The performance of homopolymer detection using dichromatic and tetrachromatic fluorogenic next-generation sequencing platforms.

OBJECTIVES: Homopolymer (HP) sequencing is error-prone in next-generation sequencing (NGS) assays, and may induce false insertion/deletions and substitutions. This study aimed to evaluate the performance of dichromatic and tetrachromatic fluorogenic NGS platforms when sequencing homopolymeric regions. RESULTS: A HP-containing plasmid was constructed and diluted to serial frequencies (3%, 10%, 30%, 60%) to determine the performance of an MGISEQ-2000, MGISEQ-200, and NextSeq 2000 in HP sequencing. An evident negative correlation was observed between the detected frequencies of four nucleotide HPs and the HP length. Significantly decreased rates (P < 0.01) were found in all 8-mer HPs in all three NGS systems at all four expected frequencies, except in the NextSeq 2000 at 3%. With the application of a unique molecular identifier (UMI) pipeline, there were no differences between the detected frequencies of any HPs and the expected frequencies, except for poly-G 8-mers using the MGI 200 platform. UMIs improved the performance of all three NGS platforms in HP sequencing. CONCLUSIONS: We first constructed an HP-containing plasmid based on an EGFR gene backbone to evaluate the performance of NGS platforms when sequencing homopolymeric regions. A highly comparable performance was observed between the MGISEQ-2000 and NextSeq 2000, and introducing UMIs is a promising approach to improve the performance of NGS platforms in sequencing homopolymeric regions.

Transcriptional analysis of the dimorphic fungus Umbilicaria muehlenbergii reveals the molecular mechanism of phenotypic transition.

The lichen-forming fungus Umbilicaria muehlenbergii undergoes a phenotypic transition from a yeast-like to a pseudohyphal form. However, it remains unknown if a common mechanism is involved in the phenotypic switch of U. muehlenbergii at the transcriptional level. Further, investigation of the phenotype switch molecular mechanism in U. muehlenbergii has been hindered by incomplete genomic sequencing data. Here, the phenotypic characteristics of U. muehlenbergii were investigated after cultivation on several carbon sources, revealing that oligotrophic conditions due to nutrient stress (reduced strength PDA (potato dextrose agar) media) exacerbated the pseudohyphal growth of U. muehlenbergii. Further, the addition of sorbitol, ribitol, and mannitol exacerbated the pseudohyphal growth of U. muehlenbergii regardless of PDA medium strength. Transcriptome analysis of U. muehlenbergii grown in normal and nutrient-stress conditions revealed the presence of several biological pathways with altered expression levels during nutrient stress and related to carbohydrate, protein, DNA/RNA and lipid metabolism. Further, the results demonstrated that altered biological pathways can cooperate during pseudohyphal growth, including pathways involved in the production of protectants, acquisition of other carbon sources, or adjustment of energy metabolism. Synergistic changes in the functioning of these pathways likely help U. muehlenbergii cope with dynamic stimuli. These results provide insights into the transcriptional response of U. muehlenbergii during pseudohyphal growth under oligotrophic conditions. Specifically, the transcriptomic analysis indicated that pseudohyphal growth is an adaptive mechanism of U. muehlenbergii that facilitates its use of alternative carbon sources to maintain survival.

Understanding and Calibration of Charge Storage Mechanism in Cyclic Voltammetry Curves.

Noticeable pseudo-capacitance behavior out of charge storage mechanism (CSM) has attracted intensive studies because it can provide both high energy density and large output power. Although cyclic voltammetry is recognized as the feasible electrochemical technique to determine it quantitatively in the previous works, the results are inferior due to uncertainty in the definitions and application conditions. Herein, three successive treatments, including de-polarization, de-residual and de-background, as well as a non-linear fitting algorithm are employed for the first time to calibrate the different CSM contribution of three typical cathode materials, LiFePO4 , LiMn2 O4 and Na4 Fe3 (PO4 )2 P2 O7 , and achieve well-separated physical capacitance, pseudo-capacitance and diffusive contributions to the total capacity. This work can eliminate misunderstanding concepts and correct ambiguous results of the pseudo-capacitance contribution and recognize the essence of CSM in electrode materials.

