bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exhaustive Proteolysis of Derivatives of Lysozyme
Authors: Sokolovsky M. , Neumann Hava 
Published: November 2013

AbstractThe specificity of pepsin action towards a protein substrate, 8‐carboxymethyllysozyme, was investigated. The complex mixture of peptides obtained after 16hr of digestion was fractionated by high voltage paper electrophoresis. The peptide fragments were identified by a computer program and were fitted along the lysozyme sequence. The peptide bonds attacked were generally those that originate from at least one hydrophobic amino acid side chain, though some bonds involving alanine, threonine, and serine, were also found to be split.
The Synthesis of 22‐Trans‐Cholesta‐5, 22, 25‐Trien‐3β OL
Authors: Ikan R. , Markus A. , Bergmann E. D. 
Published: November 2013

Abstract22‐Trans‐cholesta‐5,22,25‐trien‐3β‐ol has been synthesized from triphenylphosphine‐2‐methyl‐but‐l‐en‐4‐ylidene and 3‐oxo‐Δ4‐bisnor‐cholenal.
On the Interpretation of Reaction Rates in Concentrated Acid Solutions
Authors: Yagil G. 
Published: November 2013

AbstractThe model of Bascombe and Bell for the indicator acidity of concentrated acid solutions is applied to the analysis of acid catalyzed reactions. A number of well studied reactions are shown to obey the relationship:magnified imagewhere Cw is the molar concentration of water not bound to proton (or to hydroxyl OH−). Values of Cw for use in the above correlation are calculated, assuming the existence of the proton in the form suggested by Eigen, H3O(H2 O)3+. The volume fractions of nonbound water are also calculated, this quantity giving even better correlation in some cases. Values of n are obtained which agree, after subtraction of water molecules given up by the proton, with the number of water molecules which can be expected to participate in the formation of the transition state of these reactions.
Applicability of the Brønsted Relation to Reactions of the Hydrated Electron
Authors: Stein G. 
Published: November 2013

AbstractThe hydrated electron, e−aq, reacts with Brønsted acids, BH+, to yield H atoms through a process of proton transfermagnified imageFor a series of Brønsted acids of charge types 1+, 0 and 1−, the rate constant, k, is related to the acid dissociation constant K according tok/p = GA(qK/p)α, where α = 0.42.Some acids give rate constants deviating from this relation. These are shown to be ambident reagents with e−aq, one pathway obeying the Brønsted relation, while the other may be nucleophilic addition of e−aq to a reaction center in B. Thus —k(e−aq), the rate of disappearance of e−aq may be greater than +k(H), the rate of formation of H atoms. To account for the results, a molecular model for the structure of e−aq forming a hydrated anion is favored. Its reaction with H+aq is discussed, accounting for recent observations on the rate of the reaction e−aq + H+aq → Haq, which in our view corresponds to proton transfer to fully ordered hydrated electrons, rather than electron addition to H+aq.
Topochemistry. Part XXXIII. The Solid‐State Photochemistry of Some Anthracene Derivatives
Authors: Heller E. , Schmidt G.M.J. 
Published: November 2013

AbstractThe solid‐state photochemistry of several substituted anthracenes has been investigated with particular reference to the behaviour of polymorphic forms of the monomers. A class of 9‐substituted anthracenes (methyl, methoxycarbonyl, chloro, bromo) crystallising in anti‐parallel, sandwich packing arrangements give centrosymmetric dianthracenes in accordance with the topochemical principle, which also operates on light‐stable monomers packing in non‐centrosymmetric space groups having axes > 8 Å (e. g. 9‐methoxy, 9‐ethoxy‐, 1‐cyano‐) and showing no short parallel interplanar contacts. Some but not all monomers, crystallising in the parallel‐stack type with a 4 Å axis, dimerise to the non‐topochemical head‐to‐tail dimer. Two monomers substituted elsewhere than in the 9‐position give the theoretical number of solution dimers but yield only one dimer in the solid state.
The Anomalous Behaviour of 18O‐Labelled Compounds. VII. The Vibrational Spectra of Isotopic Sodium Sulphates
Authors: Pinchas S. , Shamir J. 
Published: November 2013

