Effect of inactivation of genes involved in ammonium regulation on the biohydrogen production of Rhodobacter capsulatus

Hydrogen production by nitrogenase is an energetically expensive process for the cell, hence strictly controlled at different levels. Ammonium is one of the substances regulating nitrogenase activity. The key proteins in the regulation of nitrogenase by ammonium are two regulatory proteins; GlnB and GlnK. In order to increase hydrogen production of Rhodobacter capsulatus DSM1710 (wild type strain) grown on agricultural materials/wastes, ammonium inhibition of nitrogenase enzyme has to be eliminated. In this study, GlnB and GlnK were targeted to be inactivated by in frame site-directed mutagenesis. The glnB mutant R. capsulatus (GP1 strain) was obtained at the end of mutagenesis studies. In the case of glnK, the suicide vector was constructed and delivered into the cells. However, glnK mutant could not be obtained.The effect of ammonium on the growth and hydrogen production of R. capsulatus GP1 was investigated and compared with DSM1710. Both DSM1710 and GP1 strains were effectively utilized acetate. The mutation did not affect cell growth significantly at different ammonium levels. Ammonium negatively affected hydrogen production of GP1 strain as well as the DMS1710. However, hydrogen production was significantly low in GP1 strain. The ammonium inhibition of hydrogen production could not be removed in glnB mutant probably due to the presence of an active GlnK protein in the cell. Therefore, GlnK has much more important role in the ammonium dependent control of nitrogenase than GlnB does. The growth and hydrogen production kinetics of R. capsulatus DSM1710 and GP1 were modelled. They were shown to fit to Logistic Model and Modified Gompertz Model, respectively.     

Effects of ammonium polyphosphate and triphenyl phosphate on the flame retardancy,thermal, and mechanical properties of glass fiber–reinforced PLA/PC composites

The purpose of this study is to increase of the flammability properties of the glass fiber (GF)–reinforced poly (lactic acid)/polycarbonate (PLA/PC) composites. Ammonium polyphosphate (APP) and triphenyl phosphate (TPP) were used as flame retardants that are including the organic phosphor to increase flame retardancy of GF‐reinforced composites. APP, TPP, and APP‐TPP mixture flame retardant including composites were prepared by using extrusion and injection molding methods. The properties of the composites were determined by the tensile test, limiting oxygen index (LOI), differential scanning calorimetry (DSC), and heat release rate (HRR) test. The minimum T_g value was observed for the TPP including PLA/PC composites in DSC analysis. The highest tensile strength was observed in GF‐reinforced PLA/PC composites. In the LOI test, GF including composite was burned with the lowest concentration of oxygen, and burning time was the longest of this composite. However, the shortest burning time was obtained by using the mixture flame retardant system. The flame retardancy properties of GF‐reinforced PLA/PC composite was improved by using mixture flame retardant. When analyzed the results of HRR, time to ignition (TTI), and mass loss rate together, the best value was obtained for the composite including APP.     

The study of disorder and nanocrystallinity in C–S–H, supplementary cementitious materials and geopolymers using pair distribution function analysis

Significant progress was achieved with the application of Rietveld method to characterize the crystalline phases in portland cement paste. However, to obtain detailed information on the amorphous or poorly crystalline phases, it is necessary to analyze the total scattering data. The pair distribution function (PDF) method has been successfully used in the study of liquids and amorphous solids. The method takes the Sine Fourier transform of the measured structure factor over a wide momentum transfer range, providing a direct measure of the probability of finding an atom surrounding a central atom at a radial distance away. The obtained experimental characteristic distances can be also used to validate the predictions by the theoretical models, such as, molecular dynamics, ab initio simulations and density functional theory. The paper summarizes recent results of PDF analysis on silica fume, rice husk ash, fly ash, ASR gel, C–S–H and geopolymers.     

Methionine-pyrene hybrid based fluorescent probe for trace level detection and estimation of Hg(II) in aqueous environmental samples: experimental and computational studies

A new fluorescent, Hg(2+) selective chemosensor, 4-methylsulfanyl-2-[(pyren-4-ylmethylene)-amino] butyric acid methyl ester (L, MP) was synthesized by blending methionine with pyrene. It was well characterized by different analytical techniques, viz. (1)H NMR, (13)C NMR, QTOF mass spectra, elemental analysis, FTIR and UV-vis spectroscopy. The reaction of this ligand with Hg(2+) was studied by steady state and time-resolved fluorescence spectroscopy. The Hg(2+) complexation process was confirmed by comparing FTIR, UV-vis, thermal, QTOF mass spectra and (1)H NMR data of the product with that of the free ligand values. The composition (Hg(2+):L=1:1) of the Hg(2+) complex in solution was evaluated by fluorescence titration method. Based on the chelation assisted fluorescence quenching, a highly sensitive spectrofluorometric method was developed for the determination of trace amounts of Hg(2+) in water. The ligand had an excitation and emission maxima at 360 nm and 455 nm, respectively. The fluorescence life times of the ligand and its Hg(2+) complex were 1.54 ns and 0.72 ns respectively. The binding constant of the ligand, L with Hg(2+) was calculated using Benesi-Hildebrand equation and was found to be 7.5630×10(4). The linear range of the method was from 0 to 16 μg L(-1) with a detection limit of 0.056 μg L(-1) for Hg(2+). The quantum yields of the ligand and its Hg(2+) complex were found to be 0.1206 and 0.0757 respectively. Both the ligand and its Hg(2+) complex have been studied computationally (Ab-initio, Hartree Fock method) to get their optimized structure and other related physical parameters, including bond lengths, bond angles, dipole moments, orbital interactions etc. The binding sites of the ligand to the Hg(2+) ion as obtained from the theoretical calculations were well supported by (1)H NMR titration. The interference of foreign ions was negligible. This method has been successfully applied to the determination of mercury(II) in industrial waste water.     

