Artificial Poly Research Articles

Stable and High-Rate silicon anode enabled by artificial Poly(acrylonitrile)–Sulfur interface engineering for advanced Lithium-ion batteries

The instability of the solid–liquid interface is a crucial problem of the silicon (Si) anode, which seriously affects the performance of the battery. Therefore, constructing an artificial interface for silicon (Si) anodes is an efficient way to restrain the volume expansion and reduce the side reactions. Herein, we develop a poly(acrylonitrile)–Sulfur (PAN-S) based artificial solid-electrolyte interphase (SEI) film on Si, which significantly improves the cycling and rate performance owing to its mechanical strength and ion transport ability. The PAN-S coated silicon anode exhibits outstanding electrochemical performance, which shows a good cycle life of 1370 mAh g−1 capacity retained after 500 cycles at 0.5C (1C = 4000 mA g−1) and outstanding rate performance of 1103 mAh g−1 retained at 4C. This work provides a facile surface engineering strategy for designing electrode materials with significant volume expansion and poor electrochemical kinetics.

Highly thermoconductive yet ultraflexible polymer composites with superior mechanical properties and autonomous self-healing functionality via a binary filler strategy.

It is still a formidable challenge to develop ideal thermal dissipation materials with simultaneous high thermal conductivity, excellent mechanical softness and toughness, and spontaneous self-healing. Herein, we report the introduction of sandwich-like boron nitride nanosheets-liquid metal binary fillers into an artificial poly(urea-urethane) elastomer to address the above issue, which confers the composite elastomer with a unique thermal-mechanical-healing combination, including a low modulus, high in-plane thermal conductivity and high mass loading of rigid fillers but self-recoverability and room-temperature self-healing.

Artificial polyhydroxyalkanoate poly[2-hydroxybutyrate-block-3-hydroxybutyrate] elastomer-like material

The first polyhydroxyalkanoate (PHA) block copolymer poly(2-hydroxybutyrate-b-3-hydroxybutyrate) [P(2HB-b-3HB)] was previously synthesized using engineered Escherichia coli expressing a chimeric PHA synthase PhaCAR with monomer sequence-regulating capacity. In the present study, the physical properties of the block copolymer and its relevant random copolymer P(2HB-ran-3HB) were evaluated. Stress–strain tests on the P(88 mol% 2HB-b-3HB) film showed an increasing stress value during elongation up to 393%. In addition, the block copolymer film exhibited slow contraction behavior after elongation, indicating that P(2HB-b-3HB) is an elastomer-like material. In contrast, the P(92 mol% 2HB-ran-3HB) film, which was stretched up to 692% with nearly constant stress, was stretchable but not elastic. The differential scanning calorimetry and wide-angle X-ray diffraction analyses indicated that the P(2HB-b-3HB) contained the amorphous P(2HB) phase and the crystalline P(3HB) phase, whereas P(2HB-ran-3HB) was wholly amorphous. Therefore, the elasticity of P(2HB-b-3HB) can be attributed to the presence of the crystalline P(3HB) phase and a noncovalent crosslinked structure by the crystals. These results show the potential of block PHAs as elastic materials.

Combining protein and RNA quantification to evaluate promoter activity by using dual-color fluorescent reporting systems.

Herein, Broccoli/mCherry and an EGFP/mCherry dual-color fluorescent reporting systems have been established to quantify the promoter activity at transcription and translation levels in eukaryotic cells. Based on those systems, four commonly used promoters (CMV and SV40 of Pol II and U6, H1 of Pol III) were accurately evaluated at both the transcriptional and translational levels by combining accurate protein and RNA quantification. Furthermore, we verified that Pol III promoters can induce proteins expression, and Pol II promoter can be applied to express RNA molecules with defined length by combining a self-cleaving ribozyme and an artificial poly(A) tail. The dual-color fluorescence reporting systems described here could play a significant role in evaluating other gene expression regulators for gene therapy.