Water masses influence bacterioplankton community structure in summer Kongsfjorden.

To ascertain the saying "Everything is everywhere, but the environment selects", it was imperative to find out the main factor influencing bacterioplankton composition at genus level of Kongsfjorden where was influenced both by glacier melting water and Atlantic water. Thus, bacterioplankton diversity was investigated using pyrosequencing. In addition, nutrients, chlorophyll a, in situ temperature and salinity were measured. There were seventeen of 33 identified genera with relative abundance > 0.1%. Redundancy analysis showed that 73.02% of bacterioplankton community variance could be explained by environmental parameters. Furthermore, most of the abundant genera demonstrated significant correlation with environment parameters revealed by correlation analysis. Moreover, phosphate, nitrate and Chl a concentration, and the abundance of top nine identified genera varied with water mass significantly as shown by analysis of variance. Our results supported the notion that environmental factors, especially water mass had significant effect on bacterioplankton distribution at genus level. Considering the high sensitivity to environmental change and low error rate in identification, bacterioplankton at genus level could be potential bio-markers for monitoring environmental changes.

Recent Progress in Rechargeable Sodium-Ion Batteries: toward High-Power Applications.

The increasing demands for renewable energy to substitute traditional fossil fuels and related large-scale energy storage systems (EES) drive developments in battery technology and applications today. The lithium-ion battery (LIB), the trendsetter of rechargeable batteries, has dominated the market for portable electronics and electric vehicles and is seeking a participant opportunity in the grid-scale battery market. However, there has been a growing concern regarding the cost and resource availability of lithium. The sodium-ion battery (SIB) is regarded as an ideal battery choice for grid-scale EES owing to its similar electrochemistry to the LIB and the crust abundance of Na resources. Because of the participation in frequency regulation, high pulse-power capability is essential for the implanted SIBs in EES. Herein, a comprehensive overview of the recent advances in the exploration of high-power cathode and anode materials for SIB is presented, and deep understanding of the inherent host structure, sodium storage mechanism, Na+ diffusion kinetics, together with promising strategies to promote the rate performance is provided. This work may shed light on the classification and screening of alternative high rate electrode materials and provide guidance for the design and application of high power SIBs in the future.

Exploring the roles of substrate-binding surface of the chaperone site in the chaperone activity of trigger factor.

Trigger factor (TF) is a key component of the prokaryotic chaperone network, which is involved in many basic cellular processes, such as protein folding, protein trafficking, and ribosome assembly. The major chaperone site of TF has a cradle-like structure in which protein substrate may fold without interference from other proteins. Here, we investigated in vivo and in vitro the roles of hydrophobic and charged patches on the edge and interior of cradle during TF-assisted protein folding. Our results showed that most of the surface of the cradle was involved in TF-assisted protein folding, which was larger than found in early studies. Although the inner surface of cradle was mostly hydrophobic, both hydrophobic and electrostatic patches were indispensable for TF to facilitate correct protein folding. However, hydrophobic patches were more important for the antiaggregation activity of TF. Furthermore, it was found that the patches on the surface of cradle were involved in TF-assisted protein folding in a spatial and temporal order. These results suggest that the folding-favorable interface between the cradle and substrate was dynamic during TF-assisted protein folding, which enabled TF to be involved in the folding of substrate in an aggressive manner rather than acting as a classic holdase.-Fan, D., Cao, S., Zhou, Q., Zhang, Y., Yue, L., Han, C., Yang, B., Wang, Y., Ma, Z., Zhu, L., Liu, C. Exploring the roles of substrate-binding surface of chaperone site in the chaperone activity of trigger factor.

