Intermolecular Interactions and Thermodynamic Properties of 3,6-Diamino-1,2,4,5-tetrazine-1,4-dioxide Dimers: A Density Functional Theoretical Study

Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at the B3LYP/6-311++G level. Vibrational frequency calculations were carried out to ascertain that each structure is a minimum (no imaginary frequencies). The intermolecular interaction energy is calculated with the basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greatest corrected binding energy among the three dimers is –42.38 kJ mol–1. The charge redistribution mainly occurs on the adjacent O(N)……H atoms between submolecules and the charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the standard thermodynamic functions (heat capacities (cop), entropies (Som ) and enthalpies (Hom)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using statistical thermodynamics. The results show that the strong hydrogen bonds dominantly contribute to the dimers, while the bonding energies are not only determined by the hydrogen bonding. The dimerization process of dimer II can occur spontaneously at room temperature.KEYWORDS 3,6-Diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112), intermolecular interaction, density functional theory (DFT), natural bond orbital (NBO) analysis, thermodynamic properties

Thermal Behaviour and Detonation Characterization of N-Benzoyl-3,3-dinitroazetidine

N-benzoyl-3,3-dinitroazetidine(BDNAZ) is a derivative of 3,3-dinitroazetidine (DNAZ). Its thermal behaviour was studied by DSC methods. The results show that there are one melting process and two exothermic decomposition processes. The kinetic parameters of the intense exothermic decomposition process were obtained from the analysis of the DSC curves. The apparent activation energy, pre-exponential factor and the mechanism function are 170.77 kJ mol–1, 1014.12 s–1 and f(α) = (1–a)–1/2, respectively. The specific heat capacity of BDNAZ was determined with a continuous Cp mode of a micro-calorimeter. The standard mole specific heat capacity ofBDNAZwas 286.31 J mol1 K–1 at 298.15 K. Using the relationship between Cp and T with the thermal decomposition parameters, the time of the thermal decomposition from initialization to thermal explosion (adiabatic time-to-explosion, tTIAD), the self-accelerating decomposition temperature (TSADT), thermal ignition temperature (TTIT), critical temperatures of thermal explosion (Tb) and period of validity (t0.9) were obtained to evaluate its thermal safety. The detonation velocity (D) and pressure (P) of BDNAZ were estimated by using the nitrogen equivalent equation according to the experimental density.KEYWORDS N-benzoyl-3,3-dinitroazetidine(BDNAZ), thermalbehaviour, non-isothermalkinetics, thermalsafety, detonation characterization

Selection of Saccharomyces cerevisiae strains for efficient very high gravity bio-ethanol fermentation processes

An optimized very high gravity (VHG) glucose medium supplemented with low cost nutrient sources was used to evaluate bio-ethanol production by 11 Saccharomyces cerevisiae strains. The industrial strains PE-2 and CA1185 exhibited the best overall fermentation performance, producing an ethanol titre of 19.2% (v/v) corresponding to a batch productivity of 2.5 g l-1 h-1, while the best laboratory strain (CEN.PK 113-7D) produced 17.5% (v/v) ethanol with a productivity of 1.7 g l-1 h-1. The results presented here emphasize the biodiversity found within S. cerevisiae species and that naturally adapted strains, such as PE-2 and CA1185, are likely to play a key role in facilitating the transition from laboratory technological breakthroughs to industrialscale bio-ethanol fermentations.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/BIO/66151/2006, SFRH/ BD/64776/2009, SFRH/BPD/44328/ 200

Mesonia sediminis sp nov., isolated from a sea cucumber culture pond

A yellow-pigmented, Gram-stain negative and facultatively anaerobic bacterium, designated MF326(T), was isolated from a sample of sediment collected from a sea cucumber culture pond in Rongcheng, China (122A degrees 14'34aEuro(3)E 36A degrees 54'36aEuro(3)N). Cells of strain MF326(T) were found to be catalase negative and oxidase positive. Optimal growth was found to occur at 30 A degrees C and pH 7.0-7.5 in the presence of 2.0-3.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MF326(T) is a member of the genus Mesonia and exhibits the high sequence similarity (94.3 %) with the type strain of Mesonia ostreae, followed by Mesonia algae (93.9 %). The dominant fatty acids of strain MF326(T) were identified as iso-C-15:0, an unidentified fatty acid with an equivalent chain-length of 13.565 and anteiso-C-15:0. The major polar lipids were found to be two unidentified lipids and phosphatidylethanolamine. The major respiratory quinone was found to be MK-6 and the genomic DNA G+C content was determined to be 40.7 mol%. On the basis of the phylogenetic analysis and differential phenotypic characteristics, it is concluded that strain MF326(T) (=KCTC 42255(T) =MCCC 1H00125(T)) should be assigned to the genus Mesonia as the type strain of a novel species, for which the name Mesonia sediminis sp. nov. is proposed.A yellow-pigmented, Gram-stain negative and facultatively anaerobic bacterium, designated MF326(T), was isolated from a sample of sediment collected from a sea cucumber culture pond in Rongcheng, China (122A degrees 14'34aEuro(3)E 36A degrees 54'36aEuro(3)N). Cells of strain MF326(T) were found to be catalase negative and oxidase positive. Optimal growth was found to occur at 30 A degrees C and pH 7.0-7.5 in the presence of 2.0-3.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MF326(T) is a member of the genus Mesonia and exhibits the high sequence similarity (94.3 %) with the type strain of Mesonia ostreae, followed by Mesonia algae (93.9 %). The dominant fatty acids of strain MF326(T) were identified as iso-C-15:0, an unidentified fatty acid with an equivalent chain-length of 13.565 and anteiso-C-15:0. The major polar lipids were found to be two unidentified lipids and phosphatidylethanolamine. The major respiratory quinone was found to be MK-6 and the genomic DNA G+C content was determined to be 40.7 mol%. On the basis of the phylogenetic analysis and differential phenotypic characteristics, it is concluded that strain MF326(T) (=KCTC 42255(T) =MCCC 1H00125(T)) should be assigned to the genus Mesonia as the type strain of a novel species, for which the name Mesonia sediminis sp. nov. is proposed

