PPyNT/NR/NBR Composites with Excellent Microwave Absorbing Performance in X-Band.

To meet the comprehensive demand for flexible microwave absorbing (MA) materials, a novel MA rubber containing homemade Polypyrrole nanotube (PPyNT) is produced based on the natural rubber (NR) and acrylonitrile-butadiene rubber (NBR) blends. To achieve the optimal MA performance in the X band, the PPyNT content and NR/NBR blend ratio are adjusted in detail. The 6 phr PPyNT filled NR/NBR (90/10) composite has the superior MA performance with the minimum reflection loss value of -56.67 dB and the corresponding effective bandwidth of 3.7 GHz at a thickness of 2.9 mm, which has the merits in virtue of achieving strong absorption and wide effective absorption band with low filler content and thickness compared to most reported microwave absorbing rubber materials over the same frequency. This work provides new insight into the development of flexible microwave-absorbing materials.

Review of the Application of Raman Spectroscopy in Qualitative and Quantitative Analysis of Drug Polymorphism.

Drug polymorphism is an important factor affecting the drugs quality and clinical efficacy. Therefore, great attention should be paid to the crystal analysis of drugs with their researching and evaluating part. With the booming development of Raman spectroscopy in recent years, more and more crystal analysis investigations were based on vibrational spectroscopy. This review mainly discussed the qualitative and quantitative analysis of active pharmaceutical ingredients (API) and pharmaceutical preparation with Raman spectroscopy. On basis of the determination of the vibration mode of drug molecules and the analysis of their chemical structure, this method had the advantages of universal, non-destructive, fast determination, low samples and cost, etc. This review provides theoretical and technical support for crystal structure, which are worth popularizing. It is expected that it will be helpful to relevant government management institutions, pharmaceutical scientific research institutions and pharmaceutical manufacturers.

Investigation of protective effect of ethanol on the natural structure of protein with infrared spectroscopy.

The stability of biological drugs with protein as an active substance depends heavily on the retention of natural protein structure during freeze-drying. Stabilizers have become important substances in the process of protein freeze-drying. In order to further understand the mechanism of the interaction between protein and stabilizers, human serum albumin (HSA) and simple hydroxyl compound ethanol were used as models. Infrared (IR) spectroscopy combined with chemometrics was implemented to investigate the changes of secondary structure and hydration of HSA when different concentrations of ethanol were considered as interference. Through the analysis of the protein secondary structure and hydrated layer, we found that the addition of ethanol-d6 increased the α-helix of HSA and reduced the disordered structure. The hydrogen bond structure around HSA was enhanced and intermolecular aggregation was reduced through the action of the water molecules. The hypothesis was verified by circular dichroism (CD) and transmission electron microscopy (TEM) observation by adding different concentrations of ethanol-d6. It was found that a small amount of ethanol could protect the native conformation of HSA. In conclusion, this study revealed the mechanism of ethanol as a protein protector, provided a new idea for protein purification process and a theoretical basis for biomolecular interaction.

Synchronization for stochastic coupled networks with Lévy noise via event-triggered control.

This paper addresses the realization of almost sure synchronization problem for a new array of stochastic networks associated with delay and Lévy noise via event-triggered control. The coupling structure of the network is governed by a continuous-time homogeneous Markov chain. The nodes in the networks communicate with each other and update their information only at discrete-time instants so that the network workload can be minimized. Under the framework of stochastic process including Markov chain and Lévy process, and the convergence theorem of non-negative semi-martingales, we show that the Markovian coupled networks can achieve the almost sure synchronization by event-triggered control methodology. The results are further extended to the directed topology, where the coupling structure can be asymmetric. Furthermore, we also proved that the Zeno behavior can be excluded under our proposed approach, indicating that our framework is practically feasible. Numerical simulations are provided to demonstrate the effectiveness of the obtained theoretical results.

Centralized/decentralized event-triggered pinning synchronization of stochastic coupled networks with noise and incomplete transitional rate.

This paper studies the synchronous problem of Markovian switching complex networks associated with partly unknown transitional rates, stochastic noise, and randomly coupling strength. In order to achieve the synchronization for these array networks, event-triggered pinning control is established and developed, in which the pinning node undergoes a self-adapted switch, governed by a Markov chain. Two types of event-triggered sampling controls, centralized and decentralized event-triggered sampling, respectively, are established. Sufficient conditions for synchronization are developed by constructing a desirable stochastic Lyapunov functional as well as by employing the properties of Markov chain and Itoˆ integration. Numerical simulations are provided to demonstrate the effectiveness of the proposed approach.

