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Tilapia as an economically important fish is also an excellent model for studying pigment cell biology and body color formation. In the present study, we engineered a red tilapia by mutation of hps5 using CRISPR/Cas9 gene editing of a target site in exon 2. Disruption of HPS5 led to a significant decrease in the numbers of melanophores and iridophores, and a significant increase in xanthophores, which led to a yellowish-transparent body color in early stages (5–30 dpf, days post fertilization). Slow recovery of iridophore numbers, and increased numbers of xanthophores with shorter nearest-neighbor distances than in wild-type fish was observed at 150 dpf, which finally led to a red tilapia with reddish pigmentation in fins. The hps5−/− mutants also showed several transparent cracks (absence of melanin, iridophores and xanthophores) in iris development. Besides, hps5 was also found to be fundamental for xanthophore development, and even the distance between each of them. Our hps5 mutants provide an excellent new model for studies of HPS5 function. Additionally, the red tilapia mutants may also have potential to serve as new germplasm for aquaculture, or function as a gene resource for genetic modification and breeding of red tilapia and the other related ornamental and food fish in aquaculture. More importantly, this study may have significant values in the area of development and evolution of pigmentation patterns of fish species. 

Abstract Mpv17 (mitochondrial inner membrane protein MPV17) deficiency causes severe mitochondrial DNA depletion syndrome in mammals and loss of pigmentation of iridophores and a significant decrease of melanophores in zebrafish. The reasons for this are still unclear. In this study, we established an mpv17 homozygous mutant line in Nile tilapia. The developing mutants are transparent due to the loss of iridophores and aggregation of pigment granules in the melanophores and disappearance of the vertical pigment bars on the side of the fish. Transcriptome analysis using the skin of fish at 30 dpf (days post fertilization) revealed that the genes related to purine (especially pnp4a) and melanin synthesis were significantly downregulated. However, administration of guanine diets failed to rescue the phenotype of the mutants. In addition, no obvious apoptosis signals were observed in the iris of the mutants by TUNEL staining. Significant downregulation of genes related to iridophore differentiation was detected by qPCR. Insufficient ATP, as revealed by ATP assay, α-MSH treatment, and adcy5 mutational analysis, might account for the defects of melanophores in mpv17 mutants. Several tissues displayed less mtDNA and decreased ATP levels. Taken together, these results indicated that mutation of mpv17 led to mitochondrial dTMP deficiency, followed by impaired mtDNA content and mitochondrial function, which in turn, led to loss of iridophores and a transparent body color in tilapia. 

Fe2O3 is an appealing anode material due to its high specific capacity (1007 mAh g− 1), low cost, natural abundance, and nontoxicity. However, its unstable structure during cycling processes has hindered its potential. In this study, we present a “green” synthesis method to fabricate stable porous Fe2O3 encapsulated in a buffering hollow structure (p-Fe2O3@h-TiO2) as an effective anode material for Li-ion batteries. The synthesis process only involves glucose as an “etching” agent, without the need for organic solvents or difficult-to-control environments. Characterizations of the nanostructures, chemical compositions, crystallizations, and thermal behaviors for the intermediate/final products confirm the formation of p-Fe2O3@h-TiO2. The synthesized Fe2O3 anode material effectively accommodates volume change, decreases pulverization, and alleviates agglomeration, leading to a high capacity that is over eleven times greater than that of the as-received commercial Fe2O3 after a long cycling process. This work provides an attractive, “green” and efficient method to convert commercially abundant resources like Fe2O3 into effective electrode materials for energy storage systems. 

Electrochemical energy storage devices (EESDs) are critical technologies in modern economy, covering numerous fields such as portable electronics, electric vehicles, etc. The expanding market of EESDs demands for extra requirements such as safety, environmental friendliness and low cost, in addition to increasingly enhanced electrochemical properties. Natural proteins are abundant, versatile bio-macromolecules involving tremendous amount of amino acids/functional groups/heteroatoms, which greatly benefit sustainable technologies for advancing performances of EESDs. Recent years, significant research on utilizing natural proteins including plant/animal proteins to fabricate active materials for enhancing performance of EESDs has been well reported. Therefore, it is important to comprehensively summarize the progress and achievements, analyze the advantages/challenges, and predict the prospective for future protein-based strategies toward high performance EESDs, which are the contents of this review. The protein-derived active materials include activated carbons, silicon, sulfur, metal alloys, transitional metal compounds, and nonprecious metal catalysts. The resulting EESDs are associated with Li-/Na-/K-ion batteries, metal–air batteries, and redox flow batteries, as well as supercapacitors. The contributions of proteins to stabilizing/protecting electrodes, and thus enhancing performance of EESDs are specifically emphasized. Furthermore, studies on genetical engineering of proteins for directing self-assembly of active material nanoparticles are introduced. 

Despite numerous reported lithium metal batteries (LMBs) with excellent cycling performance achieved in labs, transferring the high performing LMBs from lab-scale to industrial-production remains challenging. Therefore, via imitating the stand-still process in battery production, a conventional but important procedure, to investigate the formation and evolution of a solid electrolyte interface (SEI) is particularly important for LMBs. Our previous studies indicate that zein (corn protein)-modified carbonate-ester electrolyte (the most commercialized) effectively improves the performance of LMBs through guiding Li- ions and repairing cracked SEI. Herein, we investigate the formation and evolution of the protein-modified SEIs on Li anodes by imitating the stand-still temperature and duration. A simulation study on the protein denaturation in the electrolyte under different temperatures demonstrates a highly unfolded configuration at elevated temperatures. The experiments show that this heat-treated-zein (H-zein) modified SEI forms quickly and becomes stable after a stand-still process of less than 100 min. Moreover, the H-zein SEI exhibits excellent wetting behavior with the electrolyte due to the highly unfolded protein structures with more functional groups exposed. The Li|Li cell with the H-zein SEI achieves prolonged cycling performance (>360 h vs.
260 h of the cell with the untreated-zein (U-zein) modified SEI). The LiFePO4|Li cell with the H-zein SEI shows much stable long-term cycling performance of capacity retention (70% vs. 42% of the cell with U-zein SEI) after 200 cycles. This study confirms that the appropriately treated protein is able to effectively improve the performance of LMBs, and will inspire future studies for the production process of LMBs toward their commercialization. 

With plenty of charges and rich functional groups, bovine serum albumin (BSA) protein provides effective transport for multiple metallic ions inside blood vessels. Inspired by the unique ionic transport function, we develop a BSA protein coating to stabilize Li anode, regulate Li+ transport, and resolve the Li dendrite growth for Li metal batteries (LMBs). The experimental and simulation studies demonstrate that the coating has strong interactions with Li metal, increases the wetting with electrolyte, reduces the electrolyte/Li side reactions, and significantly suppresses the Li dendrite formation. As a result, the BSA coating exhibits excellent stability in the electrolyte and improves the performance of Li|Cu and Li|Li cells as well as the LiFePO4|Li batteries. This work reveals that LMBs can benefit from the biological function of BSA, i.e., special transport capability of metallic ions, and lays an important foundation in design of protein-based materials for effectively enhancing the electrochemical performance of energy storage systems.