THP9 enhances seed protein content and nitrogen-use efficiency in maize.

Teosinte, the wild ancestor of maize (Zea mays subsp. mays), has three times the seed protein content of most modern inbreds and hybrids, but the mechanisms that are responsible for this trait are unknown1,2. Here we use trio binning to create a contiguous haplotype DNA sequence of a teosinte (Zea mays subsp. parviglumis) and, through map-based cloning, identify a major high-protein quantitative trait locus, TEOSINTE HIGH PROTEIN 9 (THP9), on chromosome 9. THP9 encodes an asparagine synthetase 4 enzyme that is highly expressed in teosinte, but not in the B73 inbred, in which a deletion in the tenth intron of THP9-B73 causes incorrect splicing of THP9-B73 transcripts. Transgenic expression of THP9-teosinte in B73 significantly increased the seed protein content. Introgression of THP9-teosinte into modern maize inbreds and hybrids greatly enhanced the accumulation of free amino acids, especially asparagine, throughout the plant, and increased seed protein content without affecting yield. THP9-teosinte seems to increase nitrogen-use efficiency, which is important for promoting a high yield under low-nitrogen conditions.

ABA-induced phosphorylation of basic leucine zipper 29, ABSCISIC ACID INSENSITIVE 19, and Opaque2 by SnRK2.2 enhances gene transactivation for endosperm filling in maize.

Opaque2 (O2) functions as a central regulator of the synthesis of starch and storage proteins and the O2 gene is transcriptionally regulated by a hub coordinator of seed development and grain filling, ABSCISIC ACID INSENSITIVE 19 (ZmABI19), in maize (Zea mays). Here, we identified a second hub coordinator, basic Leucine Zipper 29 (ZmbZIP29) that interacts with ZmABI19 to regulate O2 expression. Like zmabi19, zmbzip29 mutations resulted in a dramatic decrease of transcript and protein levels of O2 and thus a significant reduction of starch and storage proteins. zmbzip29 seeds developed slower and had a smaller size at maturity than those of the wild type. The zmbzip29;zmabi19 double mutant displayed more severe seed phenotypes and a greater reduction of storage reserves compared to the single mutants, whereas overexpression of the two transcription factors enhanced O2 expression, storage-reserve accumulation, and kernel weight. ZmbZIP29, ZmABI19, and O2 expression was induced by abscisic acid (ABA). With ABA treatment, ZmbZIP29 and ZmABI19 synergistically transactivated the O2 promoter. Through liquid chromatography tandem-mass spectrometry analysis, we established that the residues threonine(T) 57 in ZmABI19, T75 in ZmbZIP29, and T387 in O2 were phosphorylated, and that SnRK2.2 was responsible for the phosphorylation. The ABA-induced phosphorylation at these sites was essential for maximum transactivation of downstream target genes for endosperm filling in maize.

Maize DDK1 encoding an Importin-4 ß protein is essential for seed development and grain filling by mediating nuclear exporting of eIF1A.

Nuclear-cytoplasmic trafficking is crucial for protein synthesis in eukaryotic cells due to the spatial separation of transcription and translation by the nuclear envelope. However, the mechanism underlying this process remains largely unknown in plants. In this study, we isolated a maize (Zea mays) mutant designated developmentally delayed kernel 1 (ddk1), which exhibits delayed seed development and slower filling. Ddk1 encodes a plant-specific protein known as Importin-4 ß, and its mutation results in reduced 80S monosomes and suppressed protein synthesis. Through our investigations, we found that DDK1 interacts with eIF1A proteins in vivo. However, in vitro experiments revealed that this interaction exhibits low affinity in the absence of RanGTP. Additionally, while the eIF1A protein primarily localizes to the cytoplasm in the wild-type, it remains significantly retained within the nuclei of ddk1 mutants. These observations suggest that DDK1 functions as an exportin and collaborates with RanGTP to facilitate the nuclear export of eIF1A, consequently regulating endosperm development at the translational level. Importantly, both DDK1 and eIF1A are conserved among various plant species, implying the preservation of this regulatory module across diverse plants.

