Effects of Fiber Angle on the Tensile Properties of Partially Delignified and Densified Wood

Partial delignification and densification provide a pathway to significant improvement in the mechanical performance of wood. In order to elucidate potential effects of this treatment on the mechanical anisotropy of wood, partially delignified and densified spruce wood veneers were characterized at varying degrees of off-axis alignment. While the tensile strength and the modulus of elasticity (MOE) were clearly improved in parallel to the axis of wood fibers, this improvement quickly leveled off at misalignment angles ≥30°. For transverse tensile strength, the performance of alkaline-treated and densified wood was even inferior to that of untreated wood. Microscopic examination revealed the presence of microscopic cracks in treated wood, which are assumed to be responsible for this observation. It is concluded that impaired transverse tensile properties are a weakness of partially delignified and densified wood and should be considered when a potential usage in load-bearing applications is intended.     

Surface glycosylation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) membrane for selective adsorption of low-density lipoprotein

A novel method of constructing a glycosylated surface on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] membrane surface for the selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylic acid followed by the chemical binding of carboxyl groups with glucosamine in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. The chemical structures of the fabricated membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes, respectively. An enzyme linked immunosorbent assay was used to measure the LDL adsorption on the plain and modified membrane surfaces. It was found that the surface glycosylation of P(3HB-co-4HB) membrane greatly enhanced the affinity interactions with LDL and the absorbed LDL could be easily desorbed with eluents, indicating a specific and reversible binding of LDL to the surface. Furthermore, the hemocompatibility of glycosylated membrane was improved as examined by platelet adhesion. The results suggest that the glycosylated P(3HB-co-4HB) membrane is promising for application in LDL apheresis therapy.     

聚乙烯亚胺非病毒基因载体结构修饰研究进展

聚乙烯亚胺（PEI）作为最经典的非病毒基因载体之一,由于其高转染效率,在基因递送领域受到极大的关注,但其毒性限制了聚乙烯亚胺的应用。本文综述了对聚乙烯亚胺进行不同的结构修饰,如多糖修饰、PEG修饰和低分子聚乙烯亚胺衍生物等,以实现在不显著降低转染效率的前提下减少细胞毒性。     

Nanocomposites Polarizing by Absorption: Dichroism in the Near-Infrared Region (NIR)

We describe the preparation of nanocomposites which exhibit dichroism in the near infrared region (NIR). These materials consist of crosslinked poly(dimethylsiloxane) (PDMS) and gold nanoparticles, coated with 1-dodecanethiol or tert-tetradecanethiol. The alkanethiols improve dispersibility of the gold particles, and accordingly composites were manufactured by diffusion of the particles into swollen self-supporting PDMS elastomer films. After drying, the films were exposed to solvents for one minute, stretched in wet state, dried again and annealed. This procedure led to formation of oriented linear gold particle assemblies within stretched polymer. If the aspect ratio of the particle assemblies is high, the absorption of polarized light in the NIR region is expected to depend on the angle between the polarization plane and the orientation direction of the particle assemblies, and this was observed to be the case.     

Fabrication of a Low Density Carbon Fiber Foam and Its Characterization as a Strain Gauge

Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel rich mixtures of ethylene and oxygen. The resulting material was studied using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Surface area analysis (BET), and Thermogravimetric Analysis (TGA). Transient and dynamic mechanical tests clearly demonstrated that the material is viscoelastic. Concomitant mechanical and electrical testing of samples revealed the material to have electrical properties appropriate for application as the sensing element of a strain gauge. The sample resistance versus strain values stabilize after a few compression cycles to show a perfectly linear relationship. Study of microstructure, mechanical and electrical properties of the low density samples confirm the uniqueness of the material: It is formed entirely of independent fibers of diverse diameters that interlock forming a tridimensional body that can be grown into different shapes and sizes at moderate temperatures. It regains its shape after loads are removed, is light weight, presents viscoelastic behavior, thermal stability up to 550 °C, hydrophobicity, and is electrically conductive.     

