On-line mass spectrometry system for measurements at single-crystal electrodes in hanging meniscus configuration

We present the construction and some first applications of an On-line electrochemical mass spectrometry system for detecting volatile products formed during electrochemical reactions at a single-crystal electrode in hanging meniscus configuration. The system is based on a small inlet tip made of porous Teflon and a Peek holder, which is brought in close proximity (ca. 10–20 μm) to the electrode surface. The tip is connected to the mass spectrometer by glass and metal tubing. Because of the small amount of gas entering the mass spectrometer, no differential pumping is needed during the measurement. The tip construction and preparation introduced here leads to reproducible voltammetry with very good cleanliness characteristics. The presence of the tip has no significant influence on the blank voltammetry of a Pt(111) in sulfuric acid, and on voltammetric responses for CO adlayer oxidation, methanol oxidation, and hydroxylamine electrochemistry on Pt(111). The formation of gaseous products in these reactions can be followed accurately and is in good agreement with earlier results obtained by other mass spectrometric or spectroscopic techniques. The time response and tailing of the setup is on the order of seconds and mainly determined by the distance between the tip and the electrode.     

Fibrous materials as artificial soil substrates

Artificial soil compositions have been used as substrates for growing plants on the basis of modified polyacrylonitrile (PAN) fibers and films of sodium alginate. The agrophysical characteristics of these artificial substrates based on modified PAN fibers indicate that such composites have low volume mass, high water capacity, and a good level of capillary water rise. These artificial substrates provide for normal plant development. At the end of the experiments, the root systems of grasses had penetrated the substrates, which provided for firm plant embedding. Most of the parameters for grass on artificial substrates correspond to those for grass grown on natural soil, and in some cases even exceed those results. The best results are obtained with fibers modified by urea (PAN-KA), because urea acts as a nutrient during growth. Artificial soils containing alginate films bearing mineral nutrients have also given good results. In that case it is possible to mount the seeds directly on the film, which provides for convenient transportation and facilitates planting. Translated from Khimicheskie Volokna, No. 4, pp. 18–22, July–August, 2008.     

Weak points of antiparallel {beta}-sheets. How are they filled up in globular proteins?

A lack of knowledge about the construction of tight packingis now the main obstacle for a successful design of artificialproteins. In this paper we examine a way of close packing antiparallelß-sandwihes. We show that there are some ‘weakpoints’ at the surfaces of ß-sheets, which cannotbe filled by the surrounding aliphatic side chains that arethe most abundant. Theoretically, these ‘weak points‘can be filled either by aromatic side chains of the same sheetor by the residues of the other parts of the protein molecule.The analysis of protein structures shows that both possibilitiesare used by nature and that there are many cases when these‘weak points’ are not filled by any atom. They remainfree and form a majority of the defects of close packing inprotein globules.     

Gamma linolenic acid (GLA) content of encapsulated evening primrose oil products

The fatty acid composition of 16 brands of evening primrose oil (EPO) capsules was determined by capillary gas chromatography. Fourteen of these EPO brands contained γ-linolenic acid (GLA) levels between 7% and 10% (mean, 8.7; range, 1.9–10.5%) and there was generally good agreement between the level of GLA claimed by the manufacturer and the level determined by analysis. Low levels of the monoenes 22∶1 and 24∶1 found in some brands may indicate contamination of EPO with borage oil.     