Spontaneous brain activity abnormalities in migraine: A meta-analysis of functional neuroimaging.

Neuroimaging studies have demonstrated that migraine is accompanied by spontaneous brain activity alterations in specific regions. However, these findings are inconsistent, thus hindering our understanding of the potential neuropathology. Hence, we performed a quantitative whole-brain meta-analysis of relevant resting-state functional imaging studies to identify brain regions consistently involved in migraine. A systematic search of studies that investigated the differences in spontaneous brain activity patterns between migraineurs and healthy controls up to April 2022 was conducted. We then performed a whole-brain voxel-wise meta-analysis using the anisotropic effect size version of seed-based d mapping software. Complementary analyses including jackknife sensitivity analysis, heterogeneity test, publication bias test, subgroup analysis, and meta-regression analysis were conducted as well. In total, 24 studies that reported 31 datasets were finally eligible for our meta-analysis, including 748 patients and 690 controls. In contrast to healthy controls, migraineurs demonstrated consistent and robust decreased spontaneous brain activity in the angular gyrus, visual cortex, and cerebellum, while increased activity in the caudate, thalamus, pons, and prefrontal cortex. Results were robust and highly replicable in the following jackknife sensitivity analysis and subgroup analysis. Meta-regression analyses revealed that a higher visual analog scale score in the patient sample was associated with increased spontaneous brain activity in the left thalamus. These findings provided not only a comprehensive overview of spontaneous brain activity patterns impairments, but also useful insights into the pathophysiology of dysfunction in migraine.

Salt Tolerant Gene 1 contributes to salt tolerance by maintaining photosystem II activity in maize.

Salt stress is a major environmental factor limiting crop growth and productivity. Here, we show that Salt-Tolerant Gene 1 (ZmSTG1) contributes to salt tolerance by maintaining photosystem activity in maize. ZmSTG1 encodes an endoplasmic reticulum localized protein and retrotransposon insertion in the promoter region causes differential expression levels in maize inbred lines. Overexpression of ZmSTG1 improved plant growth vigor, and knockout of ZmSTG1 weakened plant growth under normal and salt stress conditions. Transcriptome and metabolome analyses indicated that ZmSTG1 might regulate the expression of lipid trafficking-related genes dependent on the abscisic acid (ABA) signaling pathway, thereby increasing the galactolipids and phospholipid concentrations in the photosynthetic membrane under salt stress. Chlorophyll fluorescence parameters showed that the knockout of ZmSTG1 led to significant impairment of plant photosystem II (PSII) activity under normal and salt stress conditions, whereas overexpression of ZmSTG1 dramatically improved plant PSII activity under salt stress conditions. We also demonstrated that the application of the salt-tolerant locus could enhance salt tolerance in hybrid maize plants. Taken together, we propose that ZmSTG1 may modulate the lipid composition in the photosynthetic membrane by affecting the expression of lipid trafficking-related genes to maintain the photosynthetic activity of plants under salt stress.

Bio-inspired Structure-editing Fluorescent Hydrogel Actuators for Environment-interactive Information Encryption.

Many living organisms have the superb structure-editing capacity for better adaptation in dynamic environments over the course of their life cycle. However, it's still challenging to replicate such natural structure-editing capacity into artificial hydrogel actuating systems for enhancing environment-interactive functions. Herein, we learn from the metamorphosis development of glowing octopus to construct proof-of-concept fluorescent hydrogel actuators with life-like structure-editing capacity by developing a universal stepwise inside-out growth strategy. These actuators could perform origami-like 3D shape deformation and also enable the postnatal growth of new structures to adapt additional actuating states for different visual information delivery by using different environment keys (e.g., temperature, pH). This study opens previously unidentified-avenues of bio-inspired hydrogel actuators/robotics and extends the potential uses for environment-interactive information encryption.

