Syntheses and Properties of Novel Copolymers of Poly(1,4‐dioxane‐2‐one) and Aliphatic Polycarbonate Based on Ketal‐Protected Dihydroxyacetone

Novel random copolymers of 1,4‐dioxane‐2‐one (DON) and 2,2‐ethylenedioxy‐1,3‐propanediol carbonate (EOPDC) are synthesized in bulk at 120 °C using Sn(Oct)₂ as a catalyst. The effects of different molar feed ratios of EOPDC/DON on the yield and molecular weight of the copolymers are investigated. The copolymers are obtained with a yield of 55.4–98%. The number‐average molecular weight of the copolymer is 0.49–4.18 × 10⁴ g mol^?1 with a polydispersity of 1.52–1.68. The poly(DON‐co‐EOPDC)s obtained are characterized by FTIR, ¹H NMR, and ¹³C NMR spectroscopy, gel‐permeation chromatography (GPC), and DSC. The hydrolytic degradation of the copolymer in phosphate buffered saline (PBS) is also investigated. The results show that both the hydrophilicity and the degradation rate of the copolymers increase with increasing copolymer DON content.     

Potential chemoprotective effects of the coffee components kahweol and cafestol palmitates via modification of hepatic N-acetyltransferase and glutathione S-transferase activities

Coffee drinking has been associated with reduced incidence of colorectal cancer, possibly via chemoprotection/modification of the metabolism of dietary heterocyclic amine carcinogens such as 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP) by kahweol and cafestol palmitates (K/C), two components of unfiltered coffee. Using the PhIP-exposed male Fisher F344 rat as a model, K/C have been shown to reduce colonic PhIP-DNA adducts by > 50%. We have used the male F344 rat to investigate the effects of dietary K/C (0.02-0.2% as a 1:1 mixture) on the metabolism of PhIP by N-acetyltransferase- (NAT), sulfotransferase- (SULT), and glutathione-dependent pathways. K/C decreased hepatic NAT-dependent PhIP activation by up to 80% in a dose-dependent manner. Conversely, hepatic glutathione S-transferase (GST) activity/expression increased, e.g., 3-4 fold toward 1-chloro-2,4-dinitrobenzene (total activity), up to 23-fold toward 4-vinylpyridine (rGSTP1), and approximately 7-fold for rGSTA2 protein. These effects had fully developed after 5 days of the test diet and persisted for at least 5 days after withdrawal of K/C. Hepatic glutathione increased two- to threefold and this increase was more short-lived than other changes. K/C did not modify hepatic SULT activity or colon NAT and GST activities. Benzylisothiocyanate and black tea, which have also been shown to reduce the formation of PhIP-DNA adducts in this model, had little effect on hepatic NAT, SULT, GST, or GSH. In primary culture of rat hepatocytes, both kahweol and cafestol palmitates reduced NAT activity by 80%. In summary, the unique potential of K/C to convert rapid acetylators to a slow acetylator phenotype, accompanied by GST induction, might contribute to chemoprevention against cancers associated with heterocyclic amines.     

Evidence for genetic heterogeneity in D‐2‐hydroxyglutaric aciduria

We performed molecular, enzyme, and metabolic studies in 50 patients with D ‐2‐hydroxyglutaric aciduria (D ‐2‐HGA) who accumulated D ‐2‐hydroxyglutarate (D ‐2‐HG) in physiological fluids. Presumed pathogenic mutations were detected in 24 of 50 patients in the D ‐2‐hydroxyglutarate dehydrogenase (D2HGDH) gene, which encodes D ‐2‐hydroxyglutarate dehydrogenase (D ‐2‐HGDH). Enzyme assay of D ‐2‐HGDH confirmed that all patients with mutations had impaired enzyme activity, whereas patients with D ‐2‐HGA whose enzyme activity was normal did not have mutations. Significantly lower D ‐2‐HG concentrations in body fluids were observed in mutation‐positive D ‐2‐HGA patients than in mutation‐negative patients. These results imply that multiple genetic loci may be associated with hyperexcretion of D ‐2‐HG. Accordingly, we suggest a new classification: D ‐2‐HGA Type I associates with D ‐2‐HGDH deficiency, whereas idiopathic D ‐2‐HGA manifests with normal D ‐2‐HGDH activity and higher D ‐2‐HG levels in body fluids compared with Type I patients. It remains possible that several classifications for idiopathic D ‐2‐HGA patients with diverse genetic loci will be revealed in future studies. Hum Mutat 31:1–5, 2010. © 2009 Wiley‐Liss, Inc.     

