bluuebunny/crossref_metadata_2025 huggingface dataset:
The Crystal and Molecular Structure of Kinamycin C p‐Bromobenzoate
Authors: Furusaki Akio , Matsui Masanori , Watanabé Tokunosuké , Ōmura Satoshi , Nakagawa Akira , Hata Tōju
Published: November 2013

The molecular structure of kinamycin C has been determined by means of an X‐ray study of its p‐bromobenzoate derivative, C31H23N2O11Br. The crystals are monoclinic, P21, with four molecules of the derivative and four molecules of benzene in a unit cell of dimensions: a = 18.404 ± 0.005, b = 21.299 ± 0.004, c = 9.049 ± 0.001 Å, and β = 90.07 ± 0.03°. Reflection intensities were measured visually from equi‐inclination Weissenberg photographs taken with Cu Ka radiation. The structure was solved by the heavy‐atom method, and was refined by the block‐diagonal‐matrix least‐squares method using anisotropic temperature factors for all the atoms. The final R factor is 8.9%. The stereostructures of the two crystallographically independent molecules are almost identical. The skeleton of the molecule is made up of four fused rings: two of these form a 1,4‐naphthoquinone system and the rest are a pyrrole and a cyclohexene ring. A cyano group is bonded to the nitrogen atom of the pyrrole ring, which is rather unusual in an antibiotic.
The Use of a Gel‐Filtration Procedure to Study the Interaction Between Inorganic Phosphate and Alkaline Phosphatase
Authors: Kaufman H. W. , Kleinberg I.
Published: November 2013

A gel‐filtration procedure has been used to examine the effects of pH, ionic strength, enzyme concentration, and concentration of inorganic orthophosphate (Pi) on the molecular interaction between alkaline phosphatase and Pi. At pH values above the isoelectric point of the enzyme, repulsion was demonstrated; this was reduced under those conditions favouring a reduction in the effective negative charge on either or both enzyme and phosphate molecules. In addition to providing information on the interaction between Pi and enzyme, the study demonstrates that the gel‐filtration procedure can be used to study repulsion between molecules. Earlier it was shown that it could be used to study attraction.
A Possible Step in the Origin of the Genetic Code
Authors: Orgel L. E.
Published: November 2013

It is suggested that the earliest coding polynucleotides contained a high proportion of alternating sequences of purines and pyrimidines, and that these sequences coded for polypeptides in which hydrophobic and hydrophylic amino acids alternated. Structural properties of such alternating polypeptides are discussed.
Internal Addition of Ketocarbenes to Conjugated Double Bonds
Authors: Becker D. , Loewenthal H. J. E.
Published: November 2013

The internal, copper‐catalysed, addition of keto‐carbenes (generated from a diazoketone group) to a double bond conjugated either to a ketone or carboxylic ester function has been found to be a feasible preparative reaction in selected cases. This, together with the facile and regiospecific hydrogenolysis of the resulting 1,2‐dicarbonyl cyclopropane intermediate, appear to constitute a convenient route to multifunctional bridged‐ring systems.
Cyclooctatetraene Tetramer
Authors: Hoesch L. , Dreiding A. S. , Oth J.F.M.
Published: November 2013

The constitution of the cyclooctatetraene tetramer, mp 182° (VI), is derived from its spectroscopic properties and from the results of catalytic hydrogenation experiments. The 1H‐NMR spectrum of VI is temperature dependent and indicates the presence of two homotropylidene residues in the molecule, one isomerizing isodynamically, the other anisodynamically. The mass spectrum of VI shows remarkable similarities with those of the cyclooctatetraene dimer, mp 76° (III) and of bullvalene (IX). The tetramer VI is concluded to be the product of a 2 + 4‐cycloaddition reaction between the cyclohexa‐1,3‐diene units of two molecules of III. The tetramer VI appears to be configurationally unique. This is explained and a configuration is proposed on the basis of the stereospecificity of the reaction leading to VI.
The Crystal and Molecular Structure of 11‐Chloro‐3,8‐Methano‐[11] Annulenone
Authors: Beddoes R. L. , Mills O. S.
Published: November 2013

