Structure of silicon nitride obtained by plasma-chemical synthesis..

X-ray diffraction results of short-range order in nanoscale powders of silicon nitride obtained by plasma-chemical synthesis are presented. It is shown that the most probable structure of nanopowder silicon nitride can be characterized by a model of a disordered network of SiN4tetrahedra.

Reconciling NMR Structures of the HIV-1 Nucleocapsid Protein (NCp7) using Extensive Polarizable Force Field Free-Energy Simulations

Using polarizable (AMOEBA) and non-polarizable (CHARMM) force fields, we compare the relative free-energy stability of two extreme conformations of the HIV-1 NCp7 nucleocapsid that had been previously experimentally advocated to prevail in solution. Using accelerated sampling techniques, we show that they differ in stability by no more than 0.75-1.9 kcal/mol depending on the reference protein sequence. While the extended form appears to be the most probable structure, both forms should thus coexist in water explaining the differing NMR findings.<br>

Reconciling NMR Structures of the HIV-1 Nucleocapsid Protein (NCp7) using Extensive Polarizable Force Field Free-Energy Simulations

Using polarizable (AMOEBA) and non-polarizable (CHARMM) force fields, we compare the relative free-energy stability of two extreme conformations of the HIV-1 NCp7 nucleocapsid that had been previously experimentally advocated to prevail in solution. Using accelerated sampling techniques, we show that they differ in stability by no more than 0.75-1.9 kcal/mol depending on the reference protein sequence. While the extended form appears to be the most probable structure, both forms should thus coexist in water explaining the differing NMR findings.<br>

Reconciling NMR Structures of the HIV-1 Nucleocapsid Protein (NCp7) using Extensive Polarizable Force Field Free-Energy Simulations

Using polarizable (AMOEBA) and non-polarizable (CHARMM) force fields, we compare the relative free-energy stability of two extreme conformations of the HIV-1 NCp7 nucleocapsid that had been previously experimentally advocated to prevail in solution. Using accelerated sampling techniques, we show that they differ in stability by no more than 0.75-1.9 kcal/mol depending on the reference protein sequence. While the extended form appears to be the most probable structure, both forms should thus coexist in water explaining the differing NMR findings.<br>

Synthesis and Anticancer Activity of Gold(I)-Chloroquine Complexes

Two new gold(I) -chloroquine complexes, Au(CQ)(Cl) (<strong>1</strong>) and Au(CQ)(tgta) (<strong>2</strong>), were prepared and their most probable structure were established through a combination of different spectroscopic and analytical techniques. Their interaction with two important targets of action, DNA and thioredoxin reductase (TrxR), were nvestigated. These studies showed that complexes <strong>1</strong> and <strong>2</strong> displayed two types of interaction with DNA, covalent binding through the metal center, and additionally a non-covalent interaction that is electrostatic in the case of complex <strong>1</strong>, but intercalative for complex <strong>2</strong>, which is similar to that displayed by free CQ. The experimental data indicated that these gold-CQ complexes also possess the ability to inhibit TrxR. These results led us to test their cytotoxicity against 6 tumor cell lines. The complexes displayed cytotoxic activity against the PC-3, SKBR-3, HT-29, LoVo and B16/BL6 lines. These finding suggest that gold(I)-CQ compounds, particularly [Au(CQ)(PPh₃)]PF₆, are promising chemotherapeutic alternatives in the search of anticancer agents.

Preparation, Characterization, and Thermal Degradation Studies ofp-Nitrophenol-Based Copolymer

Polycondensation reaction was employed to synthesize a new copolymer resin (p-NP-4,4′-MDA-F) from p-nitrophenol (p-NP) and 4,4′-methylene dianiline (4,4′-MDA) with formaldehyde (F) in presence of 2 M hydrochloric acid as a catalyst at130±1°C. The resin was characterized by elemental analysis and spectral studies such as UV-visible, FT-IR, and1H-NMR spectra which were used to confine the most probable structure of synthesized copolymer. Thermal degradation pattern and kinetics have been investigated by thermogravimetric analysis. Thermal degradation curve have been studied with minute detail for each degradation step. Friedman, Chang, Sharp-Wentworth, Freeman-Carroll, and Coat-Redfern methods have been implemented in order to compute the kinetic parameters, that is, thermal activation energy (Ea), order of reaction (n), and frequency factor (z).