[Review on Analytical Methods of Doping Elements in Synthetic Crystals]

During the synthesis of crystal material, specific dopant can enhance the qualities and performance of crystals, while the types, concentrations and distributions of doping elements also have significant influence on the structures and properties of artificial crystals. Hence, it is very important to determine the concentrations of doping elements for further improving the crystal material formulas, crystal growth process, andits quality control. Currently, the analysis techniques for doping elements’ characterization include atomic spectrometry, X-ray fluorescence spectrometry, inorganic mass spectrometry, electron probe microanalysis, etc. The principles, advantages and disadvantages of these techniques are discussed in this paper. Considering the specialties and scope of application, it is necessary to choose the suitable methods to improve the efficiency and accuracy. Meanwhile, the developing trends of analysis methods for doping elements are also prospected.

Correlation between Poynting flux and soft electron precipitation in the dayside polar cap boundary regions

Observations have revealed large Poynting flux and soft electron precipitation around the cusp region, which have strong impacts on the polar ionosphere/thermosphere. Simulations also confirmed that Poynting flux and soft electron precipitation significantly change the neutral density and dynamics around the dayside polar cap boundary regions. However, no detailed study has been conducted to show if they should coincide with each other or not. Our analysis of Defense Meteorological Satellite Program (DMSP) satellite data reveals a complex correlation between them. Poynting flux and soft particle precipitation are coincident in some cases (match cases), but a clear displacement between them can also be identified in others (nonmatch cases). In the 29 cusp crossings from F13 we investigated, the ratio between nonmatch and match cases is close to 1:4. In nonmatch cases, the displacement between the Poynting flux enhancement and soft particle precipitation enhancement can be as large as 1° in geomagnetic latitude.

PABPC1 interacts with AGO2 and is responsible for the microRNA mediated gene silencing in high grade hepatocellular carcinoma

MicroRNAs (miRNA) have been considered as oncogenes, tumor suppressors, or modulators involved in the tumorigenesis and metastasis of hepatocellular carcinoma (HCC) today. As miRNA induces mRNA degradation or translation inhibition in RNA-induced silencing complex (RISC), the changes in RISC and its interacted proteins might contribute to the functional alternations of miRNA. To explore the molecular function of RISC in HCC, we co-purified RISC interacted proteins by anti-AGO2 antibody and identified 12 AGO2 binding proteins by mass spectrometry. Among them, we found PABPC1 was over-expressed in HCC, especially in high grade HCC. Further studies showed PABPC1 interacted with AGO2 in the cytoplasm of HCC cells. This interaction increased the recruitment of mRNA to RISC and enhanced the inhibition efficiency of miRNA. In general, PABPC1 acted as an oncogene in HCC as it induced cell proliferation by promoting entry into the S phase and enhanced the anchorage independent growth. Our study identified a novel method by which the activities of miRNA could be enhanced with the increase of PABPC1 in HCC and could explain why several miRNAs play critical roles in HCC progression without clear level changes. This finding would benefit the diagnosis and treatment of HCC.

MiR-183/-96/-182 cluster is up-regulated in most breast cancers and increases cell proliferation and migration

Introduction

The miR-183/-96/-182 cluster is a conserved polycistronic microRNA (miRNA) cluster which is highly expressed in most breast cancers. Although there are some sporadic reports which demonstrate the importance of each miRNA in this cluster in breast cancer, the biological roles of this cluster as a whole and its regulation mechanisms in breast cancer are still unclear. We compared the expression of this cluster in different cancer types, analyzed the regulation mechanism of this cluster, identified new target genes, and examined the impact of this cluster on breast cancer cells.

Methods

The miRNA level was detected by LNA-based northern blot and Real-time PCR, and was also analyzed from TCGA dataset. Bioinformatics research and luciferase assay were applied to find the promoter regions and transcription factors. To investigate the biological effects of the miR-183/-96 /-182 cluster in breast cancer, we generated miR-96, miR-182 and miR-183 overexpression stable cell lines to check the overdose effects; we also used miR-Down™ antagomir for each miRNA as well as miR-183/-96 /-182 cluster sponge lentivirus to check the knockdown effects. Growth, migration, cell cycle profile and survival of these cells was then monitored by colony formation assay, MTT assay, cell wound healing assay, flow cytometry and microscopy. The target gene was validated by Real-time PCR, luciferase assay, Western blot and Phalloidin/DAPI counterstaining.