The crystal structure of a benzhomotropone, 11‐chloro‐3,8‐methano‐[11] annulenone, has been solved and refined to R = 4.5%. The crystals are monoclinic, a = 6.854, b = 7.681, c = 19.324 Å, β = 108.54°, spacegroup P21/c. The molecule exhibits alternation of bond lengths with evidence of slight π‐electron delocalisation. Principal bond lengths are CC(mean) 1.344, CC(mean) 1.442, CCl 1.748 and CO 1.231 Å
Topochemistry Part XXXV. The Formation of Mixed Dimers from Solid Solutions of Trans‐Cinnamic Acids and Trans‐Cinnamides
Authors: Hung J. D. , Lahav M. , Luwisch M. , Schmidt G.M.J.
Published: November 2013

Irradiation (λ >300 nm) of eight two‐component solid solutions of β‐arylacrylamides, prepared by melting and crystallising equimolar quantities of the amides tr‐ArCH:CHCONE where Ar=C6H5, p‐MeOC6H4, p‐ClC6H4, p‐MeC6H4, and 2‐thienyl, which appeared in the α crystal form, gave three photoproducts for each system studied: two α‐truxillic homodimers, derived from the respective monomers, and an α‐truxillic heterodimer. No other isomers were found. Similarly, two‐component solid solutions were prepared by melting and crystallising ring‐substituted cinnamic acids (tr‐ArCH:CHCO2H, where Ar=C6H5 (α‐form), p—ClC6H4(β), p‐MeC6H4(α), p‐MeOC6H4(γ), o‐ClC6H4(β) and o‐CH3C6H4(γ)) and irradiated. A solid solution of two α‐type acids (each photodimerising in the solid to α‐truxillic acid) behaved like the amides, affording two α‐truxillic homodimers and an α‐truxillic heterodimer. A solid solution of an α‐type acid with a β‐type acid (photodimerising to β‐truxinic acids) gave six photoproducts: three α‐truxillic acid dimers and three β‐truxinic acid dimers (i.e., four homodimers and two heterodimers). Irradiation of a solution of a γ‐type acid (non‐photodimerising in the solid state) with an α‐type acid afforded α‐truxillic dimers (two homodimers and one heterodimer). The above results are consistent with mutual miscibility of the two components which gives rise to mixed crystal formation and subsequent photo‐behaviour within each crystal which is characteristic of the particular lattice type. However, irradiation of the mixed crystals from p‐methoxycinnamic acid (γ‐type) and p‐chlorocinnamic acid (β‐type), which afford two α‐truxillic dimers (methoxy‐homodimer and methoxy, chloro‐heterodimer) and two β‐truxinic dimers (chloro‐homodimer and methoxy, chloro‐heterodimer) indicates that new phases, unobserved for the pure compounds, can also be generated. The new dimers were all characterised by the NMR and mass spectra of their dimethyl ester derivatives and, when possible, by conversion to known compounds.
Molecular Packing Modes. Part X. The Crystal and Molecular Structures of Trans, Trans‐Muconic Acid
Authors: Bernstein J. , Leiserowitz L.
Published: November 2013

trans, trans‐Muconic acid C6H6O4 crystallises in the space group magnified image, with a = 8.982, b = 9.895, c = 3.787 Å, α = 103.68, β=75.27, γ= 101.58°, and two centrosymmetric molecules per unit cell. The structure was solved from 1671 reflections measured by an ω/2θ scan with Mo Kα radiation on an IBM 1800 computer‐controlled Siemens diffractometer, and refined anisotropically (on F2) to R = 0.078. The geometries in the carbon chains of the two independent molecules are essentially identical; their bond lengths match to within 0.003 Å. The carboxyl group of one molecule is statistically disordered (C‐O 1.257, 1.275 Å) whereas in the second molecule the bond lengths differ significantly (1.236, 1.294 Å), indicating a greater degree of order. A careful consideration of the packing mode allows us to interpret the difference between the two molecules.
Multichain Polyproline Coated with Histidyl and Glutamyl Residues — A Potent Synthetic Immunogen
Authors: Shaltiel Shmuel , Mozes Edna , Sela Michael
Published: November 2013