Intra-Kernel Reallocation of Proteins in Maize Depends on VP1-Mediated Scutellum Development and Nutrient Assimilation.

During maize (Zea mays) seed development, the endosperm functions as the major organ for storage of photoassimilate, serving to nourish the embryo. α-Zeins and globulins (GLBs) predominantly accumulate in the maize endosperm and embryo, respectively. Here, we show that suppression of α-zeins by RNA interference (αRNAi) in the endosperm results in more GLB1 being synthesized in the embryo, thereby markedly increasing the size and number of protein storage vacuoles. Glb genes are strongly expressed in the middle-to-upper section of the scutellum, cells of which are significantly enlarged by αRNAi induction. Elimination of GLBs caused an apparent reduction in embryo protein level, regardless of whether α-zeins were expressed or suppressed in the endosperm, indicating that GLBs represent the dominant capacity for storage of amino acids allocated from the endosperm. It appears that protein reallocation is mostly regulated at the transcriptional level. Genes differentially expressed between wild-type and αRNAi kernels are mainly involved in sulfur assimilation and nutrient metabolism, and many are transactivated by VIVIPAROUS1 (VP1). In vp1 embryos, misshapen scutellum cells contain notably less cellular content and are unable to respond to αRNAi induction. Our results demonstrate that VP1 is essential for scutellum development and protein reallocation from the endosperm to embryo.

Maize VKS1 Regulates Mitosis and Cytokinesis During Early Endosperm Development.

Cell number is a critical factor that determines kernel size in maize (Zea mays). Rapid mitotic divisions in early endosperm development produce most of the cells that make up the starchy endosperm; however, the mechanisms underlying early endosperm development remain largely unknown. We isolated a maize mutant that shows a varied-kernel-size phenotype (vks1). Vks1 encodes ZmKIN11, which belongs to the kinesin-14 subfamily and is predominantly expressed in early endosperm development. VKS1 dynamically localizes to the nucleus and microtubules and plays key roles in the migration of free nuclei in the coenocyte as well as in mitosis and cytokinesis in early mitotic divisions. Absence of VKS1 has relatively minor effects on plants but causes deformities in spindle assembly, sister chromatid separation, and phragmoplast formation in early endosperm development, thereby resulting in reduced cell proliferation. Severities of aberrant mitosis and cytokinesis within individual vks1 endosperms differ, thereby resulting in varied kernel sizes. Our discovery highlights VKS1 as a central regulator of mitosis in early maize endosperm development and provides a potential approach for future yield improvement.

Plant evolution and environmental adaptation unveiled by long-read whole-genome sequencing of Spirodela.

Aquatic plants have to adapt to the environments distinct from where land plants grow. A critical aspect of adaptation is the dynamics of sequence repeats, not resolved in older sequencing platforms due to incomplete and fragmented genome assemblies from short reads. Therefore, we used PacBio long-read sequencing of the Spirodela polyrhiza genome, reaching a 44-fold increase of contiguity with an N50 (a median of contig lengths) of 831 kb and filling 95.4% of gaps left from the previous version. Reconstruction of repeat regions indicates that sequentially nested long terminal repeat (LTR) retrotranspositions occur early in monocot evolution, featured with both prokaryote-like gene-rich regions and eukaryotic repeat islands. Protein-coding genes are reduced to 18,708 gene models supported by 492,435 high-quality full-length PacBio complementary DNA (cDNA) sequences. Different from land plants, the primitive architecture of Spirodela's adventitious roots and lack of lateral roots and root hairs are consistent with dispensable functions of nutrient absorption. Disease-resistant genes encoding antimicrobial peptides and dirigent proteins are expanded by tandem duplications. Remarkably, disease-resistant genes are not only amplified, but also highly expressed, consistent with low levels of 24-nucleotide (nt) small interfering RNA (siRNA) that silence the immune system of land plants, thereby protecting Spirodela against a wide spectrum of pathogens and pests. The long-read sequence information not only sheds light on plant evolution and adaptation to the environment, but also facilitates applications in bioenergy and phytoremediation.

