Expression of fatty acid related gene promotes astaxanthin heterologous production in Chlamydomonas reinhardtii.

Natural astaxanthin is a high-value ketone carotenoid mainly derived from Haematococcus pluvialis, which is an excellent antioxidant for human consumption. To study the role of lipids in accumulation of astaxanthin, the H. pluvialis-derived astaxanthin synthesis pathway genes (ß-carotene ketolase gene, BKT and ß-carotene hydroxylase gene, BCH) and fatty acid elongation gene (mitochondrial trans-2-enoyl-coa reductase gene, MECR) were heterologously co-expressed in C. reinhardtii. Zeaxanthin, the precursor of astaxanthin synthesis, was significantly increased after BKT and BCH were expressed. In contrast, the α-carotene that competes with astaxanthin synthesis for lycopene decreased significantly. This redistribution of carbon flow was conducive to the synthesis of astaxanthin. In addition, the transformant only expressed astaxanthin metabolism related genes (BKT, BCH) would lead to an increase in total lipid, a decrease in monounsaturated fatty acids and an increase in polyunsaturated fatty acids. On this basis, the expression of MECR gene further increased the total lipid, and the relative content of different fatty acids also changed. The astaxanthin content of algal strains transformed with BKT and BCH genes was nearly 50% higher than that of the wild type. On this basis, the astaxanthin content of transformants expressing MECR gene related to long-chain fatty acid synthesis was increased by 227.5%. In this study, an astaxanthin production model similar to H. pluvialis by combining carotenoid metabolism and fatty acid metabolism was constructed in C. reinhardtii. The results suggest that the increase in astaxanthin is indeed linked to the regulation of fatty acid metabolism, and this link may involve the type of fatty acids and the dynamics of astaxanthin ester in cells. The strategy of promoting the synthesis of fatty acids has potential to achieve efficient production of astaxanthin in C. reinhardtii.

Correction: Aromatic amine electrochemical sensors based on a Co-MOF: a hydrogen bond-induced specific response.

Correction for 'Aromatic amine electrochemical sensors based on a Co-MOF: a hydrogen bond-induced specific response' by Xiao-qin Wu et al., Dalton Trans., 2022, 51, 16861-16869, https://doi.org/10.1039/d2dt02049a.

An ultra-fast UV-electrochemical sensor based on Cu-MOF for highly sensitive and selective detection of ferric ions.

A 2D Cu-MOF: {[CuL(H2O)]}n (Cu-1, H2L = 3,4-ethylene dioxythiophene-2,5-dicarboxylic acid) was synthesized using the hydrothermal method. Cu-1 showed excellent solvent stability and was used to fabricate a UV ferric ion sensor. An ultra-low limit of detection (LOD) at 14.5 fM was obtained. Furthermore, N,N-dimethylformamide (DMF) as a 'turn-off' switch was introduced into the Cu-1 framework to construct another 2D Cu-MOF: {[CuL(DMF)]}n (Cu-2) by a single crystal to single crystal (SCSC) transformation method. Cu-2 lost the ability to recognize ferric ions and the switching effect of Fe3+ recognition was realized. Cyclic voltammograms (CVs) were employed to investigate this conversion process and provided a way for explaining the interaction mechanism between Cu-1 and ferric ions. We present an approach for designing and synthesizing MOFs that are suitable for ion sensing.

Aromatic amine electrochemical sensors based on a Co-MOF: a hydrogen bond-induced specific response.

A 2D Co-MOF, {[Co2(L2-)2(bipy)](DMA)·2H2O}n (Co-1, H2L = 2,5-thienedioic acid; bipy = 2,2'-bipyridine; DMA = N,N'-dimethyl acetamide), was synthesized by hydrothermal method. Co-1 has excellent air stability. When modifying the surface of a glassy carbon electrode (GCE) with Co-1, the obtained electrochemical senor Co-1/GCE shows excellent sensitivity towards 1,3-dinitrobenzene (m-DNB) and 2,4-dinitroaniline (2,4-DNA), although the electrochemical conductivity of Co-1 is not that good. The detection limits were as low as 0.0286 µM and 0.161 µM, respectively. DFT studies showed that the main interaction between Co-1 and the guest molecules is via hydrogen bonding, formed by the -NO2 group and the coordinated H2O molecule from the Co-1 skeleton. Furthermore, the characteristic signals of both m-DNB and 2,3-DNA can still be observed in a mimicked industrial waste-water system containing 17 kinds of organic interferents, indicating high selectivity of the Co-1/GCE sensor.

Multifractal dimensions of soil particle size distribution reveal the erodibility and fertility of alpine grassland soils in the Northern Tibet Plateau.