AbstractThe infrared and Raman spectra of normal and 89.5 atom % 18O‐labelled sodium sulphate have been measured both for the solid salts and for their aqueous solutions. All the fundamentals of S16O2−4 and S18O2−4 have been observed. The observed isotopic frequency ratios of these fundamentals agree excellently with theory.
The Volumetric Determination of Potassium by Heterometric Titration
Authors: Ben‐Bassat A.H.I. , Azrad Anath 
Published: November 2013

AbstractHeterometric procedures for the volumetric determination of potassium are proposed. The use of direct and reverse titrations, precipitate‐forming ligands as titrants, and the addition of solvents like ethanol make possible the determination of a large number of cations and anions as their insoluble compounds. Two procedures are described: one uses direct heterometric titrations for the formation of the potassium tetraphenylboron precipitate (K‐TPB) for samples of concentrations between 40 and 60 ppm K+; the second uses indirect titrations for the formation of K2Na[Co(NO2)6] in acetic acid ‐ ethanol media, for samples containing 4–10 mg K+. The end point of the heterometric titration is obtained by photometric measurement of the optical absorption of suspensions.
The Synthesis of 8‐Cyclohexyl‐8‐Phosphabicyclo[3.2.1]Oct‐3‐Yl Tropate
Authors: Kashman Y. , Awerbouch O. 
Published: November 2013

AbstractThe preparation and characterization of the phosphorus analogues of cyclohexylnortropine and cyclohexylnorpseudotropine tropates‐ the two C‐3 epimeric 8‐cyclohexyl‐8‐phosphabicyclo[3.2.1] oct‐3‐yl tropates are reported.
Model Experiments Towards Stepwise Degradation of RNA in Dimethylsulphoxide
Authors: Steinschneider A. 
Published: November 2013

AbstractModel experiments for stepwise degradation of RNA starting from the 3′OH terminus under anhydrous conditions are described. Using dimethylsulphoxide as the solvent, the cis‐glycol grouping of adenosine 5′‐phosphate is converted to the corresponding dialdehyde when periodic acid is used as the oxidant. Subsequently, the elimination of the phosphoryl residue proceeds instantaneously and quantitatively upon addition of aniline at 45°.
On the Pressure Distribution in Uncharged Membranes During Osmotic Plow
Authors: Banin A. , Low P.F. 
Published: November 2013

AbstractExperiments indicated that adsorptive forces lower the potential energy of water inside uncharged cellulose acetate membranes. As a result it is postulated that the steady‐state pressure distribution during osmosis is affected. In particular, a sudden rise in pressure should occur across the water‐membrane interface. Thus, in this region, water may flow against a pressure gradient.
Steranes and Triterpanes of Israeli Shale
Authors: Ikan R. , Bortinger A. 
Published: November 2013

AbstractSteranes (cholestane, stigmastane) and triterpanes (lupane, gammacerane) were identified in a bitumen obtained from a shale of Nebi Musa, near Jericho, using combined gas‐liquid — mass spectroscopic technique.
Spin Polarization in the Photoexcitation of the Triplet State of Phenazine in a Rigid Glass
Authors: Levanon H. , Weissman S. I. 
Published: November 2013

AbstractPhenazine dissolved in a rigid toluene glass is excited to its triplet state by illumination with a modulated light source. The ESR signal is modulated, the nature of the modulation depending on the kinetics of population and depopulation of the triplet sublevels. Modulation of the ESR signal varies across the spectrum because of the dependence of the kinetics on orientation.
Thermal Isomerization of 1,5‐Dimethyl‐1‐Cyclooctene
Authors: Suga K. , Watanabe S. , Fujita T. , Shimada T. 
Published: November 2013

AbstractIsoprene is selectively dimerized to 1,5‐dimethyl‐1,5‐cyclooctadiene by the catalyst composed of nickel naphthenate, triethylaluminium and tri‐o‐cresylphosphite. At 500° and atmospheric pressure, 1,5‐dimethyl‐1‐cyclooctene thermally isomerizes to 2,6‐dimethyl‐1,7‐octadiene.
Isolation, Properties and Partial Sequence of the Cytochrome C of the Camel, Camelus Dromedarius
Authors: Schejter A. , Grosman Z. , Sokolovsky M. 
Published: November 2013

