Evidence for voltage-dependent S4 movement in sodium channels

AbstractThe mutation R1448C substitutes a cysteine for the outermost arginine in the fourth transmembrane segment (S4) of domain 4 in skeletal muscle sodium channels. We tested the accessibility of this cysteine residue to hydrophilic methanethiosulfonate reagents applied to the extracellular surface of cells expressing these mutant channels. The reagents irreversibly increase the rate of inactivation of R1 448C, but not wild-type, channels. Cysteine modification is voltage dependent, as if depolarization extends this residue into the extracellular space. The rate of cysteine modification increases with depolarization and has the voltage dependence and kinetics expected for the movement of a voltage sensor controlling channel gating

The Population Genetics of Alternaria tenuissima in Four Regions of China as Determined by Microsatellite Markers Obtained by Transcriptome Sequencing

A total of 32,284 unigenes were obtained from the transcriptome of Alternaria tenuissima, a pathogenic fungus causing foliar disease in tomato, using next-generation sequencing (NGS) technology. In total, 24,670 unigenes were annotated using five databases, including NCBI non-redundant protein, Swiss-Prot, euKaryotic Orthologous Groups, Kyoto Encyclopedia of Genes and Genomes, and the Gene Ontology. A total of 1,140 simple sequence repeats were also identified for use as molecular markers. Sixteen of the simple sequence repeat loci were selected to study the population structure of A. tenuissima. A population genetic analysis of 191 A. tenuissima isolates, sampled from four geographic regions in China, indicated that A. tenuissima had a high level of genetic diversity, and that the selected simple sequence repeat markers could reliably capture the genetic variation. The null hypothesis of random mating was rejected for all four geographic regions in China. Isolation by distance was observed for the entire data set, but not within clusters, which is indicative of barriers to gene flow among geographic regions. The analyses of Bayesian and principal coordinates, however, did not separate four geographic regions into four separate genetic clusters. The different levels of historical migration rates suggest that isolation by distance did not represent a major biological obstacle to the spread of A. tenuissima. The potential epidemic spread of A. tenuissima in China may occur through the transport of plant products or other factors. The presented results provide a basis for a comprehensive understanding of the population genetics of A. tenuissima in China

上转换荧光点亮软物质体内成像新思路

传统的非侵入性活体生物成像技术主要是基于计算机断层扫描和核磁共振成像等技术，这些技术由于其相对较低的分辨率和对组织的损伤而受到限制。通过从介观尺度将稀土上转换纳米颗粒均匀地组装到丝素蛋白生物支架，使其具备在近红外激发下产生可见光波段发射光的上转换荧光性能。该团队使用低功率连续980 nm波长的近红外激光穿透大鼠皮肤和组织、激发植入的蚕丝丝素生物支架，产生可见光（绿光）图像。揭示了蚕丝生物支架的生物相容性、力学性能和生物降解性，以及组织细胞与生物支架的相互作用。丝素蛋白生物支架是一种软物质，上转换荧光技术为体内软物质成像提供了新思路。【中文摘要】首次采用上转换荧光技术实现了丝素蛋白生物支架体内生物成像，解决了传统体内软物质材料生物成像难以实现实时、高分辨、深穿透和低损伤的局限。【Abstract】In biomedical applications, it is very desirable to monitor the in vivo state of implanted devices, i.e., tracking the location, the state, and the interaction between the implanted devices and cell tissues. To achieve this goal, a generic strategy of soft materials meso-functionalization is presented. This is to acquire silk fibroin (SF) materials with added functions, i.e., in vivo bioimaging/sensing. The functionalization is by 3D materials assembly of functional components, lanthanide(Ln)-doped upconversion nanoparticles (UCNPs) on the mesoscopic scale to acquire upconversion fluorescent emission. To implement the meso-functionalization, the surfaces of UCNPs are modified by the hydroxyl groups (—OH) from SiO2 or polyethylene glycol coating layers, which can interact with the carbonyl groups (C==O) in SF scaffolds. The functionalized silk scaffolds are further implanted subcutaneously into mice, which allows the silk scaffolds to have fluorescent in vivo bioimaging and other biomedical functions. This material functionalization strategy may lead to the rational design of biomaterials in a more generic way.The work was supported by the 111 Project (Grant No. B16029), National Natural Science Foundation of China (Grant Nos. 21404087, 61674050, and U1405226), Fujian Provincial Department of Science and Technology (Grant Nos. 2017J06019, 2014H6022, and 2015J05109), Natural Science Foundation of Guangdong Province (Grant No. 2015A030310007), 1000 Talents Program, and President Foundation from Xiamen University (Grant No. 20720160088), NUS tear 1 funding (WBS: R-144-000-367-112)

