Targeted cultivation of diatoms in mariculture wastewater by nutrient regulation and UV-C irradiation.

Mariculture wastewater poses environmental challenges due to pollution and eutrophication. Targeted cultivation of diatoms in wastewater can help alleviate these issues while generating beneficial algae biomass, however reliable operating methods are lacking. We proposed a novel method for treating mariculture wastewater that employed UV-C irradiation and nutrient regulation to achieve targeted diatom cultivation. This study first examined growth of four diatom species (Nitzschia closterium, Chaetoceros muelleri, Cyclotella atomus, and Conticribra weissflogii) in mariculture wastewater. C. muelleri and C. weissflogii demonstrated better adaptability compared to N. closterium and C. atomus. Additionally, the growth and nutrient utilization of C. muelleri were studied under varying concentrations of silicate, phosphate, ammonium, and trace elements in wastewater. Optimal growth was observed at 500 µmol/L silicate, 0.6 mg/L phosphate, and 4 mg/L ammonium. Ammonium proved to be a more effective nitrogen source than urea and nitrate in promoting growth at this low level. Surprisingly, trace element supplementation did not significantly impact growth. Finally, this study utilized UV-C irradiation as a pre-treatment method for wastewater prior to nutrient adjustment, significantly enhancing the growth of C. muelleri. Overall, this study provides guidance on regulating key nutrients and pre-treatment method to optimize diatom biomass production from mariculture wastewater. This approach not only addresses environmental challenges associated with mariculture but also contributes to sustainable aquaculture practices through the recovery of valuable aquatic resources.

Long noncoding RNA and mRNA profiling of hypothalamic-pituitary-mammary gland axis in lactating sows under heat stress.

Heat stress (HS) seriously affects sow lactation performance and Long non-coding RNAs (lncRNAs) play vital roles in the regulation of transcription and post transcription. However, the mechanism of lncRNAs expression affecting lactation performance on the hypothalamus-pituitary-mammary axis of sows is still unclear. In this study, we performed RNA sequencing and bioinformatics analysis of the hypothalamus, pituitary, and mammary gland tissues of lactating sows under HS and thermal comfort. In total, the analysis identified 658, 6021, and 6745 differently expressed (DE) mRNAs, 26, 126, and 169 DE lncRNAs between comparison groups in the hypothalamus, pituitary, and mammary glands, respectively. The hormone genes and most DE mRNAs encoding heat shock protein were differently expressed in the HS group. In addition, 2, 60, and 86 pairs of DE lncRNAs and mRNAs correlation were observed in those tissues, respectively. Some lncRNAs may be involved in the regulation of lactation performance in the HS sows.

DNA-carbon dots function as fluorescent vehicles for drug delivery.

Carbon dots (CDs) are a new representative in the carbon-based material family, attracting tremendous interest in a large variety of fields, including biomedicine. In this report, we described a facile and green system for synthesizing DNA-CDs using genomic DNA isolated from Escherichia coli. DNA-CDs can be purified using a simple column centrifugation-based system. During DNA-CD synthesis, ribose was collapsed, accompanied by the release of nitrogen, and several new bonds (C-OH, N-O, and N-P) were formed, while the other covalent bonds of DNA were largely maintained. The presence of abundant chemical groups, such as amino or hydroxyl groups on DNA-CDs, may facilitate their future functionalization. These highly biocompatible DNA-CDs can serve as a new type of fluorescent vehicle for cell imaging and drug delivery studies. Our research may hasten the development of CDs for prominent future biomedical applications.

Protein-gold hybrid nanocubes for cell imaging and drug delivery.

Multifunctional biocompatible nanomaterials containing both fluorescent and vehicle functions are highly favored in bioimaging, therapeutic, and drug delivery applications. Nevertheless, the rational design and synthesis of highly biocompatible multifunctional materials remain challenging. We present here the development of novel protein-gold hybrid nanocubes (PGHNs), which were assembled using gold nanoclusters, bovine serum albumin, and tryptophan as building blocks. The green-synthesized PGHNs in this study are blue-emitting under UV exposure and cube-shaped with a size of approximately 100 nm. These hybrid nanomaterials are highly biocompatible as shown by cytotoxicity experiments and can be readily internalized by different types of cells. Moreover, PGHNs can act as nanovehicles that successfully deliver dyes or drugs into the cells. The protein-metal hybrid nanocubes can serve as a new type of dual-purpose tool: a blue-emitting cell marker in bioimaging investigation and a nanocarrier in drug delivery studies.

