PURIFICATION AND PARTIAL CHARACTERIZATION OF TWO PROTEINACEOUS α-AMYLASE INHIBITORS FROM TRITICALE

A total of six α-amylase inhibitory proteins (isoinhibitors) were extracted from triticale (Triticum X Secale) seeds and two of them were purified to homogeneity. The isoinhibitors were extracted by 70% ethanol and produced, by Sephadex G-100 chromatography, two peaks that exhibited α-amylase inhibitory activity. Further purification of the most active peak by DEAE-cellulose chromatography resulted in six active fractions. Two of them designated as TAI-5 and TAI-6, considered to be homogeneous by both acidic and alkaline electrophoresis, were partially characterized. The isoelectric points were 4.80 and 4.70, and the molecular weights 39, 200 and 29, 200, respectively. Under dissociating conditions the molecular weights were 13, 500 and 13, 000, suggesting that the isoinhibitors are composed of three and two subunits, respectively. Both isoinhibitors were stable at different pHs, relatively stable at 98C, and resistant to proteolysis by trypsin, chymotrypsin and pepsin. The optimum interaction pH for both isoinhibitors with human salivary amylase was 7.9. They exhibited specificity to human salivary and porcine pancreatic α-amylases, but had no inhibitory activity on Bacillus subtillis, Aspergillus oryzae and endogenous triticale α-amylases.     

Thermodynamic Aspects of the Roasting Processes in the Pre-treatment of Nickelferrous Garnierites

Abstract

The chemistry of pre-calcination and reduction roast processes with H₂ + H₂O gaseous mixture was analyzed, in order to find the best nickel and cobalt recoveries after selective roasting of nickelferrous laterites

A thermodynamic analysis of the pre-reduction of garnieritic ores aiming NiO and CoO reduction showed that the low NiO activity in the ore demands highly aggressive reducing conditions to attain reasonable nickel recoveries. Between 650-850°C, the highest nickel recoveries through amoniacal leaching was obtained at 750°C with 60% H₂ + 40% H₂0. Tests at 900°C revealed an unexpected high nickel recovery probably due to the presence of metallic iron which acted as a solvent for metallic nickel, favoring in consequence its metallization.     

RADIO AND NETWORK COMPARISONS FOR MSBN AND GSM SYSTEMS IN A GEOSTATIONARY SATELLITE ENVIRONMENT

One of the most frequently debated issues in satellite communications concerns the comparison between time division multiple access (TDMA) and code division multiple access (CDMA) systems. Although, in our view, a general answer to this problem cannot be found, this paper presents comparisons of two systems utilizing the above-mentioned access techniques, both from a radio and a network point of view. In particular, the mobile satellite business network (MSBN), (a CDMA system currently being developed by the European Space Agency (ESA) for general satellite applications) and the full integrated extension to satellite systems of the global system for mobile communication (GSM) (the well-known frequency division multiplex (FDM)/TDMA pan-European mobile cellular system) are compared by taking, as the reference payload, the L-band land mobile (LLM) satellite (a spot-beam geostationary satellite whose launch should take place at the end of 1997). Reasonable assumptions take into account the fact that, on one hand, the MSBN system is not completely defined and, on the other, the GSM is applied in a context different from the one specified by the European Telecommunication Standard Institute (ETSI). Performance comparisons are carried out in terms of flexibility and number of available channels for the same quality requirements, emitted power levels, propagation environment and interference levels coming from adjacent satellites. It is concluded that MSBN is more flexible than GSM and that, as regards capacity, an advantage of GSM over MSBN is present in the transportable mobile case, whereas, in the vehicular mobile case, MSBN shows an advantage over GSM. © 1996 by John Wiley & Sons, Ltd.     