The effect of fat on the gastric responses to foods

Summary 1. In eight series of triplicate tests on persons in good health and with normal secretory responses who were fed test meals of foods cooked with fat, the day to day variations in gastric evacuation times ranged from 0 to 30 minutes with an average deviation from the mean of ±17 minutes. 2. Experiments with meals of foods in which moderate quantities of fats were incorporated intimately by either baking or frying according to good culinary procedure revealed no relationship between the fat contents of the foods and the times required for complete evacuation of the foods from the subjects’ stomachs. 3. The experiments indicated a parallelism between the protein contents of the test meals and the gastric evacuation times. 4. No significant differences were observed between the influences of a hydrogenated vegetable fat and of butter upon the rates of evacuation from the subjects’ stomachs of meals of potatoes in which these fats had been incorporated intimately by good culinary technic. Within the limits of error of the experimental procedure, French fried and Lyonnaise potatoes containing moderate amounts of fat were evacuated from the stomachs as rapidly as boiled potatoes. 5. Gastric emptying times for meals of doughnuts did not differ significantly from gastric evacuation times for meals of bread and butter supplying equivalent amounts of fat. 6. The addition to a test meal of glucose in water of either hydrogenated vegetable fat or butter fat in amounts equivalent to two-thirds the weight of the glucose retarded the evacuation of the glucose meal from the stomach. 7. Excess fat, added to potatoes by pan-frying in hydrogenated vegetable fat or butter to the extent of making the potatoes “greasy,” such as may occur in poor culinary practice, prolonged the emptying time of the stomach beyond the period for boiled potatoes. 8. An explanation has been suggested for this retardation of the emptying of the stomach effected both by digestible fats added to glucose solutions and by foods containing fats in excess of that which is incorporated intimately in these foods by good culinary methods. This paper was presented before the meeting of the American Oil Chemists’ Society, Chicago, Illinois, October 27, 1944. This work was supported by a grant from Lever Brothers Company, Cambridge, Massachusetts.     

A method to synthesize CdSe nanocrystals

CdSe nanocrystals (NCs) have great application prospects in various fields due to their novel properties. Some high-cost and toxic materials such as tri-n-octylphosphine oxide (TOPO) are used in the popular method to synthesize CdSe NCs. Based on this, a new low-cost, environmentfriendly and safe solvent was introduced in the synthesis of CdSe NCs in this paper. The prepared CdSe NCs were characterized by ultraviolet-visible spectra (UV-Vis), photoluminescence (PL), transmission electron micrograph (TEM), energy disperse X-ray spectra (EDX) and X-ray diffraction (XRD). The CdSe NCs obtained which show a good PL property are monodisperse, size-tunable and of high crystallinity. It indicates that the new solvent A is a good substitute for the solvent used in the classic route and achieves a greener synthesis of CdSe NCs. __________ Translated from Journal of Tianjin University, 2007, 40(3): 280–284 [译自: 天津大学学报]     

Antioxidant properties of α-tocopherol derivatives and relationship of antioxidant activity to biological activity

A series of α-tocopherol analogs substituted at the 5-methyl group were evaluated for their ability to protect β-carotene dissolved in hydrogenated, tocopherol-stripped corn oil from air oxidation. These results were compared with the ability of these compounds to prevent the development of dietary necrotic liver degeneration in rats and vitamin E deficiency-induced muscular dystrophy in rabbits. Although a good correlation was seen between the antioxidant activities of some of the compounds and their biological activities, in the case of other compounds the correlation was poor. The importance of the phytyl side chain of the tocopherols and their derivatives for their antioxidant activities was evident from these studies.     

Elaboration of platinum-modified NiAl coatings by combustion synthesis: Simultaneous repairing and coating of Ni-based superalloys

The “SHS build-up process” under high gas pressure was previously reported in literature by the authors in order to repair damaged turbine blades. In this process, a brazing foil is inserted between a substrate of Ni-based superalloy and a reactant compact made of the 50 at % Ni-50 at % Al mixture. The heat released during the combustion synthesis of the Ni + Al compact gives rise to interdiffusion of the elements and consequently to joining at the interface. This study reports the effect of Pt addition to the Ni + Al compact on the SHS build-up process. Indeed, the turbine blades need to be coated after repairing to protect them against corrosion. The aim of this investigation was to show the feasibility of this process for simultaneous repairing and coating. Good results were obtained: the joint quality was found to be good and even with a content of 18 at % Pt, the Pt-aluminide coatings retained the β-NiAl structure without PtAl₂ precipitates. Moreover, these coatings are free of porosity and after 100 h of air treatment, a homogenous oxide layer free of porosity was formed.      

