CRISPR-Cas9-assisted genome editing in E. coli elevates the frequency of unintended mutations.

Cas-assisted lambda Red recombineering techniques have rapidly become a mainstay of bacterial genome editing. Such techniques have been used to construct both individual mutants and massive libraries to assess the effects of genomic changes. We have found that a commonly used Cas9-assisted editing method results in unintended mutations elsewhere in the genome in 26% of edited clones. The unintended mutations are frequently found over 200 kb from the intended edit site and even over 10 kb from potential off-target sites. We attribute the high frequency of unintended mutations to error-prone polymerases expressed in response to dsDNA breaks introduced at the edit site. Most unintended mutations occur in regulatory or coding regions and thus may have phenotypic effects. Our findings highlight the risks associated with genome editing techniques involving dsDNA breaks in E. coli and likely other bacteria and emphasize the importance of sequencing the genomes of edited cells to ensure the absence of unintended mutations.

Saikosaponin D mitigate pilocarpine-induced astrocyte injury by regulating the NLRP3/caspase-1 signaling pathway.

Studies have shown that saikosaponin D (SSD) has favorable neurotherapeutic effects. Therefore, the objective of this study was to explore the efficacy and possible molecular mechanisms of SSD on pilocarpine (PP)-induced astrocyte injury. Primary astrocytes were isolated from juvenile rats and identified using immunofluorescence. The cells were treated with PP and/or SSD for 6 h and 12 h, respectively, followed by measurement of their viability through 3-(4,5-dimethylthiazol)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Next, quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the expression levels of Glial fibrillary acidic protein (GFAP), C3, S100 calcium binding protein A10 (S100a10), pentraxin 3 (Ptx3), toll-like receptor 4 (TLR4), and RAG in astrocytes after different treatments. Enzyme-linked immunosorbent assay and biochemical tests were utilized to evaluate the level of inflammatory factors [interleukin (IL)-1ß, IL-6, and tumor necrosis factor alpha (TNF-α)] secreted by cells and the content of oxidative stress-related factors (malondialdehyde [MDA] and glutathione [GSH]) or enzyme activity (catalase [CAT] and glutathione peroxidase [GPX]) in cells. The JC-1 mitochondrial membrane potential (MMP) fluorescence probe was used to measure the MMP in astrocytes. Additionally, western blot was applied to test the expression of proteins related to the nod-like receptor protein 3 (NLRP3)/caspase-1 signaling pathway. PP treatment (1 mM) induced cell injury by significantly reducing the viability of astrocytes and expression of cellular markers. SSD treatment (4 µM) had no toxicity to astrocytes. Besides, SSD (4 µM) treatment could significantly up-regulate the cell viability and marker expression of PP-induced astrocytes. Furthermore, SSD could be employed to inhibit inflammation (reduce IL-1ß, IL-6, and TNF-α levels) and oxidative stress (decrease MDA level, elevate GSH level, the activity of CAT and GPX), and ameliorate mitochondrial dysfunction (upregulate JC-1 ratio) in PP-induced astrocytes. Moreover, further mechanism exploration revealed that SSD treatment significantly reduced the activity of the NLRP3/caspase-1 signaling pathway activated by PP induction. SSD increased cell viability, inhibited inflammation and oxidative stress response, and ameliorated mitochondrial dysfunction in PP-induced astrocyte injury model, thus playing a neuroprotective role. The mechanism of SSD may be related to the inhibition of the NLRP3/caspase-1 inflammasome.

Synonymous edits in the Escherichia coli genome have substantial and condition-dependent effects on fitness.

CRISPR-Cas-based genome editing is widely used in bacteria at scales ranging from construction of individual mutants to massively parallel libraries. This procedure relies on guide RNA-directed cleavage of the genome followed by repair with a template that introduces a desired mutation along with synonymous "immunizing" mutations to prevent re-cleavage of the genome after editing. Because the immunizing mutations do not change the protein sequence, they are often assumed to be neutral. However, synonymous mutations can change mRNA structures in ways that alter levels of the encoded proteins. We have tested the assumption that immunizing mutations are neutral by constructing a library of over 50,000 edits that consist of only synonymous mutations in Escherichia coli. Thousands of edits had substantial effects on fitness during growth of E. coli on acetate, a poor carbon source that is toxic at high concentrations. The percentage of high-impact edits varied considerably between genes and at different positions within genes. We reconstructed clones with high-impact edits and found that 69% indeed had significant effects on growth in acetate. Interestingly, fewer edits affected fitness during growth in glucose, a preferred carbon source, suggesting that changes in protein expression caused by synonymous mutations may be most important when an organism encounters challenging conditions. Finally, we showed that synonymous edits can have widespread effects; a synonymous edit at the 5' end of ptsI altered expression of hundreds of genes. Our results suggest that the synonymous immunizing edits introduced during CRISPR-Cas-based genome editing should not be assumed to be innocuous.

