A novel synthesis method for cyclodextrins from maltose in water-organic solvent systems

A novel enzymatic synthesis method of cyclodextrin (CD) from low-mol-wt maltose using cyclomaltodextrin glucanotransferase (CGTase) fromBacillus macerans has been developed in various water-organic solvent systems. A Β-CD was synthesized in a two-phase system consisting of water and cyclohexane. However, no CDs could be synthesized in an aqueous buffer solution. A maximal yield of Β- CD has been obtained at a cyclohexane content volume of 44%. This synthesis has been obtained only at low temperatures, i.e., 7‡C, and did not take place at 50‡C. In addition, various organic solvents have been used for the enzymatic synthesis of CD from maltose. Consequently, Β-CD could be synthesized in various water-organic solvent systems, e.g., cyclohexane, benzene, xylene, and chloroform, but no enzymatic reaction occurred using aliphaticn-hydrocarbon solvents such as hexane, dodecane, and hexadecane. Furthermore, α- and Β- CD could be synthesized in water mixture solutions using organic solvents having an alcoholic group (e.g., ethanol, propanol, butanol, and pentanol) in a wide range of the reaction temperatures, typically 7–50‡C. In this temperature range, α- and Β-CD were also formed and the maximal yield from maltose to Β-CD of approx 13% was reached in 60 h.     

Group contributions to the infinite dilution partial molar volumes of alkanes, alcohols, and glycols in polar organic solvents

Densities of binary mixtures of polar organic solvents with alcohols were measured at 25‡C. The solvents studied were N,N-dimethylformamide, dimethylsulfoxide, and formamide while alcohols were butanol, pentanol, hexanol, and 1,4-butanediol. Density measurements of hydrocarbons (from pentane to dodecane and some heptane isomers) + N,N-dimethylformamide were also performed. From these data the apparent molar volumes of alcohols and hydrocarbons as functions of concentration were calculated. The standard partial molar volumes were obtained by extrapolation to infinite dilution and are discussed in terms of group contributions.     

Stability quotients of neodymium acetate complexes from 20 to 70‡C by laser-induced photoacoustic spectroscopy

The formation of Nd(III) acetate complexes in aqueous solution is studied by laser-induced photoacoustic spectroscopy and spectrophotometry. Stability quotients for the complexes Nd(CH₃COO)²⁺ and Nd(CH₃COO)² and dissociation quotients for acetic acid are determined at 20, 35, 50 and 70‡C in NaClO₄ medium of ionic strength 2.2m (2.0M at 20‡C). The 20‡C results are consistent with previous values determined by potentiometry and energy transfer from Tb(III). The temperature dependence of the stability quotients is consistent with the measured enthalpies of reaction at 25‡C.     

Excess molar volumes of the (cyclohexane + pentane,or hexane,or heptane,or octane,or nonane) systems at the temperature 298.15 K

The densities of the (cyclohexane + pentane, or hexane, or heptane, or octane, or nonane) systems were measured at the temperature 298.15 K by means of a vibrating-tube densimeter. Their respective excess molar volumes were calculated and correlated using the fourth-order Redlich—Kister equation, with the maximum likelihood principle being applied in the determination of the adjustable parameters. The values of excess molar volumes were negative for the cyclohexane + pentane system, whereas they were positive for the other systems with the values increasing with the number of carbon atoms in the respective alkane molecules.     

Enthalpies of transfer of ubiquinone-0 from water to aqueous surfactant solutions at various temperatures

Mixing and dilution enthalpies of aqueous solutions of 2,3-dimethoxy-5-methyl-1,4-benzoquinone (UQ₀) and of N,N-dimethyl-dodecylamine-N-oxide (DDAO) were measured and used to calculate the enthalpies of transfer δH(W →W +S) of UQ₀ from water to DDAO aqueous solutions at 20‡, 25‡, 30‡, and 35‡C. From the dependence of δH(W →W +S) on surfactant concentration, the distribution constant between aqueous and micellar phases and the standard transfer enthalpy of UQ₀ from water to DDAO micelles were evaluated along with the standard transfer free energy and entropy. The approach used required knowledge of the CMC and micellization enthalpy at each temperature. Thus, the thermodynamics of micellization of DDAO was studied by means of dilution enthalpy measurements at the several temperatures.     