The roles and signaling pathways of prolyl-4-hydroxylase 2 in the tumor microenvironment.

Tumor hypoxia is a well-known microenvironmental factor that causes cancer progression and resistance to cancer treatment. Proline hydroxylases (PHDs), a small protein family, belong to an evolutionarily conserved superfamily of dioxygenases, considered the central regulator of the molecular hypoxia response. Prolyl-4-hydroxylase 2 (PHD2), one member of PHDs family, regulates the stability of the hypoxia-inducible factor-1 alpha (HIF-1α) in response to oxygen availability. During hypoxia, the inhibition of PHD2 permits the accumulation of HIF-1α, allowing the cellular adaptation to oxygen limitation, causing activation of numerous genes, which enhances the angiogenesis, metastasis and invasiveness. Accurate regulation of oxygen homeostasis is essential, and which implies PHD2 may have a regulatory role in the pathogenesis of cancer. Although ample evidence exists for a positive correlation between HIFs and tumor formation, metastasis and poor prognosis, the function of the PHD2 in carcinogenesis is less well understood. Despite their original role as the oxygen sensors of the cell and many of the its functions are clearly conveyed through the HIF system, PHD2 is currently known to display HIF-independent and hydroxylase-independent functions in cancer cells and stroma in the control of different cellular pathways. In this review, we summarize the recent advances in the structure, regulation and functions of PHD2 in cancer microenvironment.

Association of an miR-502-binding site polymorphism in the 3'-untranslated region of SET8 with colorectal cancer.

The histone methyltransferase SET8 is regulated by microRNA-502 through the binding site in its 3'-untranslated region, and the rs16917496 polymorphism at the miR-502-binding site in the SET8 gene has been implicated in a number of cancer types. The rs16917496 polymorphism including CC, CT and TT genotypes was analyzed in patients with colorectal cancer; the CC genotype was identified to be independently associated with longer post-operative survival times using multivariate analysis (relative risk, 2.406; 95% confidence interval, 1.017-5.691; P=0.046). In addition, decreased SET8 expression was associated with the SET8 CC genotype and longer survival times for patients with colorectal cancer. The results of the present study indicated that miR-502 mediates SET8 expression at least partly by altering the binding affinity between miR-502 and SET8 so as to modify the colorectal cancer outcome. The results indicate that SET8 may be a novel target for colorectal cancer therapy.

Synchronization of Nonlinearly and Stochastically Coupled Markovian Switching Networks via Event-Triggered Sampling.

This paper studies the exponential synchronization problem for a new array of nonlinearly and stochastically coupled networks via events-triggered sampling (ETS) by self-adaptive learning. The networks include the following features: 1) a Bernoulli stochastic variable is introduced to describe the random structural coupling; 2) a stochastic variable with positive mean is used to model the coupling strength; and 3) a continuous time homogeneous Markov chain is employed to characterize the dynamical switching of the coupling structure and pinned node sets. The proposed network model is capable to capture various stochastic effect of an external environment during the network operations. In order to reduce networks' workload, different ETS strategies for network self-adaptive learning are proposed under continuous and discrete monitoring, respectively. Based on these ETS approaches, several sufficient conditions for synchronization are derived by employing stochastic Lyapunov-Krasovskii functions, the properties of stochastic processes, and some linear matrix inequalities. Numerical simulations are provided to demonstrate the effectiveness of the theoretical results and the superiority of the proposed ETS approach.

Genetic polymorphisms of microRNA machinery genes predict overall survival of esophageal squamous carcinoma.

