Palladium-catalyzed alkylation of unactivated C(sp3)–H bonds with primary alkyl iodides at room temperature: facile synthesis of β-alkyl α-amino acids

Practical synthesis of β-alkyl α-amino acidsviaC(sp³)–H alkylation at room temperature.

Enhanced water retention and proton conductivity of proton exchange membranes by incorporating hollow polymer microspheres grafted with sulfonated polystyrene brushes

The paper describes the synthesis of hollow polymer microspheres with sulfonated polystyrene brushes and investigation of the enhanced water retention and proton conductivity of proton exchange membranes.

Facilitated transport of small molecules and ions for energy-efficient membranes

In nature, the biological membrane can selectively transport essential small molecules/ions through facilitated diffusion via carrier proteins. Intrigued by this phenomenon and principle, membrane researchers have successfully employed synthetic carriers and carrier-mediated reversible reactions to enhance the separation performance of synthetic membranes. However, the existing facilitated transport membranes as well as the relevant facilitated transport theories have scarcely been comprehensively reviewed in the literature. This tutorial review primarily covers the two aspects of facilitated transport theories: carrier-mediated transport mechanisms and facilitated transport chemistries, including the design and fabrication of facilitated transport membranes. The applications of facilitated transport membranes in energy-intensive membrane processes (gas separation, pervaporation, and proton exchange membrane fuel cells) have also been discussed. Hopefully, this review will provide guidelines for the future research and development of facilitated transport membranes with high energy efficiency.

Functionalized carbon nanotube via distillation precipitation polymerization and its application in nafion-based composite membranes

The objective of this study is to develop a novel approach to in situ functionalizing multiwalled carbon nanotubes (MWCNTs) and exploring their application in Nafion-based composite membranes for efficient proton conduction. Covalent grafting of acrylate-modified MWCNTs with poly(methacrylic acid-co-ethylene glycol dimethacrylate), poly(vinylphosphonic acid-co-ethylene glycol dimethacrylate), and sulfonated poly(styrene-co-divinylbenzene) was achieved via surface-initiated distillation precipitation polymerization. The formation of core-shell structure was verified by TEM images, and polymer layers with thickness around 30 nm were uniformly covered on the MWCNTs. The graft yield reached up to 93.3 wt % after 80 min of polymerization. The functionalized CNTs (FCNTs) were incorporated into the Nafion matrix to prepare composite membranes. The influence of various functional groups (-COOH, -PO3H2, and -SO3H) in FCNTs on proton transport of the composite membranes was studied. The incorporation of FCNTs afforded the composite membranes significantly enhanced proton conductivities under reduced relative humidity. The composite membrane containing 5 wt % phosphorylated MWCNTs (PCNTs) showed the highest proton conductivity, which was attributed to the construction of lower-energy-barrier proton transport pathways by PCNTs, and excellent water-retention and proton-conduction properties of the cross-linked polymer in PCNTs. Moreover, the composite membranes exhibited an enhanced mechanical stability.

Enhanced CO2 permeability of membranes by incorporating polyzwitterion@CNT composite particles into polyimide matrix

In this study, polyzwitterion is introduced into a CO2 separation membrane. Composite particles of polyzwitterion coated carbon nanotubes (SBMA@CNT) are prepared via a precipitation polymerization method. Hybrid membranes are fabricated by incorporating SBMA@CNT in polyimide matrix and utilized for CO2 separation. The prepared composite particles and hybrid membranes are characterized by transmission electron microscopy (TEM) with element mapping, field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC) and an electronic tensile machine. Water uptake and water state of membranes are measured to probe the relationship among water uptake, water state and CO2 transport behavior. Hybrid membranes show significantly enhanced CO2 permeability compared to an unfilled polyimide membrane at a humidified state. A hybrid membrane with 5 wt % SBMA@CNT exhibits the maximum CO2 permeability of 103 Barrer with a CO2/CH4 selectivity of 36. The increase of CO2 permeability is attributed to the incorporation of the SBMA@CNT composite particles. First, SBMA@CNT form interconnected channels for CO2 transport due to the facilitated transport effect of the quaternary ammonium in repeat unit of pSBMA. Second, SBMA@CNT improve water uptake and adjust water state of membrane, which further increases CO2 permeability. Meanwhile, the variation of CO2/CH4 selectivity is dependent on the bound water portion in the membrane. A gas permeation test at a dry state and a pressure test are conducted to further probe the membrane separation performance.