Maize transcription factor ZmNF-YC13 regulates plant architecture.

Leaf angle and leaf orientation value (LOV) are critical agronomic traits for maize plant architecture. The functions of NUCLEAR FACTOR Y (NF-Y) members in regulating plant architecture have not been reported yet. Here, we identified a regulator of maize plant architecture, NF-Y subunit C13 (ZmNF-YC13). ZmNF-YC13 was highly expressed in the leaf base zone of maize plants. ZmNF-YC13 overexpressing plants showed upright leaves with narrow leaf angle and larger LOV, while ZmNF-YC13 knockout plants had larger leaf angle and smaller LOV compared with wild-type plants. The changes in plant architecture were due to the changes in the expression of cytochrome P450 family members. ZmNF-YC13 interacts with two NF-Y subunit B members (ZmNF-YB9 and ZmNF-YB10) of the LEAFY COTYLEDON1 sub-family, and further recruits NF-Y subunit A (ZmNF-YA3) to form two NF-Y complexes. The two complexes can both activate the promoters of transcriptional repressors (ZmWRKY76 and ZmBT2), and the promoters of PLASTOCHRON group genes can be repressed by ZmWRKY76 and ZmBT2 in maize protoplasts. We propose that ZmNF-YC13 functions as a transcriptional regulator and, together with ZmNF-YBs and ZmNF-YA3, affects plant architecture by regulating the expression of ZmWRKY76 and ZmBT2, which repress the expression of cytochrome P450 family members in PLASTOCHRON branch.

The complete chloroplast genome of greater duckweed (Spirodela polyrhiza 7498) using PacBio long reads: insights into the chloroplast evolution and transcription regulation.

BACKGROUND: Duckweeds (Lemnaceae) are aquatic plants distributed all over the world. The chloroplast genome, as an efficient solar-powered reactor, is an invaluable resource to study biodiversity and to carry foreign genes. The chloroplast genome sequencing has become routine and less expensive with the delivery of high-throughput sequencing technologies, allowing us to deeply investigate genomics and transcriptomics of duckweed organelles. RESULTS: Here, the complete chloroplast genome of Spirodela polyrhiza 7498 (SpV2) is assembled by PacBio sequencing. The length of 168,956 bp circular genome is composed of a pair of inverted repeats of 31,844 bp, a large single copy of 91,210 bp and a small single copy of 14,058 bp. Compared to the previous version (SpV1) assembled from short reads, the integrity and quality of SpV2 are improved, especially with the retrieval of two repeated fragments in ycf2 gene. There are a number of 107 unique genes, including 78 protein-coding genes, 25 tRNA genes and 4 rRNA genes. With the evidence of full-length cDNAs generated from PacBio isoform sequencing, seven genes (ycf3, clpP, atpF, rpoC1, rpl2, rps12 and ndhA) are detected to contain type-II introns. The ndhA intron has 50% more sequence divergence than the species-barcoding marker of atpF-atpH, showing the potential power to discriminate close species. A number of 37 RNA editing sites are recognized to have cytosine (C) to uracil (U) substitutions, eight of which are newly defined including six from the intergenic regions and two from the coding sequences of rpoC2 and ndhA genes. In addition, nine operon classes are identified using transcriptomic data. It is found that the operons contain multiple subunit genes encoding the same functional complexes comprising of ATP synthase, photosynthesis system, ribosomal proteins, et.al., which could be simultaneously transcribed and coordinately translated in response to the cell stimuli. CONCLUSIONS: The understanding of the chloroplast genomics and the transcriptomics of S.polyrhiza would greatly facilitate the study of phylogenetic evolution and the application of genetically engineering duckweeds.

Gut microbiota in children with juvenile idiopathic arthritis: characteristics, biomarker identification, and usefulness in clinical prediction.

