Efficient electrocatalytic acetylene semihydrogenation by electron–rich metal sites in N–heterocyclic carbene metal complexes

Electrocatalytic acetylene semihydrogenation is a promising alternative to thermocatalytic acetylene hydrogenation due to its environmental benignity and economic efficiency, but its performance is far below that of the thermocatalytic reaction because of strong competition from side reactions, including hydrogen evolution, overhydrogenation and carbon–carbon coupling reactions. We develop N–heterocyclic carbene–metal complexes, with electron–rich metal centers owing to the strongly σ–donating N–heterocyclic carbene ligands, as electrocatalysts for selective acetylene semihydrogenation. Experimental and theoretical investigations reveal that the copper sites in N–heterocyclic carbene–copper facilitate the absorption of electrophilic acetylene and the desorption of nucleophilic ethylene, ultimately suppressing the side reactions during electrocatalytic acetylene semihydrogenation, and exhibit superior semihydrogenation performance, with faradaic efficiencies of ≥98 % under pure acetylene flow. Even in a crude ethylene feed containing 1 % acetylene (1 × 104 ppm), N–heterocyclic carbene–copper affords a specific selectivity of >99 % during a 100–h stability test, continuous ethylene production with only ~30 ppm acetylene, a large space velocity of up to 9.6 × 105 mL·gcat−1·h−1, and a turnover frequency of 2.1 × 10−2 s−1, dramatically outperforming currently reported thermocatalysts.

Melatonin - A Cutaneous Perspective

Melatonin (MLT) is an endogenous hormone secreted from the pineal gland, located deep in the brain in the epithalamus associated with numerous biological activities. The primary function of melatonin is to regulate sleep-wake cycles. However, research over the last few years has enlightened a range of functions associated with this molecule, including anti-inflammatory, direct and indirect antioxidant activity, regenerative tissue benefits, and preservation of mitochondrial function. Melatonin’s anti-inflammatory and antioxidant support, coupled with its mitochondrial modulation, makes it a vital molecule to use for skin health homeostasis. The cutaneous melatoninergic system’s widespread expression and pleiotropic activity provides for a high level of cell-specific selectivity. Several skin cells, including normal and malignant keratinocytes, melanocytes, fibroblasts and hair follicles, express melatonin receptors. Melatonin also has receptor-independent effects that protect against oxidative stress and can reduce ultraviolet radiation-induced damage. Several functions of melatonin in the skin have been experimentally implicated such as hair growth cycling, fur pigmentation, melanoma control, suppression of ultraviolet-induced damage to the skin cell. Melatonin may play a role in treating several dermatoses e.g., atopic eczema, psoriasis, melasma, ulcer healing, and malignant melanoma. There is a plethora of functional melatonin properties, which still await to be fully appreciated by dermatologists. The current review emphasizes few of the established uses and few emerging potentialities that render melatonin a promising candidate for managing several diseases.

Engineering Li/Na selectivity in 12-Crown-4–functionalized polymer membranes

Lithium is widely used in contemporary energy applications, but its isolation from natural reserves is plagued by time-consuming and costly processes. While polymer membranes could, in principle, circumvent these challenges by efficiently extracting lithium from aqueous solutions, they usually exhibit poor ion-specific selectivity. Toward this end, we have incorporated host–guest interactions into a tunable polynorbornene network by copolymerizing 1) 12-crown-4 ligands to impart ion selectivity, 2) poly(ethylene oxide) side chains to control water content, and 3) a crosslinker to form robust solids at room temperature. Single salt transport measurements indicate these materials exhibit unprecedented reverse permeability selectivity (∼2.3) for LiCl over NaCl—the highest documented to date for a dense, water-swollen polymer. As demonstrated by molecular dynamics simulations, this behavior originates from the ability of 12-crown-4 to bind Na+ ions more strongly than Li+ in an aqueous environment, which reduces Na+ mobility (relative to Li+) and offsets the increase in Na+ solubility due to binding with crown ethers. Under mixed salt conditions, 12-crown-4 functionalized membranes showed identical solubility selectivity relative to single salt conditions; however, the permeability and diffusivity selectivity of LiCl over NaCl decreased, presumably due to flux coupling. These results reveal insights for designing advanced membranes with solute-specific selectivity by utilizing host–guest interactions.

