bluuebunny/crossref_metadata_2025 huggingface dataset:
ChemInform Abstract: Systematic Study on Free Radical Hydrothiolation of Unsaturated Monosaccharide Derivatives with Exo‐ and Endocyclic Double Bonds.
Authors: Lazar Laszlo , Csavas Magdolna , Hadhazi Adam , Herczeg Mihaly , Toth Marietta , Somsak Laszlo , Barna Terezia , Herczegh Pal , Borbas Aniko
Published: November 2013

The photoinduced radical‐mediated hydrothiolation reactions show highly varying overall conversions depending not only on the substitution pattern and electron‐density of the double bond but also on the nature and the substitution pattern of the thiol partner.
ChemInform Abstract: Xinshengin, the First Altenusin with Tetracyclic Skeleton Core from Phialophora spp.
Authors: Ye Feng , Chen Guo‐Dong , He Jun‐Wei , Li Xiao‐Xia , Sun Xiang , Guo Liang‐Dong , Li Yan , Gao Hao
Published: November 2013

Xinshengin (I), the first tetracyclic altenusin with an unprecedented altenuene/tetrahydrofuran‐fused skeleton core, is obtained from cultures of the endolichenic fungal strain Phialophora spp., along with the new natural compound phialophoriol (II) and a known altenusin.
ChemInform Abstract: Biologically Relevant Silver(I)—N‐Heterocyclic Carbene Complexes: Synthesis, Structure, Intramolecular Interactions, and Applications.
Authors: Budagumpi Srinivasa , Haque Rosenani A. , Endud Salasiah , Ur Rehman Ghani , Salman Abbas Washeel
Published: November 2013

Review: 135 refrs.
ChemInform Abstract: Biocatalysis in Organic Chemistry and Biotechnology: Past, Present, and Future
Authors: Reetz Manfred T.
Published: November 2013

Review: < 100 refs.
ChemInform Abstract: Recent Advances in the Chemical Synthesis of Glycosylphosphatidylinositols (GPIs): Expanding Synthetic Versatility for Investigating GPI Biology
Authors: Swarts Benjamin M.
Published: November 2013

Review: 84 refs.
ChemInform Abstract: Enantioselective Hydrogenation of Isoquinolines
Authors: Zhao Dongbing , Glorius Frank
Published: November 2013

Review: [11 refs.]
ChemInform Abstract: A Voyage into the Synthesis and Photophysics of Homo‐ and Heterobinuclear Ensembles of Phthalocyanines and Porphyrins
Authors: de la Torre Gema , Bottari Giovanni , Sekita Michael , Hausmann Anita , Guldi Dirk M. , Torres Tomas
Published: November 2013

Review: 281 refs.
ChemInform Abstract: Iridium Catalysis: Application of Asymmetric Reductive Hydrogenation
Authors: Cadu Alban , Andersson Pher G.
Published: November 2013

Review: 141 refs.
ChemInform Abstract: Reversible Phase Transformation at the Solid—Liquid Interface: STM Reveals
Authors: Zhang Xue‐Mei , Zeng Qing‐Dao , Wang Chen
Published: November 2013

Review: 99 refs.
ChemInform Abstract: Isotope Effects as Probes for Enzyme Catalyzed Hydrogen‐Transfer Reactions
Authors: Roston Daniel , Islam Zahidul , Kohen Amnon
Published: November 2013

Review: 95 refs.
ChemInform Abstract: CD Spectra of Chiral Extended π‐Electron Compounds: Theoretical Determination of the Absolute Stereochemistry and Experimental Verification
Authors: Harada Nobuyuki , Kuwahara Shunsuke
Published: November 2013

Review: 70 refs.
PTEN knockdown alters dendritic spine/protrusion morphology, not density
Authors: Haws Michael E. , Jaramillo Thomas C. , Espinosa Felipe , J. Widman Allie , Stuber Garret D. , Sparta Dennis R. , Tye Kay M. , Russo Scott J. , Parada Luis F. , Stavarache Mihaela , Kaplitt Michael , Bonci Antonello , Powell Craig M.
Published: November 2013

