Novel Au Catalysis Strategy for the Synthesis of Au@Pt Core-Shell Nanoelectrocatalyst with Self-Controlled Quasi-Monolayer Pt Skin

Design of catalytically active Pt-based catalysts with minimizing the usage of Pt is a major issue in fuel cells. Herein, for the first time, we have developed a Au catalytic reduction strategy to synthesize a Au@Pt core-shell electrocatalyst with a quasi-monolayer Pt skin spontaneously formed from the gold surface catalysis. In the presence of presynthesized gold nanocrystals (used as the catalyst and Au seeds) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (used as reductant), under the Au surface catalysis, platinum ions can be reduced and deposited on the gold nanocrystals to form a Pt skin surface with a quasi-monatomic thickness. In the present strategy, Pt ions can be reduced only under the catalysis of gold surface and thus when the surface of Au NPs is covered by a monatomic Pt layer, the reduction reaction of Pt ions will be spontaneously turned off. Therefore, the significant advantage of this synthesis strategy is that the formation of quasi-monolayer Pt skin surface can be self-controlled and is completely free of controlling the dosage of platinum ions and the size distribution of Au cores. The synthesized Au@Pt core@shell structure exhibited enhanced electrocatalytic activities for oxygen reduction reaction and methanol oxidation reaction, which are 6.87 and 10.17 times greater than those of Pt/C catalyst, respectively. The present study provides a new strategy for obtaining high-performance bimetallic/multimetallic electrocatalysts with high utilization of precious metals.

Impact and consequences of polyphenols and fructooligosaccharide interplay on gut microbiota in rats

Both fructooligosaccharide (FOS) and polyphenols can be individually and directly transferred to the large intestine of mammals and are beneficial for human health as they reshape the composition of gut microbiota. The combination impact of FOS and polyphenols on rats' gut microbiota and the corresponding consequences on rats were investigated via MiSeq sequencing technique and bioinformatics. The results showed that the combination of different phenolic compounds and FOS displayed distinct impact on the host. The addition of catechin to a FOS diet inhibited Firmicutes and enhanced Bacteroidetes. Moreover, the content of each short chain fatty acid fluctuated in various groups because different unique bacterial species survived or were inhibited under three conditions. On the other aspects, the supplement of catechin controlled the body weight (BW), up-regulated serum leptin, induced more soluble carbohydrates and less soluble polysaccharides in feces, and inhibited or activated some specific genera. The inhibition of genera by catechin could be responsible for the degradation of carbohydrates in gut and the activation of genera might be keystones for the increment of serum leptin. The effect of consuming FOS and/or polyphenols on the health of hosts needs to be further explored.

Printable Fluorescent Hydrogels Based on Self-Assembling Peptides

Fluorescent hydrogels (FH) have a variety of potential applications in the field of soft electronics. However, fabrication of mechanically stable and printable fluorescent hydrogels remains challenging. Here, we report a kind of fluorescent hydrogel based on the co-assembly of peptide motif and transition metal ions. The metal ions are captured in the hydrogel network at specific positions through covalently linked ligands on the peptide hydrogelators. This efficiently prevents the aggregation and self-quenching of organometallic chromophores. In addition, the formation of metal-ligand complexes introduces additional interactions to stabilize the hydrogel network, making the FH even more stable after the incorporation of metal ions. The FH is optically transparent but highly fluorescent. By using three different metal ions, the white light fluorescent supramolecular hydrogel has been achieved. As a proof-of-principle, we demonstrate the printability of the hydrogels to various patterns. We anticipate that with the improved fluorescent performance and stability, this kind of FH can find broad applications in extrusion-based 3D printing for the construction of soft electronics.

