Search

The bacterial CRISPR-Cas9 system has emerged as an effective tool for sequence-specific gene knockout through non-homologous end joining (NHEJ), but it remains inefficient for precise editing of genome sequences. Here we develop a reporter-based screening approach for high-throughput identification of chemical compounds that can modulate precise genome editing through homology-directed repair (HDR). Using our screening method, we have identified small molecules that can enhance CRISPR-mediated HDR efficiency, 3-fold for large fragment insertions and 9-fold for point mutations. Interestingly, we have also observed that a small molecule that inhibits HDR can enhance frame shift insertion and deletion (indel) mutations mediated by NHEJ. The identified small molecules function robustly in diverse cell types with minimal toxicity. The use of small molecules provides a simple and effective strategy to enhance precise genome engineering applications and facilitates the study of DNA repair mechanisms in mammalian cells.

In order to investigate the hot deformation behavior of an in situ 2 wt.% TiB2-reinforced 6061 Al matrix composite (hereafter labeled as TiB2/6061 Al composite), hot compression tests were conducted over the deformation temperatures of 300-500 °C and the strain rates of 0.001-10 s−1. The flow stress of the TiB2/6061 Al composite decreases with the deformation temperature increasing and strain rate decreasing during the hot compression process. The Arrhenius constitutive equation with the activation energy to be 335.6 kJ mol−1 was constructed to characterize the flow stress behavior. Hot compression can effectively eliminate the casting void defects of the studied composite and significantly improve the distribution of TiB2 particles in the composite matrix. The existence of TiB2 particles in the studied composite can result in inadequate dynamic recrystallization, and T6 heat treatment can control the microstructure of the hot deformed TiB2/6061 Al composite. [ABSTRACT FROM AUTHOR]

Architected materials comprising periodic arrangements of cells have attracted considerable interest in various fields because of their unconventional properties and versatile functionality. Although some better properties may be exhibited when this homogeneous layout is broken, most such studies rely on a fixed material geometry, which limits the design space for material properties. Here, combining heterogeneous and homogeneous assembly of cells to generate tunable geometries, a hierarchically architected material (HAM) capable of significantly enhancing mechanical properties is proposed. Guided by the theoretical model and 745 752 simulation cases, generic design criteria are introduced, including dual screening for unique mechanical properties and careful assembly of specific spatial layouts, to identify the geometry of materials with extreme properties. Such criteria facilitate the potential for unprecedented properties such as Young's modulus at the theoretical limit and tunable positive and negative Poisson's ratios in an ultra‐large range. Therefore, this study opens a new paradigm for materials with extreme mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract There is a large published literature presenting information regarding the toxicology of CO in humans. There is information showing that CO-Hb levels below 15% are not associated with clinical adverse signs or symptoms in healthy individuals and smokers have CO-Hb levels around 6%, but may be above 10% on occasion. It has also been found that CO at low levels may have positive effects in SCD. It has been reported that non-toxic levels of CO extend the red cell life span in SCD patients (Beutler E, 1975.). Further, CO might play a role in preventing sickle cell formation by preventing the polymerization of hemoglobin (Sirs JA, 1963), and it has been reported that CO might have a preventative effect on the occurrence of clinical symptoms of SCD (Yallop D et al, 2007). Inhaled CO administered in low concentrations to transgenic sickle mice for one hour per day, 3 days per week for 10 weeks, was non-toxic and substantially decreased white cell counts and cellular inflammatory signals (Beckman J et al, 2009). This research program hypothesizes that CO, when administered orally at non-toxic levels, results in CO-Hb levels that will result in benefit to patients with SCD through two mechanisms: reducing the sickling phenomenon of red cells and by reducing the inflammatory response in these patients. It also hypothesizes that the safest and most efficient mode of administration of CO is by the oral route via a solution with a known dose of CO. Methods The carbon monoxide (CO) is obtained from a commercial source. The liquid formulation (LF) is composed of a mixture of the following components: water, proteins, lipids and carbohydrates ( PLC Mixture). The CO is instilled into this LF and tested for CO concentration. The principle of the method used for CO measurement is to allow the CO and added Hb to interact and to measure the CO-Hb formed by using the dithionite reduction method employing a spectrophotometer. (A.H. Chalmers 1991).The container is weighed before and after CO instillation to determine the occurrence of CO gas leakage. The container for the CO-LF is of low gas permeability. Once CO instillation in the LF is complete, the containers of CO-LF are sealed and labeled. The prepared containers are stored at 2-8°C for no longer than 72 hours. The CO content in blood is expressed as ‘%’ of total hemoglobin (CO-Hb) and mg/L in the CO-LF. CO-LF was administered via esophageal-placed gavage using Sprague-Dawley rats with jugular venous catheters. Results In the first study, there were 5 groups of 4 non-anemic rats studied, with each group comprising of a different LF made with the following percent of PLC Mixture combined with water: 50% PLC Mixture, 20% PLC Mixture, 10% PLC Mixture, 5% PLC Mixture, and 0% PLC Mixture (water only). Two 3 mL doses of CO-LF were administered to each rat one hour apart. Data generated showed levels of CO-Hb at baseline varying between 0 and 1.1 %. After the administration of the test article, the highest CO-Hb levels were 6.1% in one animal at 1 hour after the first dose, and 9.6% one hour after the second dose in one animal. The levels of CO-Hb fell at different rates depending upon the dose and formulation. The PK data for the first study is shown in Table 1. Differences among the test articles were not statistically different. The PK parameters evaluated over 24 hours were not impacted by the administered PLC Mixture, but animals receiving CO-50% PLC Mixture showed an initial fall to baseline levels, then a second rise in CO-Hb levels peaking in one animal at 3.1% at 48 hours. Such late increments were not seen with other CO-LF’s. The second PK study was comprised of 2 groups of 4 anemic rates, and employed CO-0% and CO-10% PLC Mixture. This study was carried out on rats made anemic by blood draw to an estimated 50% blood volume. The PK characteristics show data similar to that seen in non-anemic rats. Conclusion This research has documented the feasibility in a proof-of-concept rat model that orally administered CO via a CO liquid formulation can produce CO-Hb levels that would be expected to impact the pathophysiology of the Sickle Cell Disease-associated micro-vasculature. The terminal half-life of orally administered CO in the rat is similar to that reported via inhaled CO. Disclosures: Gomperts: Hillhurst Biopharmaceuticals Inc: Equity Ownership, Patents & Royalties. Forman:Hillhurst Biopharmaceuticals Inc: Equity Ownership, Patents & Royalties.