Heterogeneous selective oxidation of formaldehyde on oxide catalysts:In situ FTIR study of formaldehyde surface species on a V-Ti-O catalyst and oxygen effect

The interaction of formaldehyde with a highly selective V-Ti-O catalyst for the oxidation of formaldehyde to formic acid is studied by Fourier-transform infrared (FTIR) spectroscopy at 70–200‡C. In a flow of formaldehyde/oxygen mixture and in a mixture without oxygen at optimal temperatures for formic acid formation (100–140‡C), methoxy groups and other oxygenates are formed in small amounts. These are two bidentate formates and covalently bound monodentate formate. The fact that similar oxygenates are observed independently of the presence of oxygen in the reaction mixture suggests the participation of the catalyst oxygen in their formation. Oxygen accelerates the desorption of bidentate formates. Bidentate formates of one type decompose in a flow of air at 100–150‡C, and bidentate formates of the other type decompose at 170–200‡C.     

Buffers for the physiological pH range: Thermodynamic constants of substituted aminopropanesulfonic acids from 5 to 55°C

ThepK ₂ values for 3-[(l,l-Dimethyl-2-hydroxymethyl)amino]-2-hydroxypropanesulfonic acid (AMPSO), and 3-[N,N-Bis(-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have been determined at 12 temperatures over the range 5 to 55‡C by measurements of the emf of cells without liquid junction containing hydrogen and silver-silver chloride electrodes. The values of pK ₂ for AMPSO and DIPSO were found to be 9.138 and 7.576, respectively, at 25‡C. The thermodynamic quantities, δG‡, δH‡, δS‡, and δC _p ^‡ were calculated from the change of the equilibrium constants with temperature. These buffer substances are useful as secondary pH standards in the physiological region of pH 7 to 9. Camille and Henry Dreyfus Fellow, 1994–1996.     

Temperature effects on surface activity and application in oxidation of toluene derivatives of CTAB-SDS with KMnO4

The γ_cmc values of CTAB-SDS decrease from 63.67 mN/m at 10‡C to 36.38 mN/m at 90‡C, slightly lower than those of either CTAB or SDS. Correspondingly, the CMC of CTAB-SDS decreases almost by half. The increase of surface activity of CTAB-SDS can be attributed to the relatively weak electrostatic interaction at high temperature, which is supported by the increase of solubility of CTAB-SDS with rise in temperature. Catalytic effect on oxidation of toluene derivatives with potassium permanganate follows the order CTAB-SDS > SDS > CTAB. This is not caused by the dissociative effect of CTAB-SDS with low surface activity at low temperature, as seen from the fact that almost all oxidative products can be retrieved for different toluene derivatives and surfactants by mimicking the conditions of reaction. In the emulsifications of toluene derivatives at 90‡C, the time that turbid water layers of surfactant solutions take to become clear is the same as that of the catalytic effect on oxidation of toluene derivatives. Thus, it can be inferred that surfactants can improve the oxidation yields of toluene derivatives by increasing the contact between two reacting phases.     

Highly active and reusable catalyst from Fe-Mg-hydrotalcite anionic clay for Friedel-Crafts type benzylation reactions

Fe-Mg-hydrotalcite (Mg/Fe = 3) anionic clay with or without calcination (at 200–800‡C) has been used for the benzylation of toluene and other aromatic compounds by benzyl chloride. Hydrotalcite before and after its calcination was characterized for surface area, crystalline phases and basicity. Both the hydrotalcite, particularly after its use in the benzylation reaction, and the catalyst derived from it by its calcination at 200–800‡C show high catalytic activity for the benzylation of toluene and other aromatic compounds. The catalytically active species present in the catalyst in its most active form are the chlorides and oxides of iron on the catalyst surface.     

