-6.23). The HOMO-LUMO energy gap and molecular electrostatic potential were used to evaluate the reactivity of promising compounds, which were then associated with antibacterial efficacy.

Tailoring copper(ii) complexes with pyridine-4,5-dicarboxylate esters for anti-Candida activity

Five novel copper(ii) complexes with pyridine-4,5-dicarboxylate esters as ligands, [Cu(NO₃)(py-2tz)(H₂O)₃]NO₃ (1), [Cu(NO₃)₂(py-2metz)(H₂O)] (2), [Cu(NO₃)₂(py-2py)(H₂O)]·H₂O (3), [CuCl₂(py-2tz)]₂ (4) and [CuCl₂(py-2metz)]_n (5) (py-2tz is dimethyl 2-(thiazol-2-yl)pyridine-4,5-dicarboxylate, py-2metz is dimethyl 2-(4-methylthiazol-2-yl)pyridine-4,5-dicarboxylate and py-2py is dimethyl 2,2'-bipyridine-4,5-dicarboxylate), were synthesized and structurally characterized by different spectroscopic and electrochemical methods. The structure of these complexes was determined by single-crystal X-ray diffraction analysis, confirming the bidentate coordination mode of the corresponding pyridine-4,5-dicarboxylate ester to the Cu(ii) ion through the nitrogen atoms. The antimicrobial potential of copper(ii) complexes 1-5 was assessed against two bacterial and two Candida species. These complexes showed better growth inhibiting activity against Candida spp. with respect to the tested bacterial species, also being moderately toxic towards normal human lung fibroblast cells (MRC-5). Complexes 1 and 4 showed the greatest ability to inhibit the filamentation of C. albicans, which is an important process during fungal infection, and these two complexes efficiently inhibited the biofilm formation of C. albicans at subinhibitory concentrations. Complex 4 also successfully prevented the adhesion of C. albicans in an in vitro epithelial cell model. The mechanism of the antifungal activity of copper(ii) complexes 1-5 was studied through their interaction with ct-DNA, as one of the possible target biomolecules, by fluorescence spectroscopy and gel electrophoresis. Finally, the ability of these complexes to bind to bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy.

Discovery of novel 2-aminonicotinonitrile derivatives with new potential autophagy activity

Background: To clarify the molecular mechanism of novel 2-aminonicotinonitrile autophagy enhancers, two series of novel 2-aminonicotinonitrile derivatives are synthesized and their structure-activity relationship and biological activity were analyzed. Results & methodology: Structure-activity relationship analysis revealed that substituents at C-4 and C-6 position of 7a contribute to enhance their autophagy-inducing activity, while C-5 position substituents have the opposite effect. The most promising compound 7g showed the strongest autophagy-inducing activity and better antiproliferative activity by inducing cell apoptosis and blocking cell cycle G1 arrest in SGC-7901 cells. Conclusion: The novel 2-aminonicotinonitrile autophagy enhancers were for the first time discovered and 7g might be a promising new autophagy enhancer with potential anticancer activity.

Spectroscopic, Theoretical and Antioxidant Study of 3d-Transition Metals (Co (II), Ni(II), Cu(II), Zn(II) Complexes with Cichoric Acid

Cichoric acid (CA) is a derivative of both caffeic acid and tartaric acid. It was isolated for the first time from Cichorium intybus L. (chicory) but it also occurs in significant amounts in Echinacea, particularly E. purpurea, dandelion leaves, basil, lemon balm and in aquatic plants, including algae and sea grasses. It has a wide spectrum of biological properties, including antioxidant, antiviral, anti-inflammatory and other. The work yielded cichoric acid complexes with selected transition metals, i.e., copper(II), nickel(II), zinc(II) and cobalt(II). In this work the dependency between the molecular structure and biological activity was discussed. The molecular structure was studied by means of infrared spectroscopy (Fourier transform infrared (FT-IR) Raman (FT-Raman)), electronic absorption spectroscopy (ultraviolet-visible (UV/VIS)) and theoretical calculations (density functional theory (DFT), Hartree-Fock (HF)). Understanding the mechanism of the effect of metals on the electronic system of ligands with biological importance will facilitate in the future the search for new, effective and natural antioxidants. The composition of the studied complexes in aqueous solutions was determined at a constant pH by the Job's method. Antioxidative properties of the tested compounds were determined using the ferric-reducing antioxidant power (FRAP), DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical method), cupric-reducing antioxidant capacity (CUPRAC) and Superoxide Dismutase Activity Assay (SOD).

