Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 25, 2015
The FTIR, Raman and UV-vis spectra of the recently synthesized tetrathia[8]circulene and tetrasel... more The FTIR, Raman and UV-vis spectra of the recently synthesized tetrathia[8]circulene and tetraselena[8]circulene compounds have been measured and interpreted in details by the density functional theory (DFT) calculations taking into account the molecular symmetry constrains. The structural and electronic features of the studied compounds have also been discussed in connection with the observed spectroscopic characteristics. Particularly, we have found that despite a slightly non-planar conformation the neutral tetrathia[8]circulene and tetraselena[8]circulene molecules demonstrate bifacial aromatic/antiaromatic nature. The inner octatetraene core is characterized by the presence of paratropic ("antiaromatic") ring currents, whereas the outer macrocycle constructed of benzene, thiophene or selenophene rings possesses the strong magnetically-induced diatropic ("aromatic") ring current. This fact suggests the general electronic and magnetic similarity of the tetrath...
ABSTRACT Abstract4‐Trimethylsilyl‐3(2H)‐furanone (4) was converted to 4‐trimethylsilyl‐3‐furyl tr... more ABSTRACT Abstract4‐Trimethylsilyl‐3(2H)‐furanone (4) was converted to 4‐trimethylsilyl‐3‐furyl triflate (5). An attempted generation of 3,4‐didehydrofuran (3a) from 5 was unfruitful. On the other hand, 3,4‐bis(trimethylsilyl)furan (6) was also converted to 4‐trimethylsilyl‐3‐furylphenyliodonium triflate (7c) and its fluoride‐promoted elimination pathway might involve a biradical intermediate 3b.
The chiral cycloocta[2,1-b:3,4-b′]dipyridine 3b has been cleanly resolved into enantiomers by chr... more The chiral cycloocta[2,1-b:3,4-b′]dipyridine 3b has been cleanly resolved into enantiomers by chromatography on swollen, microcrystalline triacetylcellulose, using ethanol as the mobile phase. A trace of ammonia had to be added to prevent acid-catalysed racemization. The free energy barrier to ring inversion was found to be close to 25 kcal mol–1, and rather insensitive to the temperature. The experimental CD spectrum could be reasonably well simulated by CNDO/S calculations, indicating that the first eluted enantiomer has the R configuration. According to the calculations, the long-wavelength CD band has no clear n→π* character.
Immune reconstitution inflammatory syndrome (IRIS) is an immuno-pathologic reaction to quiescent ... more Immune reconstitution inflammatory syndrome (IRIS) is an immuno-pathologic reaction to quiescent opportunistic microbial pathogens upon restoration of underlying immune defects. Here we report a Honduran patient with HIV/AIDS who developed a facial rash worsening on antiretroviral therapy and increasing CD4 count. Culture and PCR analysis from the skin biopsy identified Leishmania panamensis, which was effectively treated with long-term liposomal amphotericin B. This is the first report of mucocutaneous leishmaniasis (MCL)-associated IRIS due to L. panamensis.
The liver biopsy has been regarded as the reference standard method of monitoring hepatic fibrosi... more The liver biopsy has been regarded as the reference standard method of monitoring hepatic fibrosis in psoriasis patients treated with methotrexate. It has also been subject to concerns over sampling error, internal and external variability, and potential for morbidity and mortality. During the past two decades, two imaging techniques, magnetic resonance elastography and transient elastography, have been developed and approved by the US Food and Drug Administration (FDA) for the assessment of hepatic fibrosis. Although high-quality, psoriasis-specific data are lacking, both methods have been shown to have outstanding efficacy in the detection of hepatic fibrosis, particularly the more advanced stages which may warrant the choice of a therapeutic alternative to methotrexate. Dermatologists should be aware of the availability of these tests and understand their limitations. Prospective studies in psoriasis and methotrexate management using these techniques are needed.