AbstractCytochrome c was purified from the heart of the camel, Camelus dromedarius. Its chemical properties are typical of eukaryotic cytochrome c. Camel heart cytochrome c consists of a single chain of 104 amino acids, a composition closely related to that of mammalian cytochrome c, and a heme peptide identical to horse cytochrome c. However, its spectrum differs from that of all other cytochrome c in having a 16% lower molar absorbancy of the reduced a band. The possible reason for this difference is discussed.
Penicillin Sensitive Formation of D‐Alanine in a Particulate System from Staphylococcus Aureus
Authors: Oppenheim B. , Burstein Y. , Patchornik A. 
Published: November 2013

AbstractA cell free system from Staphylococcus aureus 52A5 which incorporates UDPMurNAc‐L‐ala‐D‐isoglu‐L‐lys‐D‐ala‐14C‐D‐ala into lipid intermediates and peptidoglycan is described. During peptidoglycan synthesis, glycine binding to the lipid intermediates and peptidoglycan is also demonstrated as well as release of the terminal D‐alanine from the pentapeptide moiety. This release of D‐alanine is strongly inhibited by penicillin G.
A Physicists View of Crystal‐Structure Determination
Authors: Lipson H. 
Published: November 2013

AbstractThe basic operations of crystal‐structure determination are described in terms of optical imaging: the collection of the diffraction data corresponds to the process of scattering by the object, and Fourier synthesis is the production of the image from the scattered radiation. The “phase problem” expresses our inability to devise an apparatus for exploring the relative phases of diffracted X‐ray beams.
On Interpretation of ESCA Spectra with Application to Thymine and Other Molecules
Authors: Rein Robert , Hartman Aba , Nir Shlomo 
Published: November 2013

Abstract1s binding energies are calculated for nitrogen atoms in thymine, pyrrole, adenine, and pyridine and for carbon atoms in thymine, adenine, pyrrole, and furan, and compared with experimental values. Calculations are performed in the framework of a perturbational model using CNDO molecular wave functions. Interactions of the 1s electron with its own atom are calculated exactly whereas interactions with neighbor atoms are calculated according to two levels of approximation: (1) Point charge approximation. (2) Rigorous calculations of integrals. Magnitudes of the different interactions and integrals are analysed. The questions of assignments of ESCA shifts and the errors inherent in the calculations are discussed.
Photoelectron‐Spectroscopic Assignment of Symmetry Species to the Lower Electronic States of Unsaturated Hydrocarbon Radical Cations
Authors: Heilbronner E. 
Published: November 2013

AbstractThe competitive through‐space and through‐bond interaction of two symmetry‐equivalent, semi‐localized orbitals φa, φb, (= π or lone‐pair orbitals) in a molecule M of Cs or higher symmetry can lead either to the natural order of the corresponding delocalized orbitals, i.e., ψ− ≈︁ (φa ‐ φb)/√2 above ψ+ ≈︁ (φa ‐ φb)/√2 or to the inverted order, i.e., ψ+ above ψ−. It is shown that one can discriminate between these two situations through an analysis of the PE spectrum of a molecule M′ which differs from M only by an additional semi‐localized orbital φc of known symmetry behaviour. The method is exemplified by an investigation of the dependence of the n‐orbital sequence in 3,6‐bridged 1,4‐cyclohexadienes on the dihedral angle between the two CCHCHC moieties.
Interatomic Distances in the Bifluoride Ion
Authors: Carrell H. L. , Donohue Jerry 
Published: November 2013

AbstractFurther refinement has been carried out on the neutron diffraction data for potassium bifluoride. Best agreement was obtained for a physically impossible model which must be rejected on other grounds. Following Ibers, the hydrogen atom is assumed to be centrally located. Combination of spectroscopic and diffraction data from sodium, potassium, and ammonium bifluorides allows a detailed analysis of the thermal motions to be made. The average F ···F distance, after correction, is found to be 2.292 ± 0.004 Å.
Structure Studies on 6a‐Thiathiophthenes and Related Compounds
Authors: Hordvik Asbjørn , Saethre Leif J. 
Published: November 2013

