Transient IR absorption study of charge carriers photogenerated in sulfur-doped TiO2

Sulfur-doped TiO2 was prepared by two methods; one was simple oxidation annealing of TiS2, the other was mixing of titanium isopropoxide and thiourea. These two sulfur-doped TiO2 preparations showed fairly different photocatalytic activity under visible light. The dynamics of photogenerated charge carriers were studied by the transient absorption measurement in the region of mid-IR. In both samples, excitation by 532 nm pulse led to photocarrier generation to the same extent. Nevertheless, the reactivity of the photocarriers was totally different. Photogenerated electrons and holes transferred to reactant gas in the latter sample, whereas they did not in the former sample. We attributed the different carrier behavior to the difference in the distribution of S atoms or particle size. These observations can explain the difference in capability of photocatalysis under visible light

Incident light dependence for photocatalytic degradation of acetaldehyde and acetic acid on S-doped and N-doped TiO2 photocatalysts

We have synthesized S (S4+)-doped and N (N3−)-doped TiO2 photocatalysts. S-doped and N-doped TiO2 loaded with Fe2O3 nanoparticles have also been prepared. These photocatalysts showed activity under a wide range of wavelengths of irradiation. Action spectra of photochemical reaction rate as a function of the incident light wavelength for oxidation of acetic acid on S-doped TiO2 was studied.The photocatalytic activities of S-doped and N-doped TiO2 photocatalysts loaded with Fe2O3 nanoparticles for oxidation of acetic acid in aqueous phase and acetaldehyde in gas phase are markedly improved compared to those of doped TiO2 without loading of Fe2O3 nanoparticles under a wide range of incident light wavelengths. The optimum amount of Fe2O3 nanoparticles loaded on S-doped TiO2 particles was different from that on N-doped TiO2 for oxidation of organic compounds. The relationship between reaction rate of photocatalytic oxidation of acetaldehyde on doped TiO2 loaded with Fe2O3 nanoparticles and amount of Fe2O3 nanoparticles is discussed

Photocatalytic selective oxidation of anionic compounds on TiO2 photocatalysts modified with quaternary ammonium base groups

Quaternary ammonium base groups were introduced onto surfaces of SiO2-covered TiO2 particles (SiO2–TiO2). Oxidation of p-toluenesulfuric acid on the surface-modified TiO2 powders proceeded more efficiently than that on SiO2-covered TiO2 particles without surface modification. On the other hand, the photocatalytic activity of surface-modified SiO2–TiO2 for oxidation of 1,4-dimethylpyridinium iodide was much lower than that of pure SiO2–TiO2. In addition, no difference in photocatalytic activity for oxidation of toluene was observed between surface-modified SiO2–TiO2 and pure SiO2–TiO2. The enhancement of the photocatalytic activity of surface-modified SiO2–TiO2 is due to electrostatic interaction between the substrate and functional groups introduced on SiO2–TiO2

Intrinsic Oncogenic Function of Intracellular Connexin26 Protein in Head and Neck Squamous Cell Carcinoma Cells

It has long been known that the gap junction is down-regulated in many tumours. One of the downregulation mechanisms is the translocation of connexin, a gap junction protein, from cell membrane into cytoplasm, nucleus, or Golgi apparatus. Interestingly, as tumours progress and reinforce their malignant phenotype, the amount of aberrantly-localised connexin increases in different malignant tumours including oesophageal squamous cell carcinoma, thus suggesting that such an aberrantly-localised connexin should be oncogenic, although gap junctional connexins are often tumour-suppressive. To define the dual roles of connexin in head and neck squamous cell carcinoma (HNSCC), we introduced the wild-type connexin26 (wtCx26) or the mutant Cx26 (icCx26) gene, the product of which carries the amino acid sequence AKKFF, an endoplasmic reticulum-Golgi retention signal, at the C-terminus and is not sorted to cell membrane, into the human FaDu hypopharyngeal cancer cell line that had severely impaired the expression of connexin during carcinogenesis. wtCx26 protein was trafficked to the cell membrane and formed gap junction, which successfully exerted cell-cell communication. On the other hand, the icCx26 protein was co-localised with a Golgi marker, as revealed by immunofluorescence, and thus was retained on the way to the cell membrane. While the forced expression of wtCx26 suppressed both cell proliferation in vitro and tumorigenicity in mice in vivo, icCx26 significantly enhanced both cell proliferation and tumorigenicity compared with the mock control clones, indicating that an excessive accumulation of connexin protein in intracellular domains should be involved in cancer progression and that restoration of proper subcellular sorting of connexin might be a therapeutic strategy to control HNSCC

Photoactive assemblies of organic compounds and biomolecules: drug-protein supramolecular systems