Climate change and human activities have seriously degraded alpine grassland, potentially affecting soil particle size distribution (PSD) and further influencing the nutrient levels and erodibility of soil. Predicting the fertility and erodibility of alpine soil using multifractal dimensions of soil PSD could be used to enhance the management and restoration of degraded alpine grasslands. In the present study, we evaluated three types of alpine grasslands: alpine meadow (AM), alpine steppe (AS), and alpine desert steppe (ADS). Fencing and grazing management measures were conducted at sites containing each grassland type. Then, we analyzed the PSDs, erodibility, and other properties of soil in the 0-20 cm soil layer. Multifractal characterization of soil PSD was calculated using the fractal scale theory. The findings showed that grassland type significantly impacted soil nutrients and the multifractal dimensions of soil PSDs, whereas management measures affected soil erodibility significantly. The proportion of finer particles decreased as follows: AM > AS > ADS. Compared to grazing, fencing enhanced clay content and reduced the proportion of coarser particles under all three grassland types. AM had higher organic carbon and nitrogen levels than AS and ADS. Multifractal dimensions were highest for AM, with ADS having higher erodibility than AM and AS. Multifractal dimensions (except for correlation dimension) also had significantly positive relationships with soil organic carbon and available nutrient content and soil erodibility, but had significantly negative correlations with soil pH, bulk density, and electrical conductivity. Thus, the multifractal dimensions of soil PSDs could be used to characterize the erodibility and fertility characteristics of soil in alpine regions, providing a reference for assessing vegetation restoration measures in the Northern Tibet Plateau.

Study of the Unique Characteristics of Multi-Elements of the Wild Astragali Radix from Shanxi Province by Inductively Coupled Plasma Mass Spectrometry.

BACKGROUND: Astragali Radix (AR) is widely used because of its dual use in medicine and food. Wild Astragali Radix from Hunyuan county of Shanxi province in China is accepted as a geo-authentic medicine with high quality and good medicinal effects. Multi-elements of Astragali Radix partially reflect its efficacy and safety. However, there has been no systemic research about the elemental analysis of geo-authentic Astragali Radix until now. OBJECTIVE: In this paper, multi-elemental profiling of Astragali Radix from Gansu, Jilin, Inner Mongolia, Shaanxi and Shanxi provinces in China was carried out. METHODS: A microwave digestion coupled with inductively coupled plasma-MS (ICP-MS), principal component analysis (PCA), and partial-least square-discriminate analysis (PLS-DA) were used for analysis of the unique elemental accumulation ability of Shanxi wild AR. RESULTS: Compared to the samples from Gansu, Jilin, Inner Mongolia, Shaanxi provinces, and the cultivated samples from Shanxi, for 53 stably detected elements, the concentrations of most elements (Ba, Cs, Ga, La, Pr, and so on) were significantly higher while a few (Cd, Cu, P, W and Zn) were significantly lower in wild Astragali Radix from Shanxi. After binary logistic regression, combinational variable Ba-P was found to be a good marker to distinguish wild Astragali Radix of Shanxi province from the samples with other origins, and the total positive prediction probability of the test samples, both bought from the market and gathered from their original field, could reach 93.8% through external validation using the model. CONCLUSION: Multi-elemental analysis coupled with PCA, PLS-DA, nonparametric analysis and binary logistic regression can be a good tool for the identification of wild Astragali Radix from Shanxi province. HIGHLIGHTS: An ICP-MS method was developed and validated for multi-elements. Fifty-three elements in Astragali Radix from samples with different origins were compared. The wild Astragali Radix from Shanxi had unique elemental characteristics. Combinational variable Ba-P is a good marker to identify wild AR from Shanxi.

Construction of a pillararene-based supramolecular polymer network and its application in efficient removal of dyes from water.

An AB-type monomer based on a pillar[5]arene host and an imidazolium salt guest was successfully synthesized through a facile way. This monomer can self-assemble into linear supramolecular polymers in chloroform. After the addition of silver ions, the imidazolium salt group coordinated with silver ions to crosslink the linear supramolecular polymers at their ends, resulting in the formation of supramolecular polymer networks. Meanwhile, after further adding iodide ions, the supramolecular polymer network changed back to the linear supramolecular polymer. As a result, the topological structure of the system can be reversibly tuned. Furthermore, this supramolecular polymer network can be applied to remove organic dyes in water, suggesting its great potential in the treatment of waste water.

Water-Stable 1D Double-Chain Cu Metal-Organic Framework-based Electrochemical Biosensor for Detecting l-Tyrosine.