BACKGROUND: Recent studies have suggested that the gut microbiota is altered in children with juvenile idiopathic arthritis (JIA). However, age, sex, and body mass index (BMI) were not matched in the previous studies, and the results are inconsistent. We conducted an age-, sex-, and BMI-matched cross-sectional study to characterize the gut microbiota in children with JIA, and evaluate its potential in clinical prediction. METHODS: A total of 40 patients with JIA and 42 healthy controls, ranging from 1 to 16 years, were enrolled in this study. Fecal samples were collected for 16S rDNA sequencing. The data were analyzed using QIIME software and R packages. Specifically, the random forest model was used to identify biomarkers, and the receiver operating characteristic curve and the decision curve analysis were used to evaluate model performance. RESULTS: A total of 39 fecal samples from patients with JIA, and 42 fecal samples from healthy controls were sequenced successfully. The Chao 1 and Shannon-Wiener index in the JIA group were significantly lower than those in the control group, and the Bray-Curtis dissimilarity also differed significantly between the two groups. The relative abundance of 4 genera, Anaerostipes, Dialister, Lachnospira, and Roseburia, decreased significantly in the JIA group compared to those in the control group. The 4 genera included microbes that produce short-chain fatty acids (SCFAs) and were negatively correlated with some rheumatic indices. Moreover, 12 genera were identified as potential biomarkers by using the nested cross-validation function of the random forest. A random forest model constructed using these genera was able to differentiate the patients with JIA from the healthy controls, and the area under the receiver operating characteristic curve was 0.7975. The decision curve analysis indicated that the model had usefulness in clinical practice. CONCLUSIONS: The gut microbiota in patients with JIA is altered and characterized by a decreased abundance of 4 SCFA-producing genera. The decreases in the 4 genera correlated with more serious clinical indices. Twelve genera could be used as biomarkers and predictors in clinical practice. TRIAL REGISTRATION: The study is registered online at the Chinese Clinical Trial Registry on 11 May 2018 (registration number: ChiCTR1800016110).

Transcriptome and metabolome reveal distinct carbon allocation patterns during internode sugar accumulation in different sorghum genotypes.

Sweet sorghum accumulates large amounts of soluble sugar in its stem. However, a system-based understanding of this carbohydrate allocation process is lacking. Here, we compared the dynamic transcriptome and metabolome between the conversion line R9188 and its two parents, sweet sorghum RIO and grain sorghum BTx406 that have contrasting sugar-accumulating phenotypes. We identified two features of sucrose metabolism, stable concentrations of sugar phosphates in RIO and opposite trend of trehalose-6-phosphate (T6P) between RIO vs R9188/BTx406. Integration of transcriptome and metabolome revealed R9188 is partially active in starch metabolism together with medium sucrose level, whereas sweet sorghum had the highest sucrose concentration and remained highly active in sucrose, starch, and cell wall metabolism post-anthesis. Similar expression pattern of genes involved in sucrose degradation decreased the pool of sugar phosphates for precursors of starch and cell wall synthesis in R9188 and BTx406. Differential T6P signal between RIO vs R9188/BTx406 is associated with introgression of T6P regulators from BTx406 into R9188, including C-group bZIP and trehalose 6-phosphate phosphatase (TPP). The inverted T6P signalling in R9188 appears to down-regulate sucrose and starch metabolism partly through transcriptome reprogramming, whereas introgressed metabolic genes could be related to reduced cell wall metabolism. Our results show that coordinated primary metabolic pathways lead to high sucrose demand and accumulation in sweet sorghum, providing us with targets for genetic improvements of carbohydrate allocation in bioenergy crops.

Spontaneous Growth of 3D Silver Mesoflowers on Poly(4-vinylpyridine) Brushes-Grafted-Graphene Oxide Films and Facile Creation of Nanoporosities over their Surface.

