bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Chromatography of Tetra‐ and Pentacyclic Triterpenes
Authors: Ikan R. , Gottlieb R. 
Published: November 2013

AbstractThe relative retention times of tetracyclic triterpene groups (lanostane, cycloartane, tirucallane), pentacyclic triterpene groups (ursane, oleanane) and modified representatives of the oleanane (taraxerane, glutinane, friedelane) and lupane groups, have been examined, using a XE‐60 phase for separation. Some correlations between structure and retention time are presented.
Determination of Kerosine Contamination in Local Gasoline by Gas Chromatography
Authors: Goren S. 
Published: November 2013

AbstractA GLC method for the detection and determination of small admixtures of kerosine (0% and above) in local gasoline is described. The method is independent of gasoline and kerosine batch variations and of gasoline grades. Making use of the relationship which was found between the heights of three successive n‐paraffin peaks (C12, C13 and C14) the kerosine contamination can be determined with an absolute error of ± 0.2%.
Electrolytic Reduction of Indigo in Pyridine Application to the Determination of Dissolved Oxygen
Authors: Hall D. A. , Elving P. J. 
Published: November 2013

AbstractThe electrochemical reduction of indigo in pyridine as solvent has been investigated in connection with the determination of oxygen dissolved in pyridine, using polarography, cyclic voltammetry, controlled electrode potential electrolysis and coulometry. In the absence of protons, the total current of the first and second reduction waves for an unsaturated solution of indigo (LiClO4 as background electrolyte) apparently represents a one‐electron transfer. In the presence of an excess of available protons (added as pyridinium nitrate), indigo is reduced in a reversible two‐electron process to indigo white (leucoindigo). The rapid conversion of indigo white to indigo by oxygen in pyridine solution can be used to determine coulometrically the concentration of oxygen in pyridine via measurement of the indigo produced on adding the pyridine‐oxygen sample to a solution of in situ electrolytically generated indigo white. The latter approach indicated a general method for the determination of dissolved oxygen in nonaqueous solvents.
Homogeneous Nucleation of 2, 4‐Dichlorophenol in Acid Aqueous Solutions
Authors: Sarig S. 
Published: November 2013

AbstractThe interfacial tension of 2, 4‐dichlorophenol/acidic solution, 23 ergs/cm2, was calculated from Nielsen's equations which combine homogeneous nucleation theory and diffusion controlled growth. The parameters measured were induction periods in the millisecond range and the technique employed was photographing the appearance of turbidity on a film moving at 50cm/sec velocity. The calculated value was compared with direct measurements of 2, 4‐dichlorophenol's surface tension in air and in solution.
Ultraviolet Absorption Spectrum of Toluene‐D8
Authors: Upadhya P. C. , Baruah G. D. , Upadhya K. N. , Rai D. K. 
Published: November 2013

AbstractThe near ultraviolet absorption spectrum of toluene‐d8 has been recorded with the help of a E1 large quartz spectrograph. The (O,O) band has been identified at 37672 cm−1. The spectrum has been analysed with the help of the excited state fundamentals 282, 378, 431, 454, 508, 700, 926, 1150 and 1432 cm−1. These frequencies have been correlated with the corresponding frequencies of the normal molecule. The ration R = ν(C6H5CH3)/ν(C6D5CD3) has been calculated for each excited state mode of vibration and compared with the corresponding value of R found for the ground state vibrations.
Metalation Reactions XII. The Alkylation of Pentenynyl‐Lithium Derivatives
Authors: Klein J. , Brenner S. , Medlik A. 
Published: November 2013

AbstractSelective monometalation of 1, 4‐enynes was performed with methyl‐lithium in ether. These monolithio compounds were alkylated with alkyl halides at the central 3‐position only to give unconjugated enynes. Dialkylation of the dilithio derivatives occurred also at the same position. However, protonation of these organometallics gave a mixture of products and trimethylsilyl chloride attacked the lithium derivative preponderantly at the 5‐position.
Growth Conditions for Crystal Pulling by the Czochralski Method
Authors: Grajower R. , Roman I. 
Published: November 2013

AbstractThe balance of heat flow at the growth interface during Czochralski crystal pulling is discussed, taking into consideration the curvature of the interface. Mechanisms are postulated according to which sudden and slow changes in the pulling rate influence the growth process and detachment of the crystal from the melt. An expression is derived for the smallest diameter to which necking down can be carried out under stable growth conditions.
Metachromasy in Clay Minerals. Part I. Sorption of Methylene‐Blue by Montmorillonite
Authors: Yariv S. , Lurie D. 
Published: November 2013