Rechargeable Mg-M (M = Li, Na and K) dual-metal-ion batteries based on a Berlin green cathode and a metallic Mg anode.

Mg-M (M = Li, Na and K) dual-metal-ion batteries featuring a dendrite-free Mg anode and an alkali-metal-ion storage cathode are promising safe energy storage systems. However, the compatibility between cathode materials and insertion cations might largely limit the electrochemical performance of the cathodes. In this work, three types of Mg-M (M = Li, Na and K) dual-metal-ion batteries are constructed with a Berlin green (FeFe(CN)6) cathode. The FeFe(CN)6 cathode is compatible with the dual-salt Mg2+/M+ (M = Li, Na and K) electrolytes, and delivers a high reversible capacity of 120 mA h g-1 at 50 mA g-1, with no capacity fading over 50 cycles in Mg-Na batteries. The Mg-Na battery also shows an outstanding rate capability, providing 85 mA h g-1 at 1000 mA g-1 and superior long-term cyclability over 800 cycles. The electrochemical performance comparison between Mg-Li, Mg-Na and Mg-K dual-metal-ion batteries demonstrates the significance of the appropriate hydrated ionic radius and dehydrated ionic radius for the insertion of cations with the FeFe(CN)6 cathode. This work provides new design strategies for stable and high energy density cathodes, and opens a new avenue for building safe and high-performance Mg-M (M = Li, Na and K) dual-metal-ion batteries for practical applications.

High Rate, Long Lifespan LiV3 O8 Nanorods as a Cathode Material for Lithium-Ion Batteries.

LiV3 O8 nanorods with controlled size are successfully synthesized using a nonionic triblock surfactant Pluronic-F127 as the structure directing agent. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques are used to characterize the samples. It is observed that the nanorods with a length of 4-8 µm and diameter of 0.5-1.0 µm distribute uniformly. The resultant LiV3 O8 nanorods show much better performance as cathode materials in lithium-ion batteries than normal LiV3 O8 nanoparticles, which is associated with the their unique micro-nano-like structure that can not only facilitate fast lithium ion transport, but also withstand erosion from electrolytes. The high discharge capacity (292.0 mAh g-1 at 100 mA g-1 ), high rate capability (138.4 mAh g-1 at 6.4 A g-1 ), and long lifespan (capacity retention of 80.5% after 500 cycles) suggest the potential use of LiV3 O8 nanorods as alternative cathode materials for high-power and long-life lithium ion batteries. In particular, the synthetic strategy may open new routes toward the facile fabrication of nanostructured vanadium-based compounds for energy storage applications.

Distribution patterns of haplotypes for symbionts from Umbilicaria esculenta and U. muehlenbergii reflect the importance of reproductive strategy in shaping population genetic structure.

BACKGROUND: The diversity of lichen fungal components and their photosynthetic partners reflects both ecological and evolutionary factors. In present study, molecular investigations of the internal transcribed spacer of the nuclear ribosomal DNA (ITS nrDNA) region were conducted to analyze the genetic diversity of Umbilicaria esculenta and U. muehlenbergii together with their associated green algae. RESULT: It was here demonstrated that the reproductive strategy is a principal reason for fungal selectivity to algae. U. muehlenbergii, which disperses via sexual spores, exhibits lower selectivity to its photosynthetic partners than U. esculenta, which has a vegetative reproductive strategy. The difference of genotypic diversity (both fungal and algal) between these two Umbilicaria species is low, although their nucleotide diversity can vary greatly. CONCLUSIONS: The present study illustrates that lichen-forming fungi with sexual reproductive strategies are less selective with respect to their photobionts; and reveals that both sexual and vegetative reproduction allow lichens to generate similar amounts of diversity to adapt to the environments. The current study will be helpful for elucidating how lichens with different reproductive strategies adapt to changing environments.

Determination of taurine in human tear fluid by capillary electrophoresis with indirect amperometric detection based on electrogenerated bromine.