Dynamic Fluorescence Sensing of Bromide Ions by Photochromic Bi(III)-Coordination Polymers Based on a Ligand Integrated by Naphthalene Diimides and Pyridinium in Solution and Films.

Bismuth(III)-based complexes have garnered increasing attention in fluorescence sensing due to their environmentally friendly and sustainable characteristics. A Bismuth(III) coordination polymer (CP),1-Cl based on a naphthalene diimides(NDI)-pyridinium is synthesized by an in situ reaction method. Notable for its sensitivity to visible light, 1-Cl shows excellent photochromic properties, and the integration of NDI and pyridinium in one ligand makes photogenerated radicals more stable. Structural analysis and theoretical calculations are employed to investigate the potential pathway of photoinduced electron transfer (ET) during the photochromic process. Notably, in aqueous solutions, 1-Cl displays an extraordinary fluorescence enhancement response to bromide ion (Br- ), resulting in a distinct transition from yellow to orange in color. The potential mechanism of fluorescence sensing has been revealed through single-crystal X-ray diffraction analysis. This insight highlights a continuous substitution process where the Cl- ions are successively replaced by Br- ions. Consequently, a single-crystal-to-single-crystal transformation (SCSC) occurs, yielding the intermediate species, 1-Cl-Br, which ultimately transforms into the final product, 1-Br. Finally, the photochromic film is successfully prepared and applied to practical applications such as ink-free printing, information anti-counterfeiting, and the visual detection of Br- ions. This work combines photochromism with fluorescence sensing, broadening the research field and practical application of photochromic materials.

Three-Dimensional Viologen-Based Lanthanide-Organic Frameworks: Photochromism and Fluorescence Detection of Quinolone Antibiotics.

Quinolone antibiotic residues, norfloxacin (NORF) and ciprofloxacin (CIP), have attracted more attention due to their frequent detection in surface water and food field, which seriously threaten the health of animals and humans. Rapid and efficient detection of NORF and CIP is critical for environmental testing and ecosystems. Herein, two novel isostructural viologen-functionalized Ln(III) complexes [Ln2L0.5(IPA)3]n (Ln = Eu, 1; Tb, 2; L = N,N'-bis (2-carboxyethyl)-4,4'-bipyridridylium dichloride, H2IPA = isophthalic acid) with a three-dimensional structure have been synthesized solvothermally. Complexes 1 and 2 exhibited reversible photochromism under UV light. In addition, complex 1 exhibits excellent pH tolerance and can be seen as an efficient fluorescent probe for the detection of NORF and CIP with detection limits of 7.90 × 10-7 and 9.48 × 10-7 M, respectively. Furthermore, the good photoresponsive and outstanding fluorescent properties of 1 were further exploited in dual-function paper involving erasable inkless printing and detection of NORF and CIP. Our work reports a new strategy for recognizing NORF and CIP based on the luminescent color change of the viologen-based Ln-MOFs, providing a new direction for the development of multifunctional materials.

Conformation- and Coordination Mode-Dependent Stimuli-Responsive Salicylaldehyde Hydrazone Zn(II) Complexes.

Luminescent Zn(II) complexes that respond to external stimuli are of wide interest due to their potential applications. Schiff base with O,N,O-hydrazone shows excellent luminescence properties with multi-coordination sites for different coordination modes. In this work, three salicylaldehyde hydrazone Zn(II) complexes (1, 2a, 2b) were synthesized and their stimuli-responsive behaviors in different states were explored. Only complex 1 exhibits reversible and self-recoverable photochromic and photoluminescence properties in solution. This may be due to the configuration eversion and the excited-state intramolecular proton transfer (ESIPT) process. In the solid state, 2a has obvious mechanochromic luminescence property, which is caused by the destruction of intermolecular interactions and the transformation from crystalline state to amorphous state. 2a and 2b have delayed fluorescence properties due to effective halogen bond interactions in structures. 2a could undergo crystal-phase transformation into its polymorphous 2b by force/vapor stimulation. Interestingly, 2b shows photochromic property, which can be attributed to the electron transfer and generation of radicals induced by UV irradiation. Due to different conformations and coordination modes, the three Zn(II) complexes show different stimuli-responsive properties. This work presents the multi-stimuli-responsive behaviors of salicylaldehyde hydrazone Zn(II) complexes in different states and discusses the response mechanism in detail, which may provide new insights into the design of multi-stimuli-responsive materials.

