Structure and properties of starch-based foams prepared by microwave heating from extruded pellets

The physical properties of microwave-foamed starch-based pellets, including density, porosity, cell structure, water absorption characteristics and mechanical properties were characterized. It was found that the physical properties of these starch-based foams produced by microwave heating are highly dependent on the raw materials and additives. Foam density decreased significantly after addition of 5.5–10.5% w/w salts, while foams containing nucleation agent (talc) were denser than the control with reduced cell size. A proprietary blowing agent did not affect the foam density markedly. Addition of salts also increased the water sorption of foams and plasticized cell walls. Mechanical behaviour of foamed pellets can be adjusted effectively by controlling the cell structure through using different additives. Mechanical properties of the foamed pellets in the elastic region as well as under large deformation (up to 40% strain) all follow a power–law relationship with foam density.     

Physical properties of polyurethane plastic sheets produced from polyols from canola oil

Polyurethane (PUR) plastic sheets were prepared by reacting polyols synthesized from canola oil with aromatic diphenylmethane diisocyanate. The properties of the material were measured by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) as well as tensile properties measurements. The effect of stoichiometric balance (i.e., OH/NCO molar ratio) on the final properties was evaluated. The concentration of elastically active network chains (EANCs), nue, of the polymer networks was calculated using rubber elasticity theory. The glass transition temperatures (Tg) for the plastic sheets with OH/NCO molar ratios of 1.0/1.0, 1.0/1.1, and 1.0/1.2 were found to be 23, 41, and 43 degrees C, respectively. The kinetic studies of the degradation process of the PUR plastics showed three well-defined steps of degradation. The PUR plastic sheets with OH/NCO molar ratio 1.0/1.1 had the highest nue, lowest number-average molecule weight between cross-links, MC, and excellent mechanical properties, indicating that this is the optimum ratio in the PUR formulations.     

Novel regenerated cellulose films prepared by coagulating with water: Structure and properties

Regenerated films were successfully prepared from cellulose/NaOH/urea solution by coagulating with water at temperature from 25 to 45 °C. The results of solid ¹³C NMR, wide angle X-ray diffraction, scanning electron microscopy (SEM) and tensile testing revealed that the cellulose films possessed homogeneous structure and cellulose II crystalline, similar to that prepared previously by coagulating with 5 wt% H₂SO₄. By changing the coagulation temperature from 25 to 45 °C, tensile strength of the films was in the range of 85-139 MPa. Interestingly, the RC35 film coagulated at 35 °C exhibited the highest tensile strength (σ_b = 139 MPa). The inclusion complex associated with cellulose, NaOH and urea hydrates in the cellulose solution were broken by adding water (non-solvent), leading to the self-association of cellulose to regenerate through rearrangement of the hydrogen bonds. This work provided low-cost and “green” pathway to prepare cellulose films, which is important in industry.     

Preparation and properties of glucagon analogs prepared by semi-synthesis from CNBr-glucagon

The semi-synthetic approach has been used to obtain new analogs of the peptide hormone glucagon. Using the highly purified 27 amino acid fragment of cyanogen bromide-treated glucagon, we have prepared, by nucleophilic addition to the lactone ring, the following derivatives: CNBr-Gly28-glucagon, CNBr-glucagon hydrazide, CNBr-glucagon n-butylamide and CNBr-glucagon biotinamide. Direct aminolysis of the lactone was successful only with sterically unhindered primary amines. Addition of an amino acid could be accomplished by formation of the peptide hydrazide followed by azide coupling. All these analogs were full agonists with decreased potency relative to the native hormone. Examination of the structure-function relationships of these new C-terminal glucagon derivatives suggests that the hydrophobic side-chain of methionine is important to the binding of glucagon to its receptor and that the C-terminal portion of glucagon is only involved in the binding of the hormone to the receptor and not in the transduction process.     

Isolation and properties of triglyceride lipase from the rabbit liver

Using affinity chromatography on heparin-Sepharose 4B, triglyceride lipase was isolated from rabbit liver tissue and purified. The specific activity of the enzyme isolated from the usual homogenate was equal to (3.8 +/- 1.2) x 10(3) mumol/hour/mg protein. After treatment of liver tissue homogenates with liquid nitrogen the enzyme activity increased severalfold as compared to the enzyme isolated from the usual homogenate. The dependences of the triglyceride lipase activity on the concentrations of the protein (enzyme), substrate (triglyceride), albumin (fatty acid acceptor) and pH were studied. The isolated form of liver triglyceride lipase was found to have two pH optima at 6.5 and 8.5.     