A new method for the determination of taurine was developed based on indirect amperometric detection after capillary electrophoresis. A serial dual-electrode detector comprising an on column Pt film electrode (upstream electrode) and an end column Pt microdisk electrode (downstream electrode) was utilized to conduct the indirect amperometric detection. Bromide is oxidized to bromine at upstream electrode and reduced back to bromide at downstream electrode. Since taurine can react with bromine quantitatively and rapidly, its concentration can therefore be determined by the decrease of the current for bromine reduction at the downstream electrode. Principal experimental parameters governing the analytical performance were investigated and optimized. Under the optimal conditions, taurine can be baseline separated from interfering amino acids and the detection limit of 0.18 µM was obtained with a linear correlation coefficient of 0.999 over the concentration range of 0.5-60 µM. The developed method has been successfully applied in the determination of taurine in human tear fluid. The taurine level obtained was in good agreement with previous reports and recoveries for taurine spiked ranged from 92-95% with relative standard deviations within 4.6%, demonstrating the reliability of the developed method in the determination of taurine in human tear fluid.

A serial dual-electrode detector based on electrogenerated bromine for capillary electrophoresis.

A new serial dual-electrode detector for CE has been designed and fabricated for postcolumn reaction detection based on electrogenerated bromine. A coaxial postcolumn reactor was employed to introduce bromide reagent and facilitate the fabrication of upstream generation electrode by simply sputtering Pt film onto the outer surface of the separation capillary. Bromide introduced could be efficiently converted to bromine at this Pt film electrode and subsequently detected by the downstream Pt microdisk detection electrode. Analytes that react with bromine could be determined by the decrease of bromine reduction current at the downstream electrode resulting from the reaction between analytes and bromine. The effects of serial dual-electrode detector working conditions including electrode potentials, bromide flow rate, and bromide concentration on analytical performance were investigated using glutathione (GSH) and glutathione disulfide (GSSG) as test analytes. Under the optimal conditions, detection limits down to 0.16 µM for GSH and 0.14 µM for GSSG (S/N = 3) as well as linear working ranges of two orders of magnitude for GSH and GSSG were achieved. Furthermore, the separation efficiency obtained by our dual-electrode detector design was greatly improved compared with previous reported design. The developed method has been successfully applied to determine the GSH and GSSG impurity in commercial GSH supplement.

Flexible high dielectric thin films based on cellulose nanofibrils and acid oxidized multi-walled carbon nanotubes.

Flexible high dielectric materials are of prime importance for advanced portable, foldable and wearable devices. A series of flexible high dielectric thin films based on cellulose nanofibrils (CNF) and acid oxidized multi-walled carbon nanotubes (o-MWCNT) was prepared in aqueous solution. Though no organic solvent was involved during the preparation, the SEM images showed that o-MWCNTs have good distribution within the CNF matrix. The dielectric constant of CNF/o-MWCNT (6.2 wt%) composite films was greatly increased from 25.24 for pure CNF to 73.88, while the loss tangent slightly decreased from 0.70 to 0.68, and the AC conductivity decreased from 3.15 × 10-7 S cm-1 for CNF to 1.77 × 10-7 S cm-1 (at 1 kHz). The abnormal decrease of loss tangent and AC conductivity were attributed to the introduction of oxide-containing groups on the surface of MWCNTs. The nanocomposite films showed excellent flexibility such that they could be bent a thousand times without visible damage. The presence of MWCNTs also helped to improve the thermal stability of the composite films. The excellent dielectric and mechanical properties of the CNF/o-MWCNT composite film demonstrate its great potential to be utilized in the field of energy storage.

High dielectric thin films based on barium titanate and cellulose nanofibrils.