Design of aromatic helical polymers for STM visualization: imaging of single and double helices with a pattern of π-π stacking.

From scanning tunneling microscopy (STM) images of rationally designed helical polymers with a pattern of π-π stacking, we successfully identified the single- and double-helical superstructures. The STM images of the helical structures revealed the smallest helical architecture (diameter ca. 1.3 nm) that has been seen so far. Furthermore, the interconversion of single and double helices was further underpinned by experimental analyses. Significantly, the formation of double helices induced different supramolecular chirality to that observed for the single helices.

Dithiothreitol-capped fluorescent gold nanoclusters: an efficient probe for detection of copper(II) ions in aqueous solution.

We report here a Green method for the synthesis of fluorescent gold nanoclusters using dithiothreitol (DTT) as both a capping agent and reducing agent at 22 °C and pH 8. The physical and chemical properties of the synthesized AuNCs@DTT were studied by TEM and UV-vis absorption, fluorescence, and X-ray photoelectron spectroscopy. AuNCs@DTT recognizes cupric ions with high selectivity and sensitivity, which allows this material to act as a copper(II) sensor in aqueous solution. A linear relationship was observed between the fluorescence intensity of the DTT capped gold nanoclusters and the concentration of copper(II) ions, in the range of 0-60 µM with a detection limit of 80 nM. The copper content in serum was also analyzed by using this copper sensor. It was shown that data obtained using the proposed method was comparable to values obtained by the traditional colorimetric method. This technique represents an alternative method for the determination of serum copper in clinical diagnosis especially for those laboratories which lack expensive analytical facilities.

Single-molecule force spectroscopy study on the mechanism of RNA disassembly in tobacco mosaic virus.

To explore the disassembly mechanism of tobacco mosaic virus (TMV), a model system for virus study, during infection, we have used single-molecule force spectroscopy to mimic and follow the process of RNA disassembly from the protein coat of TMV by the replisome (molecular motor) in vivo, under different pH and Ca(2+) concentrations. Dynamic force spectroscopy revealed the unbinding free-energy landscapes as that at pH 4.7 the disassembly process is dominated by one free-energy barrier, whereas at pH 7.0 the process is dominated by one barrier and that there exists a second barrier. The additional free-energy barrier at longer distance has been attributed to the hindrance of disordered loops within the inner channel of TMV, and the biological function of those protein loops was discussed. The combination of pH increase and Ca(2+) concentration drop could weaken RNA-protein interactions so much that the molecular motor replisome would be able to pull and disassemble the rest of the genetic RNA from the protein coat in vivo. All these facts provide supporting evidence at the single-molecule level, to our knowledge for the first time, for the cotranslational disassembly mechanism during TMV infection under physiological conditions.

Novel insights into the synergistic interaction of a thioredoxin reductase inhibitor and TRAIL: the activation of the ASK1-ERK-Sp1 pathway.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cell death in various types of cancer cells but has little or no effects on normal cells. Unfortunately, not all cancer cells respond to TRAIL; therefore, TRAIL sensitizing agents are currently being explored. Here, we reported that 6-(4-N,N-dimethylaminophenyltelluro)-6-deoxy-ß-cyclodextrin (DTCD), a cyclodextrin-derived diorganyl telluride which has been identified as an excellent inhibitor of thioredoxin reductase (TrxR), could sensitize TRAIL resistant human ovarian cancer cells to undergo apoptosis. In vitro, DTCD enhanced TRAIL-induced cytotoxicity in human ovarian cancer cells through up-regulation of DR5. Luciferase analysis and CHIP assays showed that DTCD increased DR5 promoter activity via Sp1 activation. Additionally, DTCD stimulated extracellular signal-regulated kinase (ERK) activation, while the ERK inhibitor PD98059 blocked DTCD-induced DR5 expression and suppressed binding of Sp1 to the DR5 promoter. We further demonstrated that DTCD could induce the release of ASK1 from its complex with Trx-1, and recovered its kinase activity. Meanwhile, suppression of ASK1 by RNA interference led to decreased ERK phosphorylation induced by DTCD. The underlying mechanisms reveal that Trx-1 is heavily oxidized in response to DTCD treatment, in accordance with the fact that DTCD could inhibit the activity of TrxR that reduces oxidized Trx-1. Moreover, using an A2780 xenograft model, DTCD plus TRAIL significantly inhibited the growth of tumor in vivo. Our results suggest that Trx/TrxR system inhibition may play a critical role in apoptosis by combined treatment with DTCD and TRAIL, and raise the possibility that their combination may be a promising strategy for ovarian carcinoma treatment.