Enhanced conversion of sterols to steroid synthons by augmenting the peptidoglycan synthesis gene pbpB in Mycobacterium neoaurum

Some species of mycobacteria have been modified to transform sterols to valuable steroid synthons. The unique cell wall of mycobacteria has been recognized as an important organelle to absorb sterols. Some cell wall inhibitors (e.g., vancomycin and glycine) have been validated to enhance sterol conversion by interfering with transpeptidation in peptidoglycan biosynthesis. Therefore, two transpeptidase genes, pbpA and pbpB, were selected to rationally modify the cell wall to simulate the enhancement effect of vancomycin and glycine on sterol conversion in a 22‐hydroxy‐23,24‐bisnorchol‐4‐ene‐3‐one (4‐HBC) producing strain (WIII). Unexpectedly, the pbpA or pbpB gene augmentation was conducive to the utilization of sterols. The pbpB augmentation strain WIII‐pbpB was further investigated for its better performance. Compared to WIII, the morphology of WIII‐pbpB was markedly changed from oval to spindle, indicating alterations of the cell wall. Biochemical analysis indicated that the altered cell wall properties of WIII‐pbpB might contribute to the positive effect on sterol utilization. The productivity of 4‐HBC was enhanced by 28% in the WIII‐pbpB strain compared to that of WIII. These results demonstrated that the modification of peptidoglycan synthesis can improve the conversion of sterols to steroid synthons in mycobacteria.     

Synthesis of high‐Tg polymers by ring‐opening metathesis polymerization of N‐cycloalkylnorbornene dicarboximide

Ring‐opening metathesis polymerization (ROMP) of N‐(1‐adamantyl)‐exo‐norbornene‐5,6‐dicarboximide (AdNDI) ( 3a ) and N‐cyclohexyl‐exo‐norbornene‐5,6‐dicarboximide (ChNDI) ( 3b ) was performed using well‐defined vinylidene ruthenium (II) catalysts Cl₂(PR₃)₂RuCCH(t‐Bu) (R = Ph and Cy). The homopolymer of 3a showed a T_g of 271 °C while poly‐ChNDI of 3b had a T_g of 129 °C. Copolymers of these monomers with norbornene (NB) demonstrated significant T_g increases compared to unsubstituted poly‐NB. Analysis of copolymers of 3a and NB isolated at the initial stages of copolymerization showed that both monomers were incorporated randomly and displayed very similar reactivity.

ROMP of 3a and 3b .     

Fluorene‐Based Single‐Chain Copolymers for Color‐Stable White Light‐Emitting Diodes

Fluorene‐based single‐chain copolymers with a white light emitter consisting of a blue and an orange chromophore have been synthesized and their photophysical and electroluminescent properties are investigated. The experimental results suggest that only a relatively small fraction of the orange‐emitting units incorporated into the fluorene is needed to achieve efficient white light emission by controlled incomplete energy transfer. A device from a copolymer with 0.02% DDQ content showed the highest external quantum efficiency of 2.64% with a luminance efficiency of 4.06 cd · A^?1 with CIE coordinates (0.28, 0.24). The EL emissions are extremely stable over a wide range of current densities.

     

EGFR family expression in breast carcinomas. c-erbB-2 and c-erbB-4 receptors have different effects on survival.

