Controlled Synthesis of Polyions of Heavy Main-Group Elements in Ionic Liquids

Ionic liquids (ILs) have been proven to be valuable reaction media for the synthesis of inorganic materials among an abundance of other applications in different fields of chemistry. Up to now, the syntheses have remained mostly “black boxes”; and researchers have to resort to trial-and-error in order to establish a new synthetic route to a specific compound. This review comprises decisive reaction parameters and techniques for the directed synthesis of polyions of heavy main-group elements (fourth period and beyond) in ILs. Several families of compounds are presented ranging from polyhalides over carbonyl complexes and selenidostannates to homo and heteropolycations.     

The Effects of Annealing After Equal Channel Angular Extrusion (ECAE) on Mechanical and Magnetic Properties of 49Fe-49Co-2V Alloy

Metallurgical and Materials Transactions A - Equal channel angular extrusion (ECAE) of 49Fe-49Co-2V, also known as Hiperco® 50A or Permendur-2V, greatly improves the strength and ductility of...     

Preparation and morphological characterization of two- and three-component natural rubber-based latex particles

Different emulsion polymerization processes allowed variation in the microstructure of composite natural rubber (NR)-based latex particles. A prevulcanized and a not-crosslinked natural rubber latex were coated with a shell of crosslinked poly(methyl methacrylate) (PMMA) or polystyrene (PS). The bipolar redox initiating system tert-butyl hydroperoxide/tetraethylene pentamine promoted a core–shell arrangement. Furthermore, PS subinclusions were introduced into the NR core. The initiators used for the subinclusion synthesis were azobisisobutyronitrile at high temperature and a redox initiation system consisting of tert-butyl hydroperoxide/dimethylaniline at low temperature. The morphology of the resulting latex interpenetrating networks (IPN) was characterized by transmission electron micros-copy (TEM) and scanning electron microscopy (SEM). Different staining methods allowed us to increase the contrast between the NR phase and the secondary polymers in the composite latex particles. A semicontinuous feeding process decreased the PS subinclusions size by a factor of 6 in comparison with a batch reaction. Depending on the NR/styrene swelling ratio, the crosslinking degree, and the polymerization temperature used, distinct differences of the phase arrangement of polymers in the latex particles were revealed. © 1996 John Wiley & Sons, Inc.     

Apparent heterogeneity of recombinant interferon γ receptors produced in prokaryotic and eukaryotic expression systems

Recombinant proteins show several types of heterogeneity and post-translational modifications which are usually related to their production system. The apparent heterogeneity of recombinant interferon γ receptors and interferon γ receptor–immunoglobulin G fusion proteins expressed in Escherichia coli, baculovirus-infected insect cells and Chinese hamster ovary cells have been studied. In general, all proteins tested showed some type of heterogeneity which was detectable by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The E. coli-derived receptor included non-native conformations involving mispaired or non-formed disulfides. This type of heterogeneity affected the biological activity of the protein. In addition, the prokaryotic protein had trapped phosphoric acid during downstream processing. The phosphoric acid entrapment did not affect ligand binding capacity. The eukaryotic proteins showed heterogeneity because of the unequal cleavage of the signal peptide and because of differences in glycosylation. The latter types of heterogeneity did not affect activity. Glycosylation-related heterogeneity was partially derived from the unequal utilization of the potential N-glycosylation sites and differently affected the apparent molecular masses and migrations of the proteins on polyacrylamide gels. The results may be useful in characterization studies of recombinant proteins.     

Intrinsic 42Ca-Labelling of Green Bean Pods for Use in Human Bioavailability Studies

A hydroponic growth procedure which enables the intrinsic ⁴²Ca-labelling of green beans ( Phaseolus vulgaris L) has been developed. Whole-plant Ca influx was measured from planting through the period of pod expansion for a crop of 60 plants grown hydroponically in a 3m²area. Total Ca influx was 10·1mmol per plant; 35% of this influx occurred during the period of pod growth. Plants were labelled with ⁴²Ca via the nutrient solution during the period of pod expansion; isotopic composition of harvested pods was nearly identical to that of the administered solution. Recovery of isotopic tracer at harvest was as follows: pods 8·4%; leaves, 61·1%; stems, 17·1%, roots, 9·0%. Pod yield was 98·8g FW per plant. ⁴²Ca-labelled green beans can be used safely to investigate Ca bioavailability in humans.     

The yeast growth control gene GRC5 is highly homologous to the mammalian putative tumor suppressor gene QM

We isolated the Saccharomyces cerevisiae GRC5 (gr owth control) gene by functional complementation in vivo of a ts (t emperature s ensitive) mutation. Phenotypic analysis suggested involvement of GRC5 in cell growth and proliferation. Mutant cells arrest their cell cycles after one to three cell divisions predominantly as mother cells with a large bud. In the region of the septum, a massive accumulation of cell wall material is observed. The mother and daughter nuclei are well separated and spindles are no longer present, while the cytoskeleton is of aberrant appearance. Arrested cells do not perform protein synthesis and are unable to mate. Furthermore, grc5-1^ts cells rapidly lose viability at the restrictive temperature (37°C) only on full media, but not under nitrogen-starvation conditions, indicating that proper response to this nutrient limitation is still intact in mutant cells after cell cycle arrest. The sequence of GRC5 translates into a basic protein of 221 amino acids with a corresponding M_r of 25·4 kDa. GRC5 is a member of the highly conserved QM gene family, members of which have been reported from plants, invertebrates and vertebrates. The amino acid sequence of GRC5 over its entire length is more than 60% identical to the human QM protein, expression of which is associated with loss of the tumorigenic phenotype in a cell line derived from Wilms' tumor, a malignancy of the embyronic kidney. Here, we show that GRC5 is an essential yeast gene, the function of which as inferred from analysis of the grc5-1^ts mutant is crucial for establishment of proper cytoskeletal structure and regulation of growth in yeast cells.