AbstractUV, visible and IR spectra of methylene‐blue sorbed on Wyoming bentonite saturated with different cations were studied and characterized. The colloidal properties of a dilute suspension of Cu montmorillonite treated with methylene‐blue was studied by heterometric titration. The organic dye can be sorbed either at the edges of the clay platelets or on oxygen sheets of the silicate layer. In the latter case sorption leads to metachromasy of the dye molecule and a shift of the absorption bands to lower values in the visible range. X‐ray patterns show that metachromasy of methylene‐blue in montmorillonite occurs also when there is only one organic layer lying parallel to the silicate sheets. Thus, metachromasy cannot be attributed to polymerization of the organic dye as was previously suggested.
The Application of Thermal Analysis Methods to the Decomposition of Sodium Bicarbonate
Authors: Simchen A.E. 
Published: November 2013

AbstractThermal analysis of sodium bicarbonate by DTA and DSC showed that the decomposition temperature of this salt is about 100±1°C. A decomposition temperature of 270°C given in the Handbooks seems to be an error. Adsorbed water is the cause of the small endotherm between 70 and 75°C.
On Some Single‐Crystal Diffraction Experiments in a Search for Direct Structural Evidence for Solid‐State Reactions
Authors: Osaki Kenji , Schmidt G. M. J. 
Published: November 2013

AbstractSolid‐state reactions were studied by X‐ray diffraction using single crystals of 1′‐bromo‐cis‐cinnamic acid, α‐trans‐cinnamic acid and trans‐cinnamide. Only in the last case was direct structural evidence for the solid‐state reaction obtained through the deformation of the X‐ray pattern of the original crystal, which indicates considerable distortion accumulated in the crystalline matrix of the reacting species.
The Structure of Cyclo‐Di‐β‐Alanyl
Authors: White D. N. J. , Dunitz J. D. 
Published: November 2013

AbstractThe crystal structure of cyclo‐di‐β‐alanyl (monoclinic; a = 11.85, b = 5.20, c = 10.66 Å, β = 94.83°; space group C2/c; Z = 4) has been determined by X‐ray analysis, using direct methods, and refined by full‐matrix least‐squares calculations. The two cis‐peptide groups, related by a twofold axis, are almost exactly planar, and the molecule occurs in a “flexible” chair conformation with N‐CH2CH2‐C torsion angle of 27°.
Singlet Exciton Collisions in Crystalline Anthracene
Authors: Bergman Amalia , Bergman David , Jortner Joshua 
Published: November 2013

AbstractWe present a new determination of the singlet‐singlet annihilation rate constant in crystalline anthracene based on simultaneous measurements of the fluorescence quantum yield and of the fluorescence decay. Optical excitation was achieved by the second harmonic of a ruby laser. A detailed kinetic scheme for singlet‐exciton kinematics is discussed with particular emphasis on the role of metastable exciton states in an organic molecular crystal. Finally, we consider the problem of stimulated emission and light amplification from crystalline anthracene and explore the possibility of utilizing this molecular crystal as an active optical element in a molecular‐crystal laser.
The Reaction of Gases with Irradiated Solids Having a Bilayer Structure
Authors: Adler George 
Published: November 2013

AbstractThe free radicals in irradiated solid amides, fatty acids and similar compounds react rapidly with ambient gases such as O2, NO, SO2, etc. The gas seems able to penetrate the lattice and reach the reaction site. This apparently depends on a particular kind of crystal structure which we term the “bilayer structure.” Some characteristics of these reactions are discussed.
An X‐Ray Study of Phosvitin, The Phosphoglycoprotein in Hens' Egg Yolk
Authors: Traub Wolfie , Perlmann Gertrude E. 
Published: November 2013

AbstractAn X‐ray diffraction study has been made of the egg‐yolk phosphoglycoprotein, phosvitin. Film specimens prepared from an aqueous solution of pH 3.3 give an oriented fibre pattern showing features characteristic of β‐pleated‐sheet structures. However, X‐ray patterns of specimens derived from solutions of pH 7.3 show no evidence of any ordered conformation. These results bear out reports, based on physiochemical studies of phosvitin in solution, of a pH‐dependent conformational transition.
Stepwise Formation of Some Bivalent Metal Chelates with Sodium Alizarin Sulphonate
Authors: Govil Pradip K. , Dwivedi Chandra D. , Banerji Samir K. 
Published: November 2013