Behaviour of calcium as a steam gasification catalyst

The catalytic coal gasification process for synthetic natural gas, which is being developed by the Exxon Research and Engineering Company, uses a potassium salt to catalyse the steam gasification of coal while it simultaneously catalyses methanation reactions in the same vessel. The catalyst is recovered from the gasifier residue and recycled, but some is lost. These relatively small, but inevitable, losses from the recovery process provide an incentive to find a lower-cost catalyst. Exploratory catalyst screening studies have shown that calcium compounds provide good catalytic activity under certain conditions. Essentially, the calcium must be atomically dispersed throughout the char to obtain good activity. Potassium compounds tend to be mobile and distribute themselves during gasification even when applied to the coal in a dry, mechanical mixture. Calcium, in contrast, is poorly active unless it is very well dispersed by chemical reaction with the organic matter. For example, it is an active catalyst when it is transferred to acid sites in coal by ion exchange. Sufficient sites occur naturally in lower-rank coals, and some of these coals have undergone ion-exchange with calcium naturally. Such coals show high reactivities during gasification for this reason. Higher-rank coals have fewer ion-exchangeable acid sites, but these can be created by a mild air-oxidation. This paper describes the experimental techniques used, to develop low-cost, calcium catalysts for the steam gasification of coal and presents the results obtained in this work.     

Direct consumption of the soybean

Efforts in some Latin American countries directed toward the use of soybeans as a primary source of proteins for human nutrition have especially focused attention on simple home-level procedures such as the soaking and cooking of soybeans and the lime-cooking of corn-soybean mixtures. Data obtained with these two procedures indicate there is great potential in using soybeans directly in human feeding. Soaking soybeans in 0.25% NaHCO₃ for 8 hr and cooking for 20 min decreases trypsin inhibitor activity more than 80%, and 40 min of cooking gives chewiness indexes similar to those of common beans with acceptable texture (10–20). The protein efficiency ratio (PER) of a mixture that was 50% soybeans and 50% common beans was 60% higher than that of common beans alone. Considering acceptability and functional characteristics of “masa” (dough) and “tortilla,” an optimum soybean level within the lime-cooking procedure was found to be 16%. Green pods of soybean varieties adapted to the tropics, at 65 to 85 days of maturation, have the same nutrient content (dry basis) as mature soybeans, with a good quality protein and a good content of B complex vitamins.     

Relative nutritional value of various dietary fats and oils

The dietary and nutritional role of fats and oils is quite complex, as evident in the new biological findings about some of their components that are essential to man. Fats and oils must be considered for both their quantitative and qualitative aspects, their fatty acid compositions and relationships with average diets in different countries should be emphasized. Because of some adverse physiological effects ascribed to saturated fatty acids, a tendency to increase the intake of polyunsaturated vegetable oils has occurred to provide a good source of essential fatty acids, mainly linoleic acid. However, saturated fats still are an important part of the diet in developed countries, especially “invisible” fats. Research must continue that is related to modifications fats and oils undergo during industrial processes which affect their nutritional value. Compositions of many fats and oils are provided.     

Investigation of the solution structure of chymotrypsin inhibitor 2 using molecular dynamics: comparison to X-ray crystallographic and NMR data

The native solution structure and dynamics of chymotrypsin inhibitor2 (CI2) have been studied using a long (5.3 ns) molecular dynamics(MD) simulation without any imposed restraints. The majorityof the experimentally observed spin–spin coupling constants,short– and long–range nuclear Overhauser effect(NOE) cross peaks and the amide hydrogen exchange behavior werereproduced by the MD simulation. This good correspondence suggeststhat the major structural features of the protein during thesimulation are representative of the true protein structurein solution. Two water molecules formed hydrogen bond bridgesbetween ß₂ and ß₃, in agreement with X–raycrystallographic data and a recent reassessment of the solutionstructure using time averaged NMR restraints during MD refinement.The active–site loop of the protein displayed the greateststructural changes and the highest mobility. When this loopregion was excluded, the average C r.m.s. deviation of the simulatedsolution structures from the crystal structure was 1.5 from0.5 to 5 3 ns. There is structural heterogeneity in particularregions of the NMR–derived solution structures, whichcould be a result of imprecision or true internal motion. Astudy of the distribution of mobility through the protein allowsus to distinguish between these two alternatives. In particular,deviations in the active–site loop appear to be a resultof heightened mobility, which is also supported by good correspondencebetween calculated and experimental S² N–H order parameters.On the other hand, other ill–defined regions of the NMR-derivedstructures are well defined in the simulation and are probablythe result of a lack of structural restraints (i.e. NOEs), asopposed to reflecting the true mobility.     