Die Wärmeleitfähigkeit von Polyäthylen im Temperaturbereich von 20 bis 200 °C

Zusammenfassung Die W?rmeleitf?higkeit von je einemPhillips-,Ziegler- und Hochdruckpoly?thylen mit hohem Molekulargewicht wurde im Temperaturbereich von 20 bis 200 ‡C gemessen. Von 20 ‡C bis zum Schmelzende zeigt sich bei den verschiedenen Poly?thylentypen ein um so gr?\erer Abfall der W?rmeleitf?higkeit, je h?her der Kristallisationsgrad bei 20 ‡C ist. Die W?rmeleitf?higkeit in der Schmelze betr?gt etwa 6 · 10⁻⁴ cal/‡C cm sec und steigt schwach mit der Temperatur an.

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Summary Thermal conductivity of three representative types of polyethylene —Phillips-, Ziegler- and high pressure-type — has been determined from 20 to 200 ‡C. The stationary method applied in this work limited the experiments to polyethylene with extremely high molecular weight. The decrease of thermal conductivity between 20 ‡C and the melting point is an increasing function of cristallinity at 20 ‡C, whereas in the liquid phase the value of about 6 · 10⁻⁴ cal/‡C cm sec is nearly the same for each of the three investigated substances; a slight increase with temperature can be observed.

     

Purification and partial characterization ofRhizomucor miehei lipase for ester synthesis

A commercialRhizomucor miehei lipase was purified by ammonium sulfate precipitation. Phenyl Sepharose 6 Fast Row hydrophobic interaction chromatography, and DEAE Sepharose Fast Flow anion-exchange chromatography. The recovery of lipase activity was 32% with a 42-fold purification. The molecular size of the purified enzyme was 31,600 Dalton and the pI 3.8. The enzyme was stable for at least 24 h within a pH range of 7.0-10.0, and 96.8% of the enzyme activity remained when kept at 30‡C for 24 h. Further, about 10–30% of the lipase activity was inhibited by K⁺, Li⁺, Ni⁺, Co²⁺, Zn²⁺, Mg²⁺, Sn²⁺, Cu²⁺, Ba²⁺, Ca²⁺, and Fe²⁺ ions and by SDS, but EDTA had no effect. Under the experimental conditions, the optimum temperature for the hydrolysis of olive oil was 50‡C (pH 8.0), and for the synthesis of 1-butyl oleate, 37‡C. It was concluded that hydrolytic activity of lipase alone is not a sufficient criterion for its synthetic potential. The optimal molar ratio of oleic acid and 1-butanol was 2:1 for 1-butyl oleate synthesis. The 1-butyl oleate yield was unaffected by purification of the enzyme after 12 h.     

über die Struktur aus der Gasphase kondensierter Schichten aus CH2-Kettenmolekeln

Zusammenfassung Die Struktur von Schichten aus CH₂-Kettenmolekeln (n-Paraffine und Abbauprodukte von Poly?thylen), die aus der Dampfphase bei Auff?ngertemperaturen zwischen −180 und +150 ‡C kondensiert wurden, wurde mit Hilfe der UR-Absorption untersucht. Bei Kondensationstemperaturen, die ungef?hr gleich oder h?her als der Schmelzpunkt der Substanzen sind, tritt auf frischen NaCl-Spaltfl?chen eine Epitaxie auf. Da das Aufwachsgesetz dieser Epitaxie bekannt ist, konnte bei den untersuchten Schichten aus der Winkelabh?ngigkeit des Absorptionsverh?ltnisses des 725 cm⁻¹-Dubletts die Gr?\e des kristallin orientierten, des kristallin nicht orientierten und des amorphen Anteils bestimmt werden. Abbauprodukte von Poly?thylen, die bei +150 ‡C auf frischen NaCl-Spaltfl?chen kondensiert wurden, haben einen kristallin orientierten Anteil von 82%. Schichten, die bei Temperaturen unterhalb des Schmelzpunktes der Substanzen kondensiert werden, haben bei Zimmertemperatur von der Unterlage unabh?ngige Texturorientierungen. Es konnten drei Typen von Texturorientierungen unterschieden werden. Zwischen dem Typ dieser bei Zimmertemperatur vorliegenden Texturorientierung und dem vorher bei der Kondensationstemperatur entstehenden Aufbau der Schichten besteht ein eindeutiger Zusammenhang.