AbstractThe stepwise protonation constants of the ligand and the stability constants of Alizarin Red S with some bivalent metal ions, Pb2+, Cu2+, Zn2+, and Hg2+ have been determined at 30° and at various ionic strengths viz. 0.02, 0.05, 0.15 and 0.20, maintained by sodium perchlorate solution. The formation of the chelate is evident from the shift between the (i) ligand and (ii) ligand and metal titration curves. From the values of the stepwise protonation constants and metal ligand stability constants at various ionic strengths, thermodynamic formation constants were evaluated by extrapolation to zero ionic strength. The order of stability constants was found to be:Cu > Pb > Zn > Hg
The Free‐Radical Cleavage of the Disulfide Bond (Studied by Pulse Radiolysis)
Authors: Shafferman A. 
Published: November 2013

AbstractReaction of H atoms with glutathione leads rapidly to H + RSSR → RS · + RSH. The first observed product is RS, the spectrum of which is obtained. The spectrum of the RS̄SR radical was obtained by direct attack of e−aq on glutathione. The rate constants of these processes were also measured.ke−aq + RSSR = (2.7 ± 0.3) × 109 M−1 sec−1kH + RSSR = (1.0 ± 0.2) × 1010 M−1 sec−1When the OD of RS̄SR is plotted vs pH a titration curve is obtained. This is due to the protonation of RS̄SR with a rate constant of 2.6 × 1010 M−1 sec−1 which is probably followed by a cleavage to RS and RSH. In both cases the RSSHR radical cannot be detected. The spectrum attributed to the RSSHR radical is more likely to be that of RS.
Isolation of Hederagenin and its Saponin from Alfalfa (Medicago Sativa)
Authors: Shany S. , Gestetner B. , Birk Yehudith , Bondi A. , Kirson I. 
Published: November 2013

AbstractA sapogenin isolated from the acid hydrolysates of roots or tops of alfalfa (Medicago sativa) has properties and constants identical to those of hederagenin. The corresponding saponin was isolated from a mixture of alfalfa saponins by successive chromatography on Al2 O3 and DEAE‐Sephadex columns. Upon acid hydrolysis it yields glucose, arabinose and hederagenin, similarly to the saponin isolated from Hedera helix.
Swelling of Anion Exchangers in Mixed Solvents. III. A Calorimetric Study
Authors: Marcus Y. , Naveh J. 
Published: November 2013

AbstractThe integral heat evolved on swelling of the anion exchange resin Dowex‐1 in chloride and perchlorate forms in water, methanol, ethanol, n‐propanol, acetone and formamide, and in aqueous mixtures of these solvents, was measured calorimetrically as a function of the cross‐linking of the resin (4,8 and 16% DVB) and the solvent composition. Heats of swelling (wetting) of the resin skeleton were also measured. These were found to be negligible compared with the heats of swelling of the exchangers which were in the range of 4–8 kcal/equiv. resin for the chloride form with water, methanol, ethanol and formamide, or their aqueous mixtures, but considerably smaller for the chloride form and solvents rich in propanol or acetone as well as for the perchlorate form. The heats of solution of the monomer analog, benzyltrimethylammonium chloride were found to be endothermic. Their relevance to the heat of swelling, and that of the heat of mixing of the solvents, was examined.
Sorption and Desorption of Water Vapour on Starch
Authors: Das Baghwan , Sethi R. K. , Chopra S. L. 
Published: November 2013

AbstractAdsorption‐desorption isotherms for water vapour on starch have been obtained by the use of quartz fibre spring technique. The specific surface area of starch has been calculated by the BET and HJ methods and the values are in close agreement with each other.
Cycloaddition of Indene with N‐Chlorosulphonyl Isocyanate
Authors: Dunkelblum E. , Shaviv A. 
Published: November 2013

AbstractThe cycloaddition of indene with N‐chlorosulphonyl isocyanate was performed at low temperature to generate the 7‐azabicyclo‐2,3‐benzo [3,2,0]‐hept‐2‐ene‐6‐one system. The structure of the cycloadduct was established by spectroscopic and chemical means.
Viscosity of Electrolytic Solutions in Dioxane‐Water Mixtures
Authors: Fuoss Raymond M. , Reynolds Anne F. 
Published: November 2013

