Inactivation of formate dehydrogenase at pH 8

The first-order inactivation rate constant as a function of the phosphate buffer concentration has been studied for recombinant formate dehydrogenases from plants Arabidopsis thaliana and soybean and for mutant formate dehydrogenase from bacterium Pseudomonas sp. 101 (PseFDH GAV). Both stabilization and destabilization of the enzyme can be observed depending on the ionic strength of the buffer.     

Comparative Study of PHA Degradation in Natural Reservoirs Having Various Types of Ecosystems

The kinetics of polyhydroxyalkanoate (PHA) degradation in natural environment in two water reservoirs having various ecological characteristics was studied. It was shown that biodegradation of polymer essentially depends on the environment temperature and inorganic composition of water. The processes of polymer degradation under aerobic and anaerobic conditions were compared. The polymer degradation was slower under anaerobic conditions.     

The structure and some electro-physical properties of TlSbS2 films

The 1m thick films of TlSbS₂ were obtained by thermal evaporation in vacuum. It has been shown that, depending on the conditions of preparation and annealing, amorphous or polycrystalline and grain-oriented layers of TlSbS₂ can be obtained. The electro-physical parameters of the films (electrical conductivity, thermoelectromotive force, and width of the forbidden band) and their changes in the transition from amorphous to crystalline were studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedehii, Fizika, Vol. 16, No. 9, pp. 37–40, 1973.The authors wish to thank S. A. Dembovskii, Dr. Chem. Sc., for supplying TlSbS₂ monocrystals.     

Surface characterisation of oxygen plasma treated electrospun polyurethane fibres and their interaction with red blood cells

In this work, the effects of oxygen plasma surface modification have been studied on electrospun polyether-based polyurethane in order to investigate the imposed limitations and possibilities to improve surface characteristics on fibrous assemblies. The evolution of induced changes in surface morphology, chemistry and wettability by the plasma treatment has been characterised for increasing plasma exposure time using scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Significant reduction in fibre diameter concomitant with progressing rough surface textures are found on the fibres in surface layers during early treatment phases while extended exposure eventually causes the fibre structure to deteriorate. Surface oxygen content and functionalities such as carbonyl and carboxyl increase slightly with longer treatments until loss of material integrity occurs. The results have also shown that oxygen plasma rapidly alters the initially strong hydrophobic character of the non-woven fibres to hydrophilic behaviour, allowing water penetration into the network, but without significant changes for increased exposure time. In addition, the response of red blood cell shape to pristine and oxygen plasma treated fibres were found to be similar. In both cases, a population of cells having fibre contact displayed protrusions while measurements showed that the cell function remain intact and indicated that the adhesion was non-specific. The reported findings yield useful process knowledge that can support the formation of well-defined fibre architectures and are valuable in the designs of electrospun polyurethane material systems utilising oxygen plasma surface modification.     

Comparison of oligonucleotide migration in a bicontinuous cubic phase of monoolein and water and in a fibrous agarose hydrogel

Porous hydrogels such as agarose are commonly used to analyze DNA and water-soluble proteins by electrophoresis. More recently lyotropic liquid crystals, such as the diamond cubic phase formed by the lipid monoolein and water, has become a new type of well-defined porous structure of interest for both hydrophilic and amphiphilic analytes. Here we compare these two types of matrixes by investigating the nature of retardation they confer to an oligonucleotide that migrates in their respective aqueous phases. The retardation for a 25-mer oligonucleotide was found to be about 35-fold stronger in the cubic phase than in an agarose hydrogel modified to have the same average pore size. According to modelling, the strong retardation is primarily due to the fact that hydrodynamic interaction with the continuous monoolein membrane is a stronger source of friction than the steric interactions (collisions) with discrete gel fibres. A secondary effect is that the regular liquid crystal has a narrower pore-size distribution than the random network of the agarose gel. In agreement with experiments, these two effects together predict that the retardation in the cubic phase is a 30-fold stronger than in an agarose gel with the same average pore radius.