BACKGROUND: MicroRNA (miRNA)-related single nucleotide polymorphisms (miR-SNPs) in miRNA processing machinery genes are implicated in carcinogenesis, as they change the expression profiles of miRNA. Six miR-SNPs in miRNA processing machinery genes, including Dicer (rs3742330), RAN (rs14035), XPO5 (rs11077), TNRC6B (rs9623117), GEMIN3 (rs197412), and GEMIN4 (rs2740348), were evaluated for their association with esophageal squamous cell carcinoma (ESCC). METHODS: The miR-SNP of the miRNA processing genes were genotyped using the polymerase chain reaction-ligase detection reaction (PCR-LDR) assay, while the XPO5 expression levels in ESCC tissues were measured by immunochemistry methods. RESULTS: Patients carrying the rs11077 AA allele exhibited a significantly increased lifespan than AC+CC carriers, as determined by univariate and multivariate analyses (relative risk: 2.490; 95% confidence interval [CI]: 1.225-5.058; P=.012). Furthermore, the rs11077 AA genotype displayed a trend for high XPO5 expression in ESCC tissues by immunochemistry analysis, and these high XPO5 expression levels were also associated with high survival rates among ESCC patients. CONCLUSION: Our results suggested that the miRNA machinery gene expression-associated miR-SNPs would modify cancer outcomes; in this light, XPO5 may be an important new target for ESCC therapy.

Disruption of rimP-SC, encoding a ribosome assembly cofactor, markedly enhances the production of several antibiotics in Streptomyces coelicolor.

BACKGROUND: Ribosome assembly cofactor RimP is one of the auxiliary proteins required for maturation of the 30S subunit in Escherichia coli. Although RimP in protein synthesis is important, its role in secondary metabolites biosynthesis has not been reported so far. Considering the close relationship between protein synthesis and the production of secondary metabolites, the function of ribosome assembly cofactor RimP on antibiotics production was studied in Streptomyces coelicolor and Streptomyces venezuelae. RESULTS: In this study, the rimP homologue rimP-SC was identified and cloned from Streptomyces coelicolor. Disruption of rimP-SC led to enhanced production of actinorhodin and calcium-dependent antibiotics by promoting the transcription of actII-ORF4 and cdaR. Further experiments demonstrated that MetK was one of the reasons for the increment of antibiotics production. In addition, rimP-SC disruption mutant could be used as a host to produce more peptidyl nucleoside antibiotics (polyoxin or nikkomycin) than the wild-type strain. Likewise, disruption of rimP-SV of Streptomyces venezuelae also significantly stimulated jadomycin production, suggesting that enhanced antibiotics production might be widespread in many other Streptomyces species. CONCLUSION: These results established an important relationship between ribosome assembly cofactor and secondary metabolites biosynthesis and provided an approach for yield improvement of secondary metabolites in Streptomyces.

Shancigusins E-I, five new glucosides from the tubers of Pleione yunnanensis.

Five new glucosides, shancigusins E-I (1-5) were isolated from the tubers of Pleione yunnanensis (Rolfe) together with 18 known compounds. The structures of these compounds were determined by extensive analyses of their spectroscopic data.

Expression of cefF significantly decreased deacetoxycephalosporin C formation during cephalosporin C production in Acremonium chrysogenum.

Deacetoxycephalosporin C (DAOC) is not only the precursor but also one of the by-products during cephalosporin C (CPC) biosynthesis. One enzyme (DAOC/DAC synthase) is responsible for the two-step conversion of penicillin N into deacetylcephalosporin C (DAC) in Acremonium chrysogenum, while two enzymes (DAOC synthase and DAOC hydroxylase) were involved in this reaction in Streptomyces clavuligerus and Amycolatopsis lactamdurans (Nocardia lactamdurans). In this study, the DAOC hydroxylase gene cefF was cloned from Streptomyces clavuligerus and introduced into Acremonium chrysogenum through Agrobacterium tumefaciens-mediated transformation. When cefF was expressed under the promoter of pcbC, the ratio of DAOC/CPC in the fermentation broth significantly decreased. These results suggested that introduction of cefF could function quite well in Acremonium chrysogenum and successfully reduce the content of DAOC in the CPC fermentation broth. This work offered a practical way to improve the CPC purification and reduce its production cost.

Endophytic fungi from Dragon's blood specimens: isolation, identification, phylogenetic diversity and bioactivity.

Endophytic fungi from Dragon's blood specimens of different locations of China were characterized taxonomically and investigated concerning their antimicrobial and antitumor activity against six pathogenic microbes and five tumor cells. A total of 49 endophytic fungi were obtained from Dragon's blood materials of Dracaena spp., 18 taxa were represented by 43 (87.8%) isolates and only six (12.2%) isolates were unknown. Twenty (40.8%) of the isolates displayed antimicrobial activity against at least one pathogenic microorganism. Three isolates YNDC07, BJDC06 and BJDC09 displayed significant antimicrobial activities against Staphylococcus aureus, Cryptococcus neoformans and Aspergillus fumigates, respectively. The results of antitumor activity by the MTT assay revealed that 26.5%, 69.4%, 48.9%, 6.1% and 42.9% of isolate fermentation broths displayed growth inhibition on HepG2 cells, SKVO3 cells, MCF7 cells, HL-60 cells and 293-T cells, respectively. HNDC09 and HNDC10 showed very strong antitumor activity against MCF7 and 293-T, respectively. The results showed that endophytic fungi in Dragon's blood samples were valuable in screening antitumor and antimicrobial bioactivity agents.