Enhancement of Long-Lived Persistent Room-Temperature Phosphorescence and Anion Exchange with I- and SCN- via Metal-Organic Hybrid Formation.

An in-depth understanding of structure-property relationships and the construction of multifunctional stimuli-responsive materials are still difficult challenges. Herein, we discovered a 4,4'-bipyridinium derivative with both photochromism and dynamic afterglow at 77 K for the first time. A one-dimensional (1D) Cd(II) coordination polymer (1) assembled by only a 4,4'-bipyridinium derivative and cadmium chloride showed photochromism, room-temperature phosphorescence (RTP), and electrochromism. Interestingly, we found that 1 underwent single-crystal-to-single-crystal transformation during the anion exchange process, and the color of the crystal changed from colorless to yellow (1-SCN-) within 10 min. Complex 1 exhibited photochromism, whereas 1-SCN- did not. The difference in the photochromic behavior between the two complexes was ascribed to the electron transfer pathway between the carboxylate groups and viologen. The DFT calculation based on the crystal structure of 1-SCN- indicated that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were mainly located on bipyridine and cadmium atoms, eliminating the possibility of electron transfer, whereas for complex 1, electron transfer was probable from O and Cl atoms to pyridinium N atoms in viologen as demonstrated by density of states (DOS) calculations. In addition, complex 1 was successfully made into test paper for the rapid detection of I- and SCN- and displayed potential applications in inkless printing, multiple encryption, and anticounterfeiting.

Solvent-Modulated Self-Assembly of Naphthalenediimide-Based Cd(II) Complexes and the Controllable Photochromism via Conformational Isomerization.

Rational regulation of the properties of photochromic materials is a challenging and meaningful work. In the present work, NDI-based complexes, namely, [Cd0.5(NDI)(HBDC)]·H2O (1) and a series of conformational isomers of {[Cd(NDI)0.5(BDC)]·MeCN}n (2), were synthesized by varying the solvent conditions (H2BDC = terephthalic acid, NDI = N,N'-bis(3-pyridylcarbonylhydrazine)-1,4,5,8-naphthalene diimide). Complex 1 exhibits a 0D mononuclear structure without photochromic behavior due to the bad conjugation of the naphthalene diimide moiety. The conformational isomers of complex 2 manifest a 3D network, showing ultra-fast photo-induced intermolecular electron transfer photochromic behavior under X-ray, UV, and visible light. However, they show different photochromic rates and coloring contrast upon photoirradiation, which originates from their difference in the distances of lone pair(COO)···π(NDI). This was realized via controlling the solvent ratio in the reaction system. In addition, compared to UV/X-ray light, 2 exhibits greater sensitivity to visible light and is an organic-inorganic hybrid material with photomodulated luminescence. Based on the excellent performance, complex 2 can be applied to filter paper, showing potential applications as an inkless printing medium and selective perception of ammonia and amine vapors in the solid state via different visual color changes.

Multistimuli-responsive materials based on a zinc(II) complex with high-contrast and multicolor switching.

The development of stimulus-responsive luminescent materials, especially those based on a single compound exhibiting multicolor and high-contrast (Δλem ≥ 100 nm) chromic properties, is a critical challenge. In this work, we synthesized and characterized a zinc(II) complex (1). As expected, 1 displays aggregation-induced emission enhancement (AIEE) in THF/H2O mixtures, and remarkable multicolor switching under external stimuli in the solid state. Complex 1 shows reversible mechanochromic luminescence behavior with a large wavelength shift (Δλem = 100 nm) during the grinding-fuming cycles, due to the phase transformation between the crystalline and amorphous states. More impressively, 1 exhibits obvious acidochromic properties (Δλem = 130 nm) which originate from the adsorption of vapor and a gas-solid reaction on the crystal surface. Furthermore, 1 exhibits electrochemical oxidation behavior accompanied by quenching of yellow-green emission due to the overlap of an emission band and an absorption band. The above-mentioned color changes under ambient light can also be observed by the naked eye during the mechanical, acid-base vapor and electrical stimulation. Based on the high-contrast and multicolor switching, complex 1 was successfully developed into test papers and films in the field of rapid detection of mechanical stimuli and HCl/NH3 vapors.