Neutralization reaction in synthesis of carbon materials for supercapacitors

Abstract(#br)We have prepared nitrogen and oxygen enriched hierarchically porous carbon (NOHPC) based on a concept of neutralization reaction. The reactant of KOH and the reaction product of KCl mixed in soybean flour acts as chemical activators and porogens during carbonization, which play different roles to produce the hierarchical porous structure containing macropores, mesopores and micropores. After the investigation of the effect of the reaction pH and carbonization temperature on the structure, the optimized NOHPC with reaction pH at 11.5 and carbonization temperature at 900 °C has a large area (2404.3 m 2 g −1 ), with a high pore volume of 1.31 cm 3 g −1 , a nitrogen content (0.42%) and an oxygen content (32.1%). When assembling supercapacitors, NOHPC has a extremely large specific capacitance (381 F g −1 at 1 A g −1 ) and large energy density (20.78–15.42 Wh kg −1 ), and possesses good rate performance. Particularly, the symmetric supercapacitor assembled based on NOHPC-900-11.5 has a good cycle stability in the voltage range of 0–1.8 V in a two-electrode system with 1 M Na 2 SO 4 as the electrolyte. It is worth noting that when Tetraethylazanium tetrafluoroborate (TEATFB) in propylene carbonate and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (EMIMNTF 2 ) are selected as electrolyte, high energy densities of 31.4 Wh kg −1 and 71.6 Wh kg −1 are achieved. The above results indicate that NOHPC prepared based on neutralization reaction is superior energy storage materials. This work has universal significance in producing high performance porous carbons from biomass

Mesoscopic-Functionalization of Silk Fibroin with Gold Nanoclusters Mediated by Keratin and Bioinspired Silk Synapse

2017年9月，厦门大学物理科学与技术学院刘向阳教授团队与河北大学闫小兵副教授团队合作, 在Small上发表此论文，第一次将功能化蚕丝用于制造阻变存储/神经元突触电子元件。这种蚕丝基生物仿生元器件, 可制成生物相容/可植入/可降解生物电子芯片, 在人工智领域以及生物医药方面，具有重要的应用前景。【Abstract】Silk fibroin (SF) offers great opportunities in manufacturing biocompatible/partially biodegradable devices with environmental benignity and biomedical applications. To obtain active SF devices of next generation, this work is to demonstrate a new functionalization strategy of the mesoscopic functionalization for soft materials. Unlike the atomic functionalization of solid materials, the meso-functionalization is to incorporate meso-dopants, i.e., functional molecules or nanomaterials, quantum dots, into the mesoscopic networks of soft materials. In this work, wool keratin (WK) molecules were adopted as mediating molecules to incorporate gold nanoclusters (AuNCs), into the mesoscopic networks of SF. It follows from our analyses that the β-crystallites between WK and SF molecules establish the binding between WK@AuNCs and the SF networks. The incorporated WK@AuNCs are electron rich and serve as electronically charged nano particles to bridge the growth of Ag filaments in bio-degradable WK@AuNCs–SF memristors. The meso-functionalization can greatly enhance the performance of SF materials and endows them with new functionalities. This can be highlighted by biocompatible/partly degradable WK@AuNCs functionalized SF resistive random-access memories, having the enhanced resistive switching memory performance, and the unique synapse characteristics and the capability of synapse learning compared with neat SF devices, and of great importance in nonvolatile memory, analog circuits, and neuromorphic applications.The work was supported by NUS tear 1 funding (WBS: R-144-000-367-112), the 111 Project (Grant No. B16029), National Natural Science Foundation of China (Grant Nos. 21404087 and 61674050, U1405226), Fujian Provincial Department of Science & Technology (Grant Nos. 2014H6022, 2015J05109), Natural Science Foundation of Guangdong Province (Grant No. 2015A030310007), 1000 Talents Program, and President Foundation from Xiamen University (Grant No. 20720160088), Ph. D. Programs Foundation of Ministry of Education of China (Grant No. 20130121110018). One of the authors, the primary affiliation of X.Y.L. is the Department of Physics, National University of Singapore. The authors are grateful to the China Scholarship Council (CSC) for the scholarship (Grant No. 201506630067) provided to one of the authors (Xing)

