Synthesis of bengamide E analogues and their cytotoxic activity

A series of bengamide E analogues were prepared from the corresponding polyketide chain and amino acids via amide coupling reactions. Opening of the polyketide chain lactone ring with α-aminolactams was successfully achieved under microwave irradiation in the presence of sodium 2-ethyl hexanoate. A cytotoxic activity evaluation against a panel of cancer cell lines (KB, HepG-2, Lu-1, MCF-7, HL-60 and Hela) indicated that the 2′R analogues were generally more cytotoxic than the 2′S analogues. Additionally, several analogues exhibited selective inhibition against various cancer cell lines: compounds 32a and 32b selectively inhibited MCF-7 cells, while 33b and 35b were more sensitive toward Lu-1 and HepG-2, respectively. Notably, some of the synthetic analogues possess cytotoxic activities with IC₅₀ values less than 1 µM.     

Some New Characterizations of Intrinsic Transversality in Hilbert Spaces

Set-Valued and Variational Analysis - Motivated by a number of questions concerning transversality-type properties of pairs of sets recently raised by Ioffe and Kruger, this paper reports several...     

Melatonin prevents doxorubicin-induced cardiotoxicity through suppression of AMPKα2-dependent mitochondrial damage

The clinical application of doxorubicin, one of the most effective anticancer drugs, has been limited due to its adverse effects, including cardiotoxicity. One of the hallmarks of doxorubicin-induced cytotoxicity is mitochondrial dysfunction. Despite intensive research over recent decades, there are no effective approaches for alleviating doxorubicin-induced cytotoxicity. Melatonin, a natural hormone that is primarily secreted by the pineal gland, is emerging as a promising adjuvant that protects against doxorubicin-induced cytotoxicity owing to its pharmaceutical effect of preserving mitochondrial integrity. However, the underlying mechanisms are far from completely understood. Here, we provide novel evidence that treatment of H9c2 cardiomyoblasts with doxorubicin strongly induced AMP-activated protein kinase α2 (AMPKα2), which translocated to mitochondria and interfered with their function and integrity, ultimately leading to cellular apoptosis. These phenomena were significantly blocked by melatonin treatment. The levels of AMPKα2 in murine hearts were tightly associated with cardiotoxicity in the context of doxorubicin and melatonin treatment. Therefore, our study suggests that the maintenance of mitochondrial integrity is a key factor in reducing doxorubicin-induced cytotoxicity and indicates that AMPKα2 may serve as a novel target in the design of cytoprotective combination therapies that include doxorubicin.Subject terms: Biochemistry, Diseases     

Microwave-Assisted Facile and Rapid Friedel–Crafts Benzoylation of Arenes Catalyzed by Bismuth Trifluoromethanesulfonate

The catalytic activity of metal triflates was investigated in Friedel–Crafts benzoylation under microwave irradiation. Friedel–Crafts benzoylation with benzoyl chloride of a variety of arenes containing electron-rich and electron-poor rings using bismuth triflate under microwave irradiation is described. This method allows the preparation of aryl ketones under solventless conditions in good to excellent yields and short reaction time. Bismuth triflate was easily recovered and reused five times without significant loss of the catalytic activity.     

Electrochemical synthesis of polyaniline nanowires on Pt interdigitated microelectrode for room temperature NH3 gas sensor application

In this work, we have successfully developed a facile and effective electrochemical route for directly growing polyaniline (PANI) nanowires (NWs) on platinum interdigitated microelectrode. The as-prepared NWs were characterized by field-emission scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy. They revealed that the PANI NWs were obtained with diameters ranging from 50 to 200 nm and length up to hundreds of micro meters, depending on growth time. The as-obtained PANI NWs on the electrode exhibited a porous nature and the conducting emeraldine type structure. The gas sensing properties of PNAI NWs were explored by monitoring NH₃ in synthetic air in the concentration range of 25–500 ppm at room temperature. The results obtained demonstrated that PANI NWs have good potential as novel room temperature sensors for practical applications.     

Anatase-rutile phase transformation of titanium dioxide bulk material: a DFT?+?U approach

The anatase-rutile phase transformation of TiO(2) bulk material is investigated using a density functional theory (DFT) approach in this study. According to the calculations employing the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional with the Vanderbilt ultrasoft pseudopotential, it is suggested that the anatase phase is more energetically stable than rutile, which is in variance with the experimental observations. Consequently, the DFT?+?U method is employed in order to predict the correct structural stability in titania from electronic-structure-based total energy calculations. The Hubbard U term is determined by examining the band structure of rutile with various values of U from 3 to 10?eV. At U?=?5?eV, a theoretical bandgap for rutile is obtained as 3.12?eV, which is in very good agreement with the reported experimental bandgap. Hence, we choose the DFT?+?U method (with U?=?5?eV) to investigate the transformation pathway using the newly-developed solid-state nudged elastic band (ss-NEB) method, and consequently obtain an intermediate transition structure that is 9.794?eV per four-TiO(2) above the anatase phase. When the Ti-O bonds in the transition state are examined using charge density analysis, seven Ti-O bonds (out of 24 bonds in the anatase unit cell) are broken, and this result is in excellent agreement with a previous experimental study (Penn and Banfield 1999 Am. Miner. 84 871-6).     

Pressure-dependent EXAFS mean-square relative displacements of germanium and silicon crystals

In this paper, the statistical moment method (SMM) has been developed to study the pressure dependence of thermodynamic quantities of germanium and silicon crystals. We have derived the analytical expressions of the pressure-dependent parallel mean-square relative displacement (MSRD) or extended X-ray absorption fine structure (EXAFS) Debye–Waller factor, mean-square displacement (MSD) as well as lattice constant and volume change of diamond-type crystals. Numerical calculations performed for these semiconductors up to 11 GPa are found to be in good and reasonable agreement with available experimental data as well as with previous theoretical studies. Our results indicate that the SMM can be efficiently used for determining the relative change of the pressure-dependent MSRDs of germanium and silicon semiconductors. The research also shows the advantage of SMM on studying other thermodynamic properties of materials under high pressures.