The Use of Copper as an Antimicrobial Agent in Health Care, Including Obstetrics and Gynecology

Health care-associated infections (HAIs) are a global problem associated with significant morbidity and mortality. Controlling the spread of antimicrobial-resistant bacteria is a major public health challenge, and antimicrobial resistance has become one of the most important global problems in current times. The antimicrobial effect of copper has been known for centuries, and ongoing research is being conducted on the use of copper-coated hard and soft surfaces for reduction of microbial contamination and, subsequently, reduction of HAIs. This review provides an overview of the historical and current evidence of the antimicrobial and wound-healing properties of copper and explores its possible utility in obstetrics and gynecology.

Identification and Characterization of a Novel pic Gene Cluster Responsible for Picolinic Acid Degradation in Alcaligenes faecalis JQ135

Picolinic acid (PA) is a natural toxic pyridine derivative. Microorganisms can degrade and utilize PA for growth. However, the full catabolic pathway of PA and its physiological and genetic foundation remain unknown. In this study, we identified a gene cluster, designated picRCEDFB4B3B2B1A1A2A3, responsible for the degradation of PA from Alcaligenes faecalis JQ135. Our results suggest that PA degradation pathway occurs as follows: PA was initially 6-hydroxylated to 6-hydroxypicolinic acid (6HPA) by PicA (a PA dehydrogenase). 6HPA was then 3-hydroxylated by PicB, a four-component 6HPA monooxygenase, to form 3,6-dihydroxypicolinic acid (3,6DHPA), which was then converted into 2,5-dihydroxypyridine (2,5DHP) by the decarboxylase PicC. 2,5DHP was further degraded to fumaric acid through PicD (2,5DHP 5,6-dioxygenase), PicE (N-formylmaleamic acid deformylase), PicF (maleamic acid amidohydrolase), and PicG (maleic acid isomerase). Homologous pic gene clusters with diverse organizations were found to be widely distributed in Alpha-, Beta-, and Gammaproteobacteria Our findings provide new insights into the microbial catabolism of environmental toxic pyridine derivatives.IMPORTANCE Picolinic acid is a common metabolite of l-tryptophan and some aromatic compounds and is an important intermediate in organic chemical synthesis. Although the microbial degradation/detoxification of picolinic acid has been studied for over 50 years, the underlying molecular mechanisms are still unknown. Here, we show that the pic gene cluster is responsible for the complete degradation of picolinic acid. The pic gene cluster was found to be widespread in other Alpha-, Beta-, and Gammaproteobacteria These findings provide a new perspective for understanding the catabolic mechanisms of picolinic acid in bacteria.

Bilateral alkylamine for suppressing charge recombination and improving stability in blade-coated perovskite solar cells

The power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) are already higher than that of other thin film technologies, but laboratory cell-fabrication methods are not scalable. Here, we report an additive strategy to enhance the efficiency and stability of PSCs made by scalable blading. Blade-coated PSCs incorporating bilateral alkylamine (BAA) additives achieve PCEs of 21.5 (aperture, 0.08 cm²) and 20.0% (aperture, 1.1 cm²), with a record-small open-circuit voltage deficit of 0.35 V under AM1.5G illumination. The stabilized PCE reaches 22.6% under 0.3 sun. Anchoring monolayer bilateral amino groups passivates the defects at the perovskite surface and enhances perovskite stability by exposing the linking hydrophobic alkyl chain. Grain boundaries are reinforced by BAA and are more resistant to mechanical bending and electron beam damage. BAA improves the device shelf lifetime to >1000 hours and operation stability to >500 hours under light, with 90% of the initial efficiency retained.

