Pramanicin analog induces apoptosis in human colon cancer cells: critical roles for Bcl-2, Bim, and p38 MAPK signaling

Pramanicin (PMC) is an antifungal agent that was previously demonstrated to exhibit antiangiogenic and anticancer properties in a few in vitro studies. We initially screened a number of PMC analogs for their cytotoxic effects on HCT116 human colon cancer cells. PMC-A, the analog with the most potent antiproliferative effect was chosen to further interrogate the underlying mechanism of action. PMC-A led to apoptosis through activation of caspase-9 and -3. The apoptotic nature of cell death was confirmed by abrogation of cell death with pretreatment with specific caspase inhibitors. Stress-related MAPKs JNK and p38 were both activated concomittantly with the intrinsic apoptotic pathway. Moreover, pharmacological inhibition of p38 proved to attenuate the cell death induction while pretreatment with JNK inhibitor did not exhibit a protective effect. Resistance of Bax -/- cells and the protective nature of caspase-9 inhibition indicate that mitochondria play a central role in PMC-A induced apoptosis. Early post-exposure elevation of cellular Bim and Bax was followed by a marginal Bcl-2 depletion and Bid cleavage. Further analysis revealed that Bcl-2 downregulation occurs at the mRNA level and is critical to mediate PMC-A induced apoptosis, as ectopic Bcl-2 expression substantially spared the cells from death. Conversely, forced expression of Bim proved to significantly increase cell death. In addition, analyses of p53-/- cells demonstrated that Bcl-2/Bim/Bax modulation and MAPK activations take place independently of p53 expression. Taken together, p53-independent transcriptional Bcl-2 downregulation and p38 signaling appear to be the key modulatory events in PMC-A induced apoptosis

Application of metal − organic frameworks

The burgeoning field of metal-organic frameworks or porous coordination polymers has received increasing interest in recent years. In the last decade these microporous materials have found several applications including storage and separation of gases, sensors, catalysis and functional materials. In order to better design new metal-organic frameworks and porous coordination polymers with specific functionalities a fundamental issue is to achieve a basic understanding of the relationship between molecular parameters and structures, preferred adsorption sites and properties by using using modern theoretical methods. The focus of this mini-review is a description of the potential and emerging applications of metal-organic framework

PEG−peptide conjugates

The remarkable diversity of the self-assembly behavior of PEG−peptides is reviewed, including self-assemblies formed by PEG−peptides with β-sheet and α-helical (coiled-coil) peptide sequences. The modes of self-assembly in solution and in the solid state are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized

Dynamic in situ reconstruction of NiSe2 promoted by interfacial Ce2 CO3 2O for enhanced water oxidation

Understanding and manipulating the structural evolution of water oxidation electrocatalysts lays the foundation to finetune their catalytic activity. Herein, we present a synthesis of NiSe2 Ce2 CO3 2O heterostructure and demonstrate the efficacy of interfacial Ce2 CO3 2O in promoting the formation of catalytically active centers to improve oxygen evolution activity. In situ Raman spectroscopy shows that incorporation of Ce2 CO3 2O into NiSe2 causes a cathodic shift of the Ni2 amp; 8594;Ni3 transition potential. Operando electrochemical impedance spectroscopy reveals that strong electronic coupling at heterogeneous interface accelerates charge transfer process. Furthermore, density functional theory calculations suggest that actual catalytic active species of NiOOH transformed from NiSe2, which is coupled with Ce2 CO3 2O, can optimize electronic structure and decrease the free energy barriers toward fast oxygen evolution reaction OER kinetics. Consequently, the resultant NiSe2 Ce2 CO3 2O electrode exhibits remarkable electrocatalytic performance with low overpotentials 268 304 mV 50 100 mA cm amp; 8722;2 and excellent stability 50 mA cm amp; 8722;2 for 120 h in the alkaline electrolyte. This work emphasizes the significance of modulating the dynamic changes in developing efficient electrocatalys

Effect of Reynolds number and lithium cation insertion on titanium anodization

This work studies the influence of using hydrodynamic conditions (Reynolds number, Re = 0 to Re = 600) during Ti anodization and Li+ intercalation on anatase TiO2 nanotubes. The synthesized photocatalysts were characterized by using Field Emission Scanning Electron Microscope (FE-SEM), Raman Confocal Laser Microscopy, Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky analysis (M-S), photoelectrochemical hydrogen production and resistance to photocorrosion tests. The obtained results showed that the conductivity of the NTs increases with Li+ intercalation and Re. The latter is due to the fact that the hydrodynamic conditions eliminate part of the initiation layer formed over the tube-tops, which is related to an increase of the photocurrent in the photoelectrochemical water splitting. Besides, the photogenerated electron-hole pairs are facilitated by Li+ intercalation. Finally, this work confirms that there is a synergistic effect between Re and Li+ intercalation

Synergistic effect between hydrodynamic conditions during Ti anodization and acidic treatment on the photoelectric properties of TiO2 nanotubes