How many differentially expressed genes: A perspective from the comparison of genotypic and phenotypic distances

Identifying differentially expressed genes is critical in microarray data analysis. Many methods have been developed by combining p-value, fold-change, and various statistical models to determine these genes. When using these methods, it is necessary to set up various pre-determined cutoff values. However, many of these cutoff values are somewhat arbitrary and may not have clear connections to biology. In this study, a genetic distance method based on gene expression level was developed to analyze eight sets of microarray data extracted from the GEO database. Since the genes used in distance calculation have been ranked by fold-change, the genetic distance becomes more stable when adding more genes in the calculation, indicating there is an optimal set of genes which are sufficient to characterize the stable difference between samples. This set of genes is differentially expressed genes representing both the genotypic and phenotypic differences between samples.

Zoledronic acid, an FPPS inhibitor, ameliorates liver steatosis through inhibiting hepatic de novo lipogenesis

Currently, there is no standard therapy for non-alcoholic fatty liver disease (NAFLD), and statins have been developed as a first-line pharmaceutical therapeutic option for NAFLD-associated dyslipidemia. However, prolonged statins therapy has side effects, as statins inhibit HMG-CoA reductase, an enzyme at the very beginning of the mevalonate pathway. Here, we found that zoledronic acid (ZA), an inhibitor of farnesyl diphosphate synthase in the downstream mevalonate pathway, could attenuate hepatic lipid accumulation and improve liver injury in both high-fat diet-induced C57BL/6J mice and ob/ob mice. Moreover, the hepatic lipid metabolism was largely inhibited after ZA administration in high-fat diet-induced obese mice. Mechanically, ZA inhibited SREBP-1c-mediated de novo lipogenesis through suppressing RhoA activation via decreasing farnesyl diphosphate and geranylgeranyl diphosphate levels. In conclusion, our data provide a novel application of ZA in improving hepatic steatosis.

Consensus datasets of mouse miRNA-mRNA interactions from multiple online resources

MiRNAs regulate gene expression by forming base pairing with mRNAs to inhibit the translation of those mRNAs. In many mammalian genomes each, about 2000 miRNAs were found to regulate roughly 60% of all the genes in that genome. Many experimental validations and computational predictions have been done on miRNA:mRNA interactions. Nonetheless, the interactions from different sources are not always consistent. In this study, we integrated multiple online resources, including mirTarBase, TarBase, miRanda, miRDB, PITA, and TargetScan, and developed eleven large-scale datasets containing miRNA:mRNA interactions that are consistent among a specific subgroup of above-mentioned online resources. In addition, a new integrated confidence score was designed to show the significance for all the miRNA:mRNA interactions.

Antibacterial activities and preservative effect of chitosan oligosaccharide Maillard reaction products on Penaeus vannamei

The purpose of this study was to understand the influence of Maillard reaction (MR) on bioactivity of chitosan oligosaccharide (COS). The antibacterial activity against Pseudomonas aeruginosa and Vibrio parahaemolyticus and preservative effect of two kinds of COS MR products (MRPs) on Penaeus vannamei were evaluated. The structures of CG (MRPs of COS and glucose) and CM (MRPs of COS and maltose) were characterized by FT-IR and their molecular weights were measured by gel permeation chromatography (GPC). The results showed that CG has enhanced antibacterial activity and preservative effect compared to COS by evaluating total volatile base-nitrogen (TVB-N), trimethylamine (TMA), pH, total bacterial count (TBC) and sensory evaluation. Meanwhile, CM showed decreased antibacterial activity and preservative effect compared to COS by evaluating TMA, pH and TBC. The results indicated that antibacterial activity and preservative effect of COS increased or decreased after MR. In other words, the type of reducing sugar involved in MR had a great impact on the functional properties of COS-saccharide MRPs and their application to be used as a food preservative.

Effect of different levels of protein concentrates supplementation on the growth performance, plasma amino acids profile and mTOR cascade genes expression in early-weaned yak calves

Objective

This study evaluated the effects of different levels of protein concentrate supplementation on the growth performance of yak calves, and correlated the growth rate to changes occurring in the plasma- amino acids, -insulin profile, and signaling activity of mammalian target of rapamycin (mTOR) cascade to characterize the mechanism through which the protein synthesis can be improved in early weaned yaks.

