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Introduction: Recombinant allergens produced by Escherichia coli (E. coli) system play an important role in the component-resolved diagnostics of allergy and vaccine development. However, incorrect folding of recombinant allergens may affect their application. Therefore, it is very important to monitor the correct folding of recombinant allergens. Currently, there is still a lack of a quality control strategy to solve this problem. In this study, a mite allergen, Der f 2, was taken as an example to establish a novel quality control strategy, which was based on chromatography to isolate the allergen, and on enzyme-linked immunosorbent assay to verify the IgE reactivity of the isolated allergen. Methods: The nucleotide sequence encoding Der f 2 was codon-optimized and cloned into pET-28a (+) plasmid. Best conditions for the expression of Der f 2 in E. coli were sought. The inclusion body of Der f 2 was denatured and purified by nickel affinity chromatography. Refolding processes were compared using glutathione redox system. The fully and partially folded proteins were separated by anion exchange chromatography, and the IgE reactivity of the isolated proteins was verified by indirect enzyme-linked immunosorbent assay. Results: An optimized 387 bp segment of the Der f 2 coding gene was successfully expressed in E. coli. Best induction conditions included preinduction bacterial density with absorbance value at 600 nm was 0.6, 1 mM isopropyl beta-d-thiogalactopyranoside at 28°C for 4 h. The Der f 2 protein after refolding was separated by chromatography and two fractions were obtained. The first fraction was identified as monomer protein and the second as aggregate by size-exclusion chromatography. Indirect enzyme-linked immunosorbent assay also confirmed that the first fraction showed higher IgE reactivity. Conclusion: In this study, a novel quality control strategy based on chromatographic separation and IgE reactivity monitoring was established in the case of mite Der f 2, which systematically evaluated the effectiveness of multiple preparation methods for the first time. It is faster and more convenient when compared with the existing methods such as size-exclusion chromatography. This strategy laid a foundation for the stable application of recombinant allergens produced by E. coli in component-resolved diagnostics and the development of molecular vaccines in the future. [ABSTRACT FROM AUTHOR]

Introduction: Artemisia species are widely spread in north hemisphere. Artemisia sieversiana pollen is one of the common pollen allergens in the north of China. At present, seven allergens were identified and had been listed officially from A. sieversiana pollen, but the remaining allergens are still insufficiently studied, which need to be found. Methods: Pectate lyase was purified from the extracts of A. sieversiana pollen by anion exchange, size exclusion, and HPLC-hydrophobic interaction chromatography. The gene of A. sieversiana pectate lyase (Art si pectate lyase) was cloned and expressed in Escherichia coli. The enzyme activity and circular dichroism (CD) spectrum of natural and recombinant proteins were analyzed. The allergenicity of Art si pectate lyase was characterized by enzyme-linked immunosorbent assay (ELISA), Western blot, inhibition ELISA, and basophil activation test. The allergen’s physicochemical properties, three-dimensional structure, sequence profiles with homologous allergens and phylogenetic tree were analyzed by in silico methods. Results: Natural Art si pectate lyase (nArt si pectate lyase) was purified from A. sieversiana pollen extracts by three chromatographic strategies. The cDNA sequence of Art si pectate lyase had a 1191-bp open reading frame encoding 396 amino acids. Both natural and recombinant pectate lyase (rArt si pectate lyase) exhibited similar CD spectrum, and nArt si pectate lyase had higher enzymatic activity. Moreover, the specific immunoglobulin E (IgE) binding rate against nArt si pectate lyase and rArt si pectate lyase was determined as 40% (6/15) in patients’ serum with Artemisia species pollen allergy by ELISA. The nArt si pectate lyase and rArt si pectate lyase could inhibit 76.11% and 47.26% of IgE binding activities to the pollen extracts, respectively. Art si pectate lyase was also confirmed to activate patients’ basophils. Its structure contains a predominant motif of classic parallel helical core, consisting of three parallel β-sheets, and two highly conserved features (vWiDH, RxPxxR) which may contribute to pectate lyase activity. Moreover, Art si pectate lyase shared the highest sequence identity of 73.0% with Art v 6 among currently recognized pectate lyase allergen, both were clustered into the same branch in the phylogenetic tree. Conclusion: In this study, pectate lyase was identified and comprehensively characterized as a novel allergen in A. sieversiana pollen. The findings enriched the allergen information for this pollen and promoted the development of component-resolved diagnosis and molecular therapy of A. sieversiana pollen allergy. [ABSTRACT FROM AUTHOR]

For atmospheric argon RF dielectric barrier discharges, a self-consistent one-dimensional fluid model based on the drift-diffusive approximations of the particles is established to investigate the role of the neutral gas temperature on the discharge process and the plasma characteristics. A finite difference method is used to solve numerically the model, and the numerical results are obtained for the cases that the neutral gas temperature varies from 300 to 600 K. It shows that an increase in the neutral gas temperature causes a decrease in the ionization rate peak and a decrease in the plasma density, but the electric field and the electron temperature do not change very much. Moreover, the discharge mode transition from α mode to α-γ mode occurs because the growing ion flux induces more secondary electron flux, even if the ions entering the sheaths decrease. In addition, the ground state ionization and the ground state excitation are the main collisions in the argon discharges. When metastable atoms are focused on, the three-body quenching is also an important collision progress. [ABSTRACT FROM AUTHOR]

C7H6F3NO2, monoclinic, P21/c (no. 14), a = 11.3688(4) Å, b = 10.6836(3) Å, c = 14.4518(5) Å, β = 112.5320(10)°, V = 1621.32(9) Å3, Z = 8, Rgt(F) = 0.0554, wRref(F2) = 0.1647, T = 170 K.