Matrine-induced apoptosis of human nasopharyngeal carcinoma cells via in vitro vascular endothelial growth factor-A/extracellular signal-regulated kinase1/2 pathway inactivation

Matrine, a main active extract from Sophora flavescens Ait, has been demonstrated to exert anticancer effects on various cancer cell lines, such as malignant melanoma, breast cancer, and lung cancer. However, it is currently unclear whether matrine could also elicit an inhibitory effect on growth of nasopharyngeal carcinoma (NPC), let alone the possible molecular mechanisms. Therefore, in a previous study, we investigated matrine-induced proliferation inhibition and apoptosis in NPC cells. It was shown that proliferation of human NPC cells (CNE1 and CNE2) was significantly diminished by matrine in a dose- and time-dependent manner, and apoptosis was induced in both 2 NPC cells, particularly in CNE2 cells. Moreover, the increased apoptosis rate in matrine-treated CNE2 cells confirmed the proapoptotic activity of matrine. We further found that matrine treatment dose- and time-dependently reduced the levels of vascular endothelial growth factor-A (VEGF-A), and inactivated extracellular signal-regulated kinase1/2 (ERK1/2), followed by increased expression of downstream target caspase-3. Overall, we conclude that matrine could induce apoptosis of human NPC cells via VEGF-A/ERK1/2 pathway, which supports the potential use of matrine in clinically treating NPC.

Enhanced proton conductivity of Nafion hybrid membrane under different humidities by incorporating metal-organic frameworks with high phytic acid loading

In this study, phytic acid (myo-inositol hexaphosphonic acid) was first immobilized by MIL101 via vacuum-assisted impregnation method. The obtained phytic@MIL101 was then utilized as a novel filler to incorporate into Nafion to fabricate hybrid proton exchange membrane for application in PEMFC under different relative humidities (RHs), especially under low RHs. High loading and uniform dispersion of phytic acid in MIL 101(Cr) were achieved as demonstrated by ICP, FT-IR, XPS, and EDS-mapping. The phytic@MIL101 was dispersed homogeneously in the Nafion matrix when the filler content was less than 12%. Hybrid membranes were evaluated by proton conductivity, mechanical property, thermal stability, and so forth. Remarkably, the Nafion/phytic@MIL hybrid membranes showed high proton conductivity at different RHs, especially under low RHs, which was up to 0.0608 S cm(-1) and 7.63 × 10(-4) S cm(-1) at 57.4% RH and 10.5% RH (2.8 and 11.0 times higher than that of pristine membrane), respectively. Moreover, the mechanical property of Nafion/phtic@MIL hybrid membranes was substantially enhanced and the thermal stability of membranes was well preserved.

N2 ameliorates neural injury during experimental ischemic stroke via the regulation of thromboxane A2 production