Drying and nondrying layer-by-layer assembly for the fabrication of sodium silicate/TiO2 nanoparticle composite films.

Influences of drying and nondrying steps on structures of layer-by-layer (LbL) assembled sodium silicate/TiO(2) nanoparticles films (donated as silicate/TiO(2) films) have been systematically investigated. The nondrying LbL assembly produces highly porous silicate/TiO(2) films with large thickness. In contrast, the silicate/TiO(2) films fabricated with a drying step after each layer deposition are flat and thin without porous structures. In situ atomic force microscopy (AFM) measurements confirm that the sodium silicate and TiO(2) nanoparticles are deposited in their aggregated forms. A N(2) drying step can disintegrate the aggregated silicate and TiO(2) nanoparticles to produce thin silicate/TiO(2) films with compact structures. Without the drying steps, the aggregated silicate and TiO(2) nanoparticles are well retained, and their LbL assembly produces highly porous silicate/TiO(2) films of large thickness. The highly porous silicate/TiO(2) films are demonstrated to be useful as reusable film adsorbents for dye removal from wastewater because they can adsorb a large amount of cationic organic dyes and decompose them under UV irradiation. The present study is meaningful for exploring drying/nondrying steps for tailoring structure and functions of LbL assembled films.

EMSA and single-molecule force spectroscopy study of interactions between Bacillus subtilis single-stranded DNA-binding protein and single-stranded DNA.

In this article, interactions between Bacillus subtilis single-stranded DNA binding proteins (BsSSB) and single-stranded DNA (ssDNA) were systematically studied. The effect of different molar ratios between BsSSB and ssDNA on their binding modes was first investigated by electrophoretic mobility shift assays (EMSAs). It is found that a high molar ratio of BsSSB to ssDNA can produce BsSSB-ssDNA complexes formed in the mode of two proteins binding one 65-nt (nucleotide) ssDNA whereas a low molar ratio facilitates the formation of BsSSB-ssDNA complexes in the mode of one protein binding one 65-nt ssDNA. Furthermore, two binding modes are in dynamic equilibrium. The unbinding force of BsSSB-ssDNA complexes was measured quantitatively in solutions with different salt concentrations by using AFM-based single-molecule force spectroscopy (SMFS). Our results show that the unbinding force is about 10 pN higher at high salt concentration (0.5 M NaCl) than at low salt concentration (0.1 M NaCl) and the lifetime of BsSSB-ssDNA complexes at high salt concentration is twice as long as that at low salt concentration. These results indicate that more tightly packed BsSSB-ssDNA complexes can form at high salt (0.5 M NaCl) concentration. In addition, the results of EMSA show that ssDNA, which is bound to BsSSB, can dissociate from BsSSB in the presence of the cDNA strand, indicating the dynamic nature of BsSSB-ssDNA interactions.

A novel 65-mer peptide imitates the synergism of superoxide dismutase and glutathione peroxidase.

Reactive oxygen species (ROS) are involved in cell growth, differentiation, and death. Excessive amounts of ROS (e.g., O(2)(-), H(2)O(2), and HO) play a role in aging as well as in many human diseases. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) are critical antioxidant enzymes in living organisms. SOD catalyzes the dismutation of O(2)(-) to H(2)O(2), and GPx catalyzes the reduction of H(2)O(2) and other harmful peroxides by glutathione (GSH). They not only function in catalytic processes but also protect each other, resulting in more efficient removal of ROS, protection of cells against injury, and maintenance of the normal metabolism of ROS. To imitate the synergism of SOD and GPx, a 65-mer peptide (65P), containing sequences that form the domains of the active center of SOD and the catalytic triad of GPx upon the incorporation of some metals, was designed on the basis of native enzyme structural models; 65P was expressed in the cysteine auxotrophic expression system to obtain Se-65P. Se-65P was converted into Se-CuZn-65P by incorporating Cu(2+) and Zn(2+). Se-CuZn-65P exhibited high SOD and GPx activities because it has a delicate dual-activity center. The synergism of the enzyme mimic was evaluated by using an in vitro model and a xanthine/xanthine oxidase/Fe(2+)-induced mitochondrial damage model system. We anticipate that the peptide enzyme mimic with synergism is promising for the treatment of human diseases and has potential applications in medicine as a potent antioxidant.

