Fluorescent small molecule donors.

Small molecule donors (SMDs) play subtle roles in the signaling mechanism and disease treatments. While many excellent SMDs have been developed, dosage control, targeted delivery, spatiotemporal feedback, as well as the efficiency evaluation of small molecules are still key challenges. Accordingly, fluorescent small molecule donors (FSMDs) have emerged to meet these challenges. FSMDs enable controllable release and non-invasive real-time monitoring, providing significant advantages for drug development and clinical diagnosis. Integration of FSMDs with chemotherapeutic, photodynamic or photothermal properties can take full advantage of each mode to enhance therapeutic efficacy. Given the remarkable properties and the thriving development of FSMDs, we believe a review is needed to summarize the design, triggering strategies and tracking mechanisms of FSMDs. With this review, we compiled FSMDs for most small molecules (nitric oxide, carbon monoxide, hydrogen sulfide, sulfur dioxide, reactive oxygen species and formaldehyde), and discuss recent progress concerning their molecular design, structural classification, mechanisms of generation, triggered release, structure-activity relationships, and the fluorescence response mechanism. Firstly, from the large number of fluorescent small molecular donors available, we have organized the common structures for producing different types of small molecules, providing a general strategy for the development of FSMDs. Secondly, we have classified FSMDs in terms of the respective donor types and fluorophore structures. Thirdly, we discuss the mechanisms and factors associated with the controlled release of small molecules and the regulation of the fluorescence responses, from which universal guidelines for optical properties and structure rearrangement were established, mainly involving light-controlled, enzyme-activated, reactive oxygen species-triggered, biothiol-triggered, single-electron reduction, click chemistry, and other triggering mechanisms. Fourthly, representative applications of FSMDs for trackable release, and evaluation monitoring, as well as for visible in vivo treatment are outlined, to illustrate the potential of FSMDs in drug screening and precision medicine. Finally, we discuss the opportunities and remaining challenges for the development of FSMDs for practical and clinical applications, which we anticipate will stimulate the attention of researchers in the diverse fields of chemistry, pharmacology, chemical biology and clinical chemistry. With this review, we hope to impart new understanding thereby enabling the rapid development of the next generation of FSMDs.

Visual monitoring of biocatalytic processes using small molecular fluorescent probes: strategies-mechanisms-applications.

Real-time monitoring of biocatalytic-based processes is significantly improved and simplified when they can be visualized. Visual monitoring can be achieved by integrating a fluorescent unit with the biocatalyst. Herein, we outline the design strategies of fluorescent probes for monitoring biocatalysis: (1) probes for monitoring biocatalytic transfer: γ-glutamine is linked to the fluorophore as both a recognition group and for intramolecular charge transfer (ICT) inhibition; the probe is initially in an off state and is activated via the transfer of the γ-glutamine group and the release of the free amino group, which results in restoration of the "Donor-π-Acceptor" (D-π-A) system and fluorescence recovery. (2) Probes for monitoring biocatalytic oxidation: a propylamine is connected to the fluorophore as a recognition group, which cages the hydroxyl group, leading to the inhibition of ICT; propylamine is oxidized and subsequently ß-elimination occurs, resulting in exposure of the hydroxyl group and fluorescence recovery. (3) Probes for monitoring biocatalytic reduction: a nitro group attached to a fluorophore as a fluorescence quenching group, this is converted to an amino group by catalytic reduction, resulting in fluorescence recovery. (4) Probes for monitoring biocatalytic hydrolysis: ß-D-galactopyranoside or phosphate acts as a recognition group attached to hydroxyl groups of the fluorophore; the subsequent biocatalytic hydrolysis reaction releases the hydroxyl group resulting in fluorescence recovery. Following these 4 mechanisms, fluorophores including cyanine, coumarin, rhodamine, and Nile-red, have been used to develop systems for monitoring biocatalytic reactions. We anticipate that these strategies will result in systems able to rapidly diagnose and facilitate the treatment of serious diseases.