A new, water soluble multichain polypeptide coated with short peptides containing histidyl and glutamyl residues was prepared, using the 2,4‐dinitro‐phenyl group for masking the imidazole imino‐nitrogen during synthesis. The polymer obtained after thiolytic deblockage (multi‐poly(L‐histidyl, L‐glutamyl)‐poly‐L‐prolyl – – poly‐L‐lysine) was shown to be a potent synthetic immunogen, capable of provoking a high titer of antibodies in mice already at the primary response, and useful for studying the genetic control of the immune response.
Comments on the Nature of the Oxidized Form of the Nickel Dimethylglyoxime Complex
Authors: Lati J. , Meyerstein D.
Published: November 2013

The pulse radiolytic technique has been used in order to prove that the central nickel atom, in the oxidized form of the nickel‐dimethyl‐glyoxime complex, is in its trivalent oxidation state.
Kinetics of Bromination of Stilbene in Chloroform in the Presence of a Macrocyclic Polyether
Authors: Shchori E. , Jagu‐Grodzinski J.
Published: November 2013

The effect of ethers on the bromination of stilbene in chloroform solutions was investigated spectrophotometrically. In the presence of hydrogen bromide the macrocyclic ether dicyclohexyl‐18‐crown‐6 (DCC) may act as a strong inhibitor, while tetrahydrofuran accelerates the bromination reaction.
The Hydroperoxy Radical in Aqueous Solutions
Authors: Czapski Gideon
Published: November 2013

The different ways to generate the hydroperoxy radical are described. Both chemical and physical properties of the radical are summarized. The features of complexes of HO2with various cations, their fast exchange and their possible role in biological systems is discussed.
The Radiosensitizing Actions of Ketonic Agents and Oxygen in Bacterial Spores Suspended in Aqueous and Non‐Aqueous Milieux
Authors: Tallentire A. , Jones A. B. , Jacobs G. P.
Published: November 2013

Increasing concentrations of the ketonic agents, diacetyl, acetone, acetophenone and p‐nitroacetophenone, cause regular increases in the radiosensitivity of aqueous anoxic spores to an extent that is some 40% of that achieved by O2 alone; no effect on radiosensitivity is observed with agents in the presence of O2. The effectiveness of these agents and O2 as radiosensitizers ranks on a molar basis in the same order as that of their electron affinities, indicating that their modes of action are in some way associated with radiation‐induced electrons. A lack of radiosensitizing action of diacetyl and p‐nitroacetophenone in dried spores and of p‐nitroacetophenone in suspensions of spores in non‐aqueous liquids supports the notion that the origin of their actions is within the water inside the cell.
Electrical Mobility of Counterions in Polyelectrolyte Solutions
Authors: Shavit Nehemia
Published: November 2013

Electrical mobilities of counterions in aqueous solutions of potassium polyacrylate, potassium polymethacrylate and sodium polymethacrylate were investigated by moving boundary electrophoresis. At constant polymer concentration, the mobility of counterions decreases with an increase in the degree of neutralization. At a constant degree of neutralization, the mobility increases with an increase in the concentration of the polyelectrolyte. The mobilities of the polyion were derived from the counterion mobility and conductance. The fraction of bound ions increases with the degree of neutralization and reaches a value of about 60%. Osmotic coefficients were evaluated from the mobility data and compared with the values derived from osmotic measurements.
Biopolymer — Small Molecule Interactions. Optical Properties of the System Biliverdin‐Serum Albumin in Aqueous Medium
Authors: Blauer G. , Zvilichovsky B.
Published: November 2013