[EN] The properties of singlet and triplet excited states are strongly medium-dependent. Hence, these species constitute valuable tools as reporters to probe compartmentalised microenvironments, including drug@protein supramolecular systems. In the present review, the attention is focused on the photophysical properties of the probe drugs (rather than those of the protein chromophores) using transport proteins (serum albumins and 1-acid glycoproteins) as hosts. Specifically, fluorescence measurements allow investigating the structural and dynamic properties of biomolecules or their complexes. Thus, the emission quantum yields and the decay kinetics of the drug singlet excited states provide key information to determine important parameters such as the stoichiometry of the complex, the binding constant, the relative degrees of occupancy of the different compartments, etc. Application of the FRET concept allows determining donor-acceptor interchromophoric distances. In addition, anisotropy measurements can be related to the orientation of the drug within the binding sites, where the degrees of freedom for conformational relaxation are restricted. Transient absorption spectroscopy is also a potentially powerful tool to investigate the binding of drugs to proteins, where formation of encapsulated triplet excited states is favoured over other possible processes leading to ionic species (i. e. radical ions), and their photophysical properties are markedly sensitive to the microenvironment experienced within the protein binding sites. Even under aerobic conditions, the triplet lifetimes of protein-complexed drugs are remarkably long, which provides a broad dynamic range for identification of distinct triplet populations or for chiral discrimination. Specific applications of the laser flash photolysis technique include the determination of drug distribution among the bulk solution and the protein binding sites, competition of two types of proteins to bind a 3 drug, occurrence of drug-drug interactions within protein binding sites, enzymatic-like activity of the protein or determination of enantiomeric compositions. The use of proteins as supramolecular hosts modifies the photoreactivity of encapsulated substrates by providing protection against oxygen or other external reagents, by imposing conformational restrictions in the binding pockets, or by influencing the stereochemical outcome. In this review, a selected group of examples is presented including decarboxylation, dehalogenation, nucleophilic addition, dimerisation, oxidation, Norrish type II reaction, photo-Fries rearrangement and 6 electrocyclisationFinancial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, RyC-2007-00476), from the EU (PCIG12-GA-2012-334257), from the Universitat Politènica de València (SP20120757) and from the Consellería de Educació, Cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged.Vayá Pérez, I.; Lhiaubet-Vallet, VL.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photoactive assemblies of organic compounds and biomolecules: drug-protein supramolecular systems. Chemical Society Reviews. 43:4102-4122. https://doi.org/10.1039/C3CS60413FS410241224

INCREASED EXPRESSION OF TOLL-LIKE RECEPTOR 4 IN HEPATOCELLULAR CARCINOMA ─ ITS CLINICOPATHOLOGICAL SIGNIFICANCE ─

Lipopolysaccharide (LPS), known as endotoxin, is produced by Gram-negative bacteria and transported from the intestine to the liver via the portal vein.　While LPS is cytotoxic and gives damages to hepatocytes, it also functions as an exogenous ligand for toll-like receptor 4 (TLR4) expressed in the plasma membrane.　Stimulated by LPS, TLR4 activates MyD88-NF-κB signaling pathway in hepatocytes, leading to tissue repair and cell proliferation.　It has thus been postulated that a combination of LPS-induced hepatic injury and TLR4-mediated tissue repair may lead to development of hepatocellular carcinoma (HCC).　As recently reported, the increased expression of TLR4 in HCC is related to poor prognosis, suggesting involvement of TLR4 in HCC progression after its development.　To explore correlation of clinicopathological characteristics of HCC with TLR4 expression, we immunostained TLR4 protein in both HCC and its neighboring non-cancerous area by using 99 resected livers bearing HCC.　In general, TLR4 expression was significantly higher in HCC areas than in non-cancerous areas.　When correlation of the increased expression of TLR4 with different clinicopathological factors was assessed, tumor size and expanding growth pattern were significantly correlated with the TLR4 expression level, suggesting that TLR4 is closely related to cell proliferation but not invasive phenotype

Transient IR Absorption Study of Charge Carriers Photogenerated in Sulfur-doped TiO2

Sulfur-doped TiO2 was prepared by two methods; one was simple oxidation annealing of TiS2, the other was mixing of titanium isopropoxide and thiourea. These two sulfur-doped TiO2 preparations showed fairly different photocatalytic activity under visible light. The dynamics of photogenerated charge carriers were studied by the transient absorption measurement in the region of mid-IR. In both samples, excitation by 532 nm pulse led to photocarrier generation to the same extent. Nevertheless, the reactivity of the photocarriers was totally different. Photogenerated electrons and holes transferred to reactant gas in the latter sample, whereas they did not in the former sample. We attributed the different carrier behavior to the difference in the distribution of S atoms or particle size. These observations can explain the difference in capability of photocatalysis under visible light