AbstractThe results from structure studies on 6a‐thiathiophthenes show that different substituent groups perturb the bonding in the three‐sulphur sequence to different degrees. Both equal and unequal SS bonds occur in symmetrically as well as in unsymmetrically substituted derivatives.The specific effect of methyl and phenyl substituents on the sulphur‐sulphur bonding may be described by the results from CNDO/2 calculations on mono‐methyl and mono‐phenyl substituted 6a‐thiathiophthenes. Molecular packing and intermolecular close contacts also seem to affect the SS bonding.The structures of equally substituted 6a‐thiathiophthene analogues with magnified image and magnified image show, when compared with the equivalent 6a‐thiathiophthene, that magnified image and magnified image cause a pronounced change in the SS bonding, while the perturbation caused by magnified image is negligible.In symmetrical 6a‐thiathiophthene analogues with magnified image and magnified image, the average bond length in the linear three‐atom sequence is 9 – 12% longer than the respective single bond.
Stevensanaloge, Durch Nickelkomplexe Katalysierte Umlagerung Von Triarylphosphoryliden Und Darstellung Sowie Strukturbestimmung Von Phosphorylid‐Nickeltricarbonylkomplexen
Authors: Heydenreich F. , Mollbach A. , Wilke G. , Dreeskamp H. , Hoffmann E. G. , Schroth G. , Seevogel K. , Stempfle W. 
Published: November 2013

AbstractThe Stevens rearrangement of the triarylphosphorusylids R3 P=CHR′ (III) (R′ = H, CH3, C2 H5) to diarylbenzylphosphines (V) is catalyzed by nickel complexes (e.g., (COD)2 Ni (I)). Attempts to prepare trimesitylphosphine‐methylene result in direct formation of dimesityl (mesitylmethyl) phosphine (XII) — the first recorded direct Stevens rearrangement of a phosphorusylid. Phosphorusylids react with nickeltetracarbonyl without rearrangement to give complexes of the type R3P=CHa · Ni(CO)3 (XIV). The structure of XIV has been established by the IR and NMR spectra and confirmed by an X‐ray structural determination.B. L. Barnett and C. Krüger, J. Cryst. Mol. Struct., im Druck.
The ylid is bonded to the nickel through the C‐atom with resulting hybridization from sp2 towards sp3.
A New X‐Ray Method for the Determination of the Quaternary Structure of Protein Complexes
Authors: Hoppe W. 
Published: November 2013

AbstractThe determination of the spatial arrangement of subunits in protein complexes is possible by an application of a new method. After appropriate labelling of the subunits with heavy atoms the distances between the subunits can be found from X‐ray experiments. Theoretical and experimental considerations allow us to deduce these distances and to find the relative positions of the subunits within the protein complex.
Photochemical Behaviour of Cyclopropa[c]Chromenes in Alcohols
Authors: Jackson B. , Hug R. , Hansen H.‐J. , Schmid H. 
Published: November 2013

AbstractCyclopropa[c] chromenes (VI, VII, VIII, IX) on irradiation with a mercury high‐pressure or low‐pressure lamp in alcoholic solutions (MeOH, EtOH, i‐PrOH) are transformed into the corresponding 2‐(1′‐alkoxy‐but‐3′‐enyl)‐phenols (cf. X, XI, trans. and cis‐XII). Possible mechanisms of this photoreaction are discussed.
Spectroscopic Studies of d‐Pilocarpine and Some Quaternary Derivatives
Authors: Ben‐Bassat A. , Lavie D. 
Published: November 2013

AbstractDetailed spectroscopic studies have been carried out on the alkaloid d‐pilocarpine as free base and after quaternization. Characteristic changes in the NMR, IR and UV spectroscopic properties have been established following quaternization. The respective mass spectra have been analysed, and characteristic fragmentation patterns are described. The amidic nature of d‐pilocarpinehydroxamic acid has been confirmed by IR, NMR and mass spectrometric measurement.
Polymeric Conductors and Semiconductors
Authors: Mark H. 
Published: November 2013

