Influence of Alternation of Sulfate Attack and Freeze-Thaw on Microstructure of Concrete

The effects of sulfate attack and freeze-thaw alternation on the concrete microstructure were systemically investigated by advanced test methods such as water absorption method, air void analysis, XRD, and SEM. The experimental results indicated that freeze-thaw damage is the major effective factor in the sulfate attack and freeze-thaw alternation test. In the alternation test, average aperture of capillary pores of specimens was smaller, pores uniformity was better, and water absorption rate was lower than those specimens used in the single freeze-thaw damage test. The average aperture and uniformity of pores could be improved by adding fly ash and slag. Damage was accumulated in many cycles of freeze-thaw and microcracks increased during the test. At the same time, the hydration products of the concrete developed into expansive gypsum, AFt, and TSA without any strength during sulfate attack. The results of the microstructure analysis form XRD and SEM are in accordance with that of AFt, about 3 μm length, around which other hydration products decomposed by C-S-H after sulfate attack resulted in loss of concrete strength

Cloning, over-expression, and characterization of a new carboxypeptidase A gene of Bacillus pumilus ML413 in Bacillus subtilis 168

Carboxypeptidase A (CPAs) are a well-studied group of zinc-containing exopeptidases that facilitate thebreakdown of proteins and peptides during metabolism. Carboxypeptidase A is typically produced in mammalian pancreatic, brain and other tissues. A new gene encoding carboxypeptidase A in the prokaryote Bacillus pumilus was amplified by polymerase chain reaction (PCR), ligated into the shuttle vector pMA5, and cloned in a GRAS bacteria-Bacillus subtilis 168 host. This gene sequence contained a 1621 bp open reading frame that encodes a protein of 540 amino acids. The optimum pH and temperature for enzyme activity were 7.5 and 50°C, respectively. The enzyme was quite stable at neutral pH and maintained about 65% activity following a 24 h incubation at 40°C. The Km of this CPA was 0.1 mM, much higher than in mammalian species. Glycerol, ammonium sulfate, and sodium citrate improved enzyme activity under optimal culture condition. The carboxypeptidase activity in recombinant B. subtilis 168 reached a maximum of 179 U ml-1 in a 5 L fermentator when cultured on improved medium. The over expression of  carboxypeptidase A in Bacillus subtilis has commercial applications.Key words: Bacillus pumilus, Bacillus subtilis 168, over-expression, orthogonal arrays, carboxypeptidase A,metallocarboxypeptidase

Circulating tumor DNA clearance predicts prognosis across treatment regimen in a large real-world longitudinally monitored advanced non-small cell lung cancer cohort

Background: Although growth advantage of certain clones would ultimately translate into a clinically visible disease progression, radiological imaging does not reflect clonal evolution at molecular level. Circulating tumor DNA (ctDNA), validated as a tool for mutation detection in lung cancer, could reflect dynamic molecular changes. We evaluated the utility of ctDNA as a predictive and a prognostic marker in disease monitoring of advanced non-small cell lung cancer (NSCLC) patients.Methods: This is a multicenter prospective cohort study. We performed capture-based ultra-deep sequencing on longitudinal plasma samples utilizing a panel consisting of 168 NSCLC-related genes on 949 advanced NSCLC patients with driver mutations to monitor treatment responses and disease progression. The correlations between ctDNA and progression-free survival (PFS)/overall survival (OS) were performed on 248 patients undergoing various treatments with the minimum of 2 ctDNA tests.Results: The results of this study revealed that higher ctDNA abundance (P=0.012) and mutation count (P=8.5x10(-4)) at baseline are associated with shorter OS. We also found that patients with ctDNA clearance, not just driver mutation clearance, at any point during the course of treatment were associated with longer PFS (P=2.2x10(-1)6, HR 0.28) and OS (P=4.5x10(-6), HR 0.19) regardless of type of treatment and evaluation schedule.Conclusions: This prospective real-world study shows that ctDNA clearance during treatment may serve as predictive and prognostic marker across a wide spectrum of treatment regimens