Methods

For this study, 48 early (3 months old) weaned yak calves were selected, and assigned into four dietary treatments according to randomized complete block design. The four blocks were balanced for body weight and sex. The yaks were either grazed on natural pasture (control diet) in a single herd or the grazing yaks was supplemented with one of the three protein rich supplements containing low (17%; LP), medium (19%; MP), or high (21%; HP) levels of crude proteins for a period of 30 days.

Results

Results showed that the average daily gain of calves increased (0.14 vs 0.23–0.26 kg; p<0.05) with protein concentrates supplementation. The concentration of plasma methionine increased (p<0.05; 8.6 vs 10.1–12.4 μmol/L), while those of serine and tyrosine did not change (p>0.05) when the grazing calves were supplemented with protein concentrates. Compared to control diet, the insulin level of calves increased (p<0.05; 1.86 vs 2.16–2.54 μIU/mL) with supplementation of protein concentrates. Addition of protein concentrates up-regulated (p<0.05) expression of mTOR-raptor, mammalian vacuolar protein sorting 34 homolog, the translational regulators eukaryotic translation initiation factor 4E binding protein 1, and S6 kinase 1 genes in both Longissimus dorsi and semitendinosus. In contrast, the expression of sequestosome 1 was down-regulated in the concentrate supplemented calves.

Conclusion

Our results show that protein supplementation improves the growth performance of early weaned yak calves, and that plasma methionine and insulin concentrations were the key mediator for gene expression and protein deposition in the muscles.

Employing shells to eliminate concentration quenching in photonic upconversion nanostructure

It is generally accepted that a lanthanide ions based upconversion material follows an activator low doping strategy (normally <3 mol%), because of the restriction of the harmful concentration quenching effect. Here, we demonstrate that this limitation can be broken in nanostructures. Simply by using an inert shell coating strategy, the concentration quenching effect for the activator (Er³⁺) could be eliminated and highly efficient upconversion luminescence realized in the activator fully doped nanostructure, e.g. NaErF₄@NaYF₄. More importantly, this novel nanostructure achieves some long-cherished desires, such as multiple-band co-excitation (∼800 nm, ∼980 nm and ∼1530 nm) and monochromic red emission. Proof-of-concept experiments are presented of the potential benefit of this structure in solar cells and anti-counterfeiting. This nanostructure offers new possibilities in realizing high upconversion emission and novel functionalities of lanthanide based nanomaterials.

Airplane wing deformation and flight flutter detection method by using three-dimensional speckle image correlation technology

Airplane wing deformation is an important element of aerodynamic characteristics, structure design, and fatigue analysis for aircraft manufacturing, as well as a main test content of certification regarding flutter for airplanes. This paper presents a novel real-time detection method for wing deformation and flight flutter detection by using three-dimensional speckle image correlation technology. Speckle patterns whose positions are determined through the vibration characteristic of the aircraft are coated on the wing; then the speckle patterns are imaged by CCD cameras which are mounted inside the aircraft cabin. In order to reduce the computation, a matching technique based on Geodetic Systems Incorporated coded points combined with the classical epipolar constraint is proposed, and a displacement vector map for the aircraft wing can be obtained through comparing the coordinates of speckle points before and after deformation. Finally, verification experiments containing static and dynamic tests by using an aircraft wing model demonstrate the accuracy and effectiveness of the proposed method.