Empirical and Theoretical Evaluation of a Tree-Shaped DNA Nanostructure with a Looped Arm (L-DNA)

Several nanostructures have been created with the advent of nanotechnology. DNA has been recognized as a new building block material in addition to its genetic coding role because of its unique features (e.g., intrinsic biocompatibility, precise tenability, specific selectivity). DNA can be organized into a variety of self-assembled nanomaterials including a sphere, a ball, and even an emoticon. In particular, a tree-shaped DNA structure possessing characteristic fractural patterns is easily controlled by size and functionality and can be exploited in various fields. Here, we report an empirical and theoretical evaluation of a Y-shaped tree DNA nanostructure with a looped arm (L-DNA). The synthesized L-DNAs were analyzed for thermal and structural stability. The melting temperature (Tm) of a Y-shaped DNA (Y-DNA) as a core unit and a model DNA nanostructure comprising of central Y-DNA and looped arm were measured individually. According to the complexity (e.g., increased length of the single stranded DNA (ssDNA) used), its yield suddenly decreased with the generation of ssDNAs with distinctive secondary structures. A complicated DNA product is predicted by considering the Tm of expected secondary structures, with increased Tm with respect to variation in salt concentrations. Therefore, the new DNA nanostructure may be utilized as a platform for various practical applications.

A New Method for Standardizing Inland Fish Community Surveys: Characterizing Habitat Associated with Small-Bodied Fish Species, Abundance, and Size Distributions in a Highly Modified Estuary

Monitoring fish assemblages in estuary environments is often difficult to standardize due to habitat complexity and gear-specific selectivity. This is further compounded by conventional sampling methods which require fish handling that might cause stress or mortality. To ameliorate these issues, we developed the Single-Platform Aquatic Species and Habitat Sampling System (Platform), an integrated and mobile concentrator net and live box prototype, coupled with a range of physical monitoring equipment. The long-term goal of the Platform is to employ non-invasive sampling techniques such as video and eDNA; however, our aim in this study was to test the Platform’s ability to sample across different habitat types and detect differences in fish assemblages. We investigated the utility of the Platform over a short time period (2 mo) in a relatively small and complex embayment within the highly modified San Francisco Estuary, California. We were able to identify clear physical distinctions among estuary/delta habitat types and detect habitat segregation by ecological groups of sampled fishes with the Platform. The Platform also detected discernable ontogenetic shifts (i.e., size differences) within estuary habitats of commonly observed fish species. These initial results demonstrate the Platform’s ability to contrast fish density, size, and species diversity, which sets the stage to advance more passive monitoring techniques, including video and eDNA methods. The Platform has the potential to fill a methodological gap in non-invasive surveying of small-bodied fish across a range of estuarine habitats, warranting further investigation of potential applications.

Regional Differences in Gene Expression of Proliferating Human Choroidal Endothelial Cells

Choroidal diseases including inflammation and neovascularization seem to have predilection for different vascular beds. In order to improve our understanding of human macular choroidal angiogenic diseases, we investigate the differences in gene expression between matched human macular and peripheral inner choroidal endothelial cells (CEC) and matched human macular inner and outer CEC. The gene expression profiles of matched, unpassaged human macular and peripheral inner CEC and matched human unpassaged macular inner and outer CEC were conducted using Affymetrix GeneChip arrays. Selected differences in gene expression were validated by real-time-PCR and immunohistochemistry. No differences in probeset expression were demonstrated between inner CECs compared with peripheral inner CECs. In comparison, there was a difference of 1.6% of probesets when matched, unpassaged proliferating human macular inner CEC and macular outer CEC from the same donors were compared. Macular inner CECs demonstrated up-regulation of probesets involved in nervous system development, growth factors, PLVAP, and collagen XVI, while macular outer CECs demonstrated up-regulation of probesets involved in immune function and intracellular signalling. There was a marked homogeneity of human macular and peripheral inner CECs. This suggests that gene expression differences in inner CECs are not responsible for the site specific selectivity of choroidal neovascularisation. Variability was noted, however, in the gene expression of matched macular inner and outer CECs. This could be explained by the differences in the roles and microenvironments of the inner and outer choroid.

Bead-Immobilized Multimodal Molecular Beacon-Equipped DNA Machinery for Specific RNA Target Detection: A Prototypical Molecular Nanobiosensor

A variety of nanostructured diagnostic tools have been developed for the precise detection of known genetic variants. Molecular beacon systems are very promising tools due to their specific selectivity coupled with relatively lower cost and time requirements than existing molecular detection tools such as next generation sequencing or real-time PCR (polymerase chain reaction). However, they are prone to errors induced by secondary structure responses to environmental fluctuations, such as temperature and pH. Herein, we report a temperature-insensitive, bead-immobilized, molecular beacon-equipped novel DNA nanostructure for detection of cancer miRNA variants with the consideration of thermodynamics. This system consists of three parts: a molecular beacon for cancer-specific RNA capture, a stem body as a core template, and a single bead for solid-support. This DNA system was selectively bound to nanosized beads using avidin–biotin chemistry. Synthetic DNA nanostructures, designed based on the principle of fluorescence-resonance enhanced transfer, were effectively applied for in vitro cancer-specific RNA detection. Several parameters were optimized for higher performance, with a focus on thermodynamic stability. Theoretical issues regarding the secondary structure of a single molecular beacon and its combinatory forms were also studied. This study provides design guidelines for new sensing systems of miRNA variation for next-generation biotechnological applications.