Semiconductor properties of melanins prepared from catecholamines

D. C. dark - and photoconductivity measurements were performed with synthetic melanins prepared by oxidative polymerization of dopamine, adrenaline, adrenochrome and adrenolutin. The melanins examined show significant differences in conductivity, thermal activation energy and photocurrent intensity values. The differences in semiconductor properties observed between the melanins reflect the structure differences of catecholamine-melanin polymers.     

Novel silicon-containing polyurethanes from vegetable oils as renewable resources. Synthesis and properties

Hydrosilylation of methyl 10-undecenoate (UDM) with phenyl tris(dimethylsiloxy)silane (PTDS) followed by a reduction of carboxylate groups was used to obtain a silicon-containing polyol with terminal primary hydroxyl groups (PSi194). Biobased silicon-containing polyurethanes, with a silicon content between 1.7% and 9.0%, were prepared from epoxidized methyl oleate-based polyether polyol (P184), PSi194, and 4,4'-methylenebis(phenyl isocyanate) (MDI). The thermal, mechanical, and flame-retardant properties of these materials were examined. The most notable change resulting from the incorporation of PSi194 is the appearance of melting endotherms of variable enthalpy and position and a downward shift in the T(g). The incorporation of silicon does not change the thermal stability but enhances the stability of the char under air atmosphere. Polyurethanes with higher silicon content no longer burn in ambient air without complementary oxygen, which suggests that these biobased materials are very interesting for applications that require fire resistance.     

Physicochemical properties of carbons prepared from pecan shell by phosphoric acid activation

Activated carbons were prepared from pecan shell by phosphoric acid activation. The pore structure and acidic surface groups of these carbons were characterized by nitrogen adsorption, Boehm titration and transmittance Fourier infrared spectroscopy (FTIR) techniques. The characterization results demonstrated that the development of pore structure was apparent at temperatures 250 degrees C, and reached 1130m(2)/g and 0.34cm(3)/g, respectively, at 500 degrees C. Impregnation ratio and soaking time at activation temperature also affected the pore development and pore size distribution of final carbon products. At an impregnation ratio of 1.5, activated carbon with BET surface area and micropore volume as high as 861m(2)/g and 0.289cm(3)/g was obtained at 400 degrees C. Microporous activated carbons were obtained in this study. Low impregnation ratio (less than 1.5) and activation temperature (less than 300 degrees C) are favorable to the formation of acidic surface functional groups, which consist of temperature-sensitive (unstable at high temperature) and temperature-insensitive (stable at high temperature) two parts. The disappearance of temperature-sensitive groups was significant at temperature 300 degrees C; while the temperature-insensitive groups are stable even at 500 degrees C. FTIR results showed that the temperature-insensitive part was mostly phosphorus-containing groups as well as some carbonyl-containing groups, while carbonyl-containing groups were the main contributor of temperature-sensitive part.     

Structure and properties of rat-thymus deoxyribonucleoprotein. A comparison of the electric birefringence and other properties of deoxyribonucleoprotein prepared by various methods

1. A comparison has been made of the properties of dNP (deoxyribonucleoprotein) prepared in various ways from rat thymus. The variables studied were: (a) extent of homogenization; (b) concentration of various metal ions; (c) concentration of EDTA; (d) extent of dialysis; (e) concentration of dNP. The chief method used for studying the dNP was that of electric birefringence; this gives information about the optical and electrical properties of molecules oriented in an electric field and about their length. 2. The extent of homogenization during the preparation affects the birefringence properties only slightly and the solubility properties of the constituent DNA not at all. However, the protein content of the dNP decreases after repeated homogenization. 3. In the presence of added Ca(2+), Mg(2+) or Na(+) an insoluble product is obtained. 4. The presence of added EDTA affects the birefringence properties only slightly. 5. In the final stage of preparation, both very limited dialysis and extensive dialysis (in terms of volume ratio) cause partial insolubility of the final product. 6. dNP prepared at low concentrations resembles in some respects dNP prepared at higher concentrations and then subjected to limited enzyme action but it is not degraded (as by extensive enzyme action); ultracentrifuge studies of the constituent DNA confirm that no degradation of the DNA has occurred. 7. It is concluded that dNP prepared at low concentrations or by extensive dialysis is denatured and that preparation of ;native' material is favoured by maintenance of a high dNP concentration and by fairly limited dialysis.     