Multiporous Supramolecular Microspheres for Artificial Photosynthesis

Artificial photosynthesis shows a promising potential for sustainable supply of nutritional ingredients. While most studies focus on the assembly of the light-sensitive chromophores to 1-D architectures in an artificial photosynthesis system, other supramolecular morphologies, especially bioinspired ones, which may have more efficient light-harvesting properties, have been far less studied. Here, MCpP-FF, a bioinspired building block fabricated by conjugating porphyrin and diphenylalanine, was designed to self-assemble into nanofibers-based multiporous microspheres. The highly organized aromatic moieties result in extensive excitation red-shifts and notable electron transfer, thus leading to a remarkable attenuated fluorescence decay and broad-spectrum light sensitivity of the microspheres. Moreover, the enhanced photoelectron production and transfer capability of the microspheres are demonstrated, making them ideal candidates for sunlight-sensitive antennas in artificial photosynthesis. These properties induce a high turnover frequency of NADH, which can be used to produce bioproducts in biocatalytic reactions. In addition, the direct electron transfer makes external mediators unnecessary, and the insolubility of the microspheres in water allows their easy retrieval for sustainable applications. Our findings demonstrate an alternative to design new platforms for artificial photosynthesis, as well as a new type of bioinspired, supramolecular multiporous materials.

Improving prediction accuracy using decision-tree-based meta-strategy and multi-threshold sequential-voting exemplified by miRNA target prediction

Lots of computational predictors have been developed for fast and large-scale analysis of biological data. However, many of them were developed long time ago when training datasets or sets of input features were rather small. Consequently, the utility of these predictors in much large datasets, which are very common in nowadays, need to be examined carefully. In addition, with the rapid development of scientific research, the expectation on the prediction accuracy of computational predictors is continuously uplifting. Therefore, developing novel strategies to improve the prediction accuracies of computational predictors becomes critical. In this study, the predictive results of existing individual miRNA target predictors were integrated into a decision-tree to make meta-prediction. When the multi-threshold sequential-voting technique was used, the prediction accuracy of the decision-tree was significantly improved by at least thirty percentage points compared to the individual predictors.

Precipitation and temperature drive seasonal variation in bioaccumulation of polycyclic aromatic hydrocarbons in the planktonic food webs of a subtropical shallow eutrophic lake in China

Hydrophobic organic contaminants (HOCs) are toxic and ubiquitous in aquatic environments and pose great risks to aquatic organisms. Bioaccumulation by plankton is the first step for HOCs to enter aquatic food webs. Trophic status is considered to dominate variations in bioaccumulation of HOCs in plankton in temperate and frigid deep oligotrophic waters. However, long-term driving factors for bioaccumulation of HOCs in planktonic food webs of subtropical shallow eutrophic waters have not been well investigated. China has the largest subtropical lake density in the Northern Hemisphere. Due to limited field data, long-term variations in the bioaccumulation of HOCs in these lakes are almost unknown. Here we take Lake Xuanwu as an example to investigate long-term variations in the bioaccumulation, and biomagnification of polycyclic aromatic hydrocarbon (PAHs) in planktonic food webs of subtropical shallow eutrophic lakes in China, and elucidate the driving factors. Our results indicate that temperature rather than nutrients dominates long-term dynamics of planktonic biomass in this lake. Precipitation significantly enhances the concentrations of the PAHs, and total suspended particles, and consequently affects the distribution of the PAHs in the water column. Biomass dilution induced by temperature dominates bioaccumulation of the PAHs by both phytoplankton and zooplankton (copepods and cladocerans). Biomagnification of the PAHs from phytoplankton to zooplankton is positively correlated with temperature. Our study suggests that temperature and precipitation drive long-term variations in the bioaccumulation of the PAHs in the planktonic food webs of this subtropical shallow eutrophic lake. Lake Xuanwu has a similar mean annual temperature, annual precipitation, sunshine duration, and nutrient levels as other subtropical shallow eutrophic lakes in China. This study may also help to understand the bioaccumulation of HOCs in planktonic food webs of other subtropical shallow eutrophic lakes.