Development of Highly Specific and Selectively Recognizing Caffeine Imprinted Polymer nanomaterials with EGDMA Crosslinker

Aims: The present study focused on selective recognition of caffeine-specific cavities in the molecularly imprinted polymer (MIP) networks. Background: The degree of crosslinking was optimized based on the template to study the rebinding capacity. Objective: The objective of the study was to selectively recognize the caffeine-specific cavities in the molecularly imprinted polymer (MIP) networks. Methods: A self-assembled co-polymerization with functional monomers (FM) as methyl acrylamide (MAA), ethylene glycol dimethyl acrylate (EDMA), cross-linking in 1:20, 40:60 ratio of FM: crosslinker, leads to caffeine with/without networks in imprinted polymers. Furthermore, the synthesized imprinted nano polymers were characterized by UV-VIS, FTIR, GC-MS, and SEM spectral analysis. The specific selective binding of caffeine and its analogues as hydrazone, naphthalene, and hypoxanthine were investigated. Results and Conclusion: It was proved from rebinding studies that imprinted nanomaterials polymers with 1:10:20, 40, and 60 (template:FM: crosslinker) had 62-70% maximum specific selectivity with particle 30-50 nm and 60-92 nm for synthesized MIPs/NIPs, respectively.

Tissue-Specific Distribution of Legacy and Emerging Organophosphorus Flame Retardants and Plasticizers in Frogs

Five types of tissues, including the liver, kidney, intestine, lung, and heart, were collected from black-spotted frogs and bullfrogs to study the tissue-specific accumulation of organophosphorus flame retardants (PFRs) and plasticizers. Thirteen PFRs and nine plasticizers were detected, with average total concentrations of 1.4–13 ng/g ww and 858–5503 ng/g ww in black-spotted frogs, 3.6–46 ng/g ww and 355–3504 ng/g ww in bullfrogs. Significant differences in pollutant concentrations among different tissues in the two frog species were found, indicating the specific selectivity distribution of PFRs and plasticizers. Overall, liver tissues exhibited significantly higher pollutant concentrations. The pollutant concentration ratios of other tissue to the sum of liver tissue and other tissues (OLR, Cother/(Cother + Cliver)) corresponding to male frogs were significantly greater than those of females, suggesting that male frogs could have higher metabolic potentials for PFRs and plasticizers. No obvious correlations between OLR and log KOW were found, indicating that the other factors (e.g., bioaccumulation pathway and metabolism) besides lipophicity could influence the deposition of PFRs and plasticizers in frog livers. Different parental transfer patterns for PFRs and plasticizers were observed in frogs when using different tissues as parental tissues. Moreover, the liver tissues had similar parental transfer mechanism with muscle tissues.

Identification of Trypanosoma cruzi Growth Inhibitors with Activity In Vivo within a Collection of Licensed Drugs

Chagas disease, caused by the parasite Trypanosoma cruzi (T. cruzi), affects more than six million people worldwide, with its greatest burden in Latin America. Available treatments present frequent toxicity and variable efficacy at the chronic phase of the infection, when the disease is usually diagnosed. Hence, development of new therapeutic strategies is urgent. Repositioning of licensed drugs stands as an attractive fast-track low-cost approach for the identification of safer and more effective chemotherapies. With this purpose we screened 32 licensed drugs for different indications against T. cruzi. We used a primary in vitro assay of Vero cells infection by T. cruzi. Five drugs showed potent activity rates against it (IC50 < 4 µmol L−1), which were also specific (selectivity index >15) with respect to host cells. T. cruzi inhibitory activity of four of them was confirmed by a secondary anti-parasitic assay based on NIH-3T3 cells. Then, we assessed toxicity to human HepG2 cells and anti-amastigote specific activity of those drugs progressed. Ultimately, atovaquone-proguanil, miltefosine, and verapamil were tested in a mouse model of acute T. cruzi infection. Miltefosine performance in vitro and in vivo encourages further investigating its use against T. cruzi.