Fabricating three-dimensional (3D) hierarchical noble-metal particles by spontaneous redox reactions between graphene and noble-metal salts still remains a great challenge. Herein, the fact that graphene oxide (GO) itself acts as both a platform for grafting polymer brushes and a reducing agent to reduce [Ag(NH3 )2 ]+ ions is taken advantages of. 3D flower-like Ag mesoparticles (Ag mesoflowers, Ag MFs) with tunable size and shapes can spontaneous grow on poly(4-vinylpyridine) brushes-grafted-graphene oxide (P4VP-g-GO) films in Ag(NH3 )2 OH solution without the use of any additional reducing agent. The residual Ag(NH3 )2 OH on 3D Ag MFs surface can be further reduced by NaBH4 , causing abundant nanoporosities over the entire Ag MFs. The resulting Ag nanoporous MFs (Ag NMFs) with larger surface-to-volume ratio and higher nanoscale roughness exhibit ultrasensitivity in surface-enhanced Raman spectroscopy (SERS) detection, and the detection limit for 4-aminothiophenol is as low as 10-13 m.

The genetic architecture of amylose biosynthesis in maize kernel.

Starch is the most abundant storage carbohydrate in maize kernel. The content of amylose and amylopectin confers unique properties in food processing and industrial application. Thus, the resurgent interest has been switched to the study of individual amylose or amylopectin rather than total starch, whereas the enzymatic machinery for amylose synthesis remains elusive. We took advantage of the phenotype of amylose content and the genotype of 9,007,194 single nucleotide polymorphisms from 464 inbred maize lines. The genome-wide association study identified 27 associated loci involving 39 candidate genes that were linked to amylose content including transcription factors, glycosyltransferases, glycosidases, as well as hydrolases. Except the waxy gene that encodes the granule-bound starch synthase, the remaining candidate genes were located in the upstream pathway of amylose synthesis, while the downstream members were already known from prior studies. The linked candidate genes could be transferred to manipulate amylose content and thus add value to maize kernel in the breeding programme.

3D hierarchical Ag nanostructures formed on poly(acrylic acid) brushes grafted graphene oxide as promising SERS substrates.

In this study, in situ generation of Ag nanostructures with various morphology on poly(acrylic acid) (PAA) brushes grafted onto graphene oxide (GO), for use as substrates for surface-enhanced Raman scattering (SERS), is demonstrated. The overall synthetic strategy involves the loading of Ag precursor ions ((Ag+ and [Ag(NH3)2]+) onto PAA brush-grafted GO, followed by their in situ reduction to Ag nanostructures of various morphology using a reducing agent (NaBH4 or ascorbic acid). Novel 3D hierarchical flowerlike Ag nanostructures were obtained by using AgNO3 as precursor and ascorbic acid as reducing agent. Using 4-aminothiophenol as probe molecules, the as-prepared hierarchical Ag nanostructures exhibited excellent SERS performance, providing enhancement factors of ∼107.

Dynamic functional network connectivity in idiopathic generalized epilepsy with generalized tonic-clonic seizure.

Idiopathic generalized epilepsy (IGE) has been linked with disrupted intra-network connectivity of multiple resting-state networks (RSNs); however, whether impairment is present in inter-network interactions between RSNs, remains largely unclear. Here, 50 patients with IGE characterized by generalized tonic-clonic seizures (GTCS) and 50 demographically matched healthy controls underwent resting-state fMRI scans. A dynamic method was implemented to investigate functional network connectivity (FNC) in patients with IGE-GTCS. Specifically, independent component analysis was first carried out to extract RSNs, and then sliding window correlation approach was employed to obtain dynamic FNC patterns. Finally, k-mean clustering was performed to characterize six discrete functional connectivity states, and state analysis was conducted to explore the potential alterations in FNC and other dynamic metrics. Our results revealed that state-specific FNC disruptions were observed in IGE-GTCS and the majority of aberrant functional connectivity manifested itself in default mode network. In addition, temporal metrics derived from state transition vectors were altered in patients including the total number of transitions across states and the mean dwell time, the fraction of time spent and the number of subjects in specific FNC state. Furthermore, the alterations were significantly correlated with disease duration and seizure frequency. It was also found that dynamic FNC could distinguish patients with IGE-GTCS from controls with an accuracy of 77.91% (P < 0.001). Taken together, this study not only provided novel insights into the pathophysiological mechanisms of IGE-GTCS but also suggested that the dynamic FNC analysis was a promising avenue to deepen our understanding of this disease. Hum Brain Mapp 38:957-973, 2017. © 2016 Wiley Periodicals, Inc.