One hundred patients with breast carcinoma followed for 7-11 years were included in the present study of EGFR family members, using immunohistochemistry and RT-PCR. By immunohistochemistry, 36%, 27%, 26%, and 82% of the tumours were positive for EGFR, c-erbB-2, c-erbB-3, and c-erbB-4. All the immunoreactive tumours were confirmed positive by RT-PCR. Tumour size, histological grade, lymph node status, S-phase fraction, and stage were confirmed to be significantly associated with both disease-free and cancer-specific survival in the present study. Methods of treatment, histological type, and ploidy had no significant effect on survival. Statistical analysis of EGFR family members in these tumours showed a significant association between c-erbB-2 expression and reduced disease-free and cancer-specific survival. c-erbB-4 expression was associated with a more favourable outcome. Co-expression of c-erbB-2 and EGFR was associated with a worse prognosis. c-erbB-4 expression, however, showed an antagonistic effect on the clinical influence of c-erbB-2 expression. In conclusion, c-erbB-2 expression in breast carcinomas is associated with an unfavourable clinical course and EGFR expression has a synergistic effect. However, c-erbB-4 antagonizes the c-erbB-2 effect on clinical course in breast carcinomas. To achieve best results with immunotherapy against the c-erbB-2 receptor, clarifying the status of c-erbB-4 expression may be of significance.     

Novel Random Low‐Band‐Gap Fluorene‐Based Copolymers for Deep Red/Near Infrared Light‐Emitting Diodes and Bulk Heterojunction Photovoltaic Cells

Summary: Novel readily soluble random low‐band‐gap conjugated copolymers (PFO–DTTP, E_g ≈ 1.77–2.00 eV) derived from 9,9‐dioctylfluorene (DOF) and 2,3‐dimethyl‐5,7‐dithien‐2‐yl‐thieno[3,4‐b]pyrazine (DTTP) were prepared. The solutions and the solid thin films of the copolymers absorbed light from 300–690 nm. Prototype photovoltaic cells from solid state composite films with the copolymer PFO–DTTP30 and [6,6]‐phenyl C₆₁ butyric acid methyl ester (PCBM) showed power conversion efficiencies up to 0.83% under an AM1.5 solar simulator (100 mW · cm⁻²). For electroluminescent devices, the emission peaks were around 734–780 nm. This indicates that the low band gap copolymers are promising materials for polymeric solar cells and deep red/near infrared light‐emitting diodes.

Synthesis of novel low‐band‐gap fluorene‐based copolymer.     

Synthesis and Characterization of a Red‐Emitting Copolymer Containing 5,8‐Quinoline Units

A novel nitrogen‐containing electroluminescent copolymer, PQV‐alt‐MOPPV has been designed and synthesized by Wittig‐Horner polymerization. Structure, thermal stability, and optical and electrochemical properties of the resulting copolymer were characterized by FT‐IR, ¹H NMR, elemental analysis, GPC, DSC, TGA, UV‐vis, PL, EL, and CV. The copolymer possesses excellent solubility in common organic solvents and good thermal stability. The absorption maxima of the copolymer in solution and a thin film are 490 and 516 nm, and the photoluminescence maxima in solution and thin film are 571 and 629 nm, respectively. The PLED (ITO/PEDOT: PSS (40 nm)/PQV‐alt‐MOPPV (80 nm)/Ca (30 nm)/Al (150 nm) shows a very pure red light emission with maximum peaks around 618 nm.

     

Self‐Assembly of ATRP‐Synthesized PCH‐b‐PtBA‐b‐PCH Triblock Copolymers Observed by Time‐Resolved SAXS

The phase behavior of PCH‐b‐PtBA‐b‐PCH triblock copolymers has been studied. Measurements in the wide‐angle region probed the existence of microphase segregation through variation of block mobility and thermal expansion coefficients. SAXS experiments pointed out that most copolymers present ordered nanostructures, mostly hexagonally packed cylinders, the morphology being confirmed by AFM. An unusual disorder‐to‐order transition is observed in one copolymer synthesized from a macroinitiator with intermediate length and the highest outer‐block molecular weight, whereas none of the copolymers shows an order‐to‐disorder transition upon heating over the temperature range analyzed.

