Substrate interaction effects on order to disorder transition behavior in block copolymer films

We present an overview of the recent progress on the phase transition in the block copolymer (BCP) films in terms of the interfacial interactions effects of the substrates and the χ (Flory-Huggins segmental interaction parameter) effects between the two blocks. For the BCP films thinner than a critical thickness (L_c) above which the transition is independent of film thickness, the order-to-disorder transition (ODT) increased or decreased with decreasing film thickness depending on the interfacial interaction types. The rapid and slow changes in the ODT were attributed to the relative magnitude of enthalpic contribution to χ between two blocks. Interestingly, a periodic amplification in the block composition for the BCP films suppressed the compositional fluctuation in the film geometry, resulting in the ODT shifts from the bulk ODTs above L_c. This effect of the BCP films was more illustrated by the ODT shift effects depending on the strength of the preferential interactions on the substrates. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Autophagic failure promotes the exocytosis and intercellular transfer of α-synuclein

The accumulation of abnormal protein aggregates is a major characteristic of many neurodegenerative disorders, including Parkinson''s disease (PD). The intracytoplasmic deposition of α-synuclein aggregates and Lewy bodies, often found in PD and other α-synucleinopathies, is thought to be linked to inefficient cellular clearance mechanisms, such as the proteasome and autophagy/lysosome pathways. The accumulation of α-synuclein aggregates in neuronal cytoplasm causes numerous autonomous changes in neurons. However, it can also affect the neighboring cells through transcellular transmission of the aggregates. Indeed, a progressive spreading of Lewy pathology among brain regions has been hypothesized from autopsy studies. We tested whether inhibition of the autophagy/lysosome pathway in α-synuclein-expressing cells would increase the secretion of α-synuclein, subsequently affecting the α-synuclein deposition in and viability of neighboring cells. Our results demonstrated that autophagic inhibition, via both pharmacological and genetic methods, led to increased exocytosis of α-synuclein. In a mixed culture of α-synuclein-expressing donor cells with recipient cells, autophagic inhibition resulted in elevated transcellular α-synuclein transmission. This increase in protein transmission coincided with elevated apoptotic cell death in the recipient cells. These results suggest that the inefficient clearance of α-synuclein aggregates, which can be caused by reduced autophagic activity, leads to elevated α-synuclein exocytosis, thereby promoting α-synuclein deposition and cell death in neighboring neurons. This finding provides a potential link between autophagic dysfunction and the progressive spread of Lewy pathology.     

Cancer cell metabolism: implications for therapeutic targets

Cancer cell metabolism is characterized by an enhanced uptake and utilization of glucose, a phenomenon known as the Warburg effect. The persistent activation of aerobic glycolysis in cancer cells can be linked to activation of oncogenes or loss of tumor suppressors, thereby fundamentally advancing cancer progression. In this respect, inhibition of glycolytic capacity may contribute to an anticancer effect on malignant cells. Understanding the mechanisms of aerobic glycolysis may present a new basis for cancer treatment. Accordingly, interrupting lactate fermentation and/or other cancer-promoting metabolic sites may provide a promising strategy to halt tumor development. In this review, we will discuss dysregulated and reprogrammed cancer metabolism followed by clinical relevance of the metabolic enzymes, such as hexokinase, phosphofructokinase, pyruvate kinase M2, lactate dehydrogenase, pyruvate dehydrogenase kinase and glutaminase. The proper intervention of these metabolic sites may provide a therapeutic advantage that can help overcome resistance to chemotherapy or radiotherapy.     

Negative-pressure wound therapy induces endothelial progenitor cell mobilization in diabetic patients with foot infection or skin defects

Non healing chronic wounds are difficult to treat in patients with diabetes and can result in severe medical problems for these patients and for society. Negative-pressure wound therapy (NPWT) has been adopted to treat intractable chronic wounds and has been reported to be effective. However, the mechanisms underlying the effects of this treatment have not been elucidated. To assess the vasculogenic effect of NPWT, we evaluated the systemic mobilization of endothelial progenitor cells (EPCs) during NPWT. Twenty-two of 29 consecutive patients who presented at the clinic of Seoul National Universty Hospital between December 2009 and November 2010 who underwent NPWT for diabetic foot infections or skin ulcers were included in this study. Peripheral blood samples were taken before NPWT (pre-NPWT) and 7–14 days after the initiation of NPWT (during-NPWT). Fluorescence-activated cell sorting (FACS) analysis showed that the number of cells in EPC-enriched fractions increased after NPWT, and the numbers of EPC colony forming units (CFUs) significantly increased during NPWT. We believe that NPWT is useful for treating patients with diabetic foot infections and skin ulcers, especially when these conditions are accompanied by peripheral arterial insufficiency. The systemic mobilization of EPCs during NPWT may be a mechanism for healing intractable wounds in diabetic patients with foot infections or skin defects via the formation of increased granulation tissue with numerous small blood vessels.     