Multistimuli-Responsive Materials Based on Zn(II)-Viologen Coordination Polymers and Their Applications in Inkless Print and Anticounterfeiting.

Recently, stimuli-responsive materials have attracted great attention, while most of them respond to single or two stimuli. Thus, it is essential to design multifunctional stimuli-responsive materials and develop their applications. The strategy that constructing high-dimensional coordination polymers facilitates the application scope of a viologen-based photochromic system is put forward and confirmed for the first time. Herein, a novel multistimuli-responsive viologen-based Zn-MOF with a two-dimensional framework has been successfully designed and synthesized. Complex 1 exhibits chromic behavior under a variety of external stimuli such as 365 nm UV, X-rays, heat, electricity, and ethylamine. More interestingly, the crystal state of complex 1 displays dual fluorescence and room-temperature phosphorescence (RTP) emission and emits a yellow afterglow when turning off the UV lamp. In addition, Eu(III)-functionalized hybrids, Eu3+@Zn-MOF, were prepared by coordinated postsynthetic modification based on viologen complexes for the first time. The sample of Eu3+@Zn-MOF inherits the photochromic characteristics of the viologen complexes and gives the distinctive fluorescence of the europium ions. Based on the multicolor switching of 1 and Eu3+@Zn-MOF, their possible practical utilization was successfully developed in the fields of inkless, erasable print media, electrochromic information tag printing, information encryption, and anticounterfeiting.

De Winter electrocardiogram pattern due to type A aortic dissection: a case report.

BACKGROUND: De Winter electrocardiograph (ECG) pattern is an atypical presentation of acute myocardial infarction (AMI) due to severe stenosis of the left anterior descending (LAD). Complications of acute aortic dissection (AD) in the setting of acute myocardial infarction (AMI) with de Winter sign are relatively rare and physicians may easily miss the diagnosis of AD. We report a case of patient with acute chest pain and de Winter ECG pattern due to AD involving the left main coronary artery (LM), LAD and left circumflex artery (LCX). CASE PRESENTATION: A 57-year-old male patient was initially diagnosed with AMI and then the diagnosis of acute AD was supported by transthoracic echocardiograph (TTE). After two stents were implanted respectively into the proximal LM-LAD and LM-LCX, he recovered from cardiogenic shock. Two months later, the patient underwent the surgery of ascending aorta replacement. After the surgery, there was no obvious chest discomfort during follow-up. CONCLUSIONS: When an ECG shows a "de Winter pattern", we should also consider the possibility of AD which result in LAD occlusion. TTE is a useful tool in screening for AD. Further research is needed to prove that percutaneous coronary intervention (PCI) may be a useful treatment strategy in the case of AD leading to severe LAD occlusion and unstable hemodynamics when there's no condition to perform aortic replacement surgery immediately.

Multi-stimuli-responsive Zn(II)-Schiff base complexes adjusted by rotatable aromatic rings.

Multifunctional luminescent materials have attracted intensive interest. However, the mechanisms behind them are still to be explored. In this work, three Zn(II) complexes based on Schiff bases (HL1 and HL2) that contain rotatable aromatic rings were designed and prepared. They exhibited different mechanochromic luminescence (MCL) and acidochromism. The polymorphous ZnL12 and ZnL1a2 crystallize in different crystal systems with different conformations. The ligands in ZnL12 adopt a more twisted conformation than those in ZnL1a2. ZnL12 exhibits MCL with high contrast, while ZnL1a2 exhibits a negligible MCL property. This may be due to the looser packing of the complex induced by the more twisted conformation of the ligand HL1. ZnL12 could undergo crystal phase transformation into ZnL1a2 by grinding/fuming cycles. To increase the flexibility of the ligand, a methylene group was introduced to result in HL2, which can improve the mechanochromic luminescence effect of the Zn(II) complex with high color contrast. The ligands involved in coordination generally adopt a more twisted conformation than those free ligands due to the steric hindrance, resulting in more obvious MCL for complexes. By comparing the luminescence of ligands and their complexes under acid-base stimulation, it is found that the acidochromic properties could be attributed to the generation of ligands at the surface of complexes via the gaseous HCl-solid Zn(II) complex reaction. The high contrast mechanochromic and acidochromic luminescence properties would lead to promising potential applications of these complexes in smart fluorescent materials, and would also provide some ideas for the design of multi-stimuli responsive molecules.