基于nano LC-MS/MS法的黄明胶胶原蛋白鉴定研究

目的 基于shotgun混合蛋白鉴定技术,系统研究黄明胶中胶原类物质组成,探讨其胶原蛋白的修饰。方法 采用胰蛋白酶酶切黄明胶样品,纳升液相串联质谱（nano-LC Q Exactive Orbitrap MS）技术,对黄明胶酶解液进行分析获得MS/MS图谱,利用PEAKS软件对获得的MS/MS图谱搜索牛科蛋白质库,以鉴定其中蛋白质组成。结果 从2个批次的黄明胶酶解液样品中鉴定了1 378个肽段,共鉴定了30蛋白质,胶原I蛋白α1链、α2链,胶原Ⅲ蛋白α1链为黄明胶的主要物质基础,研究发现黄明胶中蛋白主要有4种修饰形式:羟基化（Hydroxylation）、脱酰胺化（Deamidation）、N-端酰胺化（Acetylation）及氧化（Oxidation）修饰。结论 黄明胶的主要物质基础源于胶原Ⅰ蛋白和胶原Ⅲ蛋白,胶原蛋白经熬制后,变性、溶出、修饰获得的产物共同构成了黄明胶的物质基础。      

E3泛素连接酶接头蛋白SPOP抑制前列腺癌的研究进展

前列腺癌（prostate cancer,Pca）是男性最常见的肿瘤之一,发病率和病死率呈逐年上升趋势,发生发展的遗传因素复杂多样。随着靶向治疗广泛应用于临床,新靶点的探索与研究在Pca的精准治疗中至关重要。研究发现E3泛素连接酶斑点型锌指结构蛋白（speckle-type POZ protein,SPOP）在Pca的发生发展中起重要抑制作用。本文重点介绍SPOP的结构、功能及其在Pca中的突变情况及相关底物;总结SPOP抑制Pca发生发展的分子机制：调控雄激素受体（androgen receptor,AR）介导的信号通路,DNA损伤修复及免疫应答;探讨SPOP在Pca中的临床意义及研究中存在的机遇与挑战。     

From the Cover: Multigeneration analysis reveals the inheritance,specificity, and patterns of CRISPR/Cas-induced gene modifications in Arabidopsis

The CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) system has emerged as a powerful tool for targeted gene editing in many organisms, including plants. However, all of the reported studies in plants focused on either transient systems or the first generation after the CRISPR/Cas system was stably transformed into plants. In this study we examined several plant generations with seven genes at 12 different target sites to determine the patterns, efficiency, specificity, and heritability of CRISPR/Cas-induced gene mutations or corrections in Arabidopsis. The proportion of plants bearing any mutations (chimeric, heterozygous, biallelic, or homozygous) was 71.2% at T1, 58.3% at T2, and 79.4% at T3 generations. CRISPR/Cas-induced mutations were predominantly 1 bp insertion and short deletions. Gene modifications detected in T1 plants occurred mostly in somatic cells, and consequently there were no T1 plants that were homozygous for a gene modification event. In contrast, ∼22% of T2 plants were found to be homozygous for a modified gene. All homozygotes were stable to the next generation, without any new modifications at the target sites. There was no indication of any off-target mutations by examining the target sites and sequences highly homologous to the target sites and by in-depth whole-genome sequencing. Together our results show that the CRISPR/Cas system is a useful tool for generating versatile and heritable modifications specifically at target genes in plants.Genome engineering tools are important for plant functional genomics research and plant biotechnology. The CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) system has been successfully used for efficient genome editing in human cell lines, zebrafish, and mouse (1–3) and recently applied to gene modification in plants (4–10). In this system a short RNA molecule guides the associated endonuclease Cas9 to generate double strand breaks (DSBs) in the target genomic DNA, which lead to sequence mutations as a result of error-prone nonhomologous end-joining (NHEJ) DNA damage repair or to gene correction or replacement as a result of homology-dependent recombination (HR) (11). It was shown that engineered CRISPR/Cas caused mutations in target genes or corrections in transgenes in transient expression assays in plant protoplasts and tobacco leaves (10). Importantly, stable expression of the CRISPR/Cas in transgenic Arabidopsis, tobacco, and rice plants led to mutations (mostly indels) in target genes and correction of a transgene (4–9). However, it was not known whether the gene mutations and corrections occurred in somatic cells only or whether some of the mutations and corrections happened in germ-line cells and thus may be heritable. Additionally, it is unclear how specific the CRISPR/Cas is in plants. Previous studies in human cell lines indicated a high frequency of off-target effect of CRISPR/Cas-induced mutagenesis (12, 13) but a lower off-target effect in mice and zebrafish (14, 15). Here we show that the CRISPR/Cas-induced transgene correction or mutations in endogenous plant genes and transgenes detected in Arabidopsis T1 plants occurred mostly in somatic cells. However, some of the gene modifications were transmitted through the germ line and were heritable in Arabidopsis T2 and T3 plants following the classic Mendelian model. Mutations caused during DSB repair were predominantly 1 bp insertion and short deletions. Furthermore, our deep sequencing and analysis did not detect any off-targets in multiple CRISPR/Cas transgenic Arabidopsis lines, indicating that the mutagenesis effect of CRISPR/Cas is highly specific in plants.