Comparative analysis of sequencing technologies for single-cell transcriptomics.

Single-cell RNA-seq technologies require library preparation prior to sequencing. Here, we present the first report to compare the cheaper BGISEQ-500 platform to the Illumina HiSeq platform for scRNA-seq. We generate a resource of 468 single cells and 1297 matched single cDNA samples, performing SMARTer and Smart-seq2 protocols on two cell lines with RNA spike-ins. We sequence these libraries on both platforms using single- and paired-end reads. The platforms have comparable sensitivity and accuracy in terms of quantification of gene expression, and low technical variability. Our study provides a standardized scRNA-seq resource to benchmark new scRNA-seq library preparation protocols and sequencing platforms

Voltage-activated gating of sodium channels

This dissertation addressed the question of sodium channel gating. The study began with an investigation of a human muscle disease--paramyotonia congenita (PC). PC is an autosomal dominant disease in which muscle stiffness is triggered by exposure to cold temperature. Genetically it is caused by point mutations in the human skeletal muscle sodium channel (hSkM1) $\alpha$-subunit. Using recombinant DNA and patch clamp techniques, we compared five PC mutants expressed in tsA201 cells with wildtype hSkM1 channels. PC mutants from diverse locations in the $\alpha$-subunit (A1156T, T1313M, L1433R, R1448H, R1448C) all exhibit a similar disturbance in channel inactivation characterized by a reduced macroscopic rate, accelerated recovery, and altered voltage dependence. There is no significant abnormality in activation of PC mutants. In contrast, mutation T704M from another muscle disease--hyperkalemic periodic paralysis (HYPP)--shows a normal inactivation rate but shifts the steady-state activation and inactivation functions along the voltage axis. This study helps in understanding of the biophysical basis of the clinical manifestations of PC and HYPP. It also revealed Na channel structural parts affecting inactivation gating. Transmembrane segment 4 (S4) has long been believed to be the voltage sensor for voltage-gated ion channels. Although without direct evidence, it had been postulated that S4s move in respond to changes of membrane potential. A further study on the PC mutant R1448C gives the first evidence of voltage dependent S4 movement. Using hydrophilic cysteine reagents (methanethio-sulfonate derivatives--MTSs), we have shown that the modification of the cysteine residue at position 1448 (C1448) with MTSs requires depolarization. The kinetics of the appearance of C1448 is also consistent with the gating kinetics of the channel. We further mutated all 8 basic residues in S4 of domain 4 to cysteines and probed the accessibilities of these cysteines to MTSs from both sides of the membrane. The second and third positions--R2C and R3C are accessible from both sides of the membrane, depending on membrane potential. The external accessibility requires depolarization and internal accessibility requires hyperpolarization. The residues from R4C to R8C stayed internally accessible at all membrane potentials. These data describe a new picture of the mechanism of charge movement in the process of Na channel gating. The new model, in which S4 moves across a short barrier, solves multiple problems in understanding the Na channel gating process