Thermo-and photoreactivities of methoxy (CH 3 O(a)) and ethoxy groups (C 2 H 5 O(a)) bonded, via the oxygen atom, to one Ti ion (monodentate adsorption form) or to two Ti ions (bidentate adsorption form) on TiO 2 have been studied by Fourier transformed infrared spectroscopy. Regardless of the similar thermal stability for the two adsorption geometries of the adsorbed alkoxy groups, difference in photoreactivity is observed by monitoring the change of their integrated IR absorptions as a function of UV irradiation time. The monodentate photooxidation rate is ∼1.5 times that of bidentate for both methoxy and ethoxy groups. CH 3 O(a) on TiO 2 is photooxidized to H 2 O(a) and HCOO(a) in the presence of O 2 . On the other hand, C 2 H 5 O(a) is photooxidized to H 2 O(a), HCOO(a), and CH 3 COO(a). A Russell-like mechanism is invoked to explain the formation of the reaction products. Possible reaction steps that control the photoreactivity of the monodentate and bidentate adsorption forms are discussed in terms of this mechanism.

Comparison of photooxidation rates of formic acid and formate on TiO 2 as well as the effect of adsorbed water on formate and formic acid photodecomposition rates have been investigated by Fourier transformed infrared spectroscopy. Adsorbed formic acid and formate are all photooxidized to CO 2 in O 2 . Formic acid on TiO 2 shows a photoreaction rate that is roughly 53 times that of formate groups for a same surface concentration. The presence of H 2 O can increase formate and formic acid photooxidation rates by a factor close to 2. In addition, photochemistry of adsorbed ethanol and ethoxy is also compared. It is found that ethanol is important for the formation of acetaldehyde, while ethoxy groups are photooxidized to adsorbed acetate, formate, and water. Possible reasons for these differences are discussed.

No abstract

Purpose: Recent evidence indicates that a tumor suppressor gene CEBPD (CCAAT/enhancer-binding protein delta) is downregulated in many cancers including cervical cancer, which provides a therapeutic potential associated with its reactivation. However, little is known for CEBPD activators and the effect of reactivation of CEBPD transcription upon anticancer drug treatment. In this study, we identified a novel CEBPD activator, 1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione (HMDB). The purpose of this study is to characterize the mechanism of HMDB-induced CEBPD activation and its potential effect in cancer therapy.Experimental Design: Methylation-specific PCR assay, reporter assay, and chromatin immunoprecipitation (ChIP) assay were performed to dissect the signaling pathway of HMDB-induced CEBPD transcription. Furthermore, a consequence of HMDB-induced CEBPD expression was linked with E2F1 and retinoblastoma (RB), which discloses the scenario of CEBPD, E2F1, and RB bindings and transcriptional regulation on the promoters of proapoptotic genes, PPARG2 and GADD153. Finally, the anticancer effect of HMDB was examined in xenograft mice.Results: We demonstrate that CEBPD plays an essential role in HMDB-mediated apoptosis of cancer cells. HMDB up-regulates CEBPD transcription through the p38/CREB pathway, thus leading to transcriptional activation of PPARG2 and GADD153. Furthermore, increased level of CEBPD attenuates E2F1-induced cancer cell proliferation and partially rescues RB/E2F1-mediated repression of PPARG2 and GADD153 transcription. Moreover, HMDB treatment attenuates the growth of A431 xenografts in severe combined immunodeficient mice mice.Conclusions: These results clearly demonstrate that HMDB kills cancer cells through activation of CEBPD pathways and suggest that HMDB can serve as a superior chemotherapeutic agent with limited potential for adverse side effects. Clin Cancer Res; 16(23); 5770-80. Ó2010 AACR.