Sulfur functionalized biocarbon sorbents for low-concentration mercury isolation.

Sulfur functionalized biocarbons were prepared from naturally abundant lignin alkali with sodium thiocyanate as an activation agent and a sulfur source. The resultant biocarbon sorbents showed a high mercury isolation ability from aqueous solutions, where high surface area and doping of sulfur significantly aid the uptake of mercury, i.e., 0.05 g of biocarbon sorbent removed 99% of mercury from 250 mL of simulated wastewater with an initial concentration of mercury of 10 mg L-1.

Establishment of a TaqMan probe-based qPCR assay for detecting microsporidia Enterospora epinepheli in grouper.

Enterospora epinepheli is an intranuclear microsporidian parasite causing serious emaciative disease in hatchery-bred juvenile groupers (Epinephelus spp.). Rapid and sensitive detection is urgently needed as its chronic infection tends to cause emaciation as well as white faeces syndrome and results in fry mortality. This study established a TaqMan probe-based real-time quantitative PCR assays targeting the small subunit rRNA (SSU) gene of E. epinepheli. The relationship between the standard curve of cycle threshold (Ct) and the logarithmic starting quantity (SQ) was determined as Ct = -3.177 lg (SQ) + 38.397. The correlation coefficient (R2 ) was 0.999, and the amplification efficiency was 106.4%. The detection limit of the TaqMan probe-based qPCR assay was 1.0 × 101 copies/µL and that is 100 times sensitive than the traditional PCR method. There is no cross-reaction with other aquatic microsporidia such as Ecytonucleospora hepatopenaei, Nucleospora hippocampi, Potaspora sp., Ameson portunus. The intra-assay and inter-assay showed great repeatability and reproducibility. In addition, the test of clinical samples showed that this assay effectively detected E. epinepheli in the grouper's intestine tissue. The established TaqMan qPCR assays will be a valuable diagnostic tool for the epidemiological investigation as well as prevention and control of E. epinepheli.

Structure-activity strategies for mechanically responsive fluorescent materials: a molecular perspective.

Mechanical response luminescence (MRL) describes the photophysical properties triggered by mechanical stimulation. Usually, MRL can be regulated by intermolecular interactions, molecular conformation or molecular packing, to achieve the desirable optical properties. Herein, at the molecular level, this review covers the factors that influence mechanically responsive fluorescent materials, involving the single- or multifactorial modulation of aliphatic chains, donor-receptor switch, substituent adjustment, and position isomerism. According to these factors, the structure-activity strategies can be summarized as: (i) the self-recovery of optical properties, from the final to initial state, can be regulated by introducing long alkyl chains to a fluorophore. (ii) The sensitivity of MRL materials can be controlled by modifying the donor-acceptor structure via the changed ICT (intramolecular charge transfer) and intramolecular interaction. (iii) The electronic and steric effects of substituents can affect ICT and intermolecular interactions, thereby resulting in high quantum yield and high-contrast MRL materials via changing the molecular stacking of crystalline states. (iv) Intermolecular interaction is modulated by the position isomerism of the substituents, which results in switched molecular packing for the extended response toward a wide range of stimuli. It is anticipated that the molecular mechanisms of these structure-activity relationships will serve as a significant reference for developing novel, high contrast, recyclable mechanical response luminous materials.

Whole-Genome Methylation Sequencing of Large Yellow Croaker (Larimichthys crocea) Liver Under Hypoxia and Acidification Stress.