ENERGY CONSUMPTION IN A CONCENTRATED ORANGE JUICE PLANT

The consumption of electricity and thermal energy for frozen concentrated orange juice (FCOJ) and citrus pulp pellets (CPP) was determined in a plant. Thermal energy accounted for 90% of the total energy consumption in the plant and its consumption for CPP exceeded that for FCOJ. The kilocalories of thermal energy per kg of water evaporated (KKWE) in the evaporators increased as the feed rate of single strength juice was decreased. At the design evaporation capacity, the steam efficiency of two tubular evaporators and two plate evaporators was found to be 0.85N and 0.82N, respectively; N being the number of effects of the evaporator. Fouling of the waste heat evaporator was a major reason for the high energy consumption in the CPP unit.     

COMBINATION OF BLACK BEAN (PHASEOLUS VULGARIS) AMYLASE INHIBITOR WITH MODIFIED PANCREATIC α-AMYLASE

Several amino acid residues important for the action of porcine pancreatic α-amylase on starch were modified using specific reagents: histidine groups by photooxidation with rose bengal or by diethylpyrocarbonate; cysteine by dithiobis nitrobenzoic acid; tryptophan by N-bromosuccimide and tyrosine by hydroxyl acetylation with N-acetylimidazole. These modifications, with the exception of cysteine, reduced the amylase activity but none of them alone was able to alter significantly the inhibition of the enzyme by a purified black bean (Phaseolus vulgaris) amylase inhibitor. Only by photooxidation that can modify several groups at the same time was the inhibitor action eliminated. The results suggested that the histidine of the amylase active site and tyrosine of the substrate binding site are not important for binding to the bean inhibitor. The terminal sugars of the amylase inhibitor were identified as mannose and xylose. Periodate oxidation of the carbohydrate moiety caused total loss of activity. The treatment of the inhibitor with α-mannosidase did not alter its inhibitor action on α-amylase.     

Cell extrusion in development and cancer,what MARCKS the difference for epithelial integrity?

Cell extrusion is an active mechanism to eliminate non-viable or supernumerary cells in healthy epithelia. It also plays a role in carcinogenesis, both in tumor growth (apical extrusion) and metastasis (basal extrusion). Embryonic tissues like the neuroepithelium, on the other hand, present rates of proliferation comparable to that of carcinomas, without the occurrence of cell extrusion. However, the downregulation or phosphorylation of actin-modulating proteins like MARCKS, causes extensive neuroepithelial apical cell extrusion. As changes in MARCKS proteins phosphorylation and expression have also been correlated to carcinogenesis, we propose here an integrated model for their functions in epithelial integrity.     

DESIGNING HOPE: RATIONALES OF MIXED‐INCOME HOUSING POLICY

Rationales used to legitimize forced dispersal and mixed‐income housing policies are socially constructed based on assumptions about concentrated poverty. This study evaluates qualitative data on public housing residents who were in the process of being dispersed as part of a HOPE VI program in order to examine their thoughts about their original home and neighborhood. Residents’ thoughts about their neighborhood are compared to policy rationales. Results indicate that current policy rationales are mostly in line with the goals and motivation of the city but are largely incongruent with the perceptions residents have of their pre‐relocation home and neighborhood. The article concludes with policy recommendations for increasing and incorporating residents’ views into policy design.     

EFFECT OF PROCESS VARIABLES ON THE QUALITY OF SWORDFISH FILLETS FLAVORED WITH SMOKE CONDENSATE

An alternative technique to traditional smoking of swordfish was evaluated. Fillets were dry salted and/or brine salted in 30% NaCl, and smoked by dipping in smoke condensate solution at different concentrations. Chemical (water‐phase salt, pH, total volatile basic nitrogen, lipid oxidation), microbiological (total mesophilic count and fecal coliforms count) and sensory analyses were carried out in order to establish which technique gave the best results in terms of sensory quality. The different salting techniques gave different water‐phase salt contents, which influenced the microbial growth and the production of volatile bases. The smoke condensate concentration was ineffective toward microbial growth, but it was a differentiating factor for sensory panel. The dry‐salted product smoked with 5% smoke condensate was preferred because it maintained the natural taste of fish, coupled with a pleasant flavor of smoke.