Seleno-cyclodextrin sensitises human breast cancer cells to TRAIL-induced apoptosis through DR5 induction and NF-κB suppression.

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) exhibits potent antitumour activity via membrane receptors on cancer cells without deleterious side-effects for normal tissue. Unfortunately, like many other cancer types, breast cancer cells develop resistance to TRAIL; therefore, TRAIL-sensitising agents are currently being explored. In this study, we report that seleno-cyclodextrin (2-selenium-bridged ß-cyclodextrin, 2-SeCD), a seleno-organic compound with glutathione peroxidase (GPx)-mimetic activity, sensitises TRAIL-resistant human breast cancer cells and xenograft tumours to undergo apoptosis. In vitro, 2-SeCD reduces the viability of cancer cells by inducing cell cycle arrest in G(2)/M phase. Furthermore, 2-SeCD efficiently sensitises MDA-MB-468 and T47D cells but not untransformed human mammary epithelial cells to TRAIL-mediated apoptosis, as evidenced by enhanced caspase activity and poly-ADP-ribose-polymerase (PARP) cleavage. From a mechanistic standpoint, we show that 2-SeCD induces the expression of TRAIL receptors DR5 but not DR4 on both mRNA and protein levels in a dose-dependent manner. Moreover, 2-SeCD treatment also suppresses TRAIL-induced nuclear factor-κB (NF-κB) pro-survival pathways by preventing cytosolic IκBα degradation and p65 nuclear translocation. Consequently, the combined administration suppresses anti-apoptotic proteins transcriptionally regulated by NF-κB. In vivo, 2-SeCD and TRAIL are well tolerated in mice, and their combination significantly inhibits the growth of MDA-MB-468 xenografts and promotes apoptosis. Up-regulation of DR5 and down-regulation of NF-κB by dual treatment were also observed in tumour tissues. Overall, 2-SeCD sensitises resistant breast cancer cells to TRAIL-based apoptosis in vitro and in vivo. These findings provide strong evidence for the therapeutic potential of this combination against breast cancers.

Artificial selenoenzymes: designed and redesigned.

Enzymes, highly evolved machinery developed by nature, catalyse reactions with formidable efficiency and specificity under mild conditions. Considerable efforts have been devoted for several decades on the development of enzyme-like catalysts with tailored properties by rationally manipulating natural and artificially synthesized host molecules. One of the great challenges is to design artificial systems with catalytic efficiencies and specificities rivalling natural components. Although most of the designed artificial enzymes present mild rate promotion, the high efficiency and specificity rivalling natural ones by artificially designed system appears. In this tutorial review, we recount the methods and strategies of design and redesign of artificial selenoenzymes on synthesized and natural hosts, with emphasis on construction of the active sites of antioxidative glutathione peroxidase (GPx) by the concept of synergy between recognition and catalysis (66 references).