Multistimulus Response of Two Tautomeric Zn(II) Complexes and Their White-Light Emission Based on Different Mechanisms.

A triphenylamine (TPA)-based 2H-quinazoline Zn(II) complex (Q-TPA-Zn) exhibiting dual fluorescence and phosphorescence emission in the solid state was designed and prepared. It possesses mechanochromic luminescence and thermochromic luminescence properties. In the solid state, the white afterglow luminescence could be observed at 77 K (CIExy: 0.27, 0.33) while cyan luminescence could be observed at 297 K. After thermolysis at 300 °C, Q-TPA-Zn could be transformed into Schiff base complex S-TPA-Zn with white fluorescence in the powder state (CIExy: 0.32, 0.38), in methanol (CIExy: 0.32, 0.39), and in dimethylformamide (CIExy: 0.26, 0.32) at room temperature. This arises from dual emission of normal* emission and tautomeric* emission induced by excited-state intramolecular proton transfer (ESIPT) from the benzimidazole NH group to the Schiff base N atom. Q-TPA-Zn could also be transformed into its isomeric form, S-TPA-Zn, through photochemical ring-opening reaction upon irradiation under 365 nm in the solution, exhibiting high-contrast photochromic luminescence. Interestingly, S-TPA-Zn could further be transformed into its zwitterionic isomer after continuous irradiation. The same ring-opening reaction could also take place for the orgainc compound Q-TPA via heating or 365 nm irradiation. The ring-opening reaction mechanism and ESIPT emission were interpreted via theoretical calculation.

A Multistimuli Responsive Crystalline Cd(II)-Viologen Coordination Polymer with Single-Crystal-Single-Crystal Transformation.

It is necessary to develop stable and fast multistimuli responsive materials due to the growing demand in our daily life. In this work, a new viologen-based Cd-complex (1) exhibits multiple thermochromic and photochromic behaviors through 10 states with 7 colors. For example, it responds to both Cu Kα/Mo Kα X-ray sources and UV dual light quickly with a color change from colorless to dark blue (1X) (Cu Kα/Mo Kα X-ray sources) and cyan (1-UV) (UV light), respectively. Interestingly, it exhibits a three-step coloration phenomenon when heated, which is unprecedented in viologen compounds. Crystal 1 undergoes a color change to pink, blue, and brown under 130, 180, and 240 °C, respectively. In addition, upon fumigation, both 1P and 1Q undergo a decoloration process to colorless (1K) and yellow (1T), respectively. Four more states (1P, 1K, 1T, and 1O) obtained via dehydration-hydration treatment are all photochromic. More importantly, via single-crystal-single-crystal transformation (SC-SC), the photochromic and thermochromic behaviors of 1 were investigated from the molecular level, which is also rather rare for thermochromic species. The detailed electron donor and the pathways for electron transfer were clearly given according to the results of crystal structure. The colorful states upon external stimuli may be attributed to the multiple pathways for electron transfer.

Multistimuli Responsive Solid-State Emission of a Zinc(II) Complex with Multicolour Switching.

The development of smart luminescent materials, especially those stimulus-responsive fluorescent materials that can switch between different colors repeatedly under external stimulation based on a single molecule, is of great significance but a challenge. In this work, a novel zinc(II)-Schiff base complex (ZnL2) was obtained and characterized. Upon exposure to the HCl and NH3 vapors, it displayed remarkable tricolor acidochromic behavior with high contrast and rapid response under the ambient light as well as UV light (365 nm). The XPS analyses of ZnL2 crystals before and after HCl/NH3 fuming show that the acidochromism originates principally from the adsorption of vapor and the gas-solid reaction equilibrium on the crystal surface. The reddish-brown color of the HCl-fumigated ZnL2 crystals could be attributed to the generation of HL at the surface of ZnL2, and red-shifted emission could be ascribed to the self-absorption effect. The single crystal X-ray diffraction data indicate that these processes cause slight changes in the molecular conformation and crystal packing. ZnL2 shows reversible mechanochromic luminescence behavior between yellow and orange emission during the grinding-fuming/heating cycles due to the modulation between amorphous and crystalline states. Moreover, ZnL2 was successfully made into test paper for the rapid detection of HCl/NH3 vapors and mechanical stimuli.