Mutations in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) are implicated in neuropsychiatric disorders including autism. Previous studies report that PTEN knockdown in neurons in vivo leads to increased spine density and synaptic activity. To better characterize synaptic changes in neurons lacking PTEN, we examined the effects of shRNA knockdown of PTEN in basolateral amygdala neurons on synaptic spine density and morphology by using fluorescent dye confocal imaging. Contrary to previous studies in the dentate gyrus, we find that knockdown of PTEN in basolateral amygdala leads to a significant decrease in total spine density in distal dendrites. Curiously, this decreased spine density is associated with increased miniature excitatory postsynaptic current frequency and amplitude, suggesting an increase in number and function of mature spines. These seemingly contradictory findings were reconciled by spine morphology analysis demonstrating increased mushroom spine density and size with correspondingly decreased thin protrusion density at more distal segments. The same analysis of PTEN conditional deletion in the dentate gyrus demonstrated that loss of PTEN does not significantly alter total density of dendritic protrusions in the dentate gyrus, but does decrease thin protrusion density and increases density of more mature mushroom spines. These findings suggest that, contrary to previous reports, PTEN knockdown may not induce de novo spinogenesis, but instead may increase synaptic activity by inducing morphological and functional maturation of spines. Furthermore, behavioral analysis of basolateral amygdala PTEN knockdown suggests that these changes limited only to the basolateral amygdala complex may not be sufficient to induce increased anxiety‐related behaviors. J. Comp. Neurol. 522:1171–1190, 2014. © 2013 Wiley Periodicals, Inc.
Life history of theGlanville fritillary butterfly in fragmented versus continuous landscapes
Authors: Duplouy Anne , Ikonen Suvi , Hanski Ilkka
Published: November 2013

Habitat loss and fragmentation threaten the long‐term viability of innumerable species of plants and animals. At the same time, habitat fragmentation may impose strong natural selection and lead to evolution of life histories with possible consequences for demographic dynamics. The Baltic populations of the Glanville fritillary butterfly (Melitaea cinxia) inhabit regions with highly fragmented habitat (networks of small dry meadows) as well as regions with extensive continuous habitat (calcareous alvar grasslands). Here, we report the results of common garden studies on butterflies originating from two highly fragmented landscapes (FL) in Finland and Sweden and from two continuous landscapes (CL) in Sweden and Estonia, conducted in a large outdoor cage (32 by 26 m) and in the laboratory. We investigated a comprehensive set of 51 life‐history traits, including measures of larval growth and development, flight performance, and adult reproductive behavior. Seventeen of the 51 traits showed a significant difference between fragmented versus CL. Most notably, the growth rate of postdiapause larvae and several measures of flight capacity, including flight metabolic rate, were higher in butterflies from fragmented than CL. Females from CL had shorter intervals between consecutive egg clutches and somewhat higher life‐time egg production, but shorter longevity, than females from FL. These results are likely to reflect the constant opportunities for oviposition in females living in continuous habitats, while the more dispersive females from FL allocate more resources to dispersal capacity at the cost of egg maturation rate. This study supports theoretical predictions about small population sizes and high rate of population turnover in fragmented habitats selecting for increased rate of dispersal, but the results also indicate that many other life‐history traits apart from dispersal are affected by the degree of habitat fragmentation.
A Selective Metal‐Mediated Approach for the Efficient Self‐Assembling of Multi‐Component Photoactive Systems
Authors: Iengo Elisabetta , Cavigli Paolo , Gamberoni Marta , Indelli M. Teresa
Published: November 2013

We report on the efficient use of different coordinative affinities to quantitatively construct a three‐component multichromophore system containing one free‐base porphyrin, one aluminium(III) monopyridylporphyrin, and one ruthenium(II) tetraphenylporphyrin in a single step. The AlIII monopyridylporphyrin plays the pivotal role in directing the correct self‐assembly process, and it behaves as the antenna unit for the photoinduced processes of interest. A two‐component system, containing the same free‐base porphyrin and one aluminium(III) tetraphenylporphyrin, was prepared for comparative studies. Both systems are remarkably stable in chlorinated solutions. Their photophysical behaviour was studied in detail by stationary and time‐resolved emission techniques. In the two‐component system, fast and efficient singlet energy transfer from the Al–porphyrin to the free‐base porphyrin is observed; in the three‐component system, upon excitation of the Al–porphyrin, a fast (<250 ps) electron transfer process from the Ru–porphyrin to the aluminium–porphyrin is observed.
Square and Butterfly Tetranuclear [Co2Ln2] Clusters Built from the Same Building Blocks but Displaying Different Magnetic Properties: Structural Variation by Means of Solvent and the Radii of Ln3+ Ions
Authors: Li Zhong‐Yi , Dai Yue , Zhang Hui , Zhu Jiang , Zhang Jian‐Jun , Liu Shu‐Qin , Duan Chun‐Ying
Published: November 2013