In this paper, a capacitor assisted AC high-voltage was employed to generate a gas–liquid discharge in pure oxygen at atmospheric pressure. The discharge images, waveforms of voltage and discharge current, and optical emission spectra of plasma were diagnosed for the purpose of investigating the discharge modes. The gas temperature (Tg), excitation temperature of hydrogen (Texc), and electron density (ne) were calculated by the spectra of OH (A2Σ–X2Π), the intensity ratio of Hα and Hβ, and the Stark broadening of Hβ, respectively. The effects of applied voltage and capacitance value on the mode transition of discharge were also discussed. It is found that due to the presence of capacitor, not only is the unlimited growth of discharge current restrained, but the transition of discharge mode is also controllable. There are three discharge modes of gas–liquid discharge oxygen plasma (GLDOP), and with the increase of applied voltage or capacitance value, discharge modes are transited from the streamer mode, to the glow-like mode, and to the abnormal glow/arc mode. With the mode transition, the Tg and Texc of GLDOP increase and the ne decreases. In contrast, the change of Tg and ne is negligible when GLDOP maintains one kind of discharge mode. [ABSTRACT FROM AUTHOR]

In this paper, a transient spark discharge is presented driven by a nanosecond pulse power with a needle-water electrode configuration in atmospheric nitrogen. The transient spark discharge concludes three phases, described as the streamer phase, the streamer-to-spark transition phase, and the spark phase. The amplitude of pulse voltage has a significant influence on the characteristics of the transient spark discharge. The streamer-to-spark transition time shortens with the increase of pulse voltage, and the spark current value increases with the increase of pulse voltage. Though the streamer-to-spark transition is not completely prevented, the gas temperature is still in a lower value (∼400 K), due to the short duration of spark current (200–400 ns). The electron density in the transient spark, calculated by the Stark broadening of the Hα line at 656 nm, is about 1.3 × 1017 cm−3, which is 2–3 orders of magnitude higher than that in other forms of gas-liquid discharge. The results indicate that the transient spark discharge plasma is in a highly non-equilibrium state and the results also present its other unique features of high electron density and abundant excited species. [ABSTRACT FROM AUTHOR]

In this study, a nanosecond‐pulsed discharge plasma is employed to modify the macroporous XAD‐2 resin to improve the adsorption performance of polycyclic aromatic hydrocarbons. After modification, XAD‐2‐20 resin shows great advantage on naphthalene (Nap) adsorption, whose adsorption capacity increased by 80.6% and 43.5% compared with the raw and XAD‐2‐30, respectively. The physiochemical properties of XAD‐2 resin are characterized by scanning electron microscope, N2 adsorption/desorption, X‐ray photoelectron spectroscopy, and Fourier‐transform infrared (FTIR) spectrum. The amount of micro‐mesoporous with a size of 2–3.5 nm are formed and many carbonyl groups (C═O) and ester or carboxylic groups (O–C═O) are introduced on the XAD‐2‐20 surface, and the value of O/C is increased from 14% to 53% compared with the raw resin. [ABSTRACT FROM AUTHOR]

A stable diffuse large-area air plasma with low gas temperature is developed under different dielectric thicknesses by using a needle array-plate electrode configuration in air at atmospheric pressure, which is excited by a bipolar nanosecond pulse power with about 20 ns rising time. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse discharge are obtained under different dielectric thicknesses. The discharge area, the average power, the power density, and the emission intensities of N2 (C3Πu → B3Πg, 0-0) and N2+ (B2Σu+ → X2Σg+, 0-0) of the nanosecond dielectric barrier discharges are investigated under different dielectric thicknesses based on the waveforms of discharge voltage and discharge current and the optical emission spectra. The gas temperature of plasma is determined to be approximately 385±5 K by measuring the optical emission spectra of the N2+ (B2Σu+ → X2Σg+, 0-0), and decreases gradually with increasing dielectric thickness. Consistently, an area of approximately 2000 mm2 plasma region under 7 needle electrodes can be formed at 1 mm thick dielectric layer. [ABSTRACT FROM AUTHOR]

Transitions between the streamer and spark modes affect the stability of gas–liquid discharges, limiting their practical applications, while the nature of such transitions is poorly understood. Here we clarify the often neglected effect of a dielectric on the gas–liquid discharge stability, using direct and indirect grounding configurations. Discharge modes and plasma characteristics in these two configurations are investigated. The discharge appears in a transient spark mode in the direct grounding while in a streamer mode in the indirect case. It is shown that the dielectric significantly improves the discharge stability. The gas temperature and electron density in the transient spark are 380 K and 1017/cm3 with a 30 kV pulse voltage, respectively, which are higher than those in the streamer mode. [ABSTRACT FROM AUTHOR]

C7H6F3NO2, monoclinic, P21/c (no. 14), a = 11.3688(4) Å, b = 10.6836(3) Å, c = 14.4518(5) Å, β = 112.5320(10)°, V = 1621.32(9) Å3, Z = 8, Rgt(F) = 0.0554, wRref(F2) = 0.1647, T = 170 K. [ABSTRACT FROM AUTHOR]

C7H6F3NO2, monoclinic, P21/c (no. 14), a = 11.3688(4) Å, b = 10.6836(3) Å, c = 14.4518(5) Å, β = 112.5320(10)°, V = 1621.32(9) Å3, Z = 8, Rgt(F) = 0.0554, wRref(F2) = 0.1647, T = 170 K. [ABSTRACT FROM AUTHOR]