Thromboxane A2 (TXA2) promotes ischemic stroke injury and has strong effects in vascular contraction and vascular endothelial cell dysfunction. Agents that reduce TXA2 production have potential for ameliorating neural injury in ischemic stroke. Thromboxane synthetase (TXS) is essential for TXA2 production, and TXS inhibitors have been developed as drugs for the prevention and treatment of stroke. However, ozagrel, a typical TXS inhibitor currently in clinical use, must be delivered via intravenous injection (I.V.). N2, 4-(2-(1H-imidazol-1-yl) ethoxy)-3-methoxybenzoate, is a potential thromboxane synthetase (TXS) inhibitor, which is being developed as an orally available formulation. The aim of this study was to investigate the effects of N2 on focal cerebral ischemia-reperfusion injury and related mechanisms. Neurological deficits, a Y-maze test and infarct volume were measured to evaluate the effects of N2 post-treatment on middle cerebral artery occlusion (MCAO)-induced ischemia/reperfusion (I/R) injury in rats. Furthermore, the influence of N2 on U46619-induced rat aorta contraction was investigated ex vivo. Moreover, we investigated the protective effects of N2 on rat brain microvessel endothelial cells (RBMECs) in hypoxia/deoxygenating (H/R) induced by Na2S2O4 in vitro. Cell viability and TXA2 biosynthesis were measured by 3-(4, 5-dimethylthiazol-2-yl)- 195 2, 5-diphenyltetrazolium bromide (MTT) and enzyme-linked immunosorbent assay (ELISA) assays, respectively. The results showed that N2 treatment effectively improves performance in neurological deficit and the Y-maze test and reduces the infarct volume in I/R rats. U46619-induced rat aorta contraction was inhibited by N2 ex vivo. Furthermore, N2 incubation improved the morphology of RBMECs, increased cell viability, and suppressed TXA2 production by inhibiting TXS during H/R damage. In summary, this study demonstrated that N2 was neural protective in focal cerebral I/R injury, which might be associated with the effects of N2 on endothelium protection and vascular contraction inhibition. In depth, the mechanisms underlying this phenomenon might be the influence of N2 on TXA2 production targeting TXS.

Zwitterionic microcapsules as water reservoirs and proton carriers within a Nafion membrane to confer high proton conductivity under low humidity

Zwitterionic microcapsules (ZMCs) based on sulfobetaine with tunable hierarchical structures, superior water retention properties, and high proton conduction capacities are synthesized via precipitation polymerization. The incorporation of ZMCs into a Nafion matrix renders the composite membranes with significantly enhanced proton conductivity especially under low humidity. The composite membrane with 15 wt % ZMC-I displayed the highest proton conductivity of 5.8 × 10(-2) S cm(-1) at 40 °C and 20% relative humidity after 90 min of testing, about 21 times higher than that of the Nafion control membrane. The increased proton conductivity is primarily attributed to the versatile roles of ZMCs as water reservoirs and proton conductors for rendering a stable water environment and an additional proton conduction pathway within the membranes. This study may contribute to the rational design of water-retaining and proton-conducting materials.

Surface characterization and osteoblast response to a functionally graded hydroxyapatite/fluoro-hydroxyapatite/titanium oxide coating on titanium surface by sol-gel method

OBJECTIVES

To improve efficacy of current titanium and its alloys, in bioactivity and speed of osseointegration, of orthopaedic implants.

MATERIALS AND METHODS

A novel triple-layered functional graded coating, consisting of a porous hydroxyapatite (HA) outermost layer, fluoro-HA (FHA) intermediate layer and titanium oxide (TiO2 ) innermost layer, was created on a titanium substrate by a multistep sol-gel method. X-ray diffraction analysis showed TiO2 anatase and apatite crystallization in the coating.

RESULTS

Morphological analysis performed by scanning electron microscopy showed excellent bonding between coating and substrate, with a thickness of ~2 μm. Scratch testing found favourable adhesion strength of the composite coating. In addition, optical microscope images suggested good biocompatibility. Considering thet in vitro cell response, osteoblasts on the coating exhibited higher cell proliferation and ALP activity compared to pure titanium and HA coating, and demonstrated excellent coating bioactivity.

CONCLUSIONS

Current results indicated that the novel TiO2 /FHA/HA coating has promising clinical applications in orthopaedic and dental implantation.

Neither cytochrome P450 family genes nor neuroendocrine factors could independently predict the SSRIs treatment in the Chinese Han population

OBJECTIVE

This study was intended to explore the relationship between the genetic polymorphisms of the 8 single nucleotide polymorphisms (SNPs) at CYP genes, neuroendocrine factors and the response to selective serotonin reuptake inhibitors (SSRIs) in Chinese Han depressive patients.

METHOD

This was a 6-week randomized controlled trial consisting of 290 Chinese Han depressive patients treated with SSRIs. 8 SNPs of CYP450 genes and 7 neuroendocrine factors were detected. Allele and genotype frequencies were compared between responders and non-responders. The relationships between neuroendocrine factors and treatment response were also analyzed.