Quantitative LC–MS/MS method in urine for the detection of drugs used to reverse the effects of chemical castration

The chemical castration law, which targets child molesters with recidivism, was introduced in Korea in 2011. For this, leuprolide, a gonadotropin-releasing hormone agonist, is used to decrease testosterone production and suppress libido. In order to achieve efficient law enforcement, it is necessary to monitor intentional ingestion of drugs that antagonize the effect of leuprolide. Therefore, an analytical method for the simultaneous detection of mirodenafil, sildenafil, tadalafil, udenafil, vardenafil, icariin, alprostadil, and yohimbine, which are the major impotence treatment drugs, legitimately or otherwise, in Korea, as well as their selected metabolites, in human urine was established and validated using liquid chromatography–tandem mass spectrometry (LC–MS/MS). First, different sample preparation methods, two solid-phase extractions with different cartridges and protein precipitation, were compared and protein precipitation was chosen for the entire study because it showed better matrix effects and recoveries. Thus, the drugs and metabolites in urine were extracted by protein precipitation and then filtered and analyzed by LC–MS/MS with polarity switching electrospray ionization. The validation results of selectivity, matrix effect, recovery, linearity, intra- and inter-assay precision and accuracy were satisfactory. The limits of detection ranged from 0.25 to 10 ng/mL, and the limits of quantification were 2.5 to 50 ng/mL. The drugs and metabolites in urine did not show any degradation under storage for 7 and 15 days at 4 and ?20 °C as well as after three freeze–thaw cycles. The developed method will be very useful for monitoring the illegal use of impotence treatment drugs.     

Recombinant Expression and Characterization of an Organic-Solvent-Tolerant α-Amylase from Exiguobacterium sp. DAU5

The enzyme from halophilic microorganisms often has unique properties such as organic-solvent-tolerance. In this study, a novel organic-solvent-tolerant α-amylase gene was cloned from the mild halophile Exiguobacterium sp. DAU5. The open reading frame (ORF) of the enzyme consisted of 1,545 bp and encoded 514 amino acids, the primary sequence revealed that it belongs to the glycoside hydrolase (GH) family 13. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed an AmyH monomer of 57 kDa. The enzyme exhibited maximal activity at 40 °C in pH?8.5 glycine–NaOH buffer, and the activity was strongly inhibited by Zn²⁺, Cu²⁺, and Fe²⁺. The α-amylase AmyH exhibited high hydrolysis activity toward soluble starch, and the major hydrolysis products were maltose, maltotriose, and maltopentaose; the AmyH could not efficiently hydrolyze oligosaccharides smaller than maltoheptaose, nor could it act on the β-1,4 or α-1,6 glucosidic bonds in xylan or pullulan, respectively. In addition, the α-amylase exhibited better tolerance to organic solvents, as it was stable in the presence of dimethylsulfoxide (DMSO), methanol, ethanol, and acetone. Base on all of these results, the enzyme could be useful for practical application in the bakery industry and in biotechnological processes that occur in the presence of organic solvents.     

Glucose Oxidase/Cellulose–Carbon Nanotube Composite Paper as a Biocompatible Bioelectrode for Biofuel Cells

Biofuel cells are devices for generating electrical energy directly from chemical energy of renewable biomass using biocatalysts such as enzymes. Efficient electrical communication between redox enzymes and electrodes is essential for enzymatic biofuel cells. Carbon nanotubes (CNTs) have been recognized as ideal electrode materials because of their high electrical conductivity, large surface area, and inertness. Electrodes consisting entirely of CNTs, which are known as CNT paper, have high surface areas but are typically weak in mechanical strength. In this study, cellulose (CL)–CNT composite paper was fabricated as electrodes for enzymatic biofuel cells. This composite electrode was prepared by vacuum filtration of CNTs followed by reconstitution of cellulose dissolved in ionic liquid, 1-ethyl-3-methylimidazolium acetate. Glucose oxidase (GOx), which is a redox enzyme capable of oxidizing glucose as a renewable fuel using oxygen, was immobilized on the CL–CNT composite paper. Cyclic voltammograms revealed that the GOx/CL–CNT paper electrode showed a pair of well-defined peaks, which agreed well with that of FAD/FADH_2, the redox center of GOx. This result clearly shows that the direct electron transfer (DET) between the GOx and the composite electrode was achieved. However, this DET was dependent on the type of CNTs. It was also found that the GOx immobilized on the composite electrode retained catalytic activity for the oxidation of glucose.     

Pretreatment for Simultaneous Production of Total Lipids and Fermentable Sugars from Marine Alga, Chlorella sp.

The goal of this study was to determine the optimal pretreatment process for the extraction of lipids and reducing sugars to facilitate the simultaneous production of biodiesel and bioethanol from the marine microalga Chorella sp. With a single pretreatment process, the optimal ultrasonication pretreatment process was 10 min at 47 KHz, and extraction yields of 6.5 and 7.1 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. The optimal microwave pretreatment process was 10 min at 2,450 MHz, and extraction yields of 6.6 and 7.0 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. Lastly, the optimal high-pressure homogenization pretreatment process was two cycles at a pressure of 20,000 psi, and extraction yields of 12.5 and 12.8 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. However, because the single pretreatment processes did not markedly improve the extraction yields compared to the results of previous studies, a combination of two pretreatment processes was applied. The yields of lipids and reducing sugars from the combined application of the high-pressure homogenization process and the microwave process were 24.4 and 24.9 % (w/w), respectively, which was up to three times greater than the yields obtained using the single pretreatment processes. Furthermore, the oleic acid content, which is a fatty acid suitable for biodiesel production, was 23.39 % of the fatty acids (w/w). The contents of glucose and xylose, which are among the fermentable sugars useful for bioethanol production, were 77.5 and 13.3 % (w/w) of the fermentable sugars, respectively, suggesting the possibility of simultaneously producing biodiesel and bioethanol. Based on the results of this study, the combined application of the high-pressure homogenization and microwave pretreatment processes is the optimal method to increase the extraction yields of lipids and reducing sugars that are essential for the simultaneous production of biodiesel and bioethanol.