Concurrent helix extension and chirality enhancement for an artificial helical foldamer complexed with sterically hindered chiral molecules

Constructing and regulating the helical structures of artificial foldamers have been constantly pursued because of their wide applications in chiral recognition, asymmetric catalysis, circularly polarized luminescence, etc. On the one hand, stabilizing the helical structures of foldamers can usually enhance the chirality by decreasing the pitches. On the other hand, the extended helix can be obtained when the π-π stacking interaction in the main chain is weakened. In general, the former aspect is inconsistent with the later. Herein, chiral 1-phenylethylamines, 2-phenylglycinols and leucinols are used as the guests to modulate the folded helix of an artificial poly(phenylenediethynylene)-based foldamer. With the aid of chiral center, the steric hindrance of the chiral guests can increase the distances between the pitches. Meanwhile, a more ordered chain arrangement is induced by such steric effect. As a result, we successfully endow the foldamers with an extended helix and enhanced chirality at the same time.

Concentration-dependent dye aggregation and disassembly triggered by the same artificial helical foldamer

Abstrct Constructing and regulating the cyanine dye aggregates have been constantly pursued because of their wide applications in photosensitizers, biological fluorescence probes, nonlinear optics, etc. However, to realize such a process using a single additive still remains a formidable challenge. Here, the aggregation and disassembly of positively charged 3,3-diethyloxadicarbocyanine iodide (DiOC2(5)) have been demonstrated just by changing the concentration of an artificial poly(phenylenediethynylene)-based helical foldamer (Poly-1) bearing L-alanine sodium pendants with an amide linker. Poly-1 possessed the negatively charged pendants and hydrophobic helical grooves. Upon simple mixing of equal DiOC2(5) and Poly-1, DiOC2(5) molecules were mainly enriched on Poly-1 surface driven by electrostatic interaction and arranged along the main chain of Poly-1, resulting in the formation of chiral H-aggregates. But, the excessive Poly-1 would attract some DiOC2(5) molecules in H-aggregates via electrostatic interaction. The isolated monomers were easy to orderly disperse into the helical grooves due to hydrophobic interaction. Meanwhile, during the aggregation and disassembly, the solution color changed from peachblow to purple red and then to purple and finally to navy blue.

Small rubber particle proteins from Taraxacum brevicorniculatum promote stress tolerance and influence the size and distribution of lipid droplets and artificial poly(cis-1,4-isoprene) bodies.

Natural rubber biosynthesis occurs on rubber particles, i.e. organelles resembling small lipid droplets localized in the laticifers of latex-containing plant species, such as Hevea brasiliensis and Taraxacum brevicorniculatum. The latter expresses five small rubber particle protein (SRPP) isoforms named TbSRPP1-5, the most abundant proteins in rubber particles. These proteins maintain particle stability and are therefore necessary for rubber biosynthesis. TbSRPP1-5 were transiently expressed in Nicotiana benthamiana protoplasts and the proteins were found to be localized on lipid droplets and in the endoplasmic reticulum, with TbSRPP1 and TbSRPP3 also present in the cytosol. Bimolecular fluorescence complementation confirmed pairwise interactions between all proteins except TbSRPP2. The corresponding genes showed diverse expression profiles in young T. brevicorniculatum plants exposed to abiotic stress, and all except TbSRPP4 and TbSRPP5 were upregulated. Young Arabidopsis thaliana plants that overexpressed TbSRPP2 and TbSRPP3 tolerated drought stress better than wild-type plants. Furthermore, we used rubber particle extracts and standards to investigate the affinity of the TbSRPPs for different phospholipids, revealing a preference for negatively charged head groups and 18:2/16:0 fatty acid chains. This finding may explain the effect of TbSRPP3-5 on the dispersity of artificial poly(cis-1,4-isoprene) bodies and on the lipid droplet distribution we observed in N. benthamiana leaves. Our data provide insight into the assembly of TbSRPPs on rubber particles, their role in rubber particle structure, and the link between rubber biosynthesis and lipid droplet-associated stress responses, suggesting that SRPPs form the basis of evolutionarily conserved intracellular complexes in plants.