Circular dichroism (CD) and light‐absorption measurements in the wavelength range 300 to 650 nm were carried out for complexes of biliverdin (∼ 2.5 × 10−5 M) with either bovine or human serum albumin (charcoal treated) in aqueous solution (25–27°C) at several protein concentrations and pH values in the range 4 to 10. In all cases investigated, two large ellipticity bands were measured near 385 nm and about 650 nm, respectively, which were of opposite sign. In addition, two smaller bands near 300 and 535 nm were resolved by computer analysis into Gaussian curves of the CD spectrum of biliverdin‐human serum albumin complexes. The main CD bands were inverted in their sign in biliverdin‐bovine serum albumin complexes when compared at pH 5 and 10. Under the conditions used, free biliverdin did not show significant optical activity. The optical activity observed for the complexes is attributed to electric transition dipole coupling of biliverdin with protein transitions and to possible formation of skewed conformations of the biliverdin chromophore upon binding, leading to inherent dissymmetry. Unlike the corresponding bilirubin complexes investigated previously, there appears to be no evidence for substantial band splitting in the small molecule occurring upon binding to the biopolymer. Thus the presence of a center methene bridge instead of an isolating methylene group, the latter allowing internal rotation in the bile pigment, appears largely to determine the mechanism of generation of optical activity. In the case of bilirubin and at excess serum albumin, the observed optical activity is considered to be due mainly to exciton coupling between electric transition dipole moments of the dipyrromethene chromophores within the asymmetrically bound bilirubin. The optical properties investigated may serve as a very sensitive measure of the different types of interaction between the biopolymer and the small conjugated molecule which result from structural and conformational differences of the molecules participating in complex formation.
Polymeric Salicylic Acid Derivatives
Authors: Weiner Ben‐Zion , Zilkha Albert
Published: November 2013

The O‐methacryloyl derivatives of methyl, ethyl and phenyl salicylate, of salicylamide and of salicyl hydrazide were prepared by the reaction of the respective compounds with methacryloyl chloride and were polymerized by heating with azobisisobutyronitrile. Preliminary evaluation of the monomeric and the polymeric compounds for analgetic activity showed that part of the compounds had a longer duration of activity than aspirin.
Synthesis of N‐Alkyl‐α‐Sulfo‐β‐Alanines
Authors: Levi Shalom , Gertner David , Zilkha Albert
Published: November 2013

A number of N‐alkyl substituted α‐sulfo‐β‐alanines were synthesized by direct sulfonation of the corresponding N‐alkyl‐β‐alanines.
Kinetics and Equilibria in the System Pyrophosphate‐Nickel (II). Evidence for Two Parallel Reaction Paths; Influence of Ionic Strength on the Ion Pair Constant
Authors: Perlmutter‐Hayman Berta , Secco F.
Published: November 2013

The kinetics of the reaction between Ni2+ and pyrophosphate have been investigated over a wider range of conditions than previously. At 25°, a variation of the ionic strength between 0.02 and 0.20 M (achieved by adding potassium nitrate at appropriate concentrations) showed that the salt effect, though acting on the formation constant of an ion pair rather than on the rate constant of the rate‐determining step, is essentially “classical”. By varying the pH between 4.5 and 7.0, at least two parallel reaction paths were observed, involving Ni2+ and the ions HP2O3−7 and H2P2O2−7. The latter path has a rate constant that is ∼28 times smaller than that of the former and makes an appreciable contribution to the observed rate only at the two lowest pH values. Possible reasons for this difference in reactivity are discussed. The rate constant for the path involving HP2O3−7 was 1.61 × 106M−1 s−1 at 25°, I = 0.1 M. The activation parameters for this path are ΔH≠ = 18.8 Kcal mole−1 and ΔS≠ = 33 e.u. All kinetic experiments were carried out by the T‐jump method. The equilibrium constants necessary for the evaluation of the results were determined by potentiometric titration.
Physical Properties of Alumina Prepared from Machtesh Ramon Ores
Authors: Wolberg A. , Eger I.
Published: November 2013

High purity alumina is prepared from local ores, containing about 35% alumina, and from low‐grade, 20%, HCl solution. Iron impurities are removed by solvent extraction, and upon pyrolysis, high grade 60% HCl gas is collected. The amorphous alumina obtained at 350°C is transformed to “transition alumina” at 600°C with an increase in surface area; subsequently at 1000–1100°C, high purity crystalline corundum is obtained. The transition‐ and amorphous alumina seem to have promising qualities for desiccant and catalytic use.
Preparation and Crystal Structures of Some Compounds of the A3 BX5 Type (A = Cs, Tl, NH4, B = Mn, Fe, Co, X = Cl, Br)
Authors: Amit M. , Horowitz (Zodkevitz) A. , Ron E. , Makovsky J.
Published: November 2013