AbstractPolymeric conductors up to conductivities of about 102 – 103 ohm cm can be made either by copolymerizing monomers which contain tetracyanoquinolines with monomers which have pronounced salt character or by introducing metal atoms or ions into highly conjugated systems such as polyenes, polyynes or pyropolymers. Both ways are also successful in preparing semiconductors with room temperature conductivities around 10−1 ohm cm and with activation energies of several millivolts.
Fulvenes and Thermochromic Ethylenes. Part 70 Syntheses in the Dibiphenylene‐Ethene (Bifluorenylidene) Series
Authors: Gosnay Ian , Bergmann Ernst D. , Rabinovitz M. , Agranat I. 
Published: November 2013

AbstractIn order to obtain a better insight into the fine‐structure of dibiphenylene‐ethene, the 1,1′‐difluoro‐, 1,1′‐dichloro, 1,1′‐ and 2,2′‐dimethyl derivatives have been prepared using a variety of methods. The attempted preparation of the pure 1,1′‐dibromo‐derivative failed.
Solid‐State Photolysis of Azobis‐3‐Phenyl‐3‐Pentane. Crystal‐Lattice Control of the Stereochemistry of Radical Disproportionation
Authors: Skinner Karen J. , Blaskiewicz Robert J. , Michael McBride J. 
Published: November 2013

AbstractThe 3‐phenyl‐3‐pentyl radicals from photolysis of azobis‐3‐phenyl‐3‐pentane (APP) in solution give 3,4‐diethyl‐3,4‐diphenylhexane and a photolabile product assumed to arise by para coupling. Photolysis of APP as a crystalline solid at −78° gives the disproportionation products 3‐phenylpentane (PPH) and 3‐phenyl‐2‐pentene (PP) as a 3:1 mixture of the E and Z isomers. This stereoisomeric ratio is surprising in terms of the solid‐state molecular conformations, for which a topochemical scheme predicts predominance of the Z isomer. Isotopic distributions in PPH, Z‐PP and E‐PP from photolysis of solid APP which was 82% deuterated in its methylene groups shows: (1) that Z‐PP is formed under strong lattice control; (2) that E‐PP is formed in a process with greater, but not complete, molecular freedom; and (3) that there is often a dynamic competition for hydrogen‐atom donation between the two radicals involved in disproportionation.
Mechanisms of Photochemical Reactions in Solution. LXXIV. The Photochemistry of 3‐Methyl‐1‐Phenoxybut‐2‐Ene.,
Authors: Carroll Felix A. , Hammond George S. 
Published: November 2013

AbstractThe photochemical reactions of 3‐methyl‐1‐phenoxybut‐2‐ene (γ,γ‐dimethylallyl phenyl ether), I, were investigated in solution and in the gas phase. Irradiation of I resulted in the formation of phenol, II, 3‐methyl‐3‐phenoxybutene, III, 1‐(2‐hydroxyphenyl)‐3‐methylbut‐2‐ene, IV, 1‐(4‐hydroxyphenyl)‐3‐methylbut‐2‐ene, V, 3‐(2‐hydroxyphenyl)‐3‐methylbutene, VI, and 3‐(4‐hydroxyphenyl)‐3‐methylbutene, VII. Formation of III ‐ VII in the gas phase was efficiently quenched by nitric oxide. The results suggest that all products were formed by a dissociation ‐ radical recombination mechanism and that none were formed by concerted processes. The absorption spectrum of I and its quantum yields for fluorescence and photochemical reaction were used to estimate the rates of the processes which deactivate its lowest‐lying excited singlet state. The results suggest that OC bond homolysis need not occur via intersystem crossing from an S1 (π, π*) to a 3σ (CO) state. Fragmentation to radicals, and perhaps rapid non‐radiative decay without chemical reaction, probably involve internal conversion with population of high vibrational levels of the CO bond. Weak electronic interaction between the aromatic nucleus and the olefinic chromophore may also be important.
Crystal Structure of Rb2CoCl4 and Rb3Mn2Cl7
Authors: Amit M. , Horowitz (Zodkevitz) A. , Makovsky J. 
Published: November 2013