Effects of climate change on bioaccumulation and biomagnification of polycyclic aromatic hydrocarbons in the planktonic food web of a subtropical shallow eutrophic lake in China

To date effects of climate change on bioaccumulation and biomagnification of chemical pollutants in planktonic food webs have rarely been studied. Recruitments of plankton have shifted earlier due to global warming. Global warming and precipitation patterns are projected to shift seasonally. Whether and how the shifts in plankton phenology induced by climate change will impact bioaccumulation and biomagnification of chemical pollutants, and how they will respond to climate change are largely unknown. Here, we combine data analysis of the past seven decades, high temporal resolution monitoring and model development to test this hypothesis with nine polycyclic aromatic hydrocarbons (PAHs) in the planktonic food web of a subtropical shallow eutrophic lake in China. We find biphasic correlations between both bioconcentration factors and bioaccumulation factors of the PAHs and the mean temperature, which depend on the recruitment temperatures of cyanobacteria, and copepods and cladocerans. The positive correlations between bioconcentration factors, bioaccumulation factors and the mean temperature will be observed less than approximately 13-18 days by 2050-2060 due to the shifts in plankton phenology. The PAHs and their bioaccumulation and biomagnification will respond seasonally and differently to climate change. Bioaccumulation of most of the PAHs will decrease with global warming, with higher decreasing rates appearing in winter and spring. Biomagnification of most of the PAHs from phytoplankton to zooplankton will increase with global warming, with higher increasing rates appearing in winter and spring. Our study provides novel insights into bioaccumulation and biomagnification of chemical pollutants in eutrophic waters under climate change scenarios.

Exogenous substances regulate silkworm fat body protein synthesis through MAPK and PI3K/Akt signaling pathways

Insect fat body is an important intermediate metabolic organ that plays an important role in protein metabolism and detoxification. In order to study the effects of TiO₂ NPs and phoxim on fat body protein synthesis through MAPK and PI3K/Akt signaling pathways in silkworms, we determined the effects of TiO₂ NPs and phoxim, alone and in combination, on fat body protein content of silkworms, analyzed the gene expression profile of the fat body, and verified the expression of characteristic genes. We found that TiO₂ NPs and phoxim alone increased the total protein content of the fat body, and up-regulated MAPK and PI3K/Akt signaling pathway genes. TiO₂ NPs up-regulated the expression of two growth and development-related genes-insulin-like peptide and neuropeptide receptor B-by 5.17 and 3.89-fold, respectively. Phoxim up-regulated the expression of detoxification genes-P450, GST, and CarE2. Pretreatment with TiO₂ NPs could reduce phoxim-increased total protein content and up-regulated MAPK and PI3K/Akt signaling pathway genes and detoxification genes; the activities of detoxification enzymes were consistent with the gene expression pattern. Our results showed that MAPK and PI3K/Akt signaling pathways both regulate fat body protein synthesis in silkworms, but the target proteins induced to express were different under different inducing factors. Our finding may provide a reference for investigating the mechanism of protein synthesis regulation through MAPK and PI3K/Akt signaling pathways.

Sublethal dose of phoxim and Bombyx mori nucleopolyhedrovirus interact to elevate silkworm mortality

BACKGROUND

Silkworm (Bombyx mori) is an economically important insect. It is relatively less resistant to certain chemicals and environment exposures such as pesticides and pathogens. After pesticide exposures, the silkworms are more susceptible to microbial infections. The mechanism underlying the susceptibility might be related to immune response and oxidative stress.

RESULTS

A sublethal dose of phoxim combined with Bombyx mori nucleopolyhedrovirus (BmNPV) elevated the silkworm mortality at 96 h. We found a higher content of H₂ O₂ and increased levels of genes related to oxidative stress and immune response after treatment with a sublethal dose of phoxim for 24 h or 48 h. However, such response decreased with longer pesticide treatment. Mortality increased by 44% when B. mori was exposed to combined treatment with BmNPV and phoxim rather than BmNPV alone. The level of examined immune-related and oxidative-stress-related genes significantly decreased in the combined treatment group compared with the BmNPV group. Our results indicated that, with long-term exposure to pesticides such as OPs, even at sublethal dose, the oxidative stress response and immune responses in silkworm were inhibited, which may lead to further immune impairment and accumulation of oxidative stress, resulting in susceptibility to the virus and harm to the silkworm.

CONCLUSION

Our study provided insights for understanding the susceptibility to pathogen after pesticide exposures, which may promote the development of better pesticide controls to avoid significant economic losses. © 2016 Society of Chemical Industry.