Modern procedures for the analysis of tocopherols

The development of reliable assay methodology for the tocopherols has been an evolutionary process which has required over 40 years to reach its present state. Today the analyst has at his disposal a choice of reliable and accurate methods of analysis for the eight tocopherols now known to exist in nature. The general sequence of procedure and the precautions to be observed are described. After suitable extraction procedures and careful saponification techniques, the tocopherols in the nonsaponifiable fraction can be assayed by a variety of chromatographic procedures including paper, thin layer (TLC), column and gas liquid chromatography (GLC). The current methodology of these procedures is reviewed in some detail with special emphasis on the more frequently used TLC and GLC techniques. The earlier methods of GLC assay separated only the mono-, di- and trimethylated tocopherols but methods are now available which provide separation of all the tocopherols. These developments were made possible by better columns and the use of derivatives of tocopherols. In addition to good separation, the GLC method is the most sensitive available for the quantitation of the tocopherols. Spectrophotometric measurements based on Emmerie Engel type reactions have been most frequently used for the final quantitative analysis of the tocopherols separated by paper, TLC, or column chromatography. One of six papers being published from the “Chemistry and Biochemistry of Tocopherols,” presented at the ISF-AOCS World Congress, Chicago, September 1970.     

Cocoa butter and confectionery fats. Studies using programmed temperature X-ray diffraction and differential scanning calorimetry

The polymorphic behavior and thermal properties of cocoa butter have been investigated by means of programmed temperature x-ray diffraction and differential scanning calorimetry. The relationship of this polymorphism to the technical problems of “tempering” and “bloom” development is discussed. Cocoa butter containing, respectively, milk fat and a bloom inhibitor, and some alternatives to cocoa butter have been studied. These results have provided information that will help determine process conditions for these particular fats.     

The use of molecular models in evaluating protein and peptide conformations

A new theoretical conformation of polypeptides and proteins designated as the “hexagonal con-formation,” which was developed through the use of molecular models, is discussed. The term “hexagonal” applies to the arrangement of the peptide chain O-atoms since the placement of the polymer backbone used in this conformation re-sults in a planar hexagonal assignment of these atoms. Fora cyclic hexapeptide, one hexagon of O-atoms results ; for a cyclic decapeptide, two hexagons result; and a protein subunit (e.g., cytochrome C) can form an extensive honeycomb network of hexagons. The coincidence of this network with a similar “second neighbor” oxygen network in water is discussed in relation to the importance of water in biological processes. Several models of complete peptide sequences assembled in the hexagonal conformation are evaluated in detail. It is suggested that in some instances the “reactivity” of these peptides may reside in an ability to disturb resonance patterns of the surrounding water in a precise manner at specific locations. Finally, the foreseeable prob-lems involved in a uniform application of the "hexagonal concept" are discussed along with the extension of the hexagonal conformation of pro-teins to cell membrane structures with their lipid bilayers. These studies were carried out in part while the author was an Institute Fellow at the City of Hope Medical Center, Duarte, California, during a sabbatical leave from The Upjohn Company.     

Detonation of nitrobenzene and propargyl alcohol

Detonation of mononitrobenzene and propargyl alcohol at reduced pressure is recorded for the first time in 10-mm-diameter steel tubes with a wall thickness of 13 mm with high-power initiation. The detonation velocities of nitrobenzene equal 25–50% of the ideal value obtained from thermodynamic calculations. The conditions for stationary detonation propagation are examined and the critical porosities for these materials are computed based on calculations of the fraction of material that is heated and burnt up during detonation. The computations are in good agreement with experiment. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 89–97, January–February 1999.     