Large yellow croaker (Larimichthys crocea) is an important aquaculture species in China. This study analysed whole-genome methylation differences in liver tissues of young fish under different hypoxic and acidification conditions. Differentially methylated regions (DMRs) and differentially methylated genes (DMGs) were identified. Gene ontology (GO) and Kyoto encyclopaedia of genes and genomes (KEGG) enrichment analyses of DMGs were conducted to explore the mechanism of coping with hypoxic acidification. The main methylation type was CG, accounting for > 70% of total methylation, significantly higher than CHG and CHH methylation types. GO enrichment analysis of DMGs revealed strong enrichment of nervous system development, cell periphery, plasma membrane, cell junction organisation, cell junction, signalling receptor activity, molecular sensor activity, cell-linked tissue junction organisation, cell-cell adhesion and nervous system development. KEGG enrichment analysis of DMR-related genes identified cell adhesion molecules, cortisol synthesis and secretion and aldosterone synthesis and secretion as the three key pathways regulating the physiological responses to hypoxia and acidification. Long-term hypoxic and acidification stress affected the immune system, nervous system and stress responses of large yellow croaker. Whole-genome sequencing analysis of exposed tissues was used to investigate changes that occur in L. crocea in response to hypoxic and acidic conditions at the DNA methylation level. The findings contribute to our comprehensive understanding of functional methylation in large yellow croaker and will support future research on the response mechanisms of this species under different environmental pressures.

Transcriptomic Analysis of Large Yellow Croaker (Larimichthys crocea) during Early Development under Hypoxia and Acidification Stress.

Fishes live in aquatic environments and several aquatic environmental factors have undergone recent alterations. The molecular mechanisms underlying fish responses to hypoxia and acidification stress have become a serious concern in recent years. This study revealed that hypoxia and acidification stress suppressed the growth of body length and height of the large yellow croaker (Larimichthys crocea). Subsequent transcriptome analyses of L. crocea juveniles under hypoxia, acidification, and hypoxia-acidification stress led to the identification of 5897 differentially expressed genes (DEGs) in the five groups. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that several DEGs were enriched in the 'protein digestion and absorption' pathway. Enrichment analysis revealed that this pathway was closely related to hypoxia and acidification stress in the five groups, and we found that genes of the collagen family may play a key role in this pathway. The zf-C2H2 transcription factor may play an important role in the hypoxia and acidification stress response, and novel genes were additionally identified. The results provide new clues for further research on the molecular mechanisms underlying hypoxia-acidification tolerance in L. crocea and provides a basic understanding of the potential combined effects of reduced pH and dissolved oxygen on Sciaenidae fishes.

Dietary jellyfish affect digestive enzyme activities and gut microbiota of Pampus argenteus.

For many years, jellyfish were described as 'dead ends' in marine food webs, due to their high-water content and low nutritional value. However, it has been confirmed that silver pomfret (Pampus argenteus) has a particular preference for preying on jellyfish. In this study, we determined the effect of consuming jellyfish on the intestinal microbes of silver pomfret. Analysis of bacterial 16S rRNA gene amplicons showed that jellyfish had a dramatic impact on the composition of the gut microbiota. The content of Proteobacteria was reduced from 99% to 51%, while Firmicutes, Bacteroidetes and Actinobacteria increased, accounting for 35%, 9% and 2% of the total flora, respectively. At the genus level, the content of Photobacterium decreased sharply to <1% of the total flora. By contrast, Lactobacillus, Burkholderia and Sphingomonas increased to 12%, 9% and 7% of the total flora, respectively. After feeding jellyfish, the functions of intestinal microbes and the activity of digestive enzymes also changed, resulting in better digestion and absorption of jellyfish. The results provide insights into the specific bacterial taxa within the silver pomfret intestinal microbiome that are impacted by jellyfish. Silver pomfret can better digest and absorb jellyfish by adjusting the intestinal microbial composition. The findings provide a theoretical basis for the digestive mechanism by which silver pomfret consume jellyfish.

Free-Standing N-Doped Porous Carbon Fiber Membrane Derived From Zn-MOF-74: Synthesis and Application as Anode for Sodium-Ion Battery With an Excellent Performance.