In the present work, the combined influence of controlled hydrodynamic conditions during Ti anodization and the acidic treatment with HClO4 on the photoelectric properties of mixed anatase/rutile TiO2 nanotubes has been studied. Anodized samples were analyzed by means of Field Emission Scanning Electronic Microscopy (FE-SEM), Confocal Raman Microscopy, electrochemical measurements (electrochemical impedance spectroscopy and Mott-Schottky analysis) and photoelectrochemical measurements. It has been observed that the use of hydrodynamic conditions increases the surface area of nanotubes, while acidic treatment enhances their conductivity. Besides, there is a clear synergistic effect between the hydrodynamic conditions and the acidic treatment, which results in higher photocurrent densities for the treated nanotubes formed under hydrodynamic conditions.Authors would like to express their gratitude for the financial support to the Ministerio of Economia y Competitividad (Project CTQ2013-42494-R).Sánchez Tovar, R.; Fernández Domene, RM.; Martinez Sanchez, A.; Blasco Tamarit, ME.; García-Antón, J. (2015). Synergistic effect between hydrodynamic conditions during Ti anodization and acidic treatment on the photoelectric properties of TiO2 nanotubes. Journal of Catalysis. 330:434-441. https://doi.org/10.1016/j.jcat.2015.08.002S43444133

Rational design of Pd-TiO2/g-C3N4 heterojunction with enhanced photocatalytic activity through interfacial charge transfer

A hybrid heterojunction-based photocatalyst is synthesized by an electrostatic self-assembly strategy including surface modification and controlled metal deposition. The interfacial contact was made by mixing negatively charged anatase TiO2 nanoparticles with positively charged g-C3N4. Visible-light deposition of Pd nanoparticles largely on TiO2 was made possible due to the charge transfer from C3N4 (excited by visible light) to the conduction band of TiO2 reducing Pd ions on contact with its surface. In order to further test the efficiency of this cascade of electron transfer across the conduction bands of the two semiconductors, photocatalytic H2 production from water was studied. Upon optimizing the ratio of the two semiconductors, increased H2 production rates were observed and attributed to enhanced charge separation. Catalysts were studied by a variety of techniques in order to probe into their properties and link them to activity. The reaction rate, under visible-light excitation, of the best sample showed an 8-fold enhancement when compared to that of Pd-C3N4 in identical conditions and the highest apparent quantum yield of 31% was achieved by a 0.1%Pd/20%TiO2/C3N4 sample in a 420- to 443-nm range

Stable All Solid State Z-Scheme Based TiO₂/M/Cd_xZn_1-Xs Photo-Catalysts for Efficient Hydrogen Generation

Water splitting to hydrogen and oxygen molecules suing semiconductors as photocatalysts to store solar energy, is one of the “Holy Grails” in solar energy conversion1. The performance of a photocatalyst is largely limited by four requirements: 1) long term stability with respect to photo corrosion, 2) a narrow band gap materials to absorb a large fraction of solar light, 3) suitable band edges that match the redox potential of water, and 4) slow charge carrier recombination systems. In particular, with respect to point 4, many artificial Z-scheme based photocatalytic systems have been widely investigated2. Recently, Rao et al.,3 reported an all-solid state Z-scheme anisotropic ZnO/Pt/Cd0.8Zn0.2S heterojunction system which exhibited a high photocatalytic activity owing to an efficient electron-hole transfer between the ZnO conduction band and the CdS valence band through Pt nanoparticles (using benzyl alcohol and acetic acid as sacrificial reagents). However, this system is not stable over the long term mainly because ZnO is stable in a very narrow pH range (6-8)4, whereas the ideal pH for hydrogen production, either by sacrificial or direct water splitting, is often outside this range. As a consequence, the original Z-scheme structure is gradually destroyed following the dissolution of the ZnO which subsequently causes the decomposition of Cd0.8Zn0.2S. In this work, we have developed a novel TiO2/Ag-Pd/Cd(Zn)S based Z-scheme photocatalytic system. This system was found to be stable in the presence of aqueous solution containing benzyl alcohol/acetic acid (the role of both has been investigated). Catalysts were prepared and characterized by XRD, XPS, TEM and UV-Vis and the catalytic tests were conducted over the complete series of the Z-Scheme system and its individual components such as Ag-Pd/TiO2 and Cd0.8Zn0.2S. The hydrogen generation rate of the best system and that of its components were 3.3 mmol/h.gcatal. (TiO2/Ag-Pd/Cd0.8Zn0.2S), 1.1 mmol/h.gcatal. (Ag-Pd/TiO2) and 0.5 mmol/h.g catal. (Cd0.8Zn0.2S) respectively under identical conditions as described below. Figure 1 <jats:p /

Enhancement of Photocatalytic Hydrogen Generation of Ni Doped CdS Enabled By Improved Ultrafast Charge Transfer

Ultrafast carrier dynamics of Cd0.992Ni0.008S nanoparticles with and without Pt have been investigated using femtosecond transient absorption spectroscopy (fs-TA) with broadband capabilities. A strong ground state bleaching (GSB) feature around 480 nm and a broad photo-induced absorption (PIA) feature around 600 nm were assigned for electron and hole signatures in Cd0.992Ni0.008S, respectively. In order to validate the inferences made from fs-TA studies, we have examined the photo-catalytic performance of Cd0.992Ni0.008S and Pt/Cd0.992Ni0.008 in the presence of a complex medium composed of acetic acid and benzyl alcohol. The results show that the Ni doping in Pt/CdS not only enhances the photocatalytic performance of the Pt/CdS but also improves the photo-stability by removing the photo-generated hole efficiently. Figure 1 <jats:p /