A series of composite films based on tetragonal barium titanate (BTO) and cellulose nanofibrils (CNF) with high dielectric constant are prepared using a casting method in aqueous solution. No organic solvent is involved during the preparation, which demonstrates the environmental friendliness of the novel material. With less than 30 wt% of filler loading, the excellent distribution of BTO nanoparticles within the CNF matrix is revealed by the FE-SEM images. The dielectric constant of the CNF/BTO (30 wt%) composite film reaches up to 188.03, which is about seven times higher than that of pure CNF (25.24), while the loss tangent only rises slightly from 0.70 to 1.21 (at 1 kHz). The thin films kept their dielectric properties on an acceptable level after repeatedly twisting or rolling 10 times. The improvement of thermal stability is observed with the presence of BTO. The outstanding dielectric properties of the CNF/BTO composite film indicates its great potential to be utilized in energy storage applications.

Mg storage properties of hollow copper selenide nanocubes.

Rechargeable Mg batteries are thought to be suitable for scalable energy-storage applications because of their high safety and low cost. However, the bivalent Mg2+ cations suffer from sluggish solid-state diffusion kinetics. Herein, a hollow morphological approach is introduced to design copper selenide cathodes for rechargeable Mg batteries. Hollow Cu2-xSe nanocubes are fabricated via a solution reaction and their Mg-storage properties are investigated in comparison to simple nanoparticles. The hollow structures accommodate the volume change during magnesiation/demagnesiation and maintain material integrity, and thus a remarkable cycling stability of over 200 cycles is achieved. A kinetic study demonstrates that a hollow structure favors solid-phase Mg2+ diffusion, and therefore the hollow Cu2-xSe nanocubes exhibit a high capacity of 250 mA h g-1 at 100 mA g-1 as well as a superior rate capability. Mechanism investigation indicates that Cu2-xSe experiences a structure conversion during which a phase transformation occurs. This work develops a facile method for the preparation of hollow copper selenides and highlights the advantages of hollow structures in the design of high-performance Mg-storage materials.

Correction to: Structure and function of the Arctic and Antarctic marine microbiota as revealed by metagenomics.

An amendment to this paper has been published and can be accessed via the original article.

Structure and function of the Arctic and Antarctic marine microbiota as revealed by metagenomics.

BACKGROUND: The Arctic and Antarctic are the two most geographically distant bioregions on earth. Recent sampling efforts and following metagenomics have shed light on the global ocean microbial diversity and function, yet the microbiota of polar regions has not been included in such global analyses. RESULTS: Here a metagenomic study of seawater samples (n = 60) collected from different depths at 28 locations in the Arctic and Antarctic zones was performed, together with metagenomes from the Tara Oceans. More than 7500 (19%) polar seawater-derived operational taxonomic units could not be identified in the Tara Oceans datasets, and more than 3,900,000 protein-coding gene orthologs had no hits in the Ocean Microbial Reference Gene Catalog. Analysis of 214 metagenome assembled genomes (MAGs) recovered from the polar seawater microbiomes, revealed strains that are prevalent in the polar regions while nearly undetectable in temperate seawater. Metabolic pathway reconstruction for these microbes suggested versatility for saccharide and lipids biosynthesis, nitrate and sulfate reduction, and CO2 fixation. Comparison between the Arctic and Antarctic microbiomes revealed that antibiotic resistance genes were enriched in the Arctic while functions like DNA recombination were enriched in the Antarctic. CONCLUSIONS: Our data highlight the occurrence of dominant and locally enriched microbes in the Arctic and Antarctic seawater with unique functional traits for environmental adaption, and provide a foundation for analyzing the global ocean microbiome in a more complete perspective. Video abstract.

Rechargeable Mg batteries based on a Ag2S conversion cathode with fast solid-state Mg2+ diffusion kinetics.