     

Amino acids of coxsackie B5 virus are critical for infection of the murine insulinoma cell line,MIN‐6

It was shown recently that 15 successive passages of a laboratory strain of the Coxsackie B virus 5 in a mouse pancreas (CBV‐5‐MPP) resulted in apparent changes in the virus phenotype, which led to the capacity to induce a diabetes‐like syndrome in mice. For further characterization of islet cell interactions with a passaged virus strain, a murine insulinoma cell line, MIN‐6, was selected as an experimental model. The CBV‐5‐MPP virus strain was not able to replicate in MIN‐6 cells in vitro but required adaptation over a few days for progeny production and the generation of cytopathic effects. In order to determine the genetic characteristics required for virus growth in MIN‐6 cells, the whole genome of the MIN‐6‐adapted virus variant was sequenced, and critical amino acids were identified by comparing the sequence with that of a virus strain passaged repeatedly in the mouse pancreas. The results of site‐directed mutagenesis demonstrated that only one residue, amino acid 94 of VP1, is a major determinant for virus adaptation to MIN‐6 cells. J. Med. Virol. 81:296–304, 2009. © 2008 Wiley‐Liss, Inc.     

Urinary levels of oxidative DNA and RNA damage among workers exposed to polycyclic aromatic hydrocarbons in silicon production: Comparison with 1‐hydroxypyrene

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous occupational and environmental pollutants and the urinary excretion of 1‐hydroxypyrene (1‐OHP) is classically measured for the determination of PAH exposure internal dose. Some of PAH are tumorigenic due to their metabolites ability to generate DNA adducts and oxidative DNA damage through the production of reactive oxygen species during metabolism. 8‐hydroxy‐7,8‐dihydro‐2′‐deoxyguanosine (8‐OHdGuo) is one of the major oxidative DNA lesions and its use as a potential biomarker of genotoxic PAH occupational exposure should be evaluated. Indeed conflicting results are frequently reported in occupational studies in terms of correlation between 8‐OHdGuo urinary levels and PAH exposure. The aim of our study was therefore to determine the potential for PAH occupational exposure to increase urinary oxidative DNA damage. The population consisted of 68 male workers employed in silicon production. The urinary concentrations of 8‐OHdGuo and its homologue in RNA, 8‐hydroxy‐7,8‐dihydroguanosine (8‐OHGuo) were determined using high performance liquid chromatography (HPLC) coupled to tandem mass spectrometry, whereas those of 1‐OHP were measured using HPLC with fluorescence detection. Individual variation rates were calculated on a working day and a working week. The results indicated that, while 1‐OHP levels strongly increased on a working day and even more on a working week, 8‐OHdGuo and 8‐OHGuo urinary levels did not show similar significant increases. Moreover, no correlation between 1‐OHP and oxidative DNA and RNA lesions was found. Consequently, urinary 8‐OHdGuo and 8‐OHGuo did not seem to be relevant biomarkers of genotoxic PAH exposure in the case of the silicon plant studied. Environ. Mol. Mutagen., 2009. © 2008 Wiley‐Liss, Inc.     