AbstractThe viscosities and densities of solutions of nine alkali halides (lithium, sodium, potassium, rubidium, and cesium chlorides; sodium fluoride, bromide and iodide; cesium iodide) and four quaternary ammonium bromides (tetramethyl, tetraethyl, tetra‐n‐propyl and tetra‐n‐butyl) have been measured over the concentration range 0.05–0.25 N in dioxane‐water mixtures containing 0–63 weight % dioxane. The Jones‐Dole B‐coefficient for the alkali halides increases as the dioxane fraction increases, to values much larger than those corresponding to the Einstein volume effect, suggesting a selective solvation of the cations. With increasing dioxane fraction, the B‐coefficients for the quaternary salts tend towards the theoretical values calculated from the known crystallographic radii of their ions.
A Pulse Radiolysis Study of Interactions in Biological Molecules
Authors: Phillips G. O. , Power D. M. , Richards J. T. 
Published: November 2013

AbstractUsing pulse radiolysis techniques, the binding of penicillin and cephalosporin drugs to proteins (bovine serum albumin and lysozyme) has been studied using rate constants obtained for reactions with solvated electrons as a monitor of the binding. The results obtained are discussed in terms of three distinct types of binding.
Addition Reactions to Methylenecyclopropanes II: Electrophilic Additions of Diphenylmethylenecyclopropane
Authors: Dunkelblum E. 
Published: November 2013

AbstractA number of addition reactions to diphenylmethylenecyclopropane (II) have been studied. Bromination and CF3COOH addition in CH3Cl2 proceeded with ring‐opening and gave the homoallylic adducts III and VI. On the other hand bromination in glyme and water gave both unrearranged and rearranged products, III and V. Reactions with NBS in the same solvent system gave the unrearranged bromohydrin V. Oxymercuration and hydroboration proceeded without ring‐cleavage, the mercury and boron attacking mainly β‐ to the phenyl groups. Two cyclopropylmercury compounds VII and IX were isolated and characterized.
Studies on the Absorption Spectra of Aqueous Bromine, Bromine—NaCl and Bromine—NaBr
Authors: Ben‐Bassat A. A. 
Published: November 2013

AbstractThe absorption spectra of aqueous bromine alone and in the presence of increasing amounts of NaCl or NaBr at acidic pH were studied. Characteristic changes in the intensity and location of certain absorption bands were observed. The spectral displacements with changes in chloride or bromide concentration indicate the formation of various complex halides. The results may provide an explanation of the changes in the sorption and oxidation processes in the interaction of aqueous bromine containing various amounts of NaCl or NaBr with cotton cellulose.
The Maturation of Connective Tissue Proteins
Authors: Gallop Paul M. , Paz Mercedes A. , Pereyra Bolivar , Blumenfeld Olga O. 
Published: November 2013

AbstractA brief review of the status of current knowledge on the maturation of connective tissue proteins is presented and includes new information relating to collagen and elastin crosslinks. Some consideration is given to pertinent methodology, such as the NaBH4 reduction technique where tritium or deuterium is either in the reagent or the solvent or in both. The most recently developed methodology involving [14C] cyanide incorporation into various maturation compounds is also briefly considered. In addition, a general overview of the field and of some of the remaining problems is given.
Dimers as Intermediates in the Assembly of Tetrameric Proteins: A Study on Lactate Dehydrogenase Isozymes
Authors: Levitzki Alexander , Tenenbaum Hana 
Published: November 2013

AbstractThe renaturation kinetics of pig heart, pig muscle, beef heart and beef muscle lactic dehydrogenases was studied. It was found that in all four cases the major intermediate in the assembly process is a lactate dehydrogenase dimer. It was found that NAD+ and NADH influence dramatically the kinetics of renaturation, probably by binding to a partially refolded subunit prior to the assembly to the fully renatured tetramer.
Chemical Relaxation Study of the Electron Transfer Between Laccase and External Redox Couples
Authors: Pecht Israel 
Published: November 2013

AbstractThe temperature jump chemical relaxation method was employed to study the electron transfer reactions between fungal laccase and two different, single electron redox couples: Mo(CN)4−/3−8 and Ru(CN)4−/3−6. The reactions were followed by measurement of the light absorption bands at 610 and 330 run. In the perturbed equilibrium of laccase with the Mo(CN)4−/3−8 only a single relaxation time was observed at 610 nm, and from its concentration dependence, the second‐order rate constants of electron transfer to and from the type 1 Cu(II) were evaluated. Similarly, at 610 nm a single concentration‐dependent relaxation time was observed in the laccase −Ru(CN)4−/3−6 equilibrium. At the 330 nni band a concentration‐independent chemical relaxation was resolved. Fluoride ions were found to have no effect on the observed rates of electron exchange with the type 1 copper ions. These results are in line with the kinetic data obtained by stopped flow and pulse radiolysis showing the type 1 Cu(II) to be the first electron accepting site. In addition, it has been found that this site may be oxidized by single electron acceptors at rather fast rates. In the reaction with the Ru(CN)4−/3−6 couple an intramolecular electron transfer to and from the 330 nm chromophore is proposed.
Structure of Haemoglobin M Boston, A Variant with a Five‐Coordinated Ferric Haem
Authors: Pulsinelli P. D. , Perutz M. F. , Nagel R. L. 
Published: November 2013