Results

The miR-183/-96/-182 cluster was highly expressed in most breast cancers, and its transcription is disordered in breast cancer. The miR-183/-96/-182 cluster was transcribed in the same pri-miRNA and its transcription was regulated by ZEB1 and HSF2. It increased breast cell growth by promoting more rapid completion of mitosis, promoted cell migration and was essential for cell survival. MiR-183 targeted the RAB21 mRNA directly in breast cancer.

Conclusion

The miR-183/-96/-182 cluster is up-regulated in most breast cancer. It functions as an oncogene in breast cancer as it increases cell proliferation and migration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0473-z) contains supplementary material, which is available to authorized users.

Refractive index sensor based on the leaky radiation of a microfiber

In this work we present a refractive index sensor based on the leaky radiation of a microfiber. The 5.3um diameter microfiber is fabricated by drawing a commercial optical fiber. When the microfiber is immersed into a liquid with larger refractive index than the effective index of fiber mode, the light will leak out through the leaky radiation process. The variation of refractive index of liquid can be monitored by measuring radiation angle of light. The refractive index sensitivity can be over 400 degree/RIU in theory. In the experiment, the variation value 0.001 of refractive index of liquid around this microfiber can be detected through this technique. This work provides a simple and sensitive method for refractive index sensing application.

Transformation bending device emulated by graded-index waveguide

We demonstrate that a transformation device can be emulated using a gradient-index waveguide. The effective index of the waveguide is spatially varied by tailoring a gradient thickness dielectric waveguide. Based on this technology, we demonstrate a transformation device guiding visible light around a sharp corner, with low scattering loss and reflection loss. The experimental results are in good agreement with the numerical results.

Simple way for achieving passive all-optical switching of continuous waves lasers using pure nematic liquid crystal

We have examined pure nematic liquid crystal (LC), 4'-pentyl-4-biphenylcarbonitrile (5-CB), with a 90° twisted alignment within a cell made of two cross-polarized absorptive plastic polarizers, and investigated the nonlinear transmission properties using cw (532 nm) lasers. We observed optically self-activated polarization switching with a factor of three lower switching power than a dye-doped LC cell with similar linear transmittance using glass substrates. We also studied the dynamics of the switching processes and observed millisecond switching time. These studies have demonstrated a simpler but more efficient way for fabricating broadband, low switching power, millisecond time scale switching, and optical limiting devices.

New lead structures in antifungal drug discovery

During the past two decades, the incidence of invasive fungal infections has been increasing dramatically. Clinical available antifungal agents have several drawbacks such as limited potency and spectrum, drug related toxicity, non-optimal pharmacokinetics, and severe resistance. There is an emergent need to develop new antifungal drugs with novel chemical structures and novel mechanism of action. This review will focus on the most significant achievements in the discovery of antifungal lead structures within last few years. In particular, we pay more attention on the structure-activity relationship of antifungal leads and provide perspectives for future antifungal drug discovery.

[Latent membrane protein-1 of EB virus and the phenotype of epithelial-mesenchymal transition and cervical lymph node metastasis in nasopharyngeal carcinoma]

OBJECTIVE

To evaluate the relation of EB virus latent membrane protein-1 (LMP-1) and the phenotype of epithelial-mesenchymal transition (EMT) and cervical lymph node metastasis in nasopharyngeal carcinoma.

METHOD

Based on histopathology and MRI imaging, nasopharyngeal biopsy tissues from 88 patients with nasopharyngeal carcinoma were divided into 3 groups: pathologic metastasis (18), MRI metastasis(40) and without metastasis (30). The expressions of LMP-1, STAT3, Twist, E-Cadherin and Vimentin were examined immunohistochemically in biopsy tissues.