Crystallization and Melting Behavior of Poly(3‐hydroxybutyrate)‐Based Blends

Summary: Blends of high molecular weight poly(R‐3‐hydroxybutyrate) (PHB) ( = 352 000 g · mol^?1), comprising of either low molecular weight poly(R‐3‐hydroxybutyrate) (D‐PHB) ( = 3 900 g · mol^?1) or poly[(R‐3‐hydroxybutyrate)‐co‐(R‐3‐hydroxyvalerate)] (PHBV) ( = 238 000 g · mol^?1) with 12 mol‐% hydroxyvalerate (HV) content as a second constituent, were investigated along with the thermal properties and morphologies. After isothermal crystallization, a lowering of the melting temperature of PHB can be observed with increasing content of the second component in the blends. This behavior points towards miscibility of the constituents both in the liquid and the solid state. Crystallization kinetics was studied under isothermal and non‐isothermal conditions. The overall kinetics of isothermal crystallization was analyzed in terms of the Avrami equation. Only one crystallization peak is observed in all cases for the PHB/D‐PHB and PHB/PHBV blends under the conditions studied. This demonstrates co‐crystallization of the constituents. The addition of D‐PHB or PHBV to PHB reduces the rate of crystallization of the blends compared to that of neat PHB. The corresponding activation energies of crystallization also decrease with an increasing concentration of the second constituent. Non‐isothermal crystallization, carried out with different cooling rates held constant, is discussed in terms of a quasi‐isothermal approach. The corresponding rate constants as functions of reciprocal undercooling show Arrhenius‐like behavior in a certain range of temperatures. At sufficiently high undercooling, the rate constants of crystallization for the isothermal process exceed those reflecting non‐isothermal conditions, whereas in the limit of low undercoolings, the rate constants become similar. Ring‐banded morphologies are observed when PHB is in excess. When the respective second component is the major component, fibrous textures of the spherulites develop.

Polarized micrograph of PHB/PHBV 90/10.     

Urinary excretion of 8-hydroxy-2-deoxyguanosine and 1-hydroxypyrene in coke-oven workers

Coke-oven workers (COWs) are occupationally exposed to high concentrations of polycyclic aromatic hydrocarbons (PAH). Urinary 8-hydroxy-2-deoxyguanosine (8-OH-dG) and 1-hydroxypyrene (1-OHP) are biological markers of oxidative DNA damage and PAH metabolism, respectively. We investigated the relationship between urinary 8-OH-dG and 1-OHP in 217 Taiwanese COWs, 55 topside-oven, and 162 sideoven workers. For topside-oven workers, mean 8-OH-dG and 1-OHP concentrations (ng/ml +/- SD) were 13.8 +/- 12.0 and 93.5 +/- 104.4, respectively. These levels were significantly higher than those for sideoven workers: 10.2 +/- 7.9 ng/ml (P = 0.04) and 19.8 +/- 28.6 ng/ml (P < 0.001), respectively. Individual urinary 8-OH-dG concentrations were directly correlated with urinary 1-OHP concentrations: the higher the 1-OHP level, the higher the 8-OH-dG level (Spearman correlation coefficients: r = 0.43, P < 0.0001, n = 217). Multiple regression analysis indicated that a 10-fold increase in 1-OHP was associated with a 1.91-fold increase in 8-OH-dG. Compared to no vitamin intake, intake of at least one multiple vitamin pill per week reduced 8-OH-dG excretion (P = 0.02). Our findings suggest that urinary 1-OHP and 8-OH-dG reflect occupational PAH exposure and oxidative DNA damage in COWs. In addition, multiple vitamins may reduce oxidative stress caused by PAH exposure.     

4,5‐Ethylene‐2,7‐Carbazole‐Based Medium‐Bandgap Conjugated Polymers with Low‐Lying HOMO Levels Toward Efficient Polymer Solar Cells with High Open‐Circuit Voltage

Three medium‐bandgap polymers based on a 4,5‐ethylene‐2,7‐dithienyl carbazole as the electron‐donating unit and different 5,6‐dialkoxy‐2,1,3‐benzothiadiazoles as the electron‐accepting units, are synthesized as polymer donors for photovoltaic applications. The three copolymers possess highest occupied molecular oribital (HOMO) levels around ?5.47 eV and medium bandgaps of about 1.94 eV. The solar cells with polymer:[6,6]‐phenyl C71‐butyric acid methyl ester (PC₇₁BM) = 1:4 as the active layer, show an especially high open‐circuit voltage (V_oc) of 0.95 V and attain good power conversion efficiency up to 5.91%. The hole mobilities of the active layer films, measured by space‐charge‐limited current (SCLC), are up to 3.5 × 10^?4 cm² V^?1 s^?1. Given the favorable medium bandgaps, low‐lying HOMO levels, and good hole mobilities, these copolymers are promising candidates for the construction of a highly efficient front cell to harvest the shorter wavelength band of the solar radiation in a tandem solar cell with high V_oc.