In recent years, algae bloom phenomenon outbreaks frequently in large-scale water bodies during summer. At present, mechanical method is used to collect cyanobacteria and reduce volume. However, the characteristics of algae, namely high viscosity, small particle size and high moisture content, lead to poor efficiency of dehydration. In order to improve the dehydration efficiency of algae and achieve the purpose of volume reduction and dehydration, the dehydration performance of Microcystis aeruginosa was studied in this paper. Three filter aid agent, including Poly Aluminium Chloride (PAC), Montmorillonite and Diatomite were added to the algae solution to improve filterability of Microcystis aeruginosa. The results showed that all of three filter aid agent have positive effect on the algae filtration rate, specific resistance, compression index and dehydration efficiency. Compared with the other two filter aid agents, the filtration rate of Diatomite is relatively faster. Meanwhile dehydration performance is better as well. When the dosage of Diatomite was 10.0g/L, the filtration rate increased from 0.108 L/h to 0.504 L/h. In addition, the compression index was reduced from 0.710 to 0.594. The specific resistance was reduced from 7.62 × 1010 s2/g to 2.35 × 108 s2 /g while the water content was decreased from 86.5% to 66.4%.

Podophyllotoxin (PTOX) is naturally produced by the plant Podophyllum species. Some of its derivatives are anticancer drugs, which are produced mainly by using chemical semi-synthesis methods. Recombinant bacteria have great potential in large-scale production of the derivatives of PTOX. In addition to introducing the correct enzymes, the transportation of PTOX into the cells is an important factor, which limits its modification in the bacteria. Here, we improved the cellular uptake of PTOX into Escherichia coli with the help of the zero-valent sulfur transporter YedE1E2 in the presence of cetyltrimethylammonium bromide (CTAB). CTAB promoted the uptake of PTOX, but induced the production of reactive oxygen species. A protein complex (YedE1E2) of YedE1 and YedE2 enabled E. coli cells to resist CTAB by reducing reactive oxygen species, and YedE1E2 was a hypothetical transporter. Further investigation showed that YedE1E2 facilitated the uptake of extracellular zero-valent sulfur across the cytoplasmic membrane and the formation of glutathione persulfide (GSSH) inside the cells. The increased GSSH minimized oxidative stress. Our results indicate that YedE1E2 is a zero-valent sulfur transporter and it also facilitates CTAB-assisted uptake of PTOX by recombinant bacteria. [ABSTRACT FROM AUTHOR]