This chapter provides information on five-membered ring systems, including furans and benzofurans... more This chapter provides information on five-membered ring systems, including furans and benzofurans. The chapter presents an example stating that five new furanosesterterpene tetronic acids named sarcotin A–E were obtained via bioactivity-guided fractionation from the sponge Sarcotragus sp. Four new furanosesquiterpenes, merrekentrones A, B, C, and D were isolated from the roots and rootstocks of Merremia kentrocaulos. Five new sesquiterpenes were provided from the crude extract of fresh and undamaged fruiting bodies of Collybia maculata. Because of the resilient properties of furans, their cycloaddition, especially Diels–Alder reaction and [4+3] cycloaddition reaction have attracted much attention. Silyloxyfurans have still been widely used as starting materials in organic synthesis. The Achmatowicz reaction of furfuryl derivatives was employed by several groups for the synthesis of functionalized α, β-unsaturated δ-1actones from α-hydroxymethyl furfuryls. Oxygen atoms in the tetrahydrofuran rings embedded in inositol-based tris(spirotetrahydrofuranyl)ionophores were useful as chelation sites towards selective alkali metal ion binding and as a result rodlike supramolecular ionic polymer frameworks were prepared and analyzed in this study. A Baylis–Hillman reaction was used for the construction of novel arylfuran scaffolds.
The Journal of investigative dermatology, Jan 25, 2015
Sézary Syndrome (SS) is an aggressive CD4+ leukemic variant of cutaneous T-cell lymphoma (CTCL). ... more Sézary Syndrome (SS) is an aggressive CD4+ leukemic variant of cutaneous T-cell lymphoma (CTCL). Epigenetic modification of cancer cell genome is often linked to the expression of important cancer-related genes. Here we addressed the hypothesis that in SS, DNA hypomethylation is involved in upregulation of PLS3, GATA6 and TWIST1, genes that are undetected in normal lymphocytes. Pyrosequencing analysis of CpG rich regions, and CpG dinucleotides within the 5' regulatory regions confirmed hypomethylation of all three genes in SS, compared to controls. We then studied how methylation regulates PLS3 transcription in vitro using PLS3-negative (Jurkat) and PLS3-positive (HT-1080) cell lines. Treatment with the hypomethylating agent 5-azacytidine induced PLS3 expression in Jurkat cells and in vitro methylation of the cloned PLS3 promoter suppressed luciferase expression in HT-1080 cells. In conclusion, we show that promoter hypomethylation is associated with PLS3, GATA6, and TWIST1 over...
The wet packing method developed in Part 1 [Wong HHC, Kwan AKH (2007) Packing density of cementit... more The wet packing method developed in Part 1 [Wong HHC, Kwan AKH (2007) Packing density of cementitious materials: part 1 measurement using a wet packing method. Mater Struct (Paper No. MAAS3281)] has been successfully applied to measure the packing densities of cementitious materials containing ordinary Portland cement (OPC), pulverised fuel ash (PFA) and condensed silica fume (CSF). The test results for
The packing characteristics of the cementitious materials have great influence on the performance... more The packing characteristics of the cementitious materials have great influence on the performance of a concrete mix, but there is so far no generally accepted method of measurement. Herein, a new method, called the wet packing method, is developed. It mixes the cementitious materials with water and then measures the apparent density and voids content of the resulting mixture at
Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no ... more Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no antiviral treatment and no vaccine. Macrophages are important in dengue pathogenesis; however, the initial target cell for DV infection remains unknown. As DV is introduced into human skin by mosquitoes of the genus Aedes, we undertook experiments to determine whether human dendritic cells (DCs) were permissive for the growth of DV. Initial experiments demonstrated that blood-derived DCs were 10-fold more permissive for DV infection than were monocytes or macrophages. We confirmed this with human skin DCs (Langerhans cells and dermal/interstitial DCs). Using cadaveric human skin explants, we exposed skin DCs to DV ex vivo. Of the human leukocyte antigen DR-positive DCs that migrated from the skin, emigrants from both dermis and epidermis, 60-80% expressed DV antigens. These observations were supported by histologic findings from the skin rash of a human subject who received an attenuated...
The Science of the total environment, Jan 10, 1998
Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, On... more Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant ...