An electrochemical biosensor based on a water-stable one-dimensional double-chain Cu(II) metal-organic framework (Cu-MOF) directly was constructed for efficiently recognizing l-tyrosine (l-Tyr) in biomimic environments. Cu-MOF: {[Cu(bpe)(fdc) (H2O)(DMF)]·0.5H2O}n (bpe = 1,2-di(4-pyridyl)ethylene, H2fdc = 2,5-furandicarboxylic acid, namely, Cu-1) was synthesized by a hydrothermal method. It was characterized by IR, scanning electron microscopy, atomic force microscopy, and PXRD techniques. Cu-1 exhibited extreme solvent and thermal stability as well as excellent electroconductive character. It was coated on a glassy carbon electrode (GCE) surface to prepare an electrochemical biosensor (Cu-1/GCE) which showed preferable biosensing ability toward l-Tyr. This Cu-MOF electrochemical biosensor showed simple operation and high sensitivity toward l-Tyr in the concentration range from 0.01 to 0.09 mM. The detection limit is 5.822 µM. Furthermore, Cu-1/GCE showed extremely excellent selectivity to l-Tyr in a biomimic environment with several amino acid interferents. This new strategy exhibits great potential applications for designing MOFs with excellent electrochemical activity.

Alkali-metal organomagnesiate complexes as catalysts for highly chemoselective crossed-Tishchenko reactions.

Five new heterobimetallic magnesiates bearing bidentate dianionic pyrrolyl ligands have been synthesized through co-complexation with alkali-metal reagents and di-n-butylmagnesium. Single-crystal X-ray structural analysis of these complexes revealed a variety of intriguing bonding modes. These alkali-metal (Li, Na, and K) organomagnesiates were utilized as catalysts for cross-coupling Tishchenko reactions with two different aldehydes. The sodium alkyl magnesiate complex {nBuMg[2-(Me3CNCH2)C4H3N]Na(Et2O)}∞ (3) was identified as a competent catalyst, as it exhibited higher catalytic activities and chemoselectivity under mild conditions.

Study of enrichment difference of 64 elements among white tea subtypes and tea leaves of different maturity using inductively coupled plasma mass spectrometry.

A microwave digestion-inductively coupled plasma mass spectrometry (ICP-MS)-based analytical method for 64 elements in white tea was developed. The determination coefficient R2 were ranged from 0.9970 to 1.0000 in 3 orders of magnitude for the 64 detected elements, and the limits of detection (LODs) of the method were from 0.0004 to 35.906 ng/mL. The stability of the method was monitored by quality control samples (QCs) and the accuracy was validated by certified reference material. Application of this method in 3 white tea subtypes showed that most of 54 elements that above LODs (Al, Pb, Cd, Hg, As, rare earth elements, and etc.) displaying gradually increasing trend in subtypes of Baihaoyinzhen, Baimudan, and Shoumei which are manufactured from tea leaves of increasing maturity, while few elements (Zn, P and Ni) decreased. Then, a further application of this method in fresh samples of the bud and the 1st, 2nd, 3rd, 4th, and 5th leaf confirmed that more mature tea leaf has higher enrichment efficiency for most elements. In conclusion, a comprehensive microwave digestion-ICP-MS-based analytical method was established and applied in the content measurements of 64 elements in 3 white tea subtypes and fresh tea leaves of different maturity, and it demonstrated that more mature tea leaf has higher enrichment efficiency for most elements.

Selenium biofortification and its effect on multi-element change in Auricularia auricular.

Auricularia auricular could be useful as a candidate for human selenium supplementation. This study examined the effects of exogenous Se on the growth, yield, nutritive value, and mineral accumulation of A. auricular. Selenate or selenite (0.5-40.0 µg g-1) had no effect on mycelium morphology or the yield of fruiting bodies. In some cases, they affected the accumulation of inter-elements and significantly decreased the concentrations of copper, iron, and chromium in the Se-enriched fruiting bodies compared to that with control treatments. The polysaccharide (116.5-131.6 µg g-1) and protein (105.2-113.4 µg g-1) content in Se-enriched fruiting bodies were not significantly different from those observed in the controls (polysaccharide, 114.1 µg g-1; protein, 105.6 µg g-1). Thus, A. auricular can absorb inorganic Se from the substrate and convert it to organic Se compounds (selenocystine (≥4.1%), selenomethionine (≥91.9%), and Se-methylselenocysteine (≥2.3%)).

A dimethoxypillar[5]arene/azastilbene host-guest recognition motif and its applications in the fabrication of polypseudorotaxanes.