Novel alginates prepared by independent control of chain stiffness and distribution of G-residues: Structure and gelling properties

The study of alginate hydrogels is of increasing interest, given their potential applications as biomaterials for tissue engineering and for encapsulating drugs and living cells. In this study, we present a new strategy for tailoring alginates on the basis of homopolymeric mannuronan, where the chain stiffness and the content of G-residues could be varied independently. Partial periodate oxidation (0–8%) followed by borohydride reduction, introducing flexible linkages through C2–C3 cleavage and ring opening, was combined with in vitro epimerization, introducing either alternating (MG) sequences (in the case of enzyme AlgE4) or G-blocks (in the case of enzyme AlgE6). Both enzymes are recombinantly expressed from Azotobacter vinelandii. Two strategies were followed: (a) oxidation/reduction followed by epimerization (b) epimerization to 90% G followed by oxidation/reduction. The resulting alginates were characterised by NMR spectroscopy and size-exclusion chromatography (SEC) with multi angular laser light scattering (MALLS) and viscosity detectors. Gels were prepared using the ‘internal setting’ method with either 10 mM or 20 mM Ca²⁺ present, and studied by small-strain oscillatory measurements. It was found that periodate oxidation, in the range P₀ = 0.02–0.06, had a pronounced influence on the gelling properties. The decrease in dynamic storage modulus (G′) could mainly be attributed to increased local flexibility and not only a decrease in G-block lengths as a consequence of oxidation. The new alginate gels are easily degradable in a mild acidic environment and the degradation is easier to control than gels made of unoxidized alginate.     

Gas-liquid chromatography of oligosaccharides released from red cell glycosphingolipids by ozonolysis

A method for the analysis of glycosphingolipids in mammalian erythrocyte membranes is described. It consists of ozonolysis and alkaline treatment of the crude lipid extract to obtain oligosaccharides from glycosphingolipids and then gas-liquid chromatography of trimethylsilyl derivatives of glycitols derived from the oligosaccharides. Typical gas-liquid chromatographic patterns of oligosaccharide components were obtained with various mammalian erythrocytes; these corresponded to the glycosphingolipid compositions. The analysis could be carried out on 10 ml of packed erythrocytes.     

Structure of adducts prepared from nicotinamide adenine dinucleotide and their oximes

Preparation of adducts from nicotinamide adenine dinucleotide and a number of oximes is described; these include acetoxime, pyruvatoxime, cyclohexanoxime, cyclopentanoxime. These adducts are closely related to the corresponding NAD-ketone adducts in their spectra properties, but they are stable in acid solutions (pH 5).     

Structure of biologically active and inactive cerebrosides prepared from Schizophyllum commune

A cerebroside fraction prepared from the mycelia of Schizophyllum commune was further fractionated into five components (I-V) by reverse-phase high-performance liquid chromatography. Fruiting-inducing activity was found in I-IV but not in V. By gas-liquid chromatography-mass spectrometry and nuclear magnetic resonance analyses it was shown that these fractions contained: I, a mixture of N-2'-hydroxypentadecanoyl-1-O-glucosyl-nonadecasphingadienine++ + and N-2'-hydroxyhexadecanoyl-1-O-glucosyl-sphingadienine; II, (4E,8E)-N-D-2'-hydroxyhexadecanoyl-1-O-beta-D-glucopyr anosyl-9-methyl-4,8- sphingadienine (Kawai and Ikeda. 1983. Biochim. Biophys. Acta. 754: 243-248); III, N-2'-hydroxyheptadecanoyl-1-O-glucosyl-nonadecasphingadienine++ +; IV, N-2'-hydroxyoctadecanoyl-1-O-glucosyl-nonadecasphinadienine; V, (4E,8E)-N-2'-hydroxytetracosanoyl-1-O-beta-glucopyrano syl-9-methyl-4,8- sphingadienine. The only structural difference observed between biologically active and inactive cerebrosides was the chain length of acyl moiety; the cerebroside having an acyl chain of 24 carbon atoms was inactive.     