Rechargeable Mg batteries are promising candidates for highly safe, large-scale energy storage batteries due to the low-cost and non-dendritic metallic Mg anode. However, exploring high-performance cathodes remains a great challenge blocking their development. Herein, a rechargeable Mg battery is established with a Ag2S conversion cathode, providing a highly reversible capacity of 120 mA h g-1 at 50 mA g-1, a superior rate capability of 70 mA h g-1 at 500 mA g-1, and an outstanding long-term cyclability over 400 cycles. The mechanism was investigated using XRD, TEM and XPS in addition to electrochemical measurements, and indicated a two-stage magnesiation: first, Mg2+ intercalation into Ag2S and then a conversion reaction to form metallic Ag0 and MgS. The solid-state Mg2+ diffusion coefficients are as high as 3.6 × 10-9 and 3.1 × 10-10 cm2 s-1 for the intercalation and conversion reactions, respectively, which explains the high performance of the Ag2S cathode. This work provides scientific insights for the selection of a promising conversion cathode by the combination of soft anions and soft transition metal cations.

CoSe2 hollow microspheres, nano-polyhedra and nanorods as pseudocapacitive Mg-storage materials with fast solid-state Mg2+ diffusion kinetics.

CoSe2 materials with different nanostructures are used as pseudocapacitive Mg-storage cathodes, which exhibit fast solid-state Mg2+ ions diffusion kinetics. In this work, CoSe2 with different nanostructures including hollow microspheres (H-CoSe2), nano-polyhedra (P-CoSe2) and nanorods (R-CoSe2) are fabricated by using facile one-step hydrothermal methods, and used as pseudocapacitive electrodes for rechargeable Mg batteries. It is observed that R-CoSe2 exhibits the highest reversible capacity of 233 mA h g-1 at 50 mA g-1 and an excellent rate capability of 116 mA h g-1 at 500 mA g-1, ascribing to the 1D nanorod structure which facilitates the solid-state Mg2+ diffusion. Benefitting from the stable hierarchical structure, H-CoSe2 exhibits a superior long-term cycling stability of 350 cycles. A mechanism study indicates that the redox reaction reversibly occurs between CoSe2 and metallic Co0. Further investigation demonstrates that the fast solid-state Mg2+ diffusion kinetics and surface-controlled pseudocapacitive behavior enhance the electrochemical performance. This work highlights a novel and efficient Mg-storage strategy of using pseudocapacitive materials, and the performance and solid-state Mg2+ diffusion kinetics of CoSe2 could be optimized by rational structural tailoring.

Zero-strain Na4Fe7(PO4)6 as a novel cathode material for sodium-ion batteries.

We report for the first time a zero-strain cathode, Na4Fe7(PO4)6, for sodium-ion batteries (SIBs). This new iron-based polyanionic cathode delivers a reversible capacity of 66.5 mA h g-1 at 5 mA g-1 with almost 100% capacity retention over 1000 cycles under 200 mA g-1, and the outstanding performance benefits from single-phase-transition processes with a tiny volume change of only ∼0.24%.

a-MoS3@CNT nanowire cathode for rechargeable Mg batteries: a pseudocapacitive approach for efficient Mg-storage.

Rechargeable Mg batteries are promising candidates for highly safe large-scale energy storage batteries owing to their low-cost and non-dendritic metallic Mg anode. However, exploration of high-performance cathodes remains a great challenge hindering their development. Herein, a new pseudocapacitive Mg-storage nanowire material (a-MoS3@CNT) is constructed with a carbon nanotube (CNT) core and an amorphous MoS3 (a-MoS3) outer layer (15 nm thick). The nanowire cathode exhibits a high reversible capacity of 175 mA h g-1 at 100 mA g-1, a good rate performance of 50 mA h g-1 at 1000 mA g-1, and an outstanding long-term cyclability over 500 cycles. Further investigation of the mechanism demonstrates that the Mg-storage of a-MoS3@CNT is mainly achieved by the pseudocapacitance of a-MoS3, in which Mg2+ ions show fast solid-state diffusion kinetics. The present results demonstrate a new approach for efficient Mg-storage using pseudocapacitive materials, and the performance and solid-state Mg2+ diffusion kinetics could be optimized by delicate morphology tailoring.