Two series of tetranuclear [Ln2Co2] clusters were built from the same [Co(CDTA)]2– building blocks but have different metal skeletons: square 1Ln compounds {[Ln2Co2(CDTA)2(μ4‐OH)(DMF)2(H2O)6]·ClO4·1.5H2O; Ln = La, Gd, and Dy} with a μ4‐OH– bridged Ln–Co–Ln–Co arrangement, and two μ3‐OH–‐bridged “butterfly” 2Ln compounds {[Ln2Co2(CDTA)2(μ3‐OH)2(H2O)6]·6H2O; Ln = Gd, Tb, Dy, and Y} with two Ln3+ ions as the “body” and two Co2+ ions as “wings”. They were prepared from the solvothermal reactions of trans‐1,2‐diaminocyclohexane‐N,N,N′,N′‐tetraacetic acid (H4DCTA), Ln(ClO4)3, and Co(ClO4)2 in DMF/H2O or H2O solvent. Their syntheses are mainly controlled by the solvent and the radii of Ln3+ ions. Light Ln3+ ions with big radii are favorable for the formation of square complexes, whereas heavy Ln3+ ions (including Y3+) with small radii promote the formation of butterfly ones. Remarkably, the middle Ln3+ ions are favorable for the formation of both structures, and in these cases the reactions are controlled by solvent (H2O or H2O + DMF). Magnetic analyses reveal the antiferromagnetic interactions between the two Co2+ ions in 1La and 2Y. Interestingly, other butterfly clusters (2Gd, 2Tb, 2Dy) show dominant ferromagnetic interactions, whereas the other square clusters (1Gd, 1Dy) show overall antiferromagnetic interactions. Details of the magnetic interaction between the metal ions are discussed.
Reaction of Tri(2‐pyridyl)phosphine with Electron‐Deficient Alkynes in Water: Stereoselective Synthesis of Functionalized Pyridylvinylphosphine Oxides
Authors: Arbuzova Svetlana N. , Gusarova Nina K. , Glotova Tatyana E. , Ushakov Igor A. , Verkhoturova Svetlana I. , Korocheva Anastasiya O. , Trofimov Boris A.
Published: November 2013

The reaction of tri(2‐pyridyl)phosphine with electron‐deficient alkynes in water proceeds under mild conditions (40–45 °C, without catalyst, 4–5 h) with liberation of pyridine to give (E)‐pyridylvinylphosphine oxides in 45–56 % yields, the only exception being the reaction with cyanophenylacetylene, which affords the corresponding vinylphosphine oxide of Z‐configuration in 40 % yield. The reaction is likely triggered by the zwitterion, the adduct of tri(2‐pyridyl)phosphine to the electrophilic acetylenes, the carbanionic center of which is then neutralized by a proton from water. The intermediate phosphonium hydroxide finally decomposes to the product.
Correcting for ascertainment bias in the COGA data set
Authors: Comuzzie Anthony G. , Williams Jeff T.
Published: November 2013

The effects of several corrections for ascertainment bias on a linkage result in the COGA data are examined. A correction that models the complete ascertainment protocol markedly reduces the evidence for linkage. Different partial corrections increase the linkage signal and recover good estimates of the population trait prevalence, but do not represent adequately the complexity of the COGA ascertainment scheme. Evidently the present size of the COGA data set cannot support a complete correction for ascertainment bias, but an effective partial correction can and should be implemented.
Power loss for multiallelic transmission/disequilibrium test when errors introduced: GAW11 simulated data
Authors: Gordon Derek , Matise Tara C. , Heath Simon C. , Ott Jurg
Published: November 2013