Distribution and enantiomeric profiles of organochlorine pesticides in surface sediments from the Bering Sea, Chukchi Sea and adjacent Arctic areas

The spatial distribution, compositional profiles, and enantiomer fractions (EFs) of organochlorine pesticides (OCPs), including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and chlordanes (CHLs), in the surface sediments in the Bering Sea, Chukchi Sea and adjacent areas were investigated. The total concentrations of DDTs, HCHs and CHLs varied from 0.64 to 3.17 ng/g dw, 0.19-0.65 ng/g dw, and 0.03-0.16 ng/g dw, respectively. No significant difference was observed between the Bering Sea and Chukchi Sea for most pollutants except for trans-CHL, ΣCHLs (sum of trans- and cis-chlordane) and p,p'-DDD. Concentration ratios (e.g., α-HCH/γ-HCH, o,p'-DDT/p,p'-DDT) indicated that the contamination in the studied areas may result from inputs from multiple sources (e.g., historical usage of technical HCHs as well as new input of dicofol). Chiral analysis showed great variation in the enantioselective degradation of OCPs, resulting in excess of (+)-enantiomer for α-HCH in thirty of the 32 detectable samples, preferential depletion of (-)-enantiomer for o,p'-DDT in nineteen of the 35 detectable samples, and nonracemic in most samples for trans- and cis-chlordane. The ecological risks of the individual OCPs as well as the mixture were assessed based on the calculation of toxic units (TUs), and the results showed the predominance of DDT and γ-HCH in the mixture toxicity of the sediment. Overall, the TUs of OCPs in sediments from both the Bering and Chukchi Seas are less than one, indicating low ecological risk potential.

Dissolved nitrous oxide and emission relating to denitrification across the Poyang Lake aquatic continuum

Most aquatic ecosystems contribute elevated N₂O to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland to lake to downriver, the study was conducted on spatial variations in N₂O emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the N₂O concentrations, the ratio of N₂O/dinitrogen (N₂) gases production, N₂O emission and denitrification rates ranged from 0.10 to 1.11μgN/L, -0.007% to 0.051%, -9.73 to 127μgN/m²/hr and 1.33×10⁴ to 31.9×10⁴μgN₂/m²/hr, respectively, across the continuum. The average N₂O concentrations, the ratio of N₂O/N₂ and N₂O emission was significantly lower in wetlands as compared to the rivers and lake (p<0.01). The significantly high denitrification rate and low N₂O emission together highlighted that most N₂O can be converted into N₂ via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact N₂O budget in an integrated aquatic ecosystems. Moreover, N₂O emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.

Exposure to famine in early life and the risk of obesity in adulthood in Qingdao: Evidence from the 1959-1961 Chinese famine

BACKGROUND AND AIMS

We aimed to evaluate the association between famine exposure during early life and obesity and obesity_max (obese at the highest weight) in adulthood.

METHODS AND RESULTS

Data were from two population-based cross-sectional surveys conducted in 2006 and 2009 in Qingdao, China. A total of 8185 subjects born between 1/1/1941 and 12/31/1971 were categorized into unexposed (born between 01/01/1962 and 12/31/1971), fetal/infant exposed (born between 01/01/1959 and 12/31/1961), childhood exposed (born between 01/01/1949 and 12/31/1958) and adolescence exposed (born between 01/01/1941 and 12/31/1948) according to their age when exposed to the Chinese famine from 1959 to 1961. Obesity was defined as BMI (body mass index) ≥28.0 and obesity_max was defined as BMI_max (BMI at the highest weight) ≥28.0. We compared fetal/infant exposed, childhood exposed and adolescence exposed to the unexposed using logistic regression models to assess the effect of famine exposure on later obesity and obesity_max. Fetal/infant exposed (OR = 1.59, P < 0.001), childhood exposed (OR = 1.42, P < 0.01) and adolescence exposed (OR = 1.86, P < 0.01) all had higher risks of obesity than the unexposed. Exposure groups were more likely to be obese at their highest weight than the unexposed, and ORs (95%CIs) for obesity_max in the fetal/infant exposed, childhood exposed and adolescence exposed were 1.49(1.20-1.86), 1.24(1.02-1.49) and 1.64 (1.40-1.93), respectively. Similar results were found in both men and women.