NOA1 Functions in a Temperature-Dependent Manner to Regulate Chlorophyll Biosynthesis and Rubisco Formation in Rice

NITRIC OXIDE-ASSOCIATED1 (NOA1) encodes a circularly permuted GTPase (cGTPase) known to be essential for ribosome assembly in plants. While the reduced chlorophyll and Rubisco phenotypes were formerly noticed in both NOA1-supressed rice and Arabidopsis, a detailed insight is still necessary. In this study, by using RNAi transgenic rice, we further demonstrate that NOA1 functions in a temperature-dependent manner to regulate chlorophyll and Rubisco levels. When plants were grown at 30°C, the chlorophyll and Rubisco levels in OsNOA1-silenced plants were only slightly lower than those in WT. However, at 22°C, the silenced plants accumulated far less chlorophyll and Rubisco than WT. It was further revealed that the regulation of chlorophyll and Rubisco occurs at the anabolic level. Etiolated WT seedlings restored chlorophyll and Rubisco accumulations readily once returned to light, at either 30°C or 15°C. Etiolated OsNOA1-silenced plants accumulated chlorophyll and Rubisco to normal levels only at 30°C, and lost this ability at low temperature. On the other hand, de-etiolated OsNOA1-silenced seedlings maintained similar levels of chlorophyll and Rubisco as WT, even after being shifted to 15°C for various times. Further expression analyses identified several candidate genes, including OsPorA (NADPH: protochlorophyllide oxidoreductase A), OsrbcL (Rubisco large subunit), OsRALyase (Ribosomal RNA apurinic site specific lyase) and OsPuf4 (RNA-binding protein of the Puf family), which may be involved in OsNOA1-regulated chlorophyll biosynthesis and Rubisco formation. Overall, our results suggest OsNOA1 functions in a temperature-dependent manner to regulate chlorophyll biosynthesis, Rubisco formation and plastid development in rice

A Novel Strategy to Construct Yeast Saccharomyces cerevisiae Strains for Very High Gravity Fermentation

Very high gravity (VHG) fermentation is aimed to considerably increase both the fermentation rate and the ethanol concentration, thereby reducing capital costs and the risk of bacterial contamination. This process results in critical issues, such as adverse stress factors (ie., osmotic pressure and ethanol inhibition) and high concentrations of metabolic byproducts which are difficult to overcome by a single breeding method. In the present paper, a novel strategy that combines metabolic engineering and genome shuffling to circumvent these limitations and improve the bioethanol production performance of Saccharomyces cerevisiae strains under VHG conditions was developed. First, in strain Z5, which performed better than other widely used industrial strains, the gene GPD2 encoding glycerol 3-phosphate dehydrogenase was deleted, resulting in a mutant (Z5ΔGPD2) with a lower glycerol yield and poor ethanol productivity. Second, strain Z5ΔGPD2 was subjected to three rounds of genome shuffling to improve its VHG fermentation performance, and the best performing strain SZ3-1 was obtained. Results showed that strain SZ3-1 not only produced less glycerol, but also increased the ethanol yield by up to 8% compared with the parent strain Z5. Further analysis suggested that the improved ethanol yield in strain SZ3-1 was mainly contributed by the enhanced ethanol tolerance of the strain. The differences in ethanol tolerance between strains Z5 and SZ3-1 were closely associated with the cell membrane fatty acid compositions and intracellular trehalose concentrations. Finally, genome rearrangements in the optimized strain were confirmed by karyotype analysis. Hence, a combination of genome shuffling and metabolic engineering is an efficient approach for the rapid improvement of yeast strains for desirable industrial phenotypes

Negative Staining and Image Classification – Powerful Tools in Modern Electron Microscopy

Vitrification is the state-of-the-art specimen preparation technique for molecular electron microscopy (EM) and therefore negative staining may appear to be an outdated approach. In this paper we illustrate the specific advantages of negative staining, ensuring that this technique will remain an important tool for the study of biological macromolecules. Due to the higher image contrast, much smaller molecules can be visualized by negative staining. Also, while molecules prepared by vitrification usually adopt random orientations in the amorphous ice layer, negative staining tends to induce preferred orientations of the molecules on the carbon support film. Combining negative staining with image classification techniques makes it possible to work with very heterogeneous molecule populations, which are difficult or even impossible to analyze using vitrified specimens

Modulation of Glucose Transporter 1 (GLUT1) Expression Levels Alters Mouse Mammary Tumor Cell Growth In Vitro and In Vivo

Tumor cells exhibit an altered metabolism characterized by elevated aerobic glycolysis and lactate secretion which is supported by an increase in glucose transport and consumption. We hypothesized that reducing or eliminating the expression of the most prominently expressed glucose transporter(s) would decrease the amount of glucose available to breast cancer cells thereby decreasing their metabolic capacity and proliferative potential