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Summary By infrared spectroscopy the structure of films of CH₂-chain molecules (n-paraffins and degradation products of polyethylene) condensed between −180 ‡C and +150 ‡C has been studied. If the condensation temperature is approximately equal to or higher than the melting point of the sample, epitaxy is observed on fresh NaCl cleavage surfaces. Since the orientation of the crystallites by epitaxy on NaCl is well known, it was possible to determine the amounts of crystalline oriented, crystalline but not oriented and amorphous parts in the condensed films by a study of angular dependence of the absorption ratio of the 725 cm⁻¹ dublett lines. Degradation products of polyethylene condensed at +150‡C on fresh NaCl cleavage surfaces show a crystalline oriented part of 82%. If the condensation temperature is below the melting point, the films show texture orientations which are independent from the sublayer. We found three different types of this orientation. There is a correlation between the type of texture orientation observed at room temperature and the structure of the films found at the condensation temperature previously.

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Herrn Professor Dr.K.- H. Hellwege danke ich wieder fur die Anregung zu der Arbeit und für zahlreiche Diskussionen. Ferner danke ich der Forschungsgesellschaft Kunststoffe e. V. für die Unterstützung der Arbeit und der Fa. Shell, Amsterdam, für die überlassung von n-Paraffinen.     

A critical review of methods for obtaining ionic volumes in solution

The various major methods for obtaining individual or “absolute” ionic standard partial molar volumes V‡(ion) from whole electrolyte data in both aqueous and nonaqueous solutions are critically reviewed. A number of undetected errors in previous analyses are pointed out, and it is demonstrated that the reported agreement amongst the various methods in aqueous solution is largely fortuitous. All methods are shown to be unsatisfactory to varying degrees, with the reference electrolyte approach, using an electrolyte such as tetraphenylarsonium tetraphenylborate, appearing to be the least objectionable of those currently available. It is recommended that, subject to future theoretical and experimental developments, the assumption that, at 25‡C: - V‡(Ph₄As⁺) - V‡(BPh₄) = 8 cm³-mol^-1, or its equivalent: V‡(Ph₄P⁺) - V‡(BPh ₄ ^- ) = 2 cm³-mol^-1 be used in all solvents.     

Study of the catalysts for fuel combustion reactions: XIX. Thermal stability of alumina promoted with lanthanum and silicon

X-ray diffraction analysis and data on the strength and specific surface area are used to study the thermal stability of a La-Si/Al₂O₃ system depending on the concentration of introduced additives and calcination temperature. The mechanisms of interactions of these elements and alumina are discussed. Silicon and lanthanum cations begin to interact at low temperatures (∼500‡C). The authors assume that silicon and lanthanum cations occupy tetrahedral and octahedral positions, respectively, in the γ-alumina lattice and thus significantly enhance its thermal stability. Up to 50% of γ-Al₂O₃ is retained at 1200‡C, and α-Al₂O₃ starts to form in the ternary system only at 1300‡C.     

Effect of the reduction temperature on the formation and activity of bimetallic Ni-Tc catalysts

The effect of the temperature on the formation, surface state, and catalytic activity in the reactions of dehydrogenation of cyclohexane and dehydrocyclization of n-hexane by Ni-Tc/-Al₂O₃ mono- and bimetallic catalysts was investigated. TcO₂, NiCl₂, and metal phases, and at a high temperature (500–700C), NiAl₂O₄ spinel and Ni-Tc clusters, were found on the surface of all of the catalysts. It was shown that the maximum activity is observed in reduction of monometallic catalysts at 500C and bimetallic catalysts at 700–800C. Synergism appeared in the bimetallic catalysts due to the formation of Ni-Tc clusters.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2486–2490, November, 1990.     