Effects of Poly(Vinylidene Fluoride) Content on Electrochemical Properties of a Graphite Negative Electrode in Lithium Secondary Batteries

We investigated the effect of poly (vinylidene fluoride) (PVdF) binder content on graphite negative electrodes for lithium secondary batteries. The negative electrode was prepared by artificial graphite powder and poly (vinylidene fluoride) binder. Scanning electron microscopy, charge/discharge test, and electrochemical impedance microscopy were conducted. As a result of electrochemical analysis, we confirmed that the electrochemical behavior varied according to the PVdF content (5, 10, 15, 50, and 90 wt%). In addition, charge/discharge test and electrochemical impedance microscopy results showed the high irreversible capacities and resistances, observed for electrodes containing PVdF contents of 50 and 90 wt%. This demonstrated that decomposition of the binder was generated during electrochemical analysis.

Enhanced production of L-sorbose from D-sorbitol by improving the mRNA abundance of sorbitol dehydrogenase in Gluconobacter oxydans WSH-003.

BackgroundProduction of L-sorbose from D-sorbitol by Gluconobacter oxydans is the first step to produce L-ascorbic acid on industrial scale. The sldhAB gene, which encodes the sorbitol dehydrogenase (SLDH), was overexpressed in an industrial strain G. oxydans WSH-003 with a strong promoter, PtufB. To enhance the mRNA abundance, a series of artificial poly(A/T) tails were added to the 3′-terminal of sldhAB gene. Besides, their role in sldhAB overexpression and their subsequent effects on L-sorbose production were investigated.ResultsThe mRNA abundance of the sldhAB gene could be enhanced in G. oxydans by suitable poly(A/T) tails. By self-overexpressing the sldhAB gene in G. oxydans WSH-003 with an optimal poly(A/T) tail under the constitutive promoter PtufB, the titer and the productivity of L-sorbose were enhanced by 36.3% and 25.0%, respectively, in a 1-L fermenter. Immobilization of G. oxydans-sldhAB6 cells further improved the L-sorbose titer by 33.7% after 20 days of semi-continuous fed-batch fermentation.ConclusionsThe artificial poly(A/T) tails could significantly enhance the mRNA abundance of the sldhAB. Immobilized G. oxydans-sldhAB6 cells could further enlarge the positive effect caused by enhanced mRNA abundance of the sldhAB.

Amorphous poly(3‐hydroxybutyrate) nanoparticles prepared with recombinant phasins and PHB depolymerase

ABSTRACTPhasin protein (PhaP) is known to anchor into the matrix of phospholipid surrounding polyhydroxyalkanoic acid (PHA) inclusion bodies formed in bacterial cells and regulate the size of the granules, as well as the number of PHA granules. To investigate the effect of phasin on the formation of artificial poly(3‐hydroxybutyrate) (P(3HB)) granules in vitro, (His)6‐tagged or GST‐fusion recombinant phasin was prepared and utilized for the artificial granule preparation. In addition, a P(3HB) depolymerase was coloaded with the recombinant phasin to prepare self‐degradable phasin‐coated P(3HB) granules. A water/chloroform two‐phase emulsion technique was used, in which the emulsification was carried out by sonication, and the chloroform in the emulsion was removed by stirring‐aided evaporation at room temperature or 65°C. Slower chloroform removal at room temperature produced better spherically shaped P(3HB) nanogranules, which were uniformly sized (∼100 to 200 nm in diameter). The self‐degradability of P(3HB) depolymerase‐loaded P(3HB) nanogranules was investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41074.

Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on growth and osteogenic differentiation of human mesenchymal stem cells.

Mesenchymal stem cell differentiation of osteoblasts is triggered by a series of signaling processes including integrin and bone morphogenetic protein (BMP), which therefore act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in an artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffold. Matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were seeded with human mesenchymal stem cells (hMSC) and cultivated over a period of 22 days, either under growth or osteoinductive conditions. During the course of culture, gene expression of alkaline phosphatase (ALP), osteocalcin (OC) and collagen I (COL-I) as well as Smad5 and focal adhesion kinase (FAK), two signal transduction molecules involved in BMP-2 or integrin signaling were analyzed. Furthermore, calcium and collagen I deposition, as well as cell densities and proliferation, were determined using fluorescence microscopy. The incorporation of BMP-2 into PLLA-collagen type I nanofibers resulted in a decrease in diameter as well as pore sizes of the scaffold. Mesenchymal stem cells showed better adherence and a reduced proliferation on BMP-containing scaffolds. This was accompanied by an increase in gene expression of ALP, OC and COL-I. Furthermore the presence of BMP-2 resulted in an upregulation of FAK, while collagen had an impact on the gene expression of Smad5. Therefore these different strategies can be combined in order to enhance the osteoblast differentiation of hMSC on PLLA based nanofiber scaffold. By doing this, different signal transduction pathways seem to be up regulated.