RESULTS

No significant differences were found in clinical features between 2 groups at the baseline. No statistical correlation was found between either the genotype or allele frequencies of SNPs in CYP1A2, CYP2C19, or CYP2D6 gene and the -efficacy of SSRIs. There were strong linkage disequilibria between rs4986894, rs1853205, and rs12767583 of CYP2C19 genes, and rs2472299, rs2472300 of CYP1A2 genes. No associations were found between the above haplotypes and the antidepressant response. No neuroendocrine factor was a significant predictor for a response to SSRI antidepressants independently. The combination of neuroendocrine factors, however, predicted the response by 76.1%.

CONCLUSION

There were no significant associations between the 6 SNPs of CYP gene polymorphisms and SSRI response. Neither cytochrome P450 family genes nor neuroendocrine factors independently predict the patients' response to the antidepressants separately. A combination of neuroendocrine factors, however, does have the potential to predict the response.

Selective neuronal differentiation of neural stem cells induced by nanosecond microplasma agitation

An essential step for therapeutic and research applications of stem cells is their ability to differentiate into specific cell types. Neuronal cells are of great interest for medical treatment of neurodegenerative diseases and traumatic injuries of central nervous system (CNS), but efforts to produce these cells have been met with only modest success. In an attempt of finding new approaches, atmospheric-pressure room-temperature microplasma jets (MPJs) are shown to effectively direct in vitro differentiation of neural stem cells (NSCs) predominantly into neuronal lineage. Murine neural stem cells (C17.2-NSCs) treated with MPJs exhibit rapid proliferation and differentiation with longer neurites and cell bodies eventually forming neuronal networks. MPJs regulate ~75% of NSCs to differentiate into neurons, which is a higher efficiency compared to common protein- and growth factors-based differentiation. NSCs exposure to quantized and transient (~150 ns) micro-plasma bullets up-regulates expression of different cell lineage markers as β-Tubulin III (for neurons) and O4 (for oligodendrocytes), while the expression of GFAP (for astrocytes) remains unchanged, as evidenced by quantitative PCR, immunofluorescence microscopy and Western Blot assay. It is shown that the plasma-increased nitric oxide (NO) production is a factor in the fate choice and differentiation of NSCs followed by axonal growth. The differentiated NSC cells matured and produced mostly cholinergic and motor neuronal progeny. It is also demonstrated that exposure of primary rat NSCs to the microplasma leads to quite similar differentiation effects. This suggests that the observed effect may potentially be generic and applicable to other types of neural progenitor cells. The application of this new in vitro strategy to selectively differentiate NSCs into neurons represents a step towards reproducible and efficient production of the desired NSC derivatives.

Recruitment of trimeric proliferating cell nuclear antigen by G1-phase cyclin-dependent kinases following DNA damage with platinum-based antitumour agents

BACKGROUND

In cycling tumour cells, the binary cyclin-dependent kinase Cdk4/cyclin D or Cdk2/cyclin E complex is inhibited by p21 following DNA damage to induce G1 cell-cycle arrest. However, it is not known whether other proteins are also recruited within Cdk complexes, or their role, and this was investigated.

METHODS

Ovarian A2780 tumour cells were exposed to the platinum-based antitumour agent 1R,2R-diaminocyclohexane(trans-diacetato)(dichloro)platinum(IV) (DAP), which preferentially induces G1 arrest in a p21-dependent manner. The Cdk complexes were analysed by gel filtration chromatography, immunoblot and mass spectrometry.

RESULTS

The active forms of Cdk4 and Cdk2 complexes in control tumour cells have a molecular size of ~140 kDa, which increased to ~290 kDa when inhibited following G1 checkpoint activation by DAP. Proteomic analysis identified Cdk, cyclin, p21 and proliferating cell nuclear antigen (PCNA) in the inhibited complex, and biochemical studies provided unequivocal evidence that the increase in ~150 kDa of the inhibited complex is consistent with p21-dependent recruitment of PCNA as a trimer, likely bound to three molecules of p21. Although p21 alone was sufficient to inhibit the Cdk complex, PCNA was critical for stabilising p21.

CONCLUSION

G1 Cdk complexes inhibited by p21 also recruit PCNA, which inhibits degradation and, thereby, prolongs activity of p21 within the complex.