The compounds Cs3 FeBr5, Cs3MnBr5,Tl3FeCl5, Tl3CoCl5, (NH4)3FeCl5 and (NH4)3CoCl5 were prepared and their crystal structures determined. Cs3FeBr5, Cs3MnBr5, Tl3FeCl5 and Tl3CoCl5 belong to the tetragonal system, space group 14/mcm, isostructural with Cs3CoCl5 [1]. (NH4)3FeCl5 and (NH4)3CoCl5 belong to the orthorhombic system, space group Pnma, isostructural with (NH4)3ZnCl5 [2].
Unsymmetrical Azoalkanes I. Thermal Decomposition of 1‐Cyano‐1′‐Methoxy‐Azo‐Iso‐Propane
Authors: Malament Donald S.
Published: November 2013

The thermal decomposition of 1‐cyano‐1′‐methoxy‐azo‐iso‐propane (CMA) in decalin, N,N‐dimethylaniline (NNDA) dimethylformamide (DMF), ethylene glycol (EG), and benzonitrile (PhCN) was studied at 54.7° to 69.7°C. A rate enhancement of about four is noted in going from decalin to ethylene glycol, which is the largest solvent effect noted for azoalkane decomposition. This is also the first example of a thermolysis of an azoalkane of type R‐N;NR′ being faster than either of its symmetrical analogs, RNNR or R′NNR′.
Stability of Side‐Chain Protecting Groups in Solid‐Phase Peptide Synthesis
Authors: Erickson Bruce W. , Merrifield R. B.
Published: November 2013

The relative first‐order rates of deprotection of N∈‐benzyloxycarbonyllysine in 2%, 10%, and 50% trifluoroacetic acid in dichloromethane at 20° are 1, 50, and 1000, respectively. The N∈‐2‐chlorobenzyloxycarbonyl group is at least 60 times more stable than the N∈‐benzyloxycarbonyl group under solid‐phase conditions, because no branched peptides (< 0.2 mole%) were formed during synthesis of decalysylvaline using Nα‐tert‐butyloxycarbonyl‐N∈‐2‐chlorobenzyloxycarbonyllysine. Since O‐2‐chlorobenzylserine, Nim‐tosylhistidine, Nim‐2,4‐dinitrophenylhistidine and S‐4‐methylbenzylcysteine were completely stable in 50% trifluoroacetic acid–dichloromethane for over 200 h, these side‐chain protecting groups should be suitable for the solid‐phase synthesis of large peptides.
Conformational Properties of Histidine Related Polymers
Authors: Scoffone E. , Peggion E.
Published: November 2013

In briefly reviewing the results of conformational studies on histidine‐related polymers, two main problems appear to be unsolved at the present time, namely, the conformations to be assigned to poly‐(1‐benzyl)‐L‐histidine · HClO4 in trifluoroethanol and to charge‐free poly‐L‐histidine (PLH) in water. In both cases the right‐handed α‐helical form must be ruled out. The optical rotatory properties are of little help in solving the problem unambiguosly, because of the complication of the side‐chain chromophores. By slow neutralization of PLH hydrochloride solutions, solid samples could be obtained in which the polymer molecules should have the same conformation as in solution. Similarly, slow addition of HClO4 to a concentrated solution of poly‐(1‐benzyl)‐L‐histidine (PBLH) causes precipitation of PBLH · HClO4 in which the same conformation as in solution should be maintained. X‐ray diffraction studies on polymer samples obtained in such a way should provide more information for the conformation of PBLH · HClO4 and of deprotonated PLH in water.
p‐Azido‐L‐Phenylalanine Peptides. I: Synthesis of Peptide Ligands for Chymotrypsin and Aminopeptidases
Authors: Escher Emanuel , Jost Rolf , Zuber Herbert , Schwyzer Robert
Published: November 2013