RESULT

LMP-1 expression was found in 35 of 88 biopsy tissues with a positive rate of 38.7%. The positive rates of LMP-1 in groups of pathologic metastasis, MRI metastasis and without metastasis were 38.9% (7/18), 47.5% (19/40) and 30.0% (9/30), respectively, and significant difference were not found among three groups. The expression of LMP-1 was positively correlated to both expressions of Twist and Vimentin (r = 0.276 and 0.282, are P < 0.01), but not to both expressions of STAT3 and E-Cadherin. The positive expressions or abnormal expression of STAT3, Twist, Vimentin and E-Cadherin were found in 57 of 88 (64.8%), 48 of 88 (54.5%), 22 of 88 (20.0%)and 53 of 88 (60.2%), respectively. Significant differences in the expression of STAT3, Twist, Vimentin and E-Cadherin were all found among groups of pathologic metastasis, MRI metastasis and without metastasis, respectively (are P < 0.05). The expression of STAT3 was positively correlated to both expressions of Twist and Vimentin (r = 0.712 and 0.316, P < 0.01).

CONCLUSION

EMT plays important role in cervical lymph node metastasis in nasopharyngeal carcinoma. LMP-1 may be only as one of upstream factors associated with the EMT, but not the decisive factor for cervical lymph node metastasis.

[Mineralogical effect correction for pressed iron ore samples in wavelength dispersive X-ray fluorescence analysis]

The possibility of correcting mineralogical effect for pressed powder pellets of iron ore samples was studied in wavelength dispersive X-ray fluorescence analysis of major and minor elements with 10 Chinese iron ore CRMs. Two methods were applied to reduce the influence of mineralogical effect. The first one is to check 20 angles for every sample before measurement to correct peak shift; another method is replacing peak intensity with peak area of the analytical line to correct the shape distortion of the spectrum. The K factors of the two methods for each element were compared to those from regular measurements. The results show that the calibration for most of the elements was improved, although to different degrees. The improvement in the calibration for sulfur is evident. The calibration for other elements can meet the general requirements except for total iron.

Homology Modeling of Lanosterol 14α-Demethylase ofCandida albicansandAspergillus fumigatusand Insights into the Enzyme-Substrate Interactions

The crystal structure of 14alpha-sterol demethylase from Mycobacterium tuberculosis (MT_14DM) provides a good template for modeling the three dimensional structure of lanosterol 14alpha-demethylase, which is the target of azole antifungal agents. Homologous 3D models of lanosterol 14alpha-demethylase from Candida albicans (CA_14DM) and Aspergillus fumigatus (AF_14DM) were built on the basis of the crystal coordinates of MT_14DM in complex with 4-phenylimidazole and fluconazole. The reliability of the two models was assessed by Ramachandran plots, Profile-3D analysis, and by analyzing the consistency of the two models with the experimental data on the P450(14DM). The overall structures of the resulting CA_14DM model and AF_14DM model are similar to those of the template structures. The two models remain the core structure characteristic for cytochrome P450s and most of the insertions and deletions expose the molecular surface. The structurally and functionally important residues such as the heme binding residues, the residues lining the substrate access channel, and residues in active site were identified from the model. To explore the binding mode of the substrate with the two models, 24(28)-methylene-24,25-dihydrolanosterol was docked into the active site of the two models and hydrophobic interaction and hydrogen-bonding were found to play an important role in substrate recognition and orientation. These results provided a basis for experiments to probe structure-function relationships in the P450(14DM). Although CA_14DM and AF_14DM shared similar core structural character, the active site of the two models were quite different, thus allowing the rational design of specific inhibitors to the target enzyme and the discovery of novel antifungal agents with broad spectrum.