Nano-elastic microspheres are particle-absorbent polymers that can be applied in plugging water. They plug pores and throats, reducing the damage from water invasion. The plug effect and flow mechanism of nano-elastic microspheres during water invasion were investigated in this paper through laboratory experiments. The results of the plugging experiments show that the nano-elastic microspheres had a higher plugging rate and formed physical plugs in the aquiferous region, thus preventing water invasion. Online nuclear magnetic resonance experiments indicated that the nano-elastic microspheres migrated from large pores to smaller ones during the flow process, forming elastic plugs in the porous media. The nano-elastic microspheres expanded in the aquiferous layer, increasing the flow resistance through both physical and elastic plugging, thereby reducing the water cut. Nano-elastic microspheres employed physical plugging to prevent water invasion and exhibited elastic flow in the porous media during the invasion. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO2) concentration is a crucial indicator of ground-level air quality, and elevated concentrations can adversely affect human health and the atmospheric environment. In this study, we utilized Tropospheric Monitoring Instrument (TROPOMI) tropospheric NO2 vertical column density data (VCD) and multi-source geographic data to establish a random forest regression (RF) model that accurately estimates NO2 concentrations near the ground in the Fenwei Plain. The model addresses the inherent limitations of traditional ground-based monitoring and provides data support for analyzing regional pollution spatial and temporal characteristics. (1) The RF model based on TROPOMI and geographic data demonstrates high estimation accuracy, with monthly average RF model fit and validation coefficient of determination (R2) reaching 0.949 and 0.875, respectively. (2) A complex nonlinear relationship exists between near-surface NO2 concentration and multi-source geographic data. The RF model’s estimations reveal clear seasonal and regional variations in near-surface NO2 concentration. Concentrations are generally highest in winter, followed by spring and autumn, and lowest in summer. The high NO2 concentrations are primarily mainly distributed in the plains and river valleys with low elevation and dense population density. The model estimation results also indicate that the estimated effect is better when the NO2 concentration fluctuates less and anthropogenic emission reduction measures significantly impact the NO2 concentration near the ground. (3) The population exposure risk results indicate that most cities in the Fenwei Plain face varying exposure risks. These findings offer valuable insights for regional NO2 pollution management. [ABSTRACT FROM AUTHOR]

Objective: Previous studies have underlined the genetic susceptibility in the pathogenesis of palindromic rheumatism (PR), but the known PR loci only partially explain the disease's genetic background. We aimed to genetically identify PR by whole‐exome sequencing (WES). Methods: This multicenter prospective study was conducted in 10 Chinese specialized rheumatology centers between September 2015 and January 2020. WES was performed in 185 patients with PR and in 272 healthy controls. PR patients were divided into PR subgroups who were negative for anti–citrullinated protein antibody (ACPA−) and positive for ACPA (ACPA+) according to ACPA titer (cutoff value 20 IU/liter). We conducted whole‐exome association analysis for the WES data. We used HLA imputation to type HLA genes. In addition, we used the polygenic risk score to measure the genetic correlations between PR and rheumatoid arthritis (RA) and the genetic correlations between ACPA− PR and ACPA+ PR. Results: Among 185 patients with PR enrolled in our study, 50 patients (27.02%) were ACPA+ and 135 PR patients (72.98%) were ACPA−. We identified 8 novel loci (in the ACPA− PR group: ZNF503, RPS6KL1, HOMER3, HLA–DRA; in the ACPA+ PR group: RPS6KL1, TNPO2, WASH2P, FANK1) and 3 HLA alleles (in the ACPA− PR group: HLA–DRB1*0803 and HLA–DQB1; in the ACPA+ PR group: HLA–DPA1*0401) that were associated with PR and that surpassed genome‐wide significance (P < 5 × 10−8). Furthermore, polygenic risk score analysis showed that PR and RA were not similar (R2 < 0.025), whereas ACPA+ PR and ACPA− PR showed a moderate genetic correlation (0.38 < R2 < 0.8). Conclusion: This study demonstrated the distinct genetic background between ACPA− and ACPA+ PR patients. Additionally, our findings strengthened that PR and RA were not genetically similar. [ABSTRACT FROM AUTHOR]