Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

/pdf/dye-sensitized-solar-cells-50b0w2bhsr.pdf

Dye-Sensitized Solar Cells

Together, histone acetyltransferases and histone deacetylases (HDACs) determine the acetylation status of histones. This acetylation affects the regulation of gene expression, and inhibitors of HDACs have been found to cause growth arrest, differentiation and/or apoptosis of many tumours cells by altering the transcription of a small number of genes. HDAC inhibitors are proving to be an exciting therapeutic approach to cancer, but how do they exert this effect?

Histone deacetylases and cancer: causes and therapies.

The opposing actions of histone acetyltransferases (HATs) and histone deacetylases (HDACs) allow gene expression to be exquisitely regulated through chromatin remodelling. Aberrant transcription due to altered expression or mutation of genes that encode HATs, HDACs or their binding partners, is a key event in the onset and progression of cancer. HDAC inhibitors can reactivate gene expression and inhibit the growth and survival of tumour cells. The remarkable tumour specificity of these compounds, and their potency in vitro and in vivo, underscore the potential of HDAC inhibitors as exciting new agents for the treatment of cancer.

Histone-deacetylase inhibitors: novel drugs for the treatment of cancer

Concentrations of acetyl–coenzyme A and nicotinamide adenine dinucleotide (NAD+) affect histone acetylation and thereby couple cellular metabolic status and transcriptional regulation. We report that the ketone body d-β-hydroxybutyrate (βOHB) is an endogenous and specific inhibitor of class I histone deacetylases (HDACs). Administration of exogenous βOHB, or fasting or calorie restriction, two conditions associated with increased βOHB abundance, all increased global histone acetylation in mouse tissues. Inhibition of HDAC by βOHB was correlated with global changes in transcription, including that of the genes encoding oxidative stress resistance factors FOXO3A and MT2. Treatment of cells with βOHB increased histone acetylation at the Foxo3a and Mt2 promoters, and both genes were activated by selective depletion of HDAC1 and HDAC2. Consistent with increased FOXO3A and MT2 activity, treatment of mice with βOHB conferred substantial protection against oxidative stress.

/pdf/suppression-of-oxidative-stress-by-b-hydroxybutyrate-an-2vmdjay6sk.pdf

Suppression of Oxidative Stress by β-Hydroxybutyrate, an Endogenous Histone Deacetylase Inhibitor

The initiation and progression of cancer is controlled by both genetic and epigenetic events. Unlike genetic alterations, which are almost impossible to reverse, epigenetic aberrations are potentially reversible, allowing the malignant cell population to revert to a more normal state. With the advent of numerous drugs that target specific enzymes involved in the epigenetic regulation of gene expression, the utilization of epigenetic targets is emerging as an effective and valuable approach to chemotherapy as well as chemoprevention of cancer.

Epigenetic therapy of cancer: past, present and future

Cyclic hydroxamic-acid-containing peptide 1 (CHAP1), designed as a hybrid of trichostatin A and trapoxin, is a lead compound for the development of potent inhibitors of histone deacetylase (HDAC). In this study, we synthesized a series of CHAP derivatives and evaluated their biological activities by monitoring the potency of their inhibition of HDAC activity, their ability to augment the expression of MHC class-I molecules in B16/BL6 cells, and their effect on cell proliferation. A structure-activity relationship study using these three assay systems revealed several requirements of their structure for the strong inhibition of HDAC not only in the cell-free situation, but also in cells. When the structures of CHAP derivatives are represented as cyclo(-Asu(NHOH)-AA(2)-AA(3)-Pro or Pip-)(n), where Asu(NHOH) and Pip are zeta-hydroxamide-alpha-aminosuberic acid and pipecolic acid, respectively, (a) the tetrapeptide structure (n = 1) was better than the octapeptide one (n = 2); (b) AA(2) and AA(3) should be hydrophobic; and (c) the combination of amino acid chirality should be LDLD for the strongest inhibition of HDAC in cells (LDLD > LLLD, LDLL > LLDL). cyclo(-L-Asu(NHOH)-D-Tyr(Me)-L-Ile-D-Pro-) or CHAP31 was selected as one of the strongest CHAPs, and its biological activity was characterized further. CHAP31 was much more stable in the presence of cultured cells (t(1/2) > 3000 h) than trichostatin A (t(1/2) = 14.7 h) or trapoxin A (t(1/2) = 2.10 h). CHAP31 exhibited antitumor activity in C57BL x DBA/2 F(1) (BD2F(1)) mice bearing B16/BL6 tumor cells. Furthermore, CHAP31 inhibited the growth in four of five human tumor lines implanted into nude mice. These results suggest CHAP31 to be promising as a novel therapeutic agent for cancer treatment.

https://cancerres.aacrjournals.org/content/canres/61/11/4459.full.pdf

Cyclic Hydroxamic-acid-containing Peptide 31, a Potent Synthetic Histone Deacetylase Inhibitor with Antitumor Activity

Quasi-solid dye sensitised solar cells filled with ionic liquid--increase in efficiencies by specific interaction between conductive polymers and gelators

Dye sensitised solar cells (DSSCs) were solidified with chemically cross-linked gelators without losing the performance of DSSCs before gelation. The electrolytes contain ionic liquids (1-methyl-3-propylimidazolium iodide) solidified with polyvinylpyridine and 1,2,4,5-tetra(bromomethyl)benzene. The solidification was carried out by baking the cells after the gel electrolyte precursors were injected in the cells. This brought about sufficient physical contacts between gel electrolytes and TiO2 nano-crystals in nano-porous TiO2 electrolytes. Small amount of water was added in order to decrease initial viscosities for ionic liquid type gel precursors, which makes it possible for the gel precursors to impregnate into nano-pores in TiO2 layers. The addition of water also has an advantage for decreasing charge transfer resistances between electrolytes and counter Pt. It was found that short circuit current (Jsc) and open crcuit voltage (Voc) increased much, when TiO2 layers with N3 dye were dipped in dilute carboxylic acid solutions and dried. Decreases in resistant of TiO2 layers were observed after the carboxylic acid treatments were carried out. This method is useful for increase in performance DSSC containing ionic liquid type electrolytes.

Quasi-solid dye sensitized solar cells solidified with chemically cross-linked gelators: Control of TiO2/gel electrolytes and counter Pt/gel electrolytes interfaces

Tamaki Kato

Papers

Cyclic Hydroxamic-acid-containing Peptide 31, a Potent Synthetic Histone Deacetylase Inhibitor with Antitumor Activity

Quasi-solid dye sensitised solar cells filled with ionic liquid--increase in efficiencies by specific interaction between conductive polymers and gelators

Quasi-solid dye sensitized solar cells solidified with chemically cross-linked gelators: Control of TiO2/gel electrolytes and counter Pt/gel electrolytes interfaces

Cyclic tetrapeptides bearing a sulfhydryl group potently inhibit histone deacetylases.

Novel histone deacetylase inhibitors: cyclic tetrapeptide with trifluoromethyl and pentafluoroethyl ketones.