Mutagenic inverted repeat assisted genome engineering (MIRAGE)

Here we describe a one-step method to create precise modifications in the genome of Saccharomyces cerevisiae as a tool for synthetic biology, metabolic engineering, systems biology and genetic studies. Through homologous recombination, a mutagenesis cassette containing an inverted repeat of selection marker(s) is integrated into the genome. Due to its inherent instability in genomic DNA, the inverted repeat catalyzes spontaneous self-excision, resulting in precise genome modification. Since this excision occurs at very high frequencies, selection for the integration event can be followed immediately by counterselection, without the need for growth in permissive conditions. This is the first time a truly one-step method has been described for genome modification in any organism.     

In vitro antioxidant activity of acetylated and benzoylated derivatives of polysaccharide extracted from Ulva pertusa (Chlorophyta)

The antioxidant activity of natural ulvan and its derivatives (acetylated and benzoylated ulvans) in vitro was determined, including scavenging activity against superoxide and hydroxyl radicals, reducing power, and chelating ability. Obvious differences in antioxidant activity between natural ulvan and its derivatives were observed, moreover, the antioxidant activity of acetylated and benzoylated ulvans was stronger than that of natural ulvan.     

柱孢鱼腥藻的铁蛋白与棕色固氮菌的钼铁蛋白的交叉互补作用

纯化的柱孢鱼腥藻铁蛋白能够与棕色固氮菌的钼铁蛋白有效地交叉反应,展现较高的活性。此异源交叉反应的乙炔还原比活及放氢比活,分别是蓝藻同源互补比活的83.8及66.7％。比较藻铁蛋白与菌钼铁蛋白异源交叉反应及藻固氮酶组分之间的同源反应的动力学特点时发现,铁蛋白对钼铁蛋白的最佳克分子比数前者(异源交叉反应)较后者(藻同源反应)为高,前者为5,后者为1;但反应的时间进程两者差别不大。     

Underestimated ecosystem carbon turnover time and sequestration under the steady state assumption: A perspective from long‐term data assimilation

It is critical to accurately estimate carbon (C) turnover time as it dominates the uncertainty in ecosystem C sinks and their response to future climate change. In the absence of direct observations of ecosystem C losses, C turnover times are commonly estimated under the steady state assumption (SSA), which has been applied across a large range of temporal and spatial scales including many at which the validity of the assumption is likely to be violated. However, the errors associated with improperly applying SSA to estimate C turnover time and its covariance with climate as well as ecosystem C sequestrations have yet to be fully quantified. Here, we developed a novel model‐data fusion framework and systematically analyzed the SSA‐induced biases using time‐series data collected from 10 permanent forest plots in the eastern China monsoon region. The results showed that (a) the SSA significantly underestimated mean turnover times (MTTs) by 29%, thereby leading to a 4.83‐fold underestimation of the net ecosystem productivity (NEP) in these forest ecosystems, a major C sink globally; (b) the SSA‐induced bias in MTT and NEP correlates negatively with forest age, which provides a significant caveat for applying the SSA to young‐aged ecosystems; and (c) the sensitivity of MTT to temperature and precipitation was 22% and 42% lower, respectively, under the SSA. Thus, under the expected climate change, spatiotemporal changes in MTT are likely to be underestimated, thereby resulting in large errors in the variability of predicted global NEP. With the development of observation technology and the accumulation of spatiotemporal data, we suggest estimating MTTs at the disequilibrium state via long‐term data assimilation, thereby effectively reducing the uncertainty in ecosystem C sequestration estimations and providing a better understanding of regional or global C cycle dynamics and C‐climate feedback.     

Study on lyotropic liquid-crystalline properties of trimethylsilyl hydroxypropylcellulose

The lyotropic liquid-crystalline behavior of trimethylsilyl hydroxypropylcellulose (TMS-HPC) is reported in this paper. The introduction of the trimethylsilyl (TMS) group in the parent HPC increases the solubility in organic solvents, and the lyotropic mesophase can be formed in concentrated acetone solution. The critical concentration (C*) in acetone is approximately 36%. The liquid crystalline nature of TMS-HPC/acetone solution was confirmed by PLM, and the mechanism of liquid crystallization was studied by FTIR and WAXD methods.     

Association between ABHD1 and DOK6 polymorphisms and susceptibility to Hirschsprung disease in Southern Chinese children

Hirschsprung disease (HSCR) is an infrequent congenital intestinal dysplasia. The known genetic variations are unable to fully explain the pathogenesis of HSCR. The α/β-hydratase domain 1 (ABHD1) interferes with the proliferation and migration of intestinal stem cells. Docking protein 6 (DOK6) is involved in neurodevelopment through RET signalling pathway. We examined the association of ABHD1 and DOK6 genetic variants with HSCR using 1470 controls and 1473 HSCR patients from Southern Chinese children. The results clarified that DOK6 rs12968648 G allele significantly increased HSCR susceptibility, in the allelic model (p = 0.034; OR = 1.12, 95%CI = 1.01~1.24) and the dominant model (p = 0.038; OR = 1.12, 95%CI = 1.01~1.25). Clinical stratification analysis showed that rs12968648 G allele was associated with increased risk of short-segment HSCR (S-HSCR), in the allelic model (p = 0.028; OR = 1.14, 95%CI = 1.01~1.28) and the additive model (p = 0.030; OR = 1.14, 95%CI = 1.01~1.28). ABHD1 rs2304678 C allele had higher risk to develop total colonic aganglionosis (TCA) in the allelic model (p = 7.04E-03; OR = 1.67, 95%CI = 1.15~2.43) and the dominant model (p = 4.12E-03; OR = 1.93, 95%CI = 1.23~3.04). DOK6 rs12968648 and ABHD1 rs2304678 had significant intergenic synergistic effect according to logical regression (p = 0.0081; OR = 0.76, 95%CI = 0.63~0.93) and multifactor dimensionality reduction (MDR, p = 0.0045; OR = 1.25, 95%CI = 1.07~1.46). This study verified two susceptible variations of HSCR on ABHD1 and DOK6. Their roles in HSCR should be conducted in further studies.     

Propagation Properties of Nanoscale Three-Dimensional Plasmonic Waveguide Based on Hybrid of Two Fundamental Planar Optical Metal Waveguides

In this paper, a nanoscale three-dimensional plasmonic waveguide (TDPW), created by depositing an Ag stripe on a SiO₂ layer with an Ag substrate, is introduced and theoretically investigated at visible and telecom wavelengths. By applying the effective index method and finite-difference time-domain numerical simulations, the authors find that the propagation properties of surface plasmon polaritons (SPPs) in the TDPW, including the propagation length and beam width, are mainly decided by the core (the SiO₂ layer just under the Ag stripe) itself, due to the much stronger localization of SPPs in the core than in the two side claddings (the SiO₂ layer without the covered Ag stripe). And propagating SPPs in the TDPW are strongly confined in the core region, even with a very small waveguide cross section. Furthermore, based on the stronger localization of propagation SPPs in the TDPW, two kinds of bending waveguides, oblique bending and 90° circular bending waveguides, are also investigated. For wavelength of 1550 nm, the 90° circular bending guide with a minimum radius as small as 2.6 μm show nearly zero radiation loss, even with a small waveguide cross section of 70?×?80 nm². The proposed TDPW is suitable for planar integration and provides a possible way for constructing various nanoscale counterparts of conventional integrated devices such as splitter, resonator, sensor, and optical switch.