First study on phosphonite-coordinated ruthenium sensitizers for efficient photocatalytic hydrogen evolution
2区 · 材料科学
作者: Swetha, T. ; Mondal, Indranil ; Bhanuprakash, K. ; Pal, Ujjwal ; Singh, Surya Prakash
For the first time we report the design and syntheses of phosphonite coordinated ruthenium(II) sensitizers bearing ĈN̂N ligand and/or terpyridine derivatives carboxylate anchor (GS11, GS12. and GS13) and its application for hydrogen production over Pt-TiO2 system. These heteroleptic complexes exhibit broad metal-to-ligand charge transfer transition band over the whole visible regime extending up to 900 nm. DFT calculations of these complexes show that the HOMO is distributed over the Ru and Cl atom whereas; LUMO is localized on the polypyridile ligand, which are anchored on TiO2 surface. Among the sensitizers tested for photocatalytic hydrogen evolution, GS12 exhibited a maximum turnover number (TON) 8605 (for 8 h), which is very high compared to the reference sensitizer (N719) with TON 163 under similar evaluation condition. The dependence of the hydrogen evolution rate at different pH using GS11, GS12, GS13, and DX-1-sensitized Pt-TiO2 has been studied and the maximum H2 production yield was obtained at pH 7 for all sensitizers.
A Structure-Activity Study of the Inhibition of HIV-1 Tat-Dependent Trans-Activation by Mixmer 2'-O-Methyl Oligoribonucleotides Containing Locked Nucleic Acid (LNA), α-L-LNA, or 2'-Thio-LNA Residues
作者: Arzumanov, Andrey ; Stetsenko, Dmitry A. ; Malakhov, Andrey D. ; Reichelt, Stefanie ; Sorensen, Mads D. ; Babu, B. Ravindra ; Wengel, Jesper ; Gait, Michael J.
The HIV-1 trans-activation responsive element (TAR) RNA stem-loop interacts with the HIV trans-activator protein Tat and other cellular factors to stimulate transcriptional elongation from the viral long terminal repeat (LTR). Inhibitors of these interactions block full-length transcription and, hence, would potentially inhibit HIV replication. We have studied structure-activity relationships in inhibition of trans-activation by steric block 2'-O-methyl (OMe) oligonucleotides chimeras (mixmers) containing locked nucleic acid (LNA) units. Inhibition was measured both in Tat-dependent in vitro transcription from an HIV-1 DNA template directed by HeLa cell nuclear extract and in a robust HeLa cell reporter assay that involves use of stably integrated plasmids to express firefly luciferase Tat dependently and Renilla luciferase Tat-independently. OMe oligonucleotides with optimally 40%-50% LNA units and a minimum of 12 residues in length were active in the cellular assay when delivered with cationic gemini surfactant GS11 at 50% inhibitory concentrations of 230 +/- 40 nM, whereas activity in the in vitro transcription assay was observed down to 9 residues. No cellular activity was observed for OMe oligonucleotides of 12 or 16 residues, which was shown to be due to poor cellular uptake. Both 12-mer mixmers containing alpha -L-LNA or 2'-thio-LNA (S-LNA) were also active in in vitro transcription and the former in cellular reporter inhibition assays, demonstrating that the property of promotion of cellular uptake by LNA is not due to specific sugar conformational effects. Covalent conjugates of OMe/LNA chimeras with Kaposi-fibroblast growth factor (K-FGF) or Transportan peptides failed to enter HeLa cells without a delivery agent but were fully active when delivered by cationic gemini surfactant, showing that in principle, peptide conjugation does not interfere with cellular activity. Thus, OMe/LNA mixmers are powerful reagents for use as steric block inhibitors of gene expression regulated by protein-RNA interactions within HeLa cell nuclei.
1999-06-30·Anticancer Research4区 · 医学
P-glycoprotein (Pgp) does not affect the cytotoxicity of flavonoids from Sophora flavescens, which also have no effects on Pgp action
4区 · 医学
作者: Choi, Sang-Un ; Kim, Kwang-Hee ; Choi, Eun-Jung ; Park, Sung-Hee ; Lee, Chong Ock ; Jung, Noh-Pal ; Yoon, Seuk-Keun ; Ryu, Shi Yong
Sophoraflavanone, kurarinone (GS08), norkurarinol (GS11), kurarinol (GS12) and kushenol K are cytotoxic flavonoids isolated from Sophora flavescens. In this study, we tested the cytotoxicity of those flavonoids to human cancer cells including P-glycoprotein (Pgp)-expressing HCT15 cells and its multidrug resistant subline, HCT15/CL02 cells. HCT15/CL02 cells revealed resistance to GS08, GS11 and GS12 about 2 fold in comparison with HCT15 cells. Nonetheless, verapamil, a Pgp inhibitor, could not increase the cytotoxicity of all the flavonoids tested. We also investigated that the flavonoids could modulate the Pgp action. At nontoxic concentrations, the flavonoids could not effect on the cytotoxicity of paclitaxel, a well-known Pgp-substrate. The flavonoids also had no effects on the accumulation of rhodamine 123 in all the cells tested at 10 microM. From the results, we concluded that Pgp had no effect on the cytotoxicity of the flavonoids, and the flavonoids also had no effect on the action of Pgp. Our results also suggested that HCT15/CL02 cells had additional mechanisms for drug resistance distinct from Pgp overexpression.