[Chemical constituents of Dendrobium candidum].

The column chromatography on silica gel, sephadex LH-20 preparative HPLC were used to separate and purify the compounds from the stems of Dendrobium candidum. Twenty compounds were isolated and identified as 3,4'-dihydroxy-5-methoxybibenzyl(1), dihydroresveratrol(2), dendromoniliside E(3), denbinobin(4),2,4,7-trihydroxy-9, 10-dihydrophenanthrene(5), aduncin(6), (-)-loliolide(7), adenosine(8), uridine(9), guanosine(10), sucrose(11), 5-hydroxymethyl-furaldehyde(12), n-octacostyl ferulate(13), defuscin(14), n-triacontyl cis-p-coumarate(15), daucosterol(16), beta-sitosterol(17), hexadecanoic acid(18), hentriacontane(19), and heptadecanoic acid(20). Their structures were elucidated on the basis of spectroscopic data and physicochemical properties. All of the compounds were isolated from this plant for the first time.

Analysis of genetic stability through intersimple sequence repeats molecular markers in micropropagated plantlets of Anoectochilus formosanus Hayata, a medicinal plant.

Anoectochilus formosanus HAYATA, commonly known as "Jewel Orchids," which has been used as Chinese folk medicines, is being subjected to a huge crisis, whose wild resources have gradually become more and more scarce. Hence, micropropagation protocol by axillary branching established for A. formosanus was employed for large-scale commercial production. In this study, due to the somaclonal variation and on the basis of some virtue of intersimple sequence repeats (ISSR) analysis, we firstly utilized the ISSR primers to investigate the genetic stability of A. formosanus propagated in vitro for a period of more than 5 years. Among the total 100 bands amplified by 17 ISSR markers, 77 bands were distributed in size from 500 bp to 1.5 kbp, while only 5 bands were beyond 1.8 kbp in size. Meanwhile, according to the cluster analysis, genetic similarity was more than 94% and the polymorphism rate was only 2.76% among the total 1810 scorable bands. All results demonstrate A. formosanus, multiplied by axillary branching, maintained high genetic fidelity even after a period of more than 5 years under in vitro propagation with only a low risk of genetic instability. The results from this study provide an important basis for giving evidence of genetic stability of A. formosanus before micropropagation for large-scale commercial production.

Complete assignments of (1)H and (13)C NMR data of three new dihydrophenanthrofurans from Pleione yunnanensis.

Three new dihydrophenanthrofurans, pleionesins A-C (1-3), together with two known dihydrophenanthrenes (4-5) were isolated from the tubers of Pleione yunnanensis (Rolfe). The complete (1)H and (13)C NMR spectra assignments of these compounds were carried out using 1D and 2D NMR experiments ((1)H, (13)C, selective 1D NOE, HSQC and HMBC).

[Comparison of rutin and syringin content between tissue culturing seedlings and botanical drug of Saussurea involucrata].

OBJECTIVE: To compare the rutin and syringin content in tissue culturing seedlings and in botanical drug of Saussurea involucrata. METHOD: The HPLC with Hydro-RP C18 (4.6 mm x 250 mm, 5 microm) column was used, a mixture of acetonitrile-water (5:95) was used as a mobile phase, with flow rate of 1 mL x min(-1), column temperature at 25 degrees C and detection wavelength at 220 nm. RESULT: The effective constituents of tissue culturing seedlings were almost similar to the botanical drug. And syringin in tissue culturing seedlings was increased 4.35 times. CONCLUSION: It has a good prospect to acquire high-quality S. involucrata by tissue culturing seedlings.

New bibenzyl derivatives from the tubers of Pleione yunnanensis.

Four new bibenzyl derivatives, shancigusins A-D (1-4) and five known bibenzyls (5-9) were isolated from the tubers of Pleione yunnanensis (Orchidaceae). The structures of these compounds were determined by extensive analyses of their spectroscopic data.