2-Tellurium-bridged ß-cyclodextrin, a thioredoxin reductase inhibitor, sensitizes human breast cancer cells to TRAIL-induced apoptosis through DR5 induction and NF-κB suppression.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exhibits potent antitumor activity via membrane receptors on cancer cells without deleterious side effects for normal tissue. Unfortunately, breast cancer cells, as many other cancer types, develop resistance to TRAIL; therefore, TRAIL sensitizing agents are currently being explored. 2-Tellurium-bridged ß-cyclodextrin (2-TeCD) is a synthetic organotellurium compound, with both glutathione peroxidase-like catalytic ability and thioredoxin reductase inhibitor activity. In the present study, we reported that 2-TeCD sensitized TRAIL-resistant human breast cancer cells and xenograft tumors to undergo apoptosis. In vitro, 2-TeCD efficiently sensitized MDA-MB-468 and T47D cells, but not untransformed human mammary epithelial cells, to TRAIL-mediated apoptosis, as evidenced by enhanced caspase activity and poly (adenosine diphosphate-ribose) polymerase cleavage. From a mechanistic standpoint, we showed that 2-TeCD treatment of breast cancer cells significantly upregulated the messenger RNA and protein levels of TRAIL receptor, death receptor (DR) 5, in a transcription factor Sp1-dependent manner. 2-TeCD treatment also suppressed TRAIL-induced nuclear factor-κB (NF-κB) prosurvival pathways by preventing cytosolic IκBα degradation, as well as p65 nuclear translocation. Consequently, the combined administration suppressed anti-apoptotic molecules that are transcriptionally regulated by NF-κB. In vivo, 2-TeCD and TRAIL were well tolerated in mice and their combination significantly inhibited growth of MDA-MB-468 xenografts and promoted apoptosis. Upregulation of DR5 and downregulation of NF-κB by the dual treatment were also observed in tumor tissues. Overall, 2-TeCD sensitizes resistant breast cancer cells to TRAIL-based apoptosis in vitro and in vivo. These findings provide strong evidence for the therapeutic potential of this combination against breast cancers.

Pulling genetic RNA out of tobacco mosaic virus using single-molecule force spectroscopy.

RNA-coat protein interactions in intact tobacco mosaic virus have been investigated for the first time directly on the single-molecule level by pulling the genetic RNA step by step out of the helical groove formed by its protein coat. The effects of pulling speed and pH on RNA-protein interactions are presented. In addition, the rebinding behavior of the detached RNA with the protein coat is discussed. Our results demonstrate the possibility of studying nucleic acid-protein interactions in more complicated systems using AFM-based single-molecule force spectroscopy.

Antioxidant enzyme mimics with synergism.

The antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase contribute dominatingly to enhance cellular antioxidant defense against oxidative stress. They act cooperatively to scavenge reactive oxygen species, and not one of them can singlehandedly clear all forms of reactive oxygen species. On the basis of the structural understanding for these natural enzymes, many mimics with multifunctional activities had been obtained by chemical synthesis, biosynthesis, and protein fusion techniques. Some of them display remarkable antioxidant cooperative effect in living model which possess potential application in medicine as potent antioxidants. This review summarizes aspects of some multifunctional mimics which have been reported so far.

A supramolecular bifunctional artificial enzyme with superoxide dismutase and glutathione peroxidase activities.

For constructing a bifunctional antioxidative enzyme with both superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, a supramolecular artificial enzyme was successfully constructed by the self-assembly of the Mn(III)meso-tetra[1-(1-adamantyl methyl ketone)-4-pyridyl] porphyrin (MnTPyP-M-Ad) and cyclodextrin-based telluronic acid (2-CD-TeO(3)H) through host-guest interaction in aqueous solution. The self-assembly of the adamantyl moieties of Mn(III) porphyrin and the beta-CD cavities of 2-CD-TeO(3)H was demonstrated by the NMR spectra. In this supramolecular enzyme model, the Mn(III) porphyrin center acted as an efficient active site of SOD and tellurol moiety endowed GPx activity. The SOD-like activity (IC(50)) of the new catalyst was found to be 0.116 microM and equals to 2.56% of the activity of the native SOD. Besides this, supramolecular enzyme model also showed a high GPx activity, and a remarkable rate enhancement of 27-fold compared to the well-known GPx mimic ebselen was observed. More importantly, the supramolecular artificial enzyme showed good thermal stability.

Patterned carbon nanotubes fabricated by the combination of microcontact printing and diblock copolymer micelles.

A convenient approach to synthesize patterned carbon nanotubes (CNTs) of three morphologies on printed substrates by combination of microcontact printing (microCP) and a plasma-enhanced chemical vapor deposition (PECVD) process is presented. Micelles of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) in toluene were used as nanoreactors to fabricate FeCl3 in the core domains, and the complex solution was used as an ink to print films with polydimethylsiloxane (PDMS) stamps, different morphologies (porous, dots and stripes patterns) of the FeCl3-loaded micellar films were left onto silicon substrates after printed. After removing the polymer by thermal decomposition, the left iron oxide cluster arrays on the substrate were used as catalysts for the growth of CNTs by the process of PECVD, where the CNTs uniformly distributed on the substrates according to the morphologies of patterned catalysts arrays.