Use of Extracellular Medium Chain Length Polyhydroxyalkanoate Depolymerase for Targeted Binding of Proteins to Artificial Poly[(3-hydroxyoctanoate)-co-(3-hydroxyhexanoate)] Granules

Polyhydroxyalkanoates (PHA), which are produced by many microorganisms, are promising polymers for biomedical applications due to their biodegradability and biocompatibility. In this study, we evaluated the suitability of medium chain length (mcl) PHA as surface materials for immobilizing proteins. Self-stabilized, artificial mcl-PHA beads with a size of 200-300 nm were fabricated. Five of six tested proteins adsorbed nonspecifically to mcl-PHA beads in amounts of 0.4-1.8 mg m(-2) bead surface area. The binding capacity was comparable to similar-sized polystyrene particles commonly used for antibody immobilization in clinical diagnostics. A targeted immobilization of fusion proteins was achieved by using inactive extracellular PHA depolymerase (ePHA(mcl)) from Pseudomonas fluorescens as the capture ligand. The N-terminal part of ePhaZ(MCL) preceding the catalytic domain was identified to comprise the substrate binding domain and was sufficient for mediating the binding of fusion proteins to mcl-PHA. We suggest mcl-PHA to be prime candidates for both nonspecific and targeted immobilization of proteins in applications such as drug delivery, protein microarrays, and protein purification.

Identification of polyadenylation signals and alternative polyadenylation in Vitis vinifera based on ESTs data

Polyadenylation, one of the post-transcriptional processing events, requires some sequence signals on the 3′ end of pre-mRNA to determine the polyadenylation site (PS). Some pre-mRNAs contain multiple polyadenylation sites, producing mature transcripts with 3′ end of variable length. To elucidate polyadenylation signals and alternative polyadenylation in Vitis vinifera, we extracted 62,811 3′ expressed sequence tags (ESTs) of V. vinifera in each UniGene entry and aligned the clustered ESTs of each transcription unit. After filtering artificial poly(A) sites, a total of 27.9% of the sequences examined were found to contain alternative polyadenylation sites. To clarify the pattern of polyadenylation signals, three datasets of sequences containing polyadenylation site were built. Analysis of sequence features in the datasets indicated that the content of uracil begins to increase up to 40% 100 nucleotides (nt) before the PS. Nearly half of the sequences examined showed stringent requirement of CA or UA at cleavage and poly(A) addition sites. The sequence at −15 nt to −25 nt upstream of the PS has been characterized as an A-rich motif, corresponding to the strict polyadenylation signal, AAUAAA, in animals. In grape, most A-rich motifs are variants of AAUAAA. PS commonly occurs following and preceding U-rich element, without a dominant specific hexanucleotide motif. The whole pattern of polyadenylation signals in V. vinifera is more similar to yeasts than animals.

Quinupristin (RP 57669): a new tool to investigate ribosome-group B streptogramin interactions.

Streptogramin antibiotics consist of two types of molecules, group A and group B. The group B molecule quinupristin (RP 57669) and the group A molecule dalfopristin (RP 54476) constitute the first water-soluble semisynthetic streptogramin, quinupristin/dalfopristin (RP 59500). When group B molecules bind to 50S subunits or to tightly coupled ribosomes, there is an increase in their fluorescence intensity, which is proportional to the concentration of the antibiotic-ribosome complex formed. We found here that the background fluorescence of unbound quinupristin is 10-fold lower than that of unbound virginiamycin S, a natural group B molecule often used experimentally. The association constants were found (i) to be similar for the binding of the two group B molecules to tightly coupled 70S ribosomes in the absence of the group A molecules (quinupristin: 3.5 x 10(7) M(-1); virginiamycin S: 2.8 x 10(7) M(-1)) and (ii) to similarly increase about 20-fold in the presence of the corresponding group A molecule (quinupristin + dalfopristin: 69 x 10(7) M(-1); virginiamycin S + virginiamycin M: 60 x 10(7) M(-1)). Similar results were obtained with 50S ribosomal subunits. Additionally, we provide evidence that the failure of the group B molecules to inhibit poly(Phe) synthesis is due to the displacement of the group B molecule during poly(Phe) polymerization on the ribosome, indicating that the artificial poly(Phe) peptide competes with the binding of the group B molecule.