Preservation of precut white cheese by modified atmosphere packaging

Effects of modified atmosphere packaging (MAP) on storage stability and quality of precut fresh and aged white cheese were investigated. Fresh or aged white cheese was cut into small cubes and packaged in five different atmospheres [0% O₂ + 0% CO₂ + 100% N₂ (MAP1), 10% O₂ + 0% CO₂ + 90% N₂ (MAP2), 0% O₂ + 75% CO₂ + 25% N₂ (MAP3), 10% O₂ + 75% CO₂ + 15% N₂ (MAP4) and aerobic (air)]. Control samples were packaged in brine and vacuum for fresh and aged white cheese, respectively. Changes in gas composition, total plate count, lactococci, lactobacilli, yeast and mould counts, proteolysis, lipolysis, pH, colour, texture and sensory properties were investigated during refrigerated storage. The best packaging treatment for the fresh cheese was MAP3, as it inhibited mould growth and protected the hardness. MAP2 can be recommended for the packaging of the aged cheese, as it decreased lipolysis.     

Polypyrrole/polyaniline conductive films obtained electrochemically on polycarbonate‐coated platinum electrodes

In this study, two‐component free‐standing films were obtained by coating a polycarbonate (PC)‐coated Pt electrode first with polypyrrole (PPy) in an organic medium and then polyaniline (PAn) in an aqueous medium using an electrochemical technique. The amount of PPy and PAn contained in the films was controlled by varying the electrolysis time. The PC/PPy/PAn films were characterized by cyclic voltammetry, conductivity, FTIR and UV–visible spectrophotometry, and thermogravimetric analysis. The resistance change of the films was determined in the temperature range of ?15 to 120 °C and their temperature sensor properties were investigated. © 2002 Society of Chemical Industry     

Enhanced dispersion of carbon nanotubes in hyperbranched polyurethane and properties of nanocomposites

Hyperbranched polyurethane (HBPU) nanocomposites with multi-walled carbon nanotubes (MWNTs) were prepared by in?situ polymerization on the basis of poly(ε-caprolactone)diol as the soft segment, 4,4'-methylene bis(phenylisocyanate) as the hard segment, and castor oil as the multifunctional group for the hyperbranched structure. A dominant improvement in the dispersion of MWNTs in the HBPU matrix was found, and good solubility of HBPU-MWNT nanocomposites in organic solvents was shown. Due to the well-dispersed MWNTs, the nanocomposites resulted in achieving excellent shape memory properties as well as enhanced mechanical properties compared to pure HBPU.     

Interdialytic blood pressure obtained by ambulatory blood pressure measurement and left ventricular structure in hypertensive hemodialysis patients

Unlike in subjects with normal renal function, the relationship between hypertension and cardiovascular morbidity and mortality in dialysis patients is still being debated. In order to clarify this issue, we performed 44-hour ambulatory blood pressure measurements (ABPM) during the interdialytic period in a group of 164 hypertensive patients, the blood pressure (BP) control based on conventional antihypertensive strategy previously, on chronic hemodialysis treatment in the Mediterranean region of Turkey. These results were then compared with their echocardiographic data. This is a cross-sectional analysis. The mean ABPM during 44 hours was close to the manually measured predialysis value, but there was a gradual increase in the ABPM values in the interdialytic period. When divided into a group with mild or no left ventricular hypertrophy (LVH) (45 patients) and severe LVH (119 patients), the latter had significantly higher BP levels in all separate periods, while the difference in predialysis BP was not significant. Patients with severe LVH had larger left atrium and left ventricular diameters, and consumed more antihypertensive drugs. Systolic BP during the night before dialysis showed the strongest relation to LVH, but interdialytic weight gain was also independently related to LVH. Yet, 56% of the patients with systolic BP <135 had severe LVH. There is not only an association between BP and presence of LVH, but it is shown that volume expansion is also an important independent determinant of LVH. This may explain the difficulty in identifying hypertension as a cardiac risk factor in these patients.