Direct nitric oxide imaging in cultured hippocampal neurons with diaminoanthraquinone and confocal microscopy

A method for the direct measurement of intracellular nitric oxide (NO) production stimulated by penicillin G (PG) in cultured hippocampal neurons with diaminoanthraquinone (DAA) using laser scanning confocal microscopy (LSCM) was developed. Intracellular DAA fluorescence could specifically represent NO production based on two facts: (1) 3-morpholinosydnonimine, a NO donor, could dose-dependently increase DAA fluorescence; and (2) haemoglobin, a NO scavenger, could inhibit the increase of DAA fluorescence. The PG dose-dependently increased the intercellular level of glutamate (Glu, 5 min after stimulation) and the intracellular NO production (30 min throughout stimulation). The increase of NO production could be reversed by N(w)-nitro- l -arginine (a NO synthase inhibitor), and also by d (-)2-amino-5-phosphonovaleric acid, a subtype of Glu receptor antagonist. These results revealed that DAA could be used to indicate real-time and kinetic intracellular NO production of hippocampal neurons with higher sensitivity, specificity and accuracy.

Synthetic fuel for imitation of municipal solid waste in experimental studies of waste incineration

Synthetic fuel is prepared to imitate municipal solid waste (MSW) in experimental studies of incineration processes. The fuel is composed based on the Environmental Protection Agency reports on the materials contained in MSW. Uniform synthetic fuel pellets are prepared using available and inexpensive components including newsprint, hardwood mulch, low density polyethylene, iron, animal feed, sand, and water to imitate paperbound, wood, yard trimming, plastic, metal, food wastes, and other materials in MSW. The synthetic fuel preparation procedure enables one to reproduce and modify the fuel for a wide range of experiments in which the mechanisms of waste incineration are addressed. The fuel is characterized using standard ASTM tests and it is shown that its parameters, such as combustion enthalpy, density, as well as moisture, ash and fixed carbon contents are adequate for the representation of municipal solid waste. In addition, chlorine, nitrogen, and sulfur contents of the fuel are shown to be similar to those of MSW. Experiments are conducted in which the synthetic fuel is used for operation of a pilot-scale incinerator research facility. Steady-state temperature operation regimes are achieved and reproduced in these experiments. Thermodynamic equilibrium flame conditions are computed using an isentropic one-dimensional equilibrium code for a wide range of fuel/air ratios. The molecular species used to represent the fuel composition included cellulose, water, iron, polyethylene, methanamine, and silica. The predicted concentrations of carbon monoxide, nitric oxides, and oxygen in the combustion products are compared with the respective experimental concentrations in the pilot-scale incinerator exhaust.

Influence of neutral cyclodextrin concentration on plate numbers in capillary electrophoresis

A quantitative theory of plate number N in capillary electrophoresis was developed for buffers containing neutral cyclodextrins (CDs) capable of forming inclusion complexes. In the theory, N was modeled by longitudinal diffusion, injection extent, width of the detection window, and the detector time constant. The apparent mobility was modeled as a weighted sum of the mobilities of the free-solution analyte and the inclusion complex. The apparent diffusion coefficient was modeled as a similarly weighted sum. Both the apparent mobility and diffusion coefficient were corrected by functions that compensated for increases of buffer temperature caused by Joule heat. The experimental N's and apparent mobilities of neutral thiourea and of the anions, dansyl D- and L-leucine, dansyl D- and L-aspartic acid, benzoate, and 4-nitrophenolate, were determined in buffers containing from 0 to 15 mM beta-CD. The binding constants, and mobilities and diffusion coefficients of the free-solution analyte and inclusion complex, were calculated as regression coefficients by fitting theory to these determinations. The regression coefficients were shown to have physicochemical meaning, as assessed by literature values, independent measurements, and theoretical predictions. The assessment showed the Nernst-Einstein equation does not relate mobilities and diffusion coefficients at the electrolyte concentration used. The interdependence of mobilities, diffusion coefficients, binding constants, and other dispersion sources was interpreted to evaluate the factors affecting the variation of N with CD concentration. From the interpretation, an approximate equation for N in low-concentration CD buffers was derived. The equation depends on free-solution and inclusion-complex mobilities and diffusion coefficients, the binding constant, the potential difference over the effective capillary length, and the number of plates in a CD-free buffer.