It is important to develop new energy storage and conversion technology to mitigate the energy crisis for the sustainable development of human society. In this study, free-standing porous nitrogen-doped carbon fiber (PN-CF) membranes were obtained from the pyrolysis of Zn-MOF-74/polyacrylonitrile (PAN) composite fibers, which were fabricated in situ by an electrospinning technology. The resulting free-standing fibers can be cut into membrane disks and directly used as an anode electrode without the addition of any binder or additive. The PN-CFs showed great reversible capacities of 210 mAh g-1 at a current density of 0.05 A g-1 and excellent cyclic stability of 170.5 mAh g-1 at a current density of 0.2 A g-1 after 600 cycles in sodium ion batteries (SIBs). The improved electrochemical performance of PN-CFs can be attributed to the rich porous structure derived by the incorporation of Zn-MOF-74 and nitrogen doping to promote sodium ion transportation.

Facile cyclization of sodium aminodiboranate to construct a boron-nitrogen-hydrogen ring.

A facile and efficient cyclization of sodium aminodiboranate to construct a boron-nitrogen-hydrogen ring is presented. This new strategy can be developed into a general method to prepare aminodiborane and its derivatives. Theoretical calculations show that a one-step cyclization mechanism is favored, where the dihydrogen bond plays an important role.

Solvent-Free Synthesis of CuO/HKUST-1 Composite and Its Photocatalytic Application.

A metal-organic framework (MOF) is one kind of crystalline microporous material and is increasingly used as a host of catalytically active guests. Nanostructured materials supported on MOFs have presented enhanced catalytic activity and stability. Templates or several steps are essential to the synthesis of MOF composites. Simple and effective MOF synthesis methods are still challenging. Nanosized copper oxide particles in MOF composites, described as nanosized CuO@HKUST-1, were prepared by a facile solvent-free reaction. These series of CuO@HKUST-1 composites exhibited excellent photocatalytic activity for production of hydrogen and methylene blue (MB) degradation under visible light. This synthesis method provides an effective way to fabricate MOF-related nanocomposite catalysts.

Time-series transcriptomic analysis of the kelp grouper Epinephelus moara in response to low salinity stress.

The Kelp grouper Epinephelus moara is one of the most widely consumed and economically important marine fish in China. The species can tolerate a wide range of salinity, but genomic resources are not available, and the molecular mechanisms underlying adaptation to salinity at the transcriptomic level remain largely unclear. In this study, the transcriptomic responses of the liver of E. moara under low salinity were investigated using the Illumina digital gene expression system. After de novo assembly, 499,356 transcripts were generated and contributed 445,068 unigenes. A total of 14, 19, 33 and 3101 genes were differentially expressed following exposure to low salinity stress for 2, 6, 24 and 48 h, respectively. Only two genes were differentially expressed in all groups. Four genes related to metabolism and ambient salinity adaption were randomly selected to validate the differentially expressed genes (DEGs) by real-time PCR. Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to analyse the functional significance of DEGs, including those responding to salinity through diverse biological processes, cellular components, molecular functions, and pathways associated with metabolic and osmotic responses. This work provides new insight into the response to salinity challenges in E. moara, and the findings expand our knowledge of the molecular basis of metabolic regulation mechanisms in this species. Additionally, the transcriptional data provide a valuable resource for future molecular and genetic studies on E. moara.

Characterization of TLR5 and TLR9 from silver pomfret (Pampus argenteus) and expression profiling in response to bacterial components.

Toll like receptor (TLR) 5 and 9 are important members of the TLR family that play key roles in innate immunity in all vertebrates. In this study, paTLR5 and paTLR9 were identified in silver pomfret (Pampus argenteus), a marine teleost of great economic value. Open reading frames (ORFs) of paTLR5 and paTLR9 are 2646 and 3225 bp, encoding polypeptides of 881 and 1074 amino acids, respectively. Sequence analysis revealed several conserved characteristic features, including signal peptides, leucine-rich repeat (LRR) motifs, and a Toll/interleukin-I receptor (TIR) domain. Sequence, phylogenetic and synteny analysis revealed high sequence identity with counterparts in other teleosts, confirming their correct nomenclature and conservation during evolution. Quantitative real-time PCR revealed that the that both TLRs were ubiquitously expressed in all investigated tissues, most abundantly in liver, kidney, spleen, intestine and gill, but lower in muscle and skin. In vitro immunostimulation experiments revealed that Aeromonas hydrophila lipopolysaccharide (LPS) and Vibrio anguillarum flagellin induced higher levels of paTLR9 and paTLR5 mRNA expression in isolated fish intestinal epithelial cells (FIECs) than Lactobacillus plantarum lipoteichoic acid (LTA), but all increased the secretion of IL-6 and TNF-α and induced cell apoptosis and necrosis. Together, these results indicate that paTLR5 and paTLR9 may function in the response to bacterial pathogens. Our findings enhance our understanding of the function of TLRs in the innate immune system of silver pomfret and other teleosts.