Solid-state and mechanical properties of aqueous chitosan-amylose starch films plasticized with polyols

The film-forming ability of chitosan and binary mixtures of chitosan and native amylose corn starch (Hylon VII) was evaluated with free films prepared by a casting/solvent evaporation method. Unplasticized and plasticized free chitosan films in aqueous acetic acid and respective films containing a mixture of chitosan and native amylose starch in acetic acid were prepared. Glycerol, sorbitol, and i-erythritol were used as plasticizers. Solid-state and mechanical properties of the films were studied by powder x-ray diffractometry (XPRD), differential scanning calorimetry (DSC), and a materials testing machine. The films composed of a mixture of chitosan and native amylose starch in acetic acid were clear and colorless. A plasticizer concentration of 20% wt/wt (of the polymer weight) ws sufficient to obtain flexible films with all samples tested. X-ray diffraction patterns and DSC thermograms indicated an amorphous state of the films independent of the type of plasticizer used. In conclusion, incorporation of native amylose com starch into chitosan films improves the consistency and the mechanical properties of the films.     

Decomposition of aqueous diphenyloxide by ozonolysis and by combined gamma-ray-ozone processing

Diphenyloxide (DPO) is one of many, rather toxic pollutants produced by combustion of fossil fuels, which are emitted to the atmosphere with flue gases and brought to ground water by rain and snow. Its decomposition is investigated by ozonolysis at room temperature and the major products like phenol, resorcinol, hydroquinone, dihydroxy-benzoic acid as well as the total yield of aldehydes and carboxylic acids were determined as a function of applied ozone concentration. In addition, the DPO-degradation was studied by a combined action of gamma-ray under continuous bubbling of a known ozone concentration. In this case the formation of the same products is observed, but their yields differ from the above ones. Based on the synergistic action of ozone and gamma-ray the DPO-radiolysis is rather efficient, leading to an initial-G-value of 11.3. Some probable reaction mechanisms are presented for explanation of the degradation process.     

Barrier properties of glycophorin-phospholipid systems prepared by different methods

Glycophorin was incorporated into large unilamellar dioleoylphosphatidylcholine vesicles by either a detergent dialysis method using octylglucoside or a method avoiding the use of detergents. The vesicles were characterized and the permeability properties and transbilayer movement of lipids in both vesicles were investigated as a function of the protein concentration and were compared to protein-free vesicles. An insight in the permeability properties of the vesicles was obtained by monitoring the ratio potassium (permeant): dextran (impermeant) trap immediately after separation of the vesicles from the external medium. Glycophorin incorporated without the use of detergents in 1:300 protein:lipid molar ratio induces a high potassium permeability for the majority of the vesicles as judged from the low potassium trap (K⁺:dextran trap = 0.21). In contrast, the vesicles in which glycophorin is incorporated via the octylglucoside method (1:500 protein:lipid molar ratio) are much less permeable to potassium (K⁺:dextran trap = 0.67 and $\text{t}\text{1}\text{2}$ of potassium efflux at 22°C is 7.5 h.). The relationship between protein-induced bilayer permeability and lipid transbilayer movement in both vesicle preparations is discussed. Addition of wheat-germ agglutinin to glycophorin-containing vesicles comprised of dioleoylphosphatidylcholine and total erythrocyte lipids caused no or just a small effect (less than 20% release of potassium) on the potassium permeability of these vesicles. Also, addition of lectin to dioleoylphosphatidylethanolamine-glycophorin bilayer vesicles in a 25:1 lipid:glycophorin molar ratio had no effect on the permeability characteristics of the vesicles. In contrast, addition of wheat-germ agglutinin to bilayer vesicles made of dioleoylphosphatidylethanolamine and glycophorin in a 200:1 molar ratio resulted in a release of 74% of the enclosed potassium by triggering a bilayer to hexagonal (H_II) phase transition. The role of protein aggregation and the formation of defects in the lipid bilayer on membrane permeability and lipid transbilayer movement is discussed.     

Metabolism of some polyols by Rhizobium meliloti

The utilization of d-mannitol, d-arabitol, and d-sorbitol by Rhizobium meliloti was studied in extracts from mannitol-grown cells. Two different polyol dehydrogenases were induced by any of these polyols: (i) a nicotinamide adenine dinucleotide (NAD)-arabitol dehydrogenase and (ii) a NAD-sorbitol dehydrogenase, whereas polyol phosphate dehydrogenases were absent. d-Arabitol dehydrogenase was observed to act on both d-arabitol and d-mannitol, but d-sorbitol dehydrogenase acted specifically on d-sorbitol. d-Arabitol was oxidized to d-xylulose, d-mannitol and d-sorbitol were oxidized to d-fructose. An adenosine triphosphate-linked hexokinase which acts on d-fructose and absence of hexose isomerase were also detected in this organism.