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 25, 2015
The FTIR, Raman and UV-vis spectra of the recently synthesized tetrathia[8]circulene and tetrasel... more The FTIR, Raman and UV-vis spectra of the recently synthesized tetrathia[8]circulene and tetraselena[8]circulene compounds have been measured and interpreted in details by the density functional theory (DFT) calculations taking into account the molecular symmetry constrains. The structural and electronic features of the studied compounds have also been discussed in connection with the observed spectroscopic characteristics. Particularly, we have found that despite a slightly non-planar conformation the neutral tetrathia[8]circulene and tetraselena[8]circulene molecules demonstrate bifacial aromatic/antiaromatic nature. The inner octatetraene core is characterized by the presence of paratropic ("antiaromatic") ring currents, whereas the outer macrocycle constructed of benzene, thiophene or selenophene rings possesses the strong magnetically-induced diatropic ("aromatic") ring current. This fact suggests the general electronic and magnetic similarity of the tetrath...
ABSTRACT Abstract4‐Trimethylsilyl‐3(2H)‐furanone (4) was converted to 4‐trimethylsilyl‐3‐furyl tr... more ABSTRACT Abstract4‐Trimethylsilyl‐3(2H)‐furanone (4) was converted to 4‐trimethylsilyl‐3‐furyl triflate (5). An attempted generation of 3,4‐didehydrofuran (3a) from 5 was unfruitful. On the other hand, 3,4‐bis(trimethylsilyl)furan (6) was also converted to 4‐trimethylsilyl‐3‐furylphenyliodonium triflate (7c) and its fluoride‐promoted elimination pathway might involve a biradical intermediate 3b.
The chiral cycloocta[2,1-b:3,4-b′]dipyridine 3b has been cleanly resolved into enantiomers by chr... more The chiral cycloocta[2,1-b:3,4-b′]dipyridine 3b has been cleanly resolved into enantiomers by chromatography on swollen, microcrystalline triacetylcellulose, using ethanol as the mobile phase. A trace of ammonia had to be added to prevent acid-catalysed racemization. The free energy barrier to ring inversion was found to be close to 25 kcal mol–1, and rather insensitive to the temperature. The experimental CD spectrum could be reasonably well simulated by CNDO/S calculations, indicating that the first eluted enantiomer has the R configuration. According to the calculations, the long-wavelength CD band has no clear n→π* character.
Immune reconstitution inflammatory syndrome (IRIS) is an immuno-pathologic reaction to quiescent ... more Immune reconstitution inflammatory syndrome (IRIS) is an immuno-pathologic reaction to quiescent opportunistic microbial pathogens upon restoration of underlying immune defects. Here we report a Honduran patient with HIV/AIDS who developed a facial rash worsening on antiretroviral therapy and increasing CD4 count. Culture and PCR analysis from the skin biopsy identified Leishmania panamensis, which was effectively treated with long-term liposomal amphotericin B. This is the first report of mucocutaneous leishmaniasis (MCL)-associated IRIS due to L. panamensis.
The liver biopsy has been regarded as the reference standard method of monitoring hepatic fibrosi... more The liver biopsy has been regarded as the reference standard method of monitoring hepatic fibrosis in psoriasis patients treated with methotrexate. It has also been subject to concerns over sampling error, internal and external variability, and potential for morbidity and mortality. During the past two decades, two imaging techniques, magnetic resonance elastography and transient elastography, have been developed and approved by the US Food and Drug Administration (FDA) for the assessment of hepatic fibrosis. Although high-quality, psoriasis-specific data are lacking, both methods have been shown to have outstanding efficacy in the detection of hepatic fibrosis, particularly the more advanced stages which may warrant the choice of a therapeutic alternative to methotrexate. Dermatologists should be aware of the availability of these tests and understand their limitations. Prospective studies in psoriasis and methotrexate management using these techniques are needed.