Over-expression of Mycobacterium neoaurum 3-ketosteroid-Δ1-dehydrogenase in Corynebacterium crenatum for efficient bioconversion of 4-androstene-3,17-dione to androst-1,4-diene-3,17-dione

Background: 3-Ketosteroid-Δ1-dehydrogenase (KSDD), a flavoprotein enzyme, catalyzes the bioconversion of 4-androstene-3,17-dione (AD) to androst-1,4-diene-3,17-dione (ADD). To date, there has been no report about characterization of KSDD from Mycobacterium neoaurum strains, which were usually employed to produce AD or ADD by fermentation. Results: In this work, Corynebacterium crenatum was chosen as a new host for heterologous expression of KSDD from M. neoaurum JC-12 after codon optimization of the KSDD gene. SDS-PAGE and western blotting results indicated that the recombinant C. crenatum harboring the optimized ksdd (ksddII) gene showed significantly improved ability to express KSDD. The expression level of KSDD was about 1.6-fold increased C. crenatum after codon optimization. After purification of the protein, we first characterized KSDD from M. neoaurum JC-12, and the results showed that the optimum temperature and pH for KSDD activity were 30°C and pH 7.0, respectively. The Km and Vmax values of purified KSDD were 8.91 μM and 6.43 mM/min. In this work, C. crenatum as a novel whole-cell catalyst was also employed and validated for bioconversion of AD to ADD. The highest transformation rate of AD to ADD by recombinant C. crenatum was about 83.87% after 10 h reaction time, which was more efficient than M. neoaurum JC-12 (only 3.56% at 10 h). Conclusions: In this work, basing on the codon optimization, overexpression, purification and characterization of KSDD, we constructed a novel system, the recombinant C. crenatum SYPA 5-5 expressing KSDD, to accumulate ADD from AD efficiently. This work provided new insights into strengthening sterol catabolism by overexpressing the key enzyme KSDD, for efficient ADD production

Influence of Inertia and Low Active Mineral Admixture on Strength and Microstructure of Cement-Based Materials

Cement-based materials were investigated by comparing the strength and microstructure of pastes and mortar containing limestone powder or low quality fly ash. The compressive strength of the mortar at 28 and 90 d was examined whose microstructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis, and differential thermal analysis (TG-DTA). The results indicated that the strength of mortar decreased with increasing mineral admixtures. The limestone powder mainly acted as inert filler and hardly took part in the chemical reaction. Low quality fly ash may accelerate the formation of hydration products in samples with more chemically bonded water. This further resulted in a higher degree of cement hydration and denser microstructure, while the overall heat of hydration was reduced. At the early stage of hydration, low quality fly ash can be considered as an inert material whereas its reactivity at the later stage became high, especially for ground low quality fly ash

In situ construction of biocompatible Z-scheme alpha-Bi2O3/CuBi2O4 heterojunction for NO removal under visible light

The design of efficient, stable and biocompatible photocatalysts for air purification is still a challenge. In this work, we report a Z-scheme alpha-Bi2O3/CuBi2O4 composite with high-quality interfaces using an in situ synthesis method. The alpha-Bi2O3/CuBi2O4 displays significantly enhanced photocatalytic activity for NO removal (30 %) in comparison with alpha-Bi2O3 (17 %) under visible light irradiation. Based on characterizations, theoretical calculations and ESR tests, the Z-scheme migration mechanism of photoinduced electrons and holes on alpha-Bi2O3/CuBi2O4 heterojunction was proposed. The formation of intermediates and products was monitored by in situ DRIFTS. The NO adsorption and activation on alpha-Bi2O3/CuBi2O4 surface are more favorable than that on alpha-Bi2O3 surface. The alpha-Bi2O3/CuBi2O4 also shows high selectivity for the conversion of NO to NO- 3. Moreover, the cytotoxicity of alpha-Bi2O3/CuBi2O4 exposed to human alveolar epithelial cell has been evaluated for its potential application in air purification. This work provides a new perspective regarding the design of Z-scheme heterojunctions by an in situ method and a promising photocatalyst suitable for air pollution control