Manganese tolerance in Verbascum olympicum Boiss. affecting elemental uptake and distribution: changes in nicotinic acid levels under stress conditions

A multielemental determination methodology in conjunction with an organic acid analysis that were supplemented with other stress parameters and an ultrastructural analysis used herein to study Verbascum olympicum Boiss. (Scrophulariaceae) under Mn stress. Uptake and accumulation characteristics of B, Cu, Fe, Mn, Mo, and Zn were evaluated in 8-week-old seedlings grown in Hoagland's nutrient solution and exposed to 5 (CK), 50, and 200 μM MnSO₄ for 7 days. Hydrogen peroxide levels were determined to evaluate oxidative stress, and changes in compatible substance levels (total phenolic contents, glutathione and glutathione disulfide levels) were determined to assess antioxidant defense mechanisms. The distribution of manganese on the root surface was characterized by scanning electron microscopy images and energy-dispersive X-ray spectroscopy analysis. The levels of nicotinic acid, which is involved in nicotinamide adenine dinucleotide biosynthesis, were determined in roots and leaves to assess tolerance mechanisms. V. olympicum exhibited the ability to cope with oxidative stress originating from excessive Mn, while increased Mn concentrations were observed in both roots and leaves. The translocation factor of B was the most affected among other studied elements under the experimental conditions. Total nicotinic acid levels exhibited a trend of reduction in the roots and leaves, which could be attributed to the appropriate metabolic progress associated with oxidative stress based on the nicotinamide adenine dinucleotide cycle that may reach glutathione in response to manganese stress during plant growth.

Comparisons of the spectroscopic and microbiological activities among coumarin-3-carboxylate, o-phenanthroline and zinc(II) complexes

Coumarins (2H-chromen-2-one) are oxygen-containing heterocyclic compounds that belong to the benzopyranones family. In this work we have synthesized different coordination complexes with coumarin-3-carboxylic acid (HCCA), o-phenanthroline (phen) and zinc(II). In the reported [Zn(CCA)₂(H₂O)₂] complex, coumarin-3-carboxylate (CCA) is acting as a bidentate ligand while in the two prepared complexes, [Zn(phen)₃]CCA(NO₃) (obtained as a single crystal) and [Zn(CCA)₂phen].4H₂O, CCA is acting as a counterion of the complex cation [Zn(phen)₃]⁺² or coordinated to the metal center along with phen, respectively. These compounds were characterized on the basis of elemental analysis and thermogravimetry. NMR, FTIR and Raman spectroscopies of the compounds and the CCA potassium salt (KCCA) allow to determine several similarities and differences among them. Finally, their behavior against alkaline phosphatase enzyme and their antimicrobial activities were also measured.

Polymer-modified halide perovskite films for efficient and stable planar heterojunction solar cells

The solution processing of polycrystalline perovskite films introduces trap states that can adversely affect their optoelectronic properties. Motivated by the use of small-molecule surfactants to improve the optoelectronic performance of perovskites, we demonstrate the use of polymers with coordinating groups to improve the performance of solution-processed semiconductor films. The use of these polymer modifiers results in a marked change in the electronic properties of the films, as measured by both carrier dynamics and overall device performance. The devices grown with the polymer poly(4-vinylpyridine) (PVP) show significantly enhanced power conversion efficiency from 16.9 ± 0.7% to 18.8 ± 0.8% (champion efficiency, 20.2%) from a reverse scan and stabilized champion efficiency from 17.5 to 19.1% [under a bias of 0.94 V and AM (air mass) 1.5-G, 1-sun illumination over 30 min] compared to controls without any passivation. Treating the perovskite film with PVP enables a V_OC of up to 1.16 V, which is among the best reported for a CH₃NH₃PbI₃ perovskite solar cell and one of the lowest voltage deficits reported for any perovskite to date. In addition, perovskite solar cells treated with PVP show a long shelf lifetime of up to 90 days (retaining 85% of the initial efficiency) and increased by a factor of more than 20 compared to those without any polymer (degrading to 85% after ~4 days). Our work opens up a new class of chemical additives for improving perovskite performance and should pave the way toward improving perovskite solar cells for high efficiency and stability.