Thermal degradation of poly(vinyl chloride): effect of oxygen on the thermal degradation of poly(vinyl chloride)

On the basis of the simultaneously measured free radical generation and HCl evolution a mechanism accounting for the effect of the oxygen on the degradation of poly(vinyl chloride) (PVC) is proposed. The mechanism is based on the reaction of oxygen with radicals generated in PVC to form unstable peroxy radicals. In addition, it is proposed that oxygen reacts directly with conjugated polyenes to form peroxy linkage.     

Extracellular pH influences the mode of cell death in human colon adenocarcinoma cells subjected to photodynamic treatment with chlorin p6

Effect of varying extracellular pH on mode of cell death induced by photodynamic action of chlorin p6 was investigated in human colon carcinoma (Colo-205) cells. At an extracellular pH of 7.4, compared to cells treated with chlorin p6 in dark, the photodynamically treated cells showed reduction in mitochondrial membrane potential, an increase in ADP/ATP ratio (1:2) and a large percentage of cells with chromatin condensation. In contrast, when photodynamic treatment and post irradiation incubation was carried out in acidic medium (pH 6.5), total loss of mitochondrial membrane potential, a marked increase in ADP/ATP ratio (1:33) and increased damage to plasma membrane were observed. Further, cells subjected to photodynamic treatment in a medium of pH 7.4 showed twofold increase in caspase-3 activity as compared to photodynamic treatment at pH 6.5. These results suggest that chlorin p6 mediated photodynamic action induces apoptotic cell death when extracellular pH is 7.4 whereas necrosis is more predominant under condition when extracellular pH is 6.5.     

Pressure dependence of the compressibility of alkali halides

The parameterC ₁=[(1/K _T )/P] _T , which describes the pressure variation of the compressibility, has been examined correlating the thermodynamical and interatomic potential approaches employing fewer approximations than has been usual heretofore. General expressions have been derived forC ₁ by including the thermal correction terms, which have generally been ignored in previous studies concerning thermal properties of ionic crystals. The parameterC ₁ has also been related to the Grüneisen parameter, , using a relation given earlier. The applicability of the derived equations is investigated and discussed for alkali halides employing few realistic potential forms. A good general accord is found with the available experimental data, which exhibits an essential improvement over other theoretical determinations.     

Purification of recombinant green fluorescent protein by three-phase partitioning

The technique of three-phase partitioning (TPP) was used to purify the green fluorescent protein (GFP) in a single step. TPP uses a combination of ammonium sulphate and tert-butanol to precipitate proteins from their crude extracts. In the first round of TPP with 20% ammonium sulphate saturation at the ratio of crude to tert-butanol 1:1 (v/v), most of the GFP remains in the lower aqueous phase. When subjected to a second round of TPP with 60% ammonium sulphate saturation at the ratio of crude to tert-butanol 1:2 (v/v) gives 78% recovery of GFP with a 20-fold purification. The sodium dodecyl sulphate-polyacrylamide gel electrophoretic (SDS-PAGE) analysis of purified preparation shows single band. The fluorescence excitation and emission spectra agreed with values reported in literature.     

SAXS investigations on chiral liquid crystalline polymers: antiferroelectric and ferrielectric structures?

The structure and phase behavior of liquid crystalline polymers (LCPs) having a common chiral side chain mesogen but different main chain structures have been investigated using small-angle X-ray scattering (SAXS). While the low molecular weight chiral side chain mesogen by itself exhibits ferroelectricity, the SAXS data of the side chain LCP with a flexible polyacrylate backbone contains a bilayered superstructure peak that is indicative of antiferroelectric order. The combined LCP with a nonpolar main chain mesogen also has a bilayered superstructure, but has a different structural organization in the proposed antiferroelectric phase compared to the side chain LCP. Further changes in the phase behavior and structural organization occur when a polar group is introduced into the main chain mesogen. A ferrielectric phase has been proposed to explain the observation of a trilayered superstructure in the corresponding SAXS data. The influence of the chemical structure and connectivity on the phase behavior and superstructure formation in the chiral LCPs is discussed.     

Polarographische Untersuchung der Nickel- und der Zinkkomplexe der Adipinsäure

Zusammenfassung Die Nickel- und Zinkkomplexe der Adipinsäure werden polarographisch untersucht. Es zeigt sich, daß Zink reversibel reduziert wird, wogegen Nickel eine irreversible Stufe ergibt. Die Stabilitätskonstanten des Zink—Adipinsäurekomplexes werden nachDeFord undHume berechnet. Der Einfluß des pH-Wertes auf die Zink- und die Nickelstufe wird untersucht. Zink und Nickel werden in Gegenwart vieler störender Kationen halbquantitativ bestimmt.

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The said complexes have been studied by polarography. Zn is found to be reversibly reduced while Ni gives an irreversible wave. Stability constants of the Zn complex are calculated byDeFord andHume method. Effect of pH on Zn and Ni wave are reported. Estimations of Zn or Ni are carried out separately or in presence of interfering cations.

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Mechanism of ruthenium tetroxide-catalysed oxidation of aldoses by alkalineN-bromoacetamide

The kinetics of oxidation of three aldoses (glucose, mannose and galactose) byN-bromoacetamide (NBA) in the presence of an alkaline solution of RuO₄ as catalyst and Hg(OAc)₂ as co-catalyst and as a scavenger for bromide have been investigated. The main products of the oxidation are the corresponding aldonic acids. The reaction is zero order with respect to aldose and OH⁻. First order dependence of the reaction on both NBA and RuO₄ at low concentrations shifts to zero order at higher concentrations. Addition of acetamide decreases the reaction rate, while addition of Hg(OAc)₂ has the opposite effect. No significant effect of ionic strength was observed. OBr⁻ is postulated as the reactive oxidising species and a mechanism involving co-catalysis by RuO₄ and Hg^II is proposed. TMC 2588     

Relevance of chemistry to white biotechnology

White biotechnology is a fast emerging area that concerns itself with the use of biotechnological approaches in the production of bulk and fine chemicals, biofuels, and agricultural products. It is a truly multidisciplinary area and further progress depends critically on the role of chemists. This article outlines the emerging contours of white biotechnology and encourages chemists to take up some of the challenges that this area has thrown up.