Many researchers are considering the use of transmission/disequilibrium tests (TDT) for trios of genotypes (father, mother, child) as a method for localizing genes associated with complex diseases. We evaluate the effect of random errors (allele changes) in trios on the power to detect linkage. For a marker in the simulated data set, one allele is associated with the fictitious disease in a certain subpopulation. For the data as given (no errors), our power to detect linkage using the multiallelic TDT (TDTmhet) is 68% (critical p‐value set at 0.0001). We introduce errors into trios at various rates (1%, 5%, or 10%), remove only trios displaying mendelian inconsistencies, and recalculate power to detect linkage. Our principal finding is that there is power loss to detect linkage with the TDTmhet when errors are introduced. We observe power losses of 8%, 16%, and 48% for error rates of 1%, 5%, and 10%, respectively. To determine the source of the power loss, we perform Monte Carlo simulations. At the 1% and 5% rates, we conclude that power loss is due primarily to loss in sample size. At the 10% rate, we observe substantial power loss due to error introduction in addition to sample size reduction. We also determine, given a particular error rate, the probability that we detect errors if we use only mendelian consistency as a check. We find that the mean detection rates for the data sets with 1%, 5%, or 10% error rates are 58%, 60%, and 62%, respectively. As a result, the apparent error rate appears to be almost half the true error rate. Based on these results, we recommend that researchers maintain error rates below 5% when using the TDTmhet for linkage, use additional methods beyond mendelian consistency checks when searching for errors in their data, and modify sample size calculations when accounting for errors in their genotype data.
Transglutaminase 2 reprogramming of glucose metabolism in mammary epithelial cells via activation of inflammatory signaling pathways
Authors: Kumar Santosh , Donti Taraka R. , Agnihotri Navneet , Mehta Kapil
Published: November 2013

Aberrant glucose metabolism characterized by high levels of glycolysis, even in the presence of oxygen, is an important hallmark of cancer. This metabolic reprogramming referred to as the Warburg effect is essential to the survival of tumor cells and provides them with substrates required for biomass generation. Molecular mechanisms responsible for this shift in glucose metabolism remain elusive. As described herein, we found that aberrant expression of the proinflammatory protein transglutaminase 2 (TG2) is an important regulator of the Warburg effect in mammary epithelial cells. Mechanistically, TG2 regulated metabolic reprogramming by constitutively activating nuclear factor (NF)‐κB, which binds to the hypoxia‐inducible factor (HIF)−1α promoter and induces its expression even under normoxic conditions. TG2/NF‐κB‐induced increase in HIF‐1α expression was associated with increased glucose uptake, increased lactate production and decreased oxygen consumption by mitochondria. Experimental suppression of TG2 attenuated HIF‐1α expression and reversed downstream events in mammary epithelial cells. Moreover, downregulation of p65/RelA or HIF‐1α expression in these cells restored normal glucose uptake, lactate production, mitochondrial respiration and glycolytic protein expression. Our results suggest that aberrant expression of TG2 is a master regulator of metabolic reprogramming and facilitates metabolic alterations in epithelial cells even under normoxic conditions. A TG2‐induced shift in glucose metabolism helps breast cancer cells to survive under stressful conditions and promotes their metastatic competence.
Vein Palygorskites in Israel and Sinai; Their Origin and Symmetry
Authors: Nathan Y. , Bentor Y.K. , Wurtzburger U.
Published: November 2013

Three palygorskites in veins have been found in Israel and a fourth in the Sinai peninsula. They all have a mountain cork appearance, and are mixed with quartz, montmorillonite and calcite. Three of them are presumably hydrothermal and monoclinic. The fourth is probably sedimentary and is orthorhombic. It is suggested that the orthorhombic ‐monoclinic transition is an order‐disorder phenomenon.
Structural Changes and Isomorphic Substitution in Illites from Limestones of Variable Degrees of Metamorphism
Authors: Gavish E. , Reynolds R. C.
Published: November 2013