The lncRNA XIST/miR-125b-2-3p axis modulates cell proliferation and chemotherapeutic sensitivity via targeting Wee1 in colorectal cancer.

BACKGROUND: Numerous reports on microRNAs have illustrated their role in tumor growth and metastasis. Recently, a new prognostic factor, miR-125b-2-3p, has been identified for predicting chemotherapeutic sensitivity in advanced colorectal cancer (CRC). However, the specific mechanisms and biological functions of miR-125b-2-3p in advanced CRC under chemotherapy have yet to be elucidated. METHODS: MiR-125b-2-3p expression was detected by real-time PCR (RT-PCR) in CRC tissues. The effects of miR-125b-2-3p on the growth, metastasis, and drug sensitivity of CRC cells were tested in vitro and in vivo. Based on multiple databases, the upstream competitive endogenous RNAs (ceRNAs) and the downstream genes for miR-125b-2-3p were predicted by bioinformatic analysis, followed by the experiments including luciferase reporter assays, western blot assays, and so on. RESULTS: MiR-125b-2-3p was significantly lowly expressed in the tissues and cell lines of CRC. Higher expression of miR-125b-2-3p was associated with relatively lower proliferation rates and fewer metastases. Moreover, overexpressed miR-125b-2-3p remarkably improved chemotherapeutic sensitivity of CRC in vivo and in vitro. Mechanistically, miR-125b-2-3p was absorbed by long noncoding RNA (lncRNA) XIST regulating WEE1 G2 checkpoint kinase (WEE1) expression. The upregulation of miR-125b-2-3p inhibited the proliferation and epithelial-mesenchymal transition (EMT) of CRC induced by lncRNA XIST. CONCLUSIONS: Lower miR-125b-2-3p expression resulted in lower sensitivity of CRC to chemotherapy and was correlated with poorer survival of CRC patients. LncRNA XIST promoted CRC metastasis acting as a ceRNA for miR-125b-2-3p to mediate WEE1 expression. LncRNA XIST-miR-125b-2-3p-WEE1 axis not only regulated CRC growth and metastasis but also contributed to chemotherapeutic resistance to CRC.

Evolutionary dynamics and structural consequences of de novo beneficial mutations and mutant lineages arising in a constant environment.

BACKGROUND: Microbial evolution experiments can be used to study the tempo and dynamics of evolutionary change in asexual populations, founded from single clones and growing into large populations with multiple clonal lineages. High-throughput sequencing can be used to catalog de novo mutations as potential targets of selection, determine in which lineages they arise, and track the fates of those lineages. Here, we describe a long-term experimental evolution study to identify targets of selection and to determine when, where, and how often those targets are hit. RESULTS: We experimentally evolved replicate Escherichia coli populations that originated from a mutator/nonsense suppressor ancestor under glucose limitation for between 300 and 500 generations. Whole-genome, whole-population sequencing enabled us to catalog 3346 de novo mutations that reached > 1% frequency. We sequenced the genomes of 96 clones from each population when allelic diversity was greatest in order to establish whether mutations were in the same or different lineages and to depict lineage dynamics. Operon-specific mutations that enhance glucose uptake were the first to rise to high frequency, followed by global regulatory mutations. Mutations related to energy conservation, membrane biogenesis, and mitigating the impact of nonsense mutations, both ancestral and derived, arose later. New alleles were confined to relatively few loci, with many instances of identical mutations arising independently in multiple lineages, among and within replicate populations. However, most never exceeded 10% in frequency and were at a lower frequency at the end of the experiment than at their maxima, indicating clonal interference. Many alleles mapped to key structures within the proteins that they mutated, providing insight into their functional consequences. CONCLUSIONS: Overall, we find that when mutational input is increased by an ancestral defect in DNA repair, the spectrum of high-frequency beneficial mutations in a simple, constant resource-limited environment is narrow, resulting in extreme parallelism where many adaptive mutations arise but few ever go to fixation.

A multi-binding site hydrazone-based chemosensor for Zn(ii) and Cd(ii): a new strategy for the detection of metal ions in aqueous media based on aggregation-induced emission.