AbstractPreviously published cell dimensions of Rb3Mn2Cl7 are confirmed and atomic positions are given. The crystal structure of low temperature Rb2CoCl4 is reported. The material was found to belong to the orthorhombic system, space group Pnma with a = 9.272 ± 0.006 Å, b = 7.283 ± 0.004, c = 12.723 ± 0.006 Å and Z = 2.
Studies on the Specificity of the Interaction Between Peptidyl‐tRNA and E. Coli Ribosomes, Initiation and Elongation Factors
Authors: Degroot N. , Panet A. , Lapidot Y. 
Published: November 2013

AbstractSeveral aspects of the binding of peptidyl‐tRNA to E. coli ribosomes were studied. The E. coli binding factor (EF1) does not increase the rate of peptidyl‐tRNA binding. From the results obtained it was concluded that two molecules of Gly2 Phe‐tRNA can bind to one and the same ribosome, but no new peptide bond was formed. Gly, Phe‐tRNA at the A site inhibited the puromycin reaction of Gly2 Phe‐tRNA at the P site of the same ribosome. The binding of peptidyl‐tRNA at the P site activates the adjacent A site for aminoacyl‐tRNA binding.
N,O‐Diarylation of N‐Hydroxycarbamates. Rearrangement and Cleavage Reactions of the Intermediate N,O‐Diarylhydroxylamines
Authors: Sheradsky Tuvia , Salemnick Gad 
Published: November 2013

AbstractThe reactions of benzyl N‐hydroxycarbamate with 2‐ and 4‐nitrofluorobenzene yielded the corresponding benzyl N‐(nitrophenoxy)carbamates. Their reaction with nitrofluorobenzenes yielded derivatives of biphenyl and of diphenyl ether. The formation of these products has been rationalized by assuming the existence of N,O‐diphenylhydroxylamines as intermediates which undergo rearrangement analogous to the benzidine rearrangement.
Synthetic Aspects of Selective Ion Exchangers
Authors: Goldstein S. , Gulko A. , Schmuckler G. 
Published: November 2013

AbstractNew anion exchange resins were prepared by the interaction of sulfonated and chloromethylated crosslinked polystyrene with hexamine, ethylene diamine, and thiourea. The conditions of preparation were based on existing information concerning the analogous monomers and were adapted to the special case of the polymeric matrix.
Raman Study of Mixed Cyanide‐Iodide Complexes of Cadmium in Aqueous Solution
Authors: Yellin N. , Marcus Y. 
Published: November 2013

AbstractThe formation of the mixed iodo‐cyano cadmate (II) complexes at coordination level four in aqueous solutions was examined by Raman spectrophotometry. The existence of the species CdI3CN2− was definitely proven, while the existence of the other species CdI2 (CN)2 2− and CdI(CN)3 2− could not be established.
Thermally Stable Polymers Derived from Itaconic Acid
Authors: Avny Yair , Saghian Nasser , Zilkha Albert 
Published: November 2013

AbstractThermally stable polyamides were prepared by reaction of aromatic diamines with pyrrolidone dicarboxylic acids obtained by reaction of itaconic acid with aromatic diamines. The reaction was carried out either by melt poly‐condensation or by converting the diacids to their active mixed anhydrides and reacting them with the diamines. Polybenzimidazoles were prepared by melt polymerization of the pyrrolidone dicarboxylic acids with 3,3′‐diamino‐benzidine. All the polymers were soluble in concentrated sulfuric acid and part of them were also partially soluble in DMF or DMSO. DTA and TGA measurements in air showed that the polyamides were stable up to about 400° and the polybenzimidazoles were stable to 500°.
Electrochemical Synthesis of Cis‐3, 4‐Dicarbomethoxycyclobutene
Authors: Leftin J. H. , Redpath D. , Pines A. , Gil‐Av E. 
Published: November 2013

AbstractAnodic oxidation of cis, trans, cis‐3, 4‐dicarbomethoxy‐1, 2‐cyclobutanedicarboxylic acid (I) yields 65% of the title compound (II), which on heating isomerizes stereoselectively into the cis, trans‐muconate III.