The overexpression and prognostic role of DCAF13 in hepatocellular carcinoma.

DDB1 and CUL4 associated factor 13 (DCAF13) is a protein coding gene located on chromosome 8q22.3, which is a hotspot amplified in various cancers. DCAF13 has been reported to be frequently amplified in breast cancer patients. However, the genetic alteration and potential role of DCAF13 in other cancers, including hepatocellular carcinoma, have not been investigated yet. In this study, we found that DCAF13 was amplified in 14.7% of the cases and its expression was upregulated (p < 0.001) in hepatocellular carcinoma samples in The Cancer Genome Atlas dataset. Increased expression of DCAF13 was also noticed in 40 paired hepatocellular carcinoma and adjacent non-tumor tissues both at messenger RNA and protein levels (p = 0.0002 and 0.0016, respectively). A positive relationship was observed between augmented DCAF13 levels and poorer tumor grade (p = 0.005), and we also found that hepatocellular carcinoma patients with increased DCAF13 expression in their tumors had significantly poorer survival compared with those with decreased DCAF13 expression (median survival time: 45.73 and 70.53 months, respectively). Multivariate Cox regression analysis showed that DCAF13 was an independent prognostic predictor of survival in hepatocellular carcinoma patients. Gene ontology and Kyoto Encyclopedia of Genes and genomes analysis indicated the potential role of DCAF13 as a crucial cell cycle regulator. Collectively, our findings revealed that the overexpression of DCAF13 in hepatocellular carcinoma was significantly associated with poor survival and may participate in the regulation of cell cycle progression.

Shape-Controlled Synthesis of Au-Polypyrrole Composites Using Poly(4-vinylpyridine) Brush Grafted on Graphene Oxide as a Reaction Chamber.

Controlling the shape of the conducting polymer-noble metal composites is a key factor in determining their properties and applications. In this paper, we demonstrate a novel strategy to fabricate Au-polypyrrole (PPy) composites with unusual morphology using poly(4-vinylpyridine) (P4VP) brush grafted on graphene oxide (GO) as a reaction chamber. When the GO/P4VP brush bearing AuCl4- ions is exposed to pyrrole vapor or directly immersed into pyrrole solution, novel Au-PPy nanotubules and flower-like Au mesoparticles-PPy composites are formed on the surface of GO/P4VP brush, respectively. The application of the as-prepared GO/P4VP/Au-PPy composites in catalysis and surface-enhanced Raman scattering (SERS) are investigated. The relevant results exhibit that the GO/P4VP/Au-PPy nanotubules can act as an efficient catalyst for reduction of 4-nitrophenol, and the GO/P4VP/flower-like Au mesoparticles-PPy composites can be used as a sensor platform for the detection of organic molecules by SERS.

Light-Switchable Self-Healing Hydrogel Based on Host-Guest Macro-Crosslinking.

A self-healing hydrogel is prepared by crosslinking acrylamide with a host-guest macro-crosslinker assembled from poly(ß-cyclodextrin) nanogel and azobenzeneacrylamide. The photoisomerizable azobenzene moiety can change its binding affinity with ß-cyclodextrin, therefore the crosslinking density and rheology property of the hydrogel can be tuned with light stimulus. The hydrogel can repair its wound autonomously through the dynamic host-guest interaction. In addition, the wounded hydrogel will lose its ability of self-healing when exposed to ultraviolet light, and the self-healing behavior can be recovered upon the irradiation of visible light. The utilizing of host-guest macro-crosslinking approach manifests the as-prepared hydrogel reversible and light-switchable self-healing property, which would broaden the potential applications of self-healing polymers.