Eleven samples of illites were separated from limestones which have undergone variable degrees of metamorphism and analyzed by X‐ray diffraction to give twelve orders of the (001) reflections. The observed structure factors were calculated with a computer and compared to calculated structure factors of a hypothetical model through a process of “refinement”. The variable parameters in the process of “refinement” were: the distance of OH, Si and O from the center of the unit cell, the temperature coefficient, and the amount of K+ and Fe+3 in the lattice of the unit cell. A one‐dimensional Fourier synthesis calculated the electron densities along the C axis within the unit cell. The percent 2M polymorph in the illites, as well as the oxygen isotope ratio of the limestones from which the illites were extracted, was also calculated. These two parameters were used as indicators of the degree of metamorphism of the samples collected. There is an inverse correlation between the proportion of 2M polymorphs and the O18/O16 ratio. There is no clear correlation between the amount of K+ in the lattice and the degree of metamorphism of the samples. There is an increase of Fe+3 substituted in the octahedral layer of the illite, with an increased degree of metamorphism of the limestones.
A Rapid Microdetermination of Water in Chlorinated Hydrocarbons by Gas Chromatography
Authors: Joseph H.
Published: November 2013

A fast and sensitive gas chromatographic procedure for the control of moisture in chlorinated hydrocarbons at the ppm level is described. The basic features are a combination of two types of polyaromatic beads as column packing, locally produced hydrogen as carrier gas, and a backflushing system. The latter reverses the carrier gas flow after elution of the water peak at increased pressure. The instrument is thus readied for subsequent analyses at intervals of 2–3 min. The system can be used for moisture analyses in most gases and liquids. It is particularly applicable where a large number of samples have to be checked continually and instant results are required.
Gas Chromatography of Tetra‐ and Pentacyclic Triterpenes
Authors: Ikan R. , Gottlieb R.
Published: November 2013

The 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

A 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

The 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

The 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

The 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.
Reactivity Trends in Condensed Benzothiophenes
Authors: Meyer A. Y. , Rappoport Z. , Elmaleh D.
Published: November 2013

Hückel‐type calculations are used to rationalize the known properties of fused benzothiophenes and to predict behavioral trends which have not been investigated as yet.
Metalation Reactions XII. The Alkylation of Pentenynyl‐Lithium Derivatives
Authors: Klein J. , Brenner S. , Medlik A.
Published: November 2013

Selective 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

The 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

UV, 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 Biological Activity of Vinyl and Butenyl Sulfone Derivatives
Authors: Allingham Y. , Asscher M.
Published: November 2013

Mono‐ and bifunctional amino‐ and quaternary ammonium derivatives of ethyl‐ and butenylsulfones have been prepared, and preliminary results on their biological activity are reported.
The Application of Thermal Analysis Methods to the Decomposition of Sodium Bicarbonate
Authors: Simchen A.E.
Published: November 2013

Thermal 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

Solid‐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

The 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

We 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

The 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

An 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

The 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

Reaction 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−1

kH + RSSR = (1.0 ± 0.2) × 1010 M−1 sec−1

When 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

A 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

The 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

Adsorption‐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

The 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.
A Statistical Mechanical Model for a Multicomponent Chain of Interconverting Links
Authors: Victor Jonathan , Reich Shimon
Published: November 2013

The expressions for force versus length and the probability distribution of length for a chain composed of links that can interconvert among several conformations are derived. The theoretical values of average chain dimensions and thermodynamic functions are compared with those of a chain of uniform links. High and low force limits are considered.
Viscosity of Electrolytic Solutions in Dioxane‐Water Mixtures
Authors: Fuoss Raymond M. , Reynolds Anne F.
Published: November 2013

The 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

Using 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

A 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

The 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

A 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

The 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

The 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

X‐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

4,4′‐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

Treatment 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

The 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

We 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.
The Use of Synthetic Polyamino Acids for the Detection and Purification of Novel Proteolytic Enzymes
Authors: Yaron Arieh
Published: November 2013

Polyamino acids were used as substrates for the detection and purification of new exopeptidases from bacteria. The enzymes, which were obtained in pure form and were characterized, include: aminopeptidase P, clostridial aminopeptidase, dipeptidocarboxypeptidase and a nonspecific dipeptidase. The possible application for sequential hydrolysis by the combined action of the two aminopeptidases was demonstrated by accomplishing complete hydrolysis of a proline‐rich nonapeptide, bradykinin. The dipeptidocarboxypeptidase, which produces dipeptides from the carboxyl end, and the dipeptidase, which then hydrolyses the dipeptides formed, indicate an efficient mechanism by which polypeptides are hydrolyzed from the carboxyl end of the molecule. The unique nature of the peptide bond, in which proline is involved through its nitrogen, is pointed out and the possible role of proline as a residue that protects terminal regions of polypeptides against the hydrolytic action of exopeptidases is discussed.
Phenylacetyl and Phenylpropionyl Amino Acids: Their Inhibitory Effect on Glutamine Synthetase and Their Resistance to Acylase. I
Authors: Lustig N. , Spiegelstein‐Klarfeld H. , Schneider E. , Lichtenstein N.
Published: November 2013