QuasistationÄre Messung der WÄrmeleitfÄhigkeit von Kunststoffen im Temperatur-bereich von −180 ‡C bis +90 ‡C

Zusammenfassung Die W?rmeleitf?higkeit einiger thermoplastischer Kunststoffe wurde im Temperaturbereich von −180 ‡C bis +90 ‡C nach einem quasistation?ren Verfahren gemessen. Eine geringfügige Zunahme der W?rmeleitf?higkeit mit wachsender Temperatur wurde bei HartPolyvinylchlorid, Polytetrafluor?thylen, Polychlortrifluor?thylen und Poly?thylenterephthalat gefunden. Bei Polytetrafluor?thylen wurde bei +20 ‡C eine Stufe in der W?rmeleitf?higkeit festgestellt. Die Stufe wird der Umwandlung monoklin-hexagonal im kristallinen Anteil des Polytetrafluor?thylens zugeordnet. Messungen an zwei Poly?thylenterephthalatproben verschiedener Dichte und damit verschiedener Kristallinit?t ergaben für die Probe mit der h?heren Dichte eine gr?\ere W?rmeleitf?higkeit als für die Probe geringerer Dichte. In ?hnlicher Weise ergibt sich bei dem h?her kristallinen Niederdruckpoly?thylen eine gr?\ere W?rmeleitf?higkeit als bei dem weniger kristallinen Hochdruckpoly?thylen. Bei Niederdruckpoly?thylen und oberhalb −50 ‡C auch bei Hochdruckpoly?thylen nimmt die W?rmeleitf?higkeit im Gegensatz zu dem Temperaturverhalten der oben genannten Substanzen mit wachsender Temperatur ab.     

Transformations of cyclohexane and benzene on the bimetallic Ru-Pt oxide catalysts

The bimetallic Ru-Pt/Al₂O₃ catalysts with an overall metal content of 1 wt. % and Pt: Ru weight ratios from 1: 3 to 3: 1 were studied. The catalytic activity for cyclohexane and benzene transformations, including hydrogenation, hydrogenolysis, and skeletal isomerization of the initial substrates and products of intermediate transformations, was studied at temperatures 180–350 °C and H₂ pressures from 1.0 to 5.0 MPa. The maximum yield of n-hexane from cyclohexane and benzene was obtained on the catalysts with a ruthenium content of 0.75–1.0%, being ∼29–30 wt.% at 40% selectivity. The selectivity to form n-hexane decreases with an increase in the cyclohexane conversion and is almost independent of the composition of the Ru-Pt system. On the catalysts under study, benzene is converted to the same products but at temperatures by 60 °C lower as compared to cyclohexane conversion. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 633–637, April, 2006.     

Dissociation kinetics of singly protonated leucine enkephalin investigated by time-resolved photodissociation tandem mass spectrometry

The yields of post-source decay (PSD) and time-resolved photodissociation (PD) at 193 and 266 nm were measured for singly protonated leucine enkephalin ([YGGFL + H]⁺), a benchmark in the study of peptide ion dissociation, by using tandem time-of-flight mass spectrometry. The peptide ion was generated by matrix-assisted laser desorption ionization (MALDI) using 2,5-dihydroxybenzoic acid as the matrix. The critical energy (E₀) and entropy (ΔS‡ at 1000 K) for the dissociation were determined by Rice-Ramsperger-Kassel-Marcus fit of the experimental data. MALDI was done for a mixture of YGGFL and Y₆ and the plume temperature determined by the kinetic analysis of [Y₆ + H]⁺ data were used to improve the precision of E₀ and ΔS‡ for [YGGFL + H]⁺. E₀ and ΔS‡ thus determined (E₀ = 0.67 ± 0.08 eV, ΔS‡=−24.4 ± 3.2 eu with 1 eu = 4.184 J K⁻¹mol⁻¹) were significantly different from those determined by blackbody infrared radiative dissociation (BIRD) (E₀ = 1.10 eV, ΔS‡ = −14.9 eu), and by surface-induced dissociation (SID) (E₀ = 1.13 eV, ΔS‡ = −10.3 eu). Analysis of the present experimental data with the SID kinetics (and BIRD kinetics also) led to an unrealistic situation where not only PSD and PD but also MALDI-TOF signals could not be detected. As an explanation for the discrepancy, it was suggested that transition-state switching occurs from an energy bottleneck (SID/BIRD) to an entropy bottleneck (PSD/PD) as the internal energy increases.     