The elimination of flavor reversion in linseed shortening by heat polymerization and solvent segregation of the oil

Summary The optimum conditions have been established for the high temperature polymerization and solvent segregation of linseed oil to produce a “non-reverting” edible shortening and an improved drying oil. The best oil is obtained by heating at 270–275° C. for 12–15 hours while carbon dioxide is continuously passed through the oil. Under these conditions the polymerized oil has a refractive index of 1.4858 to 1.4861 at 25° C. and yields 60–65% of acetone soluble oil with a refractive index of 1.4830 to 1.4834 at 25° C. and an acid value of less than 1%, calculated as oleic acid. Pie crusts containing shortenings made from the acetone soluble fraction of the oil have been judged to be of good quality. The best shortenings were obtained by hydrogenating to a refractive index of 1.4615-1.4605 (60° C.). Macodonald College Journal Series No. 209. Issued as paper No. 145 of the Canadian Committee on Food Preservation.     

Critical diameter for and fluctuations in detonation of solutions of dinitrotoluene in nitroglycol

The critical detonation diameters of nitroglycol and solutions of dinitrotoluene in nitroglycol in paper shells are measured. The frequency of the detonation fluctuations is determined. Data with glass and paper shells are the same. The frequency of the fluctuations is independent of the concentration of the solution at ≈7 MHz. The detonation parameters of these solutions are compared with systems which detonate in a low-frequency (≈2 MHz) spin regime. When the dinitrotoluene content of the solution is ≤15%, the critical detonation diameter is constant and equal to that for nitroglycol, but as the dinitrotoluene concentration is raised, the critical detonation diameter increases. The experimental results are in good agreement with theory. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 97–102, May–June 1999.     

Quantitation of cholesterol oxidation products in unirradiated and irradiated meats

A method to detect 7-ketocholesterol, cholesterol-5β,6β-epoxide, cholesterol-5α,6α-epoxide, 4-cholesten-3-one, 4,6-cholestadien-3-one and 4-cholestene-3,6-dione in unirradiated and irradiated beef, pork and veal was developed by use of chloroform-methanol-water extraction, solid-phase extraction, column separation, thin-layer chromatography and gas chromatography. This method recovered 78–88% of the cholesterol oxidation products and detected the cholesterol oxidation products at 10 ppb or higher. Irradiation of the meats to a dose of 10 kGy increased these compounds, except 4,6-cholestadien-3-one for all three types of meat, over unirradiated, and except cholesterol-5α,6α-epoxide and 4-cholesten-3-one for the pork. All the cholesterol oxidation products in the unirradiated meats increased during storage at 0–4°C for 2 wk with some exceptions for the pork. The increases of cholesterol oxidation products in stored irradiated meats were greater than those in the unirradiated.     

Solution-polymerized rubbers with superior breakdown properties

Natural rubber breaks down readily during mechanical mixing, and rubber processors have traditionally made good use of this property. Emulsion SBR rubber breaks down with greater difficulty and some polybutadiene rubbers, not at all. This paper describes a new class of solution elastomers, both polybutadiene and butadiene–styrene copolymers, designed to undergo controlled breakdown during processing. They can be made by reacting active polymer lithium molecules with tin compounds to produce star-shaped molecules containing a central tin atom connected by tin–carbon bonds. When such a product is mixed with an organic (stearic) acid, some of the tin bonds are ruptured and the desired breakdown occurs. The extent of breakdown can be controlled by the mixing conditions and the amount of organic acid employed. There are numerous applications in which these rubbers process more easily and display better properties than conventional rubbers. Data on breakdown under various conditions and physical properties of the compounds are presented in this paper. In addition to the superior processing characteristics, these products introduce a new concept of elastomer breakdown. The breaking of a polymer chain at a carbon–tin bond by a chemical agent eliminates the need for breaking carbon–carbon bonds by mechanical energy or oxidative degradation. Accomplishing polymer breakdown by a controlled reaction, rather than by conventional means, has long been an unsolved problem of the rubber industry.