The preparation of a number of phenylacetyl and 3‐phenylpropionyl derivatives of amino acids is described. Derivatives containing more than one aromatic group markedly inhibit ovine brain glutamine synthetase. All phenylacetyl and phenylpropionyl derivatives tested were resistant to hog kidney acylase I.
The Thermal Effects of Nucleation and Crystallization of KBr and KCL Solutions. III. The Heat of Crystallization and the Co‐Precipitation of Lead Ions
Authors: Glasner Abraham , Tassa Menachem
Published: November 2013

Salt solutions saturated at 44° C and containing varying amounts of lead ions were allowed to cool to about 29°C in 5.5 h. The total heat, ΔHt, evolved decreased to 2/3 of its highest value with the increase of Pb2+‐concentration, while the amount of salt crystallized, Wc, decreased to nil. The distribution coefficient of Pb2+ between crystals and solution was 10.5 and 9.8 for KBr and KCl respectively. The high lead content improved the perfection of the crystals. The results are consistent with a two‐stage mechanism of crystallization: heterogeneous nucleation by complex ions and growth of crystals by the addition of bloc nuclei.
Boron Phosphate: Preparation in Aqueous Medium; Physical and Chemical Characterization
Authors: Ashboren (Araten) David
Published: November 2013

Heating equimolar amounts of pure phosphoric and boric acids in aqueous solution yields, at 130°, a solid boron phosphate of the composition R = P2O5/B2O3 = 1:1.71. Increasing the calcination temperature to 575° increases R to 1:1.29 due to evaporation of boron‐values. Further heating to 850° causes no additional weight losses. The specific surface decreases monotonically with the calcination temperature, from 7.4 to 0.5 m2/g. X‐ray diffraction data indicate that up to 10 min heating at 800°, increased calcination temperature causes a monotonic decrease in the unit cell dimensions, while prolonged heating (48 h) at this temperature reverses this trend.
Hydration Numbers of Some Acids and Salts
Authors: Feilchenfeld H. , Fuchs J.
Published: November 2013

Hydration numbers of some inorganic salts and strong acids were determined by measuring the change of reaction rate with free water concentration.
The Liquid/Solid Alkylation of Alkali Metal Pyrazolates
Authors: Mayer‐Sommer Georg E. , Schmidt Gerhard M. J.
Published: November 2013

The reactions of the lithium, sodium, potassium and cesium derivatives of 3‐methyl‐5‐carbomethoxy‐pyrazole, of 3‐methyl‐5‐ethyl‐pyrazole and of 3‐methyl‐5‐methoxy‐methylene‐pyrazole with methyl iodide, allyl bromide and benzyl chloride were investigated in 1,2‐dimethoxy‐ethane solution and at a liquid/solid interface (suspension of the pyrazole in a 1:1 mixture of n‐hexane and n‐heptane). Comparison of the ratios of the two nitrogen alkylated products formed from the reaction in solution and at the liquid/solid interface, suggests that the latter ratio is determined by the size of the alkali metal cation and by the presence of a coordination centre placed non‐symmetrically with respect to the mirror plane passing through the nitrogen‐nitrogen bond. It is suggested that a “cation in the way” effect is responsible for the liquid/solid‐interface alkylation results.
Ortho Effects. I. The Mechanisms of the H3O and CH3O2 Elimination from the Molecular Ion of N‐Methyl Ortho‐Nitro‐Para‐Toluidine
Authors: Zaretskii Zeev V. I. , Amit Boaz , Patchornik Avraham
Published: November 2013

The molecular ion of the N‐methyl ortho‐nitro‐para‐toluidine (I) readily eliminates H3O. The sources of the H atoms lost were proved by deuterium labeling to be an HNCH3 group as well as, probably, the C‐methyl group of the aromatic ring. The interaction between the N‐methyl and nitro groups in I also leads to the expulsion of CH3O2 from the molecular ion.