Bioconversion of different agro-residues into edible protein byPleurotus sajor-caju

Pleurotus sajor-caju, an edible mushroom, is a source of protein-rich food.Pleurotus sajor-caju has broad temperature (15–25‡C) and pH (4-6) optima for its growth, thus making it suitable for village-level applications, where it can be cultivated in a generally artificially uncontrolled environment. In the present investigations, the following agro-residues have been used for cultivation of this mushroom: paddy straw, wheat straw, bagasse,Cyamposis tetragonoloba, Sorghum vulgare, Pennesitum typhoideum, mango leaves, banana leaves,Zea mays, etc. and some residues mixed with other materials such as cotton seeds, fiscus fruits,Azadirachta indica leaves, etc. All the substrates (400 g) were pasteurized at 60‡C, soaked in water, packed in polythene bags, and inoculated with 8% wheat spawn on a dry weight basis. The cultivation was carried out for 2 months, during which four crops were harvested. The temperature was 10–25‡C and relative humidity was maintained at 80–90%. The maximum yields in percent of fruit bodies obtained were as follows: banana leaves, 125 (91.8), paddy straw, 124.2 (90.6), wheat straw, 111.7 (90),Sorghum vulgare, 108.8 (92.9),Cyamposis tetragonoloba, 108.3 (91.5), followed by others. The maximum yields in percent of fruit bodies obtained in combinations of some substrates were as follows: paddy straw + cotton seeds, 148.3 (91.3),Cyamopsis tetragonoloba + Azadirachta indica leaves, 105.8 (91.5),Sorghum vulgare + Azadirachta indica leaves, 103.8 (91.8); the figures in parentheses represent the percent moisture content. The biochemical changes effected as a result of mushroom growth in terms of utilization of cellulose, hemicellulose, and lignin were presented.     

Production and partial characterization of extracellular peroxidases produced bystreptomyces avermitilis UAH30

The effect of a number of environmental parameters (pH, temperature, carbon and nitrogen ratio of nutrient) on the production of extracellular peroxidase enzymes byStreptomyces avermitilis UAH30 was examined. Maximum specific peroxidase activity (0.12 U/mg of protein) was obtained after 72 hours of 1 incubation at 45‡C in a minimal salt medium (pH 7.5) containing 0.6% (w/v) yeast extract and 0.6% (w/v) xylan corresponding to a C:N ratio of 4 to 1. A study of the effect of incubation on peroxidase activity showed that the enzyme was stable and active for at least one hour after incubation at 50‡C while at higher temperatures the stability and activity of the peroxidase was reduced such that at 60‡C the peroxidase activity has a half life of 20 min while at 80‡C the half life was reduced to 5 min. The activation energy for deactivation as a result of thermal denaturation of the enzyme was calculated to be 80 ±7 kJ/mol. The optimum pH for the activity occurred between a pH range of 6.5–8.5 with pKa₁ and pKa₂ of 5.1 ±0.1 and 9.7 ±0.1, respectively. The K_m and V_max for the peroxidase activity were determined to be 1.45 mM and 0.31 unit per mg protein respectively using 2,4dicholorophenol (2,4-DCP) as a substrate. Characterization of the peroxidase activity revealed activity against L,3–4 dihydroxyphenylalanine and guaiacol, while no inhibition of peroxidase activity could be detected with the haem inhibitors such as potassium cyanide and sodium azide, suggesting the lack of haem component in the tertiary structure. Aspects of using the crude peroxidase preparation in the pulp and paper industry are discussed.