The flavohaemoprotein hmp maintains redox homeostasis in response to reactive oxygen and nitrogen species in Corynebacterium glutamicum

Abstract Background During the production of L-arginine through high dissolved oxygen and nitrogen supply fermentation, the industrial workhorse Corynebacterium glutamicum is exposed to oxidative stress. This generates reactive oxygen species (ROS) and reactive nitrogen species (RNS), which are harmful to the bacteria. To address the issue and to maintain redox homeostasis during fermentation, the flavohaemoprotein (Hmp) was employed. Results The results showed that the overexpression of Hmp led to a decrease in ROS and RNS content by 9.4% and 22.7%, respectively, and improved the survivability of strains. When the strains were treated with H2O2 and NaNO2, the RT-qPCR analysis indicated an up-regulation of ammonium absorption and transporter genes amtB and glnD. Conversely, the deletion of hmp gives rise to the up-regulation of eight oxidative stress-related genes. These findings suggested that hmp is associated with oxidative stress and intracellular nitrogen metabolism genes. Finally, we released the inhibitory effect of ArnR on hmp. The Cc-ΔarnR-hmp strain produced 48.4 g/L L-arginine during batch-feeding fermentation, 34.3% higher than the original strain. Conclusions This report revealed the influence of dissolved oxygen and nitrogen concentration on reactive species of Corynebacterium glutamicum and the role of the Hmp in coping with oxidative stress. The Hmp first demonstrates related to redox homeostasis and nitrite metabolism, providing a feasible strategy for improving the robustness of strains

Study on Strength and Microstructure of Cement-Based Materials Containing Combination Mineral Admixtures

The compressive strength of complex binders containing two or three blended mineral admixtures in terms of glass powder (GP), limestone powder (LP), and steel slag powder (SP) was determined by a battery solution type compressive testing machine. The morphology and microstructure characteristics of complex binder hydration products were also studied by microscopic analysis methods, such as XRD, TG-DTA, and SEM. The mechanical properties of the cement-based materials were analyzed to reveal the most appropriate mineral admixture type and content. The early sample strength development with GP was very slow, but it rapidly grew at later stages. The micro aggregate effect and pozzolanic reaction mutually occurred in the mineral admixture. In the early stage, the micro aggregate effect reduced paste porosity and the small particles connected with the cement hydration products to enhance its strength. In the later stage, the pozzolanic reaction of some components in the complex powder occurred and consumed part of the calcium hydroxide to form C-S-H gel, thus improving the hydration environment. Also, the produced C-S-H gel made the structure more compact, which improved the structure’s strength

Host mRNA decay proteins influence HIV-1 replication and viral gene expression in primary monocyte-derived macrophages

Abstract Background Mammalian cells harbour RNA quality control and degradative machineries such as nonsense-mediated mRNA decay that target cellular mRNAs for clearance from the cell to avoid aberrant gene expression. The role of the host mRNA decay pathways in macrophages in the context of human immunodeficiency virus type 1 (HIV-1) infection is yet to be elucidated. Macrophages are directly infected by HIV-1, mediate the dissemination of the virus and contribute to the chronic activation of the inflammatory response observed in infected individuals. Therefore, we characterized the effects of four host mRNA decay proteins, i.e., UPF1, UPF2, SMG6 and Staufen1, on viral replication in HIV-1-infected primary monocyte-derived macrophages (MDMs). Results Steady-state expression levels of these host mRNA decay proteins were significantly downregulated in HIV-1-infected MDMs. Moreover, UPF2 and SMG6 inhibited HIV-1 gene expression in macrophages to a similar level achieved by SAMHD1, by directly influencing viral genomic RNA levels. Staufen1, a host protein also involved in UPF1-dependent mRNA decay and that acts at several HIV-1 replication steps, enhanced HIV-1 gene expression in MDMs. Conclusions These results provide new evidence for roles of host mRNA decay proteins in regulating HIV-1 replication in infected macrophages and can serve as potential targets for broad-spectrum antiviral therapeutics