Diverse and abundant antibiotic resistance genes from mariculture sites of China's coastline.

With the rapid development of mariculture in China, large amounts of antibiotics are being discharged into the aquatic environment. Little information is available regarding antibiotics and corresponding antibiotic resistance genes (ARGs) associated with maricultural environments in China. Sediments from eleven typical mariculture areas along the whole coastline of China were collected, and the sediment in Meijijiao in southern China was used as a non-mariculture control. The results revealed that antibiotics and their corresponding ARGs were widely distributed in most maricultural sediments, and present at low concentrations in samples from Meijijiao. The sulfonamide-resistance genes were prevalent, and the sul1 and sul2 in Penglai were the highest detected by using quantitative PCR. Moreover, remarkable differences in ARGs among different sites were observed. Due to the limited availability of primers to detect ARGs, illumina high-throughput sequencing was also used for profiling ARGs, and the results showed that the abundance of bacA in all samples was the highest compared to other ARGs, followed by mexF and mexB. This is the first study to comprehensively investigate the antibiotic resistance profile in typical mariculture areas along the whole coast of China. This study provides insights into the impacts of mariculture on the profiles of bacterial and ARG compositions in China.

Cloning, characterization, and function of MyD88 in silvery pomfret (Pampus argenteus) in response to bacterial challenge.

Myeloid differentiation factor 88 (MyD88) is a key and universal downstream adapter for most Toll-like receptors (TLRs) and plays an important role in both the innate and adaptive immune response. In this study, the full-length cDNA of MyD88 (PAMyD88) from silvery pomfret (Pampus argenteus) was cloned and characterized. The PAMyD88 cDNA is 1545bp in length and contains an 876bp open reading frames (ORF). Multiple sequence alignment and phylogenetic tree analyzes revealed that the amino acid sequence of PAMyd88 was homologous to a variety of previously MyD88 molecules characterized from other species. The quantitative real-time reverse transcription-PCR analysis showed that the PAMyD88 mRNA was broadly expressed in all examined tissues, with higher levels observed in the immune-relevant organs. The results showed a significant up-regulation of the TLR2 and PAMyD88 transcript levels in response to L. plantarum and C. butyricum and a substantial expression level of TLR4 and PAMyD88 induced by V. anguillarum. Additionally, a challenge with V. anguillarum resulted in significant apoptosis, whereas the L. plantarum and C. butyricum induced only low levels of apoptosis. These data provide insight into the roles of PAMyD88 in the TLR signaling pathway in response to probiotic and pathogenic bacteria in silvery pomfrets.

Hierarchical Metal-Organic Framework Hybrids: Perturbation-Assisted Nanofusion Synthesis.