The Infectious Transcripts of Sweet Clover Necrotic Mosaic Virus Bipartite Genome Constructed by the Polymerase Chain Reaction.

Based on the complete nucleotide sequences of sweet clover necrotic mosaic virus (SCNMV) genome, full-length cDNA clones derived from RNA-1 and RNA-2 were constructed by the polymerase chain reaction with proper primers. RNA-1 and RNA-2 transcripts capped or uncapped with m7GpppG were efficiently generated, were infectious and induced symptoms identical with those caused by native viral RNAs when coinoculated to test plants Chenopodium quinoa, C. amaranticolor and Phaseolus vulgaris 'Red Kidney' bean. However, infectivity of these transcripts were less than that of the native viral RNA. In addition, the uncapped transcripts were less infectious than the capped transcripts, particularly on Red Kidney bean. The progeny SCNMV particles derived from the transcript infection had infectivity similar to that of the native viral RNA-generated virions. Both the capped and the uncapped transcripts containing an artificial poly(A)61 tail were not infectious.

The formation of a defective small subunit of the mitochondrial ribosomes in petite mutants of Saccharomyces cerevisiae

The involvement of mitochondrial protein synthesis in the assembly of the mitochondrial ribosomes was investigated by studying the extent to which the assembly process can proceed in petite mutants of Saccharomyces cerevisiae which lack mitochondrial protein synthetic activity due to the deletion of some tRNA genes and/or one of the rRNA genes on the mtDNA. Petite strains which retain the 15-S rRNA gene can synthesize this rRNA species, but do not contain any detectable amounts of the small mitochondrial ribosomal subunit. Instead, a ribonucleoparticle with a sedimentation coefficient of 30 S (instead of 37 S) was observed. This ribonucleoparticle contained all the small ribosomal subunit proteins with the exception of the var1 and three to five other proteins, which indicates that the 30-S ribonucleoparticle is related to the small mitochondrial ribosomal subunit (37 S). Reconstitution experiments using the 30-S particle and the large mitochondrial ribosomal subunit from a wild-type yeast strain indicate that the 30-S particle is not active in translating the artificial message poly(U). The large mitochondrial ribosomal subunit was present in petite strains retaining the 21-S rRNA gene. The petite 54-S subunit is biologically active in the translation of poly(U) when reconstituted with the small subunit (37 S) from a wild-type strain. The above results indicate that mitochondrial protein synthetic activity is essential for the assembly of the mature small ribosomal subunit, but not for the large subunit. Since the var1 protein is the only mitochondrial translation product known to date to be associated with the mitochondrial ribosomes, the results suggest that this protein is essential for the assembly of the mature small subunit.

Isolation and characterization of trout testis protamine mRNAs lacking Poly(A)

Poly(A) − protamine mRNA was isolated from trout testis cells in a very pure form, and artificial poly(A) − protamine mRNA molecules were derived from it by enzymatic deadenylation with RNAase H from calf thymus after hybridization with oligo(dT). The deadenylated protamine mRNA was found to be active in a wheat germ cell-free system and yielded a labeled product which co-migrated with authentic protamine. These deadenylated mRNA molecules were subsequently used as markers on denaturing polyacrylamide gels to identify and allow the purification of the poly(A) − protamine components known to exist in vivo in the total cellular poly(A) − RNA. RNA species of molecular weights similar to the enzymatically deadenylated subcomponents of protamine mRNA were observed in the natural poly(A) RNA population of the testis cells. These naturally occurring poly(A) − protamine mRNAs were isolated by preparative gel electrophoresis and further characterized by 3H-poly(U) hybridization assay, by hybridization to complementary DNA made against highly purified poly(A) + protamine mRNA, and by their ability to direct protamine synthesis in a cell-free system.