A multi-binding site chemosensor, N-(3-methoxy-2-hydroxybenzylidene)-3-hydroxy-2-naphthahydrazone (H3L), with excited-state intramolecular proton transfer (ESIPT) behaviour was prepared and characterized. It possesses no aggregation-induced emission (AIE) characteristics but can detect Cd2+ and Zn2+ ions selectively in the "off-on" mode based on the AIE of their complexes in the media of THF/HEPES and THF/H2O, respectively, which will provide a new strategy for target detection based on AIE. The detection limits of Zn2+ and Cd2+ were 9.85 × 10-9 M and 1.27 × 10-7 M, respectively. The aggregates of the complexes formed in the detection system were confirmed by DLS data and SEM images. The corresponding Zn2+ (1) and Cd2+ (2) complexes were prepared to investigate the response mechanism. Powder X-ray diffraction and single crystal X-ray diffraction proved that complex 1 is the species formed in the detection system. The chemosensor coordinates with the Cd2+ and Zn2+ ions in different formation and coordination modes, leading to the emission position of the aggregates at 560 and 645 nm, respectively, based on which Cd2+ ions were successfully differentiated from Zn2+ ions. Moreover, the detection of Cd2+ and Zn2+ ions was realized qualitatively via test paper and quantitatively in water.

A new family of lanthanide coordination polymers based on 3,3'-[(5-carboxylato-1,3-phenylene)bis(oxy)]dibenzoate: synthesis, crystal structures and magnetic and luminescence properties.

Six two-dimensional (2D) coordination polymers (CPs), namely, poly[{µ5-3,3-[(5-carboxylato-1,3-phenylene)bis(oxy)]dibenzoato-κ6O1:O1':O3,O3':O5:O5'}bis(N,N-dimethylformamide-κO)lanthanide(III)], [Ln(C21H11O8)(C3H7NO)2]n, with lanthanide/Ln = cerium/Ce for CP1, praseodymium/Pr for CP2, neodymium/Nd for CP3, samarium/Sm for CP4, europium/Eu for CP5 and gadolinium/Gd for CP6, have been prepared by solvothermal methods using the ligand 3,3'-[(5-carboxy-1,3-phenylene)bis(oxy)]dibenzoic acid (H3cpboda) in the presence of Ln(NO3)3. The complexes were characterized by single-crystal X-ray and powder diffraction, IR spectroscopy, elemental analysis and thermogravimetric analysis (TGA). All the structures of this family of lanthanide CPs are isomorphous with the triclinic space group P-1 and reveal that they have the same 2D network based on binuclear LnIII units, which are further extended via interlayer C-H...π interactions into a three-dimensional supramolecular structure. The carboxylate groups of the cpboda3- ligands link adjacent LnIII ions and form binuclear [Ln2(RCOO)4] secondary building units (SBUs), in which each binuclear LnIII SBU contains four carboxylate groups from different cpboda3- ligands. Moreover, with the increase of the rare-earth Ln atomic radius, the dihedral angles between the aromatic rings gradually increase. Magnetically, CP6 shows weak antiferromagnetic coupling between the GdIII ions. The solid-state luminescence properties of CP2, CP5 and CP6 were examined at ambient temperature and CP5 exhibits characteristic red emission bands derived from the Eu3+ ion (CIE 0.53, 0.31), with luminescence quantum yields of 22%. Therefore, CP5 should be regarded as a potential optical material.

A density functional study on the formaldehyde recognition by Al-doped ZnO nanosheet.

Experimental works have shown that doping ZnO nanosheets by the Al atom meaningfully increases their sensitivity toward HCHO gas. Here, we applied density functional theory calculations to study the Al-doping effect on the sensitivity of a ZnO nanosheet to HCHO gas, explaining the experimental results. We found that the pristine ZnO nanosheet weakly interacts with the HCHO with adsorption energy (Ead) of -9.3 kcal/mol, and the sensing response (S) value of 2.2 at 623 K. After the Al-doping process, the Ead and S values increase to -40.7 kcal/mol and 83.9, respectively, indicating an excellent agreement with the experimental results. We showed a relation between the HOMO-LUMO gap and the S value, confirming with the experimental results. Also, the proposed Al-doped ZnO nanosheet shows a good selectivity to HCHO gas at the presence of H2, NH3, C2H5OH, CO, and CH4 gases. A short recovery time of 18 s is predicted for Al-ZnO-based sensor which is comparable with the experimental value of 26 s. Finally, we conclude that the Al-doping makes the ZnO nanosheet a promising HCHO gas sensor with a high sensitivity, an excellent selectivity, and short recovery time.