Pillar[n]arenes, known as the fifth generation of host macrocycles since 2008, have become a popular topic over the past ten years. Until now, the studies of pillar[n]arenes were mainly focused on pillar[5]arenes owing to their easy synthesis and high yields. In particular, 1,4-dimethoxypillar[5]arene (DMP5), which shows a simple structure, efficient synthesis and high yield, has played important roles in the construction of various advanced supramolecular architectures. However, DMP5 has only displayed host-guest binding properties towards some guests. Therefore, the investigation of the host-guest chemistry of DMP5 should be able to greatly promote the development of pillararene chemistry. Herein, a photosensitive azastilbene derivative was chosen as a neutral guest to study the host-guest binding and stimuli-responsive behavior with DMP5. In addition, the binding behavior of DMP5 towards a series of analogous neutral guest molecules was investigated to study the driving forces of the host-guest interaction between DMP5 and the azastilbene guest. Moreover, the [2]pseudorotaxane based on DMP5 and the azastilbene guest was used to construct a polypseudorotaxane via metal coordination.

Gemini-Type Supramolecular Amphiphile Based on a Water-Soluble Pillar[5]arene and an Azastilbene Guest and Its Application in Stimuli-Responsive Self-Assemblies.

Supramolecular amphiphiles are a type of intriguing building blocks to fabricate self-assembled nanostructures that can be applied in diverse fields. Gemini-type supramolecular amphiphiles, containing two hydrophobic tails and two hydrophilic head groups linked by a spacer, are good candidates to fabricate many advanced materials that are able to apply in surface modification, drug/gene delivery, and solubilization. Pillararenes, the fifth generation of macrocyclic host molecules, have been used to fabricate many supramolecular amphiphiles that played important roles in biomedical fields and materials science. However, compared with single-chain and bola-type supramolecular amphiphiles, the studies of gemini-type supramolecular amphiphiles based on pillararenes are very rare. Herein, a new strategy to prepare gemini-type supramolecular amphiphiles was reported. A new acid-responsive host?guest recognition motif in water on the basis of a 4,4?-azastilbene derivative (G1) and a water-soluble pillar[5]arene (WP5) was fabricated. The gemini-type supramolecular amphiphile was constructed by an azastilbene amphiphilic guest (G2) and WP5. Then its application in stimuli-responsive self-assemblies was investigated. G2 self-assembled into nanoribbons in water. Upon addition of WP5, the gemini-type supramolecular amphiphile formed, leading to the formation of disklike micelles. After further addition of hydrochloric acid, the morphology changed into nanosheets.

Potassium complexes containing bidentate pyrrole ligands: synthesis, structures, and catalytic activity for the cyclotrimerization of isocyanates.

Bidentate pyrrolyl ligands, 2-(t-butyliminomethyl)pyrrole and 2-(t-butylaminomethyl)pyrrole, reacted with KH to give complexes [C4H3N(2-CH[double bond, length as m-dash]NtBu)K(THF)]n (1) and [C4H3N(2-CH2NHtBu)K]n (2), respectively. Each has been characterized by C, H and N microanalysis, NMR spectroscopy, and single crystal X-ray structural analysis. The X-ray structure of complex 1 (n≥ 1) demonstrated that it exists as a 1D zig-zag coordination polymer in the solid state. Conversely, the structure of complex 2 (n≥ 1) showed that it is a 2D supramolecular network. They proved to be an effective class of catalysts for cyclotrimerization of isocyanate in excellent yield under mild conditions.

Design of a Zn-MOF biosensor via a ligand "lock" for the recognition and distinction of S-containing amino acids.

Two new 2D Zn(ii) metal-organic frameworks (MOFs) {[Zn2(L)2(µ2-O)(H2O)3]·3DMA}n (Zn-1) and [Zn2(L)2(2,2'-bipy)(µ2-O)(H2O)2]n (Zn-2) (H2L = 2,5-thiophene dicarboxylic acid, bipy = 2,2'-dipyridyl) were designed and synthesized. Through the strategy of introducing bipy as a "lock", Zn-1 was transferred to Zn-2via a crystal-to-crystal process, which showed significantly enhanced solvent and air stability compared to that of Zn-1. Without post modification, Zn-2 was used as an electrode modified material to construct sensors for the electrochemical recognition and distinction of S-containing amino acids, including l-cysteine, l-methionine and l-cystine.

Cloning of nitrite reductase gene from Haematococcus pluvialis and transcription and enzymatic activity analysis at different nitrate and phosphorus concentration.