CONCLUSION

Exposure to famine in early life was associated with increased risks of obesity and obesity_max in adulthood. Preventing undernutrition in early life appears beneficial to reduce the prevalence of later obesity.

B. amyloliquefaciens TCCC 11319, a new Cr(iii)-tolerant bacterium for chromium-tanned leather shaving disposal

A strain of B. amyloliquefaciens, TCCC11319, was isolated from tannery soil and identified by 16S rRNA gene sequencing.

Integrated Strategy Improves the Prediction Accuracy of miRNA in Large Dataset

MiRNAs are short non-coding RNAs of about 22 nucleotides, which play critical roles in gene expression regulation. The biogenesis of miRNAs is largely determined by the sequence and structural features of their parental RNA molecules. Based on these features, multiple computational tools have been developed to predict if RNA transcripts contain miRNAs or not. Although being very successful, these predictors started to face multiple challenges in recent years. Many predictors were optimized using datasets of hundreds of miRNA samples. The sizes of these datasets are much smaller than the number of known miRNAs. Consequently, the prediction accuracy of these predictors in large dataset becomes unknown and needs to be re-tested. In addition, many predictors were optimized for either high sensitivity or high specificity. These optimization strategies may bring in serious limitations in applications. Moreover, to meet continuously raised expectations on these computational tools, improving the prediction accuracy becomes extremely important. In this study, a meta-predictor mirMeta was developed by integrating a set of non-linear transformations with meta-strategy. More specifically, the outputs of five individual predictors were first preprocessed using non-linear transformations, and then fed into an artificial neural network to make the meta-prediction. The prediction accuracy of meta-predictor was validated using both multi-fold cross-validation and independent dataset. The final accuracy of meta-predictor in newly-designed large dataset is improved by 7% to 93%. The meta-predictor is also proved to be less dependent on datasets, as well as has refined balance between sensitivity and specificity. This study has two folds of importance: First, it shows that the combination of non-linear transformations and artificial neural networks improves the prediction accuracy of individual predictors. Second, a new miRNA predictor with significantly improved prediction accuracy is developed for the community for identifying novel miRNAs and the complete set of miRNAs. Source code is available at:https://github.com/xueLab/mirMeta

Accurate Quantitative Sensing of Intracellular pH based on Self-ratiometric Upconversion Luminescent Nanoprobe

Accurate quantitation of intracellular pH (pH_i) is of great importance in revealing the cellular activities and early warning of diseases. A series of fluorescence-based nano-bioprobes composed of different nanoparticles or/and dye pairs have already been developed for pH_i sensing. Till now, biological auto-fluorescence background upon UV-Vis excitation and severe photo-bleaching of dyes are the two main factors impeding the accurate quantitative detection of pH_i. Herein, we have developed a self-ratiometric luminescence nanoprobe based on förster resonant energy transfer (FRET) for probing pH_i, in which pH-sensitive fluorescein isothiocyanate (FITC) and upconversion nanoparticles (UCNPs) were served as energy acceptor and donor, respectively. Under 980 nm excitation, upconversion emission bands at 475 nm and 645 nm of NaYF₄:Yb³⁺, Tm³⁺ UCNPs were used as pH_i response and self-ratiometric reference signal, respectively. This direct quantitative sensing approach has circumvented the traditional software-based subsequent processing of images which may lead to relatively large uncertainty of the results. Due to efficient FRET and fluorescence background free, a highly-sensitive and accurate sensing has been achieved, featured by 3.56 per unit change in pH_i value 3.0-7.0 with deviation less than 0.43. This approach shall facilitate the researches in pH_i related areas and development of the intracellular drug delivery systems.