Metal-organic frameworks (MOFs) represent a new family of microporous materials; however, microporous-mesoporous hierarchical MOF materials have been less investigated because of the lack of simple, reliable methods to introduce mesopores to the crystalline microporous particles. State-of-the-art MOF hierarchical materials have been prepared by ligand extension methods or by using a template, resulting in intrinsic mesopores of longer ligands or replicated pores from template agents, respectively. However, mesoporous MOF materials obtained through ligand extension often collapse in the absence of guest molecules, which dramatically reduces the size of the pore aperture. Although the template-directed strategy allows for the preparation of hierarchical materials with larger mesopores, the latter requires a template removal step, which may result in the collapse of the implemented mesopores. Recently, a general template-free synthesis of hierarchical microporous crystalline frameworks, such as MOFs and Prussian blue analogues (PBAs), has been reported. This new method is based on the kinetically controlled precipitation (perturbation), with simultaneous condensation and redissolution of polymorphic nanocrystallites in the mother liquor. This method further eliminates the use of extended organic ligands and the micropores do not collapse upon removal of trapped guest solvent molecules, thus yielding hierarchical MOF materials with intriguing porosity in the gram scale. The hierarchical MOF materials prepared in this way exhibited exceptional properties when tested for the adsorption of large organic dyes over their corresponding microporous frameworks, due to the enhanced pore accessibility and electrolyte diffusion within the mesopores. As for PBAs, the pore size distribution of these materials can be tailored by changing the metals substituting Fe cations in the PB lattice. For these, the textural mesopores increased from approximately 10 nm for Cu analogue (mesoCuHCF), to 16 nm in Co substituted compound (mesoCoHCF), and to as large as 30 nm for the Ni derivative (mesoNiHCF). While bulk PB and analogues have a higher capacitance than hierarchical analogues for Na-batteries, the increased accessibility to the microporous channels of PBAs allow for faster intercalated ion exchange and diffusion than in bulk PBA crystals. Thus, hierarchical PBAs are promising candidates for electrodes in future electrochemical energy storage devices with faster charge-discharge rates than batteries, namely pseudocapacitors. Finally, this new synthetic method opens the possibility to prepare hierarchical materials having bimodal distribution of mesopores, and to tailor the structural properties of MOFs for different applications, including contrasting agents for MRI, and drug delivery.

Hierarchically superstructured prussian blue analogues: spontaneous assembly synthesis and applications as pseudocapacitive materials.

Hierarchically superstructured Prussian blue analogues (hexacyanoferrate, M=Ni(II) , Co(II) and Cu(II) ) are synthesized through a spontaneous assembly technique. In sharp contrast to macroporous-only Prussian blue analogues, the hierarchically superstructured porous Prussian blue materials are demonstrated to possess a high capacitance, which is similar to those of the conventional hybrid graphene/MnO2 nanostructured textiles. Because sodium or potassium ions are involved in energy storage processes, more environmentally neutral electrolytes can be utilized, making the superstructured porous Prussian blue analogues a great contender for applications as high-performance pseudocapacitors.

Encapsulation of large dye molecules in hierarchically superstructured metal-organic frameworks.

Microporous metal-organic frameworks (MOFs) represent a new family of microporous materials, offering potential applications in gas separation and storage, catalysis, and membranes. The engineering of hierarchical superstructured MOFs, i.e., fabricating mesopores in microporous frameworks during the crystallization stage is expected to serve a myriad of applications for molecular adsorption, drug delivery, and catalysis. However, MOFs with mesopores are rarely studied because of the lack of a simple, effective way to construct mesoscale cavities in the structures. Here, we report the use of a perturbation-assisted nanofusion technique to construct hierarchically superstructured MOFs. In particular, the mesopores in the MOF structure enabled the confinement of large dye species, resulting in fluorescent MOF materials, which can serve as a new type of ratiometric luminescent sensors for typical volatile organic compounds.

Mesoporous Prussian blue analogues: template-free synthesis and sodium-ion battery applications.

The synthesis of mesoporous Prussian blue analogues through a template-free methodology and the application of these mesoporous materials as high-performance cathode materials in sodium-ion batteries is presented. Crystalline mesostructures were produced through a synergistically coupled nanocrystal formation and aggregation mechanism. As cathodes for sodium-ion batteries, the Prussian blue analogues all show a reversible capacity of 65 mA h g-1 at low current rate and show excellent cycle stability. The reported method stands as an environmentally friendly and low-cost alternative to hard or soft templating for the fabrication of mesoporous materials.