p‐Azido‐L‐phenylalanine peptides as ligands for α‐chymotrypsin and aminopeptidases were synthesized in two ways: (i) by direct incorporation of f‐butoxycarbonyl‐p‐azido‐L‐phenylalanine or its active esters, or (ii) by conversion of the nitro groups of the corresponding p‐nitrophenylalanine‐containing peptides into azido functions. Both procedures yielded O‐t‐butylthreonyl‐p‐azidophenylalanylproline (L, L, L) which, like its parent tripeptide O‐t‐butylthreonyl‐phenylalanylproline (L, L, L), acted as a competitive inhibitor for leucine aminopeptidase (Ki ≈ 7 to 8 × 10−6 M). The two peptides p‐azidophenylalanylphenylalanine (L, L) and p‐azido‐phenylalanylphenylalanylproline (L, L, L) proved to be substrates for leucine aminopeptidase and for both aminopeptidases I and II from Bacillus stearothermophilus. Acetyl‐p‐azidophenylalanine ethyl ester (L) is a substrate of α‐chymotrypsin with Km ≈ 6 × 10−4 M, closely resembling that of N‐acetyltyrosine ethyl ester (L), Km ≈ 5.4 × 10−4 M, but with an approximately 100‐fold reduced maximum velocity of hydrolysis (Vm ≈ 1.3 s−1 versus 211 s−1). The results obtained with photo‐affinity labelling will be described in a forthcoming paper.
Structure and Substrate Specificity in the Serine Enzymes
Authors: Blow D. M.
Published: November 2013

Available data on the primary and secondary specificities of chymotrypsin, trypsin, elastase and subtilisin are reviewed in relation to their structures. For chymotrypsin and trypsin, proper binding in the main specificity pocket S1 is sufficient to ensure almost perfect orientation of the substrate for hydrolysis. For these enzymes further binding at S2 and S3 increases the binding energy slightly but has little effect on kcat. For subtilisin and elastase, binding at S2–S4 is important to maintain the correct orientation of the hydrolyzed bond. The mechanism proposed for subtilisin, whereby movements of 1 Å at P′1 stabilize the transition state of the reaction, seems unlikely to occur in chymotrypsin. For all these enzymes, proper orientation of the leaving group at S1 can have a further significant effect on kcat. Slight differences between the secondary specificities of trypsin and chymotrypsin are likely, owing to the presence of tyrosine at residue 151 and the deletion of residue 218 in trypsin.
Binding of d‐Amino Acid Residues to the Aromatic Binding Sites of α‐Chymotrypsin, Subtilisin Novo and Subtilisin Carlsberg
Authors: Bosshard Hans Rudolf
Published: November 2013

Inhibition of CT†, S. Novo and S. Carlsberg by peptides (virtual substrates) of the structure Z‐L‐Ala‐L‐Ala‐L(or D)P1‡ and Ac‐L(or D)‐P1 has been studied. P1 stands for a variety of amino acids. Standard free energies of binding, ΔF°, were determined from inhibition experiments with ester substrates. The differences between standard free energies of binding of configurational isomers to CT are similar (ΔΔF° = −0.5 to −0.8 kcal/mole) regardless of the structure of the side chain of P1. Binding of both isomers is governed by the same pKa, 7.3. These findings are interpreted as follows: LLD tripeptides as compared to LLL tripeptides differ in the interaction of the carboxyl group and the Ca‐proton of P1 with subsite S1 of CT. Acetyl‐D‐amino acids as compared to the L‐enantiomers differ in the positioning of the carboxyl and the acetyl group on the enzyme. All inhibitors preserve the hydrophobic S1‐P1 interaction irrespective of the configuration of P1. In contrast, ΔΔF°‐values for inhibitor binding to S. Novo and S. Carlsberg scatter between −0.2 and −1.6 kcal/mole indicating grossly different, and probably multiple binding modes for the individual inhibitors. The impact of the latter finding on the mapping technique is discussed.
Comparative Studies of the Active Site Region of Lysozymes from Eleven Different Sources
Authors: Sharon Nathan , Eshdat Yuval , Maoz Ilana , Bernstein Yael , Prager Ellen M. , Wilson Allan C.
Published: November 2013