This chapter provides information on five-membered ring systems, including furans and benzofurans... more This chapter provides information on five-membered ring systems, including furans and benzofurans. The chapter presents an example stating that five new furanosesterterpene tetronic acids named sarcotin A–E were obtained via bioactivity-guided fractionation from the sponge Sarcotragus sp. Four new furanosesquiterpenes, merrekentrones A, B, C, and D were isolated from the roots and rootstocks of Merremia kentrocaulos. Five new sesquiterpenes were provided from the crude extract of fresh and undamaged fruiting bodies of Collybia maculata. Because of the resilient properties of furans, their cycloaddition, especially Diels–Alder reaction and [4+3] cycloaddition reaction have attracted much attention. Silyloxyfurans have still been widely used as starting materials in organic synthesis. The Achmatowicz reaction of furfuryl derivatives was employed by several groups for the synthesis of functionalized α, β-unsaturated δ-1actones from α-hydroxymethyl furfuryls. Oxygen atoms in the tetrahydrofuran rings embedded in inositol-based tris(spirotetrahydrofuranyl)ionophores were useful as chelation sites towards selective alkali metal ion binding and as a result rodlike supramolecular ionic polymer frameworks were prepared and analyzed in this study. A Baylis–Hillman reaction was used for the construction of novel arylfuran scaffolds.
The Journal of investigative dermatology, Jan 25, 2015
Sézary Syndrome (SS) is an aggressive CD4+ leukemic variant of cutaneous T-cell lymphoma (CTCL). ... more Sézary Syndrome (SS) is an aggressive CD4+ leukemic variant of cutaneous T-cell lymphoma (CTCL). Epigenetic modification of cancer cell genome is often linked to the expression of important cancer-related genes. Here we addressed the hypothesis that in SS, DNA hypomethylation is involved in upregulation of PLS3, GATA6 and TWIST1, genes that are undetected in normal lymphocytes. Pyrosequencing analysis of CpG rich regions, and CpG dinucleotides within the 5' regulatory regions confirmed hypomethylation of all three genes in SS, compared to controls. We then studied how methylation regulates PLS3 transcription in vitro using PLS3-negative (Jurkat) and PLS3-positive (HT-1080) cell lines. Treatment with the hypomethylating agent 5-azacytidine induced PLS3 expression in Jurkat cells and in vitro methylation of the cloned PLS3 promoter suppressed luciferase expression in HT-1080 cells. In conclusion, we show that promoter hypomethylation is associated with PLS3, GATA6, and TWIST1 over...
The wet packing method developed in Part 1 [Wong HHC, Kwan AKH (2007) Packing density of cementit... more The wet packing method developed in Part 1 [Wong HHC, Kwan AKH (2007) Packing density of cementitious materials: part 1 measurement using a wet packing method. Mater Struct (Paper No. MAAS3281)] has been successfully applied to measure the packing densities of cementitious materials containing ordinary Portland cement (OPC), pulverised fuel ash (PFA) and condensed silica fume (CSF). The test results for
The packing characteristics of the cementitious materials have great influence on the performance... more The packing characteristics of the cementitious materials have great influence on the performance of a concrete mix, but there is so far no generally accepted method of measurement. Herein, a new method, called the wet packing method, is developed. It mixes the cementitious materials with water and then measures the apparent density and voids content of the resulting mixture at
Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no ... more Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no antiviral treatment and no vaccine. Macrophages are important in dengue pathogenesis; however, the initial target cell for DV infection remains unknown. As DV is introduced into human skin by mosquitoes of the genus Aedes, we undertook experiments to determine whether human dendritic cells (DCs) were permissive for the growth of DV. Initial experiments demonstrated that blood-derived DCs were 10-fold more permissive for DV infection than were monocytes or macrophages. We confirmed this with human skin DCs (Langerhans cells and dermal/interstitial DCs). Using cadaveric human skin explants, we exposed skin DCs to DV ex vivo. Of the human leukocyte antigen DR-positive DCs that migrated from the skin, emigrants from both dermis and epidermis, 60-80% expressed DV antigens. These observations were supported by histologic findings from the skin rash of a human subject who received an attenuated...
The Science of the total environment, Jan 10, 1998
Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, On... more Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant ...
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