Haematococcus pluvialis is an economic microalga to produce astaxathin. To study the nitrogen metabolic process of H. pluvialis, the transcription level and enzyme content of nitrite reductase at different nitrate and phosphorus concentrations were studied. In this research, nitrite reductase gene (nir) was first cloned from H. pluvialis, which consists of 5592 nucleotides and includes 12 introns. The cDNA ORF is 1776 bp, encoding a 592 amino acid protein with two conserved domains. Phylogenetic analysis showed that the nir gene in H. pluvialis had the highest affinity with other freshwater green algae. Nitrogen and phosphorus play an important role in the growth of H. pluvialis. The single factor experiments of nitrogen on growth conditions showed that the group with 0.2 g/L NaNO3 had a relative high biomass. The single factor experiments of phosphorus on growth conditions showed that the group with 0.06 g/L K2HPO4 had a relative high biomass. The transcription level and enzymatic activity of nitrite reductase were detected at different nitrate and phosphorus concentrations. In the absence of nitrogen and phosphorus in the medium, nitrite reductase activity is the highest. This research provides theoretical guidance for optimization of culture medium for H. pluvialis and also provides an experimental basis for understanding of nitrogen metabolism pathway in H. pluvialis.

New Insights into the Ligand Nature of Carbene: Synthesis and Characterizations of Six-Coordinate Iron(II) Carbene Porphyrin Complexes.

Several six-coordinate iron(II) carbene tetra(pentafluorophenyl)porphyrin (TFPP) complexes, [Fe(TFPP)(CPh2)(1-EtIm)] (1-EtIm = 1-ethylimidazole) and [Fe(TFPP)(CPh2)(1,2-Me2Im)] (1,2-Me2Im = 1,2-dimethylimidazole), are isolated and studied by UV-vis, single-crystal X-ray, and Mössbauer spectroscopies. The single-crystal structural studies revealed noteworthy features including strong and "hard" axial carbene bonds (Fe-C) but "flexible" trans ligand bonds (Fe-NIm). The Mössbauer spectra of [Fe(TFPP)(CPh2)(1-EtIm)] and [Fe(TFPP)(CPh2)(1,2-Me2Im)] are obtained on solid-state samples between 25 and 295 K, which give very large Δ EQ values (1.8-1.9 mm/s), suggesting a weak effect of the trans imidazole ligands. Comparisons with diatomic carbon-donor ligands (CO, CS, and CN-) demonstrate considerably stronger π bonding of the :CPh2 carbene.

Exploring cysteine regulation in cancer cell survival with a highly specific "Lock and Key" fluorescent probe for cysteine.

To probe the regulatory roles of cysteine (Cys) in cancer cell survival, a highly selective and sensitive fluorescent Cys probe SiR was developed by employing a novel "lock and key" strategy, which allows Cys to be detected without any interference or probe consumption caused by the intracellular high concentration of glutathione (GSH). Using SiR, we confirmed that inhibiting cystine (Cys2) transporter system xc - to deplete intracellular Cys is more efficient than inhibiting glutamate-cysteine ligase GCL to deplete intracellular GSH for sensitizing cancer cells to chemotherapy. Moreover, with the probe, a possible self-protection mechanism of cancer cells was indicated: when extracellular Cys sources are blocked, cancer cells could still survive by multidrug resistance protein transporter (Mrp1)-mediated export of intracellular GSH/GSSG as sources to supply intracellular Cys for resisting detrimental oxidative stress. Based on this finding, we further confirmed that abrogating the self-protection mechanism is an even more efficient strategy for sensitizing cancer cells to chemotherapy.

Reduction of CO2 into Methylene Coupled with the Formation of C-S Bonds under NaBH4/I2 System.

A selective four-electron reduction of CO2 with thiophenol using NaBH4 as a reductant is described to access dithioacetals. This reaction provides a novel synthetic method for the highly selective conversion of CO2 into methylene, and a new access to molecular structures via formation of C-S bonds using CO2 as the C1 source.

Extensive intraspecific gene order and gene structural variations between Mo17 and other maize genomes.

Maize is an important crop with a high level of genome diversity and heterosis. The genome sequence of a typical female line, B73, was previously released. Here, we report a de novo genome assembly of a corresponding male representative line, Mo17. More than 96.4% of the 2,183 Mb assembled genome can be accounted for by 362 scaffolds in ten pseudochromosomes with 38,620 annotated protein-coding genes. Comparative analysis revealed large gene-order and gene structural variations: approximately 10% of the annotated genes were mutually nonsyntenic, and more than 20% of the predicted genes had either large-effect mutations or large structural variations, which might cause considerable protein divergence between the two inbred lines. Our study provides a high-quality reference-genome sequence of an important maize germplasm, and the intraspecific gene order and gene structural variations identified should have implications for heterosis and genome evolution.