AbstractX‐ray analysis of the natural valency hybrid α+ M Boston2 βdeoxy2 shows that the ferric iron atoms in the abnormal α subunits are bonded to the phenolate side chains of the tyrosines that have replaced the distal histidines; the iron atoms are displaced to the distal side of the porphyrin ring and are not bonded to the proximal histidines. The resulting changes in tertiary structure of the α subunits stabilize the haemoglobin tetramer in the quaternary deoxy structure, which lowers the oxygen affinity of the normal β subunits and causes cyanosis. The strength of the bond from the ferric iron to the phenolate oxygen appears to be the main factor responsible for the many abnormal properties of haemoglobin M Boston.
The Behavior of Cleavable Crosslinking Reagents Based on the Disulfide Group
Authors: Wang Kuan , Richards Frederic M. 
Published: November 2013

Abstract4,4′‐Bisphenyldiazonium disulfide fluoroborate and dimethyl‐3,3′‐dithiobispropionimidate dihydrochloride were synthesized and tested as reversible cross‐linking reagents. Rabbit muscle aldolase, human hemoglobin and human erythrocyte membrane proteins can be successfully crosslinked by these reagents. The crosslinked products can be cleaved into their components in high yield by thiols, under mild conditions. A simple diagonal sodium dodecyl sulfate gel electrophoresis technique was developed to identify electrophoretically the components of crosslinked products. The application and possible complications of bifunctional reagents containing disulfide bonds are discussed.
Reduction of Insulin with Tributylphosphine
Authors: Rüegg U. Th. , Rudinger J. 
Published: November 2013

AbstractTreatment of bovine insulin with 3 mole of tributylphosphine in the presence of excess ethylene imine in aqueous 1‐propanol at pH 8.2 leads to complete reduction and aminoethylation, affording the aminoethylated insulin A and B chains in excellent yield. Reduction with 1 mole of tributylphosphine under the same conditions is attended by disulphide exchange: The product is a mixture of partially reduced and aminoethylated species which, on further reduction and carboxymethylation, afford A‐ and B‐chain derivatives with varying ratios of S‐aminoethyl‐ and S‐carboxymethyl substituents.
The Use of Bromoacetyl Derivatives for the Affinity Labeling of Proteins
Authors: Naider Fred , Becker Jefferey M. , Wilchek Meir 
Published: November 2013

AbstractThe use of bromoacetyl derivatives in the determination of structure‐function relationships in proteins is reviewed. Specific attention is paid to the advantages of the bromoacetyl functional group in the design and synthesis of active‐site‐directed reagents. Modification studies on staphylococcal nuclease and myeloma protein 315C are discussed in detail. Reagents containing the bromoacetyl group at prescribed distances from the binding center of the affinity label are described. Information gained from these studies gives insight into the spatial orientation of the amino acid side chains near the active sites of proteins.
Immobilized Lactate Dehydrogenases
Authors: Dixon Jack E. , Stolzenbach Francis E. , Lee Ching‐Lun Tsao , Kaplan Nathan O. 
Published: November 2013

AbstractWe have covalently attached pure chicken H4 and M4 lactate dehydrogenase to porous glass beads by a variety of chemical methods. The attachment of these isoenzymes by the glutaraldehyde and diazo linkages generates immobilized enzymes that are stable for months, show decreased substrate (pyruvate) inhibition and exhibit a pH‐rate profile independent of pH. These insolubilized catalysts exhibit apparent Km values similar to those of the native enzymes. A comparison of the glutaraldehyde‐ and aryl glass‐bound isoenzymes indicates that the former linkage allows for greater stability toward pH and heat denaturation and is also more resistant to attack by proteolytic enzymes. There is also evidence that in the presence of 5.3 M lithium chloride no subunits are dissociated from the glass‐bound enzymes. Upon renaturation, the glutaraldehyde‐glass‐bound enzyme affords an almost quantitative recovery of activity, while the native and aryl‐glass‐bound enzymes give approximately thirty per cent recovery. The degree of antibody inhibition exhibited by the immobilized enzymes was also examined.