Fast energy relaxation of hot carriers near the Dirac point of graphene

We investigate energy relaxation of hot carriers in monolayer and bilayer graphene devices, demonstrating that the relaxation rate increases significantly as the Dirac point is approached from either the conduction or valence band. This counterintuitive behavior appears consistent with ideas of charge puddling under disorder, suggesting that it becomes very difficult to excite carriers out of these localized regions. These results therefore demonstrate how the peculiar properties of graphene extend also to the behavior of its nonequilibrium carriers.

Topographical distribution pattern of cervical intraepithelial neoplasia across the cervix

OBJECTIVE

The distribution of cervical intraepithelial neoplasia (CIN) lesions across the cervix was determined.

METHODS

A total of 575 women whose pathological diagnosis after cervical conization was confirmed as CIN were studied; 146 had low-grade CIN and 429 had high-grade CIN. CIN lesion location on the cervix was recorded using 12-h clock face notation.

RESULTS

In both groups, 12 o'clock was the most common and 2 o'clock the least common lesion location. The most severe lesions were most often located at 8 o'clock and 7 o'clock, in the low- and high-grade groups, respectively. The 2 o'clock site was the least frequent site for the most severe lesion in both groups. Lesions were found more frequently on the posterior lip of the cervix than on the anterior lip, and on the right side of the cervix than on the left side, in both groups.

CONCLUSIONS

The distribution of CIN lesions is not randomly distributed across the cervix. The 12, 8 and 7 o'clock sites, and the posterior lip and right side of the cervix, should be targeted during colposcopy-directed biopsy of patients with CIN lesions as this may improve diagnostic accuracy.

Rasgrp2 regulates the permissiveness of NIH3T3 cells to a herpes simplex virus 1 mutant with inactivated ICP34.5 gene

We have previously reported that mtHSV, a herpes simplex virus 1 (HSV-1) mutant with an inactivated gene for β-galactosidase, can efficiently lyse tumor but not normal cells. However, the mechanism of this selective oncolytic activity is so far unclear. In this study, using the phage display screening we identified the cellular protein binding to HSV-1 mutant (mtHSV) as (Ras guanyl releasing protein 2) Rasgrp2 which regulates the Ras signaling pathway. Rasgrp2 was found to bind directly to purified mtHSV as well as to mtHSV present within infected HeLa cells where it aggregated on the cell membrane. NIH3T3 cells were found nonpermissive to mtHSV but they became permissive following transformation with the Rasgrp2 gene. This effect was linked to the activation of the Ras-PKR signaling pathway. These observations indicate a key role of Rasgrp2 in the mtHSV infection of NIH3T3 cells and are important for the potential use of mtHSV in cancer therapy.

Two novel phenethylamine alkaloids from streptomyces sp. YIM10049

Two novel phenethylamine alkaloids were isolated from Streptomyces sp. YIM 10049. On the basis of spectral data, their structures were determined as (S)-N-(cu-phenylethyl)-2 -hydroxyl-acrylimine (1) and (S)-N-nitroso-1-amino-p-hydroxy phenylethanol (2). Three known compounds, indole-3-carboxylic acid (3), cyclo(L-Ala-L-Tyr)(4), and bis(2-ethylhexyl) phthalate (5), were also isolated and characterized. Compound 1 is a rare enol tautomer, and compound 2 an unusual phenethylamine alkaloid with a N-NO group.

Two Novel Phenethylamine Alkaloids from Streptomyces sp. YIM10049

Two novel phenethylamine alkaloids were isolated from Streptomyces sp. YIM 10049. On the basis of spectral data, their structures were determined as (S)-N- (α-phenylethyl)-2-hydroxyl-acrylimine (1) and (S)-N-nitroso-1-amino- p-hydroxy phenylethanol (2). Three known compounds, indole-3-carboxylic acid (3), cyclo(L-Ala-L-Tyr)(4), and bis(2-ethylhexyl) phthalate (5), were also isolated and characterized. Compound 1 is a rare enol tautomer, and compound 2 an unusual phenethylamine alkaloid with a N-NO group.