Lysozymes from 11 different sources were examined for their ability to react with the affinity label 2′,3′‐epoxypropyl β‐glycoside of di‐(N‐acetyl‐D‐glucosamine) and in some cases with the corresponding derivative of tri‐(N‐acetyl‐D‐glucosamine). Their fluorescence spectra, in the presence or absence of tri‐(N‐acetyl‐D‐glucosamine), and their transglycosylase activity were also examined. The results obtained suggest that these lysozymes can be classified into two groups: Group I includes the lysozymes derived from the egg‐whites of bobwhite quail, chachalaca, duck, hen, Japanese quail, ring‐necked pheasant and turkey, and from human leukemic urine; Group II includes the lysozymes from bacteriophage T4, goose egg‐white and papaya latex. The lysozymes of group I are irreversibly inactivated by the epoxypropyl β‐glycosides and exhibit similar fluorescence spectra which shift to the blue upon the addition of tri‐(N‐acetyl‐D‐glucosamine). Moreover, they catalyse the transfer of disaccharide residues from the bacterial cell wall tetra saccharide to N‐acetyl‐D‐glucosamine, D‐glucose, D‐mannose and L‐fucose, at rates which are similar for the different enzymes. It is concluded that the active sites of the enzymes of Group I are all similar, and that they differ from those of the other three lysozymes.
The Thermal Effects of Nucleation and Crystallization of KBr and KCl Solutions. II. The Heat Of Nucleation and the Supersaturated Solution
Authors: Glasner Abraham , Tassa Menachem
Published: November 2013

It is shown that the induction period commonly observed in the crystallization of salts from aqueous solutions is due to a heterogeneous nucleation process made apparent by the release of heat. The metastable supersaturated solution is therefore a solution of particles, and the supersaturation limit can be extended by the addition of a good nucleator. In the case of KBr and KCl the halogenoplumbate complex ions are good nucleators. The heat evolved during the nucleation process is proportional to the concentration of the lead ions and the supersaturation limit is a kinetic function of the concentration of the lead ions. The size of the fine particles that can be held in a supersaturated solution and σ, “the crystal‐liquid surface tension”, were determined by the use of the Ostwald‐Freundlich equation. The thermal effects can thus be quantitatively accounted for.
The Redox Potential of the O2–O−2 System in Aqueous Media
Authors: Ilan Yael A. , Meisel Dan , Czapski Gidon
Published: November 2013

O−2 radicals were formed in the presence of 2,5‐ dimethyl benzoquinone (DMBQ). The equilibrium constant of the electron transfer reaction DMBQ + O−2 ⇌ DMBQ− + O2 was determined. From this value and from E0(DMBQ/DMBQ−) we calculated the redox potential of the couple O2/O−2, as E0 (O2/O−2) = −0.33 V.
Solvolysis of 1‐p‐Methoxyphenyl‐2‐Methylpropen‐1‐Yl Trifluoroacetate and 3,5‐Dinitrobenzoate
Authors: Rappoport Zvi , Kaspi Joseph
Published: November 2013

The reactions of 1‐p‐methoxyphenyl‐2‐methylpropen‐1‐yl trifluoroacetate (I–OCOCF3) and 3,5‐dinitrobenzoate (I–ODNB) in AcOH/NaOAc or with amines in 2,2,2‐trifluoroethanol (TFE) were investigated. In TFE, I–ODNB gives trifluoroethyl 3,5‐dinitrobenzoate (II) and the ketone AnCOCHMe2 (III) in a second order reaction with five amines and with CF3 CH2 ONa, and I–OCOCF3 gives a second order reaction with 2,6‐lutidine. In AcOH/NaOAc, I–OCOCF3 gives the corresponding acetate I–OAc, and I–ODNB gives I–OAc and III. The kAcOH/kAcOD values are 5.5–6.2 for I–OCOCF, and 1.03 ± 0.05 for I–ODNB. It is suggested that the rate determining step in TFE is the attack of CF3 CH2O− (formed from the amine and TFE) on the carbonyl of the ester group in a BAC2 mechanism. In AcOH, an electrophilic addition‐elimination mechanism (AdE–E) for the reaction of I–OCOCF3 is supported by the solvent isotope effect. The solvent isotope effect and the products from I–ODNB in AcOH are consistent with an SN1 mechanism, but since the kCl/kODNB ratