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1

Confinement of polar optical phonons in quasi-one-dimensional Wurtzite GaN-based quantum well wires: propagating and half-space phonon modes

100%

Zhang L., Shi J.-J.

Open Physics

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2007

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vol. 5

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issue 3

324-341

EN

With the aid of the macroscopic dielectric continuum and Loudon’s uniaxial crystal models, the propagating (PR) and half-space (HS) optical phonon modes and corresponding Fröhlich-like electron-phonon interaction Hamiltonians in a quasi-one-dimensionality (Q1D) wurtzite quantum well wire (QWW) structure are derived and studied. Numerical calculations on a wurtzite GaN/Al0.15Ga0.85N QWW are performed, and discussion is focused mainly on the dependence of the frequency dispersions of PR and HS modes on the free wave-number k z in the z-direction and on the azimuthal quantum number m. The calculated results show that, for given k z and m, there usually exist infinite branches of PR and HS modes in the high-frequency range, and only finite branches of HS modes in the low-frequency range in wurtzite QWW systems. The reducing behaviors of the PR modes to HS modes, and of the HS mode to interface phonon mode have been observed clearly in Q1D wurtzite heterostructures. Moreover, the dispersive properties of the PR and HS modes in Q1D QWWs have been compared with those in Q2D quantum well structures. The underlying physical reasons for these features have also been analyzed in depth.

2

Human neutrophil peptide 3 could be functionally expressed in Rhodobacter sphaeroides

71%

Nie X., Zhang L., Hu Z., Liu Y., Zhao Z.

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2015

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vol. 62

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issue 2

259-263

EN

Human neutrophil peptides (HNPs) possess high antimicrobial activities against a broad spectrum of microorganisms. Rhodobacter sphaeroides is the best-characterized photosynthetic bacterium and exhibits potential as a novel expression system. Up to date, no literature has been reported regarding expression of HNP3 in Rb. sphaeroides. In the present study, the HNP3 gene fragment was amplified by SOE PCR and ligated into photosynthetic bacteria light-harvesting complex 2 (LH2) expression vector leading to HNP3 fusion protein expression vector. The HNP3 fusion protein was successfully expressed as rapidly evaluated by the LH2 characteristic peaks at ~800 nm and ~850 nm before purification and SDS/PAGE. Subsequently, the HNP3 fusion protein was purified by one-step affinity chromatography, and could be rapidly detected by the color and the spectral absorption at ~800 nm and ~850 nm before SDS/PAGE. Antimicrobial activity assay suggested that the HNP3 fusion protein exhibited high antimicrobial activity towards E. coli. The present study may supply an insight into employing the novel Rb. sphaeroides expression system, exhibiting dramatic advantages over currently used commercial expression system, to heterologously express human neutrophil peptides.

3

High-grade mutant OmpF induces decreased bacterial survival rate

61%

Zhao Z.-p., Liu T.-t., Zhang L., Luo M., Nie X., Li Z.-x., Pan Y.

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2014

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vol. 61

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issue 2

369-373

EN

OmpF plays very important roles in the influx of antibiotics and bacterial survival in the presence of antibiotics. However, high-grade mutant OmpF and its function in decreasing bacterial survival rate have not been reported to date. In the present study, we cloned a high-grade mutant OmpF (mOmpF) and sequence analysis suggested that over 45 percent of the DNA sequence was significantly mutated, leading to dramatic changes in over 55 percent of the amino acid sequence. mOmpF protein was successfully expressed. When grown in the presence of antibiotic, the bacterial survival rate decreased and the antibiotic inhibition zone became larger with the increase of the mOmpF. It was concluded that concentration of high-grade mutant mOmpF dramatically influenced the bacterial survival rate. The study presented here may provide insights into better understanding of the relationships between structure and function of OmpF.

4

Two Gln187 mutants of human soluble APRIL inhibit proliferation of lung carcinoma A549 cells

52%

Dai S., Zheng Y., Chen B., Gao M., Zhang Y., Zhang L., Gong W., He F.

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issue 4

703-710

EN

Soluble APRIL (sAPRIL), the active form of a proliferation-inducing ligand (APRIL), is implicated in the proliferation of tumor cells. Suppressing APRIL function has been considered as a potential strategy for the therapy of APRIL-associated tumors. In the present study, we generated human sAPRIL and its two mutants, Gln187-D-sAPRIL (Gln187 deleted) and Gly187-sAPRIL (Gln187 replaced by Gly). In vitro experiments showed that the two mutants had similar specific binding capacity to lung carcinoma A549 cells compared to the wild-type sAPRIL, and both, especially Gly187-sAPRIL, exhibited significant antagonistic effect on sAPRIL-induced tumor cell proliferation in a dose-dependent manner, which might be predominantly mediated by blocking sAPRIL-induced MEK and ERK phosphorylation but not p38MAPK or JNK signaling. In vivo experiments with nude mice bearing A549 cell-derived xenograft tumor showed that only the Gly187-sAPRIL mutant could significantly suppress the tumor growth. These results suggest that Gln187 may be a crucial amino acid in APRIL-mediated tumor cell proliferation via the MEK-ERK signaling pathway and that the sAPRIL mutants may serve as novel potential antagonists of APRIL for the therapy of APRIL-associated cancers.

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Confinement of polar optical phonons in quasi-one-dimensional Wurtzite GaN-based quantum well wires: propagating and half-space phonon modes

Human neutrophil peptide 3 could be functionally expressed in Rhodobacter sphaeroides

High-grade mutant OmpF induces decreased bacterial survival rate

Two Gln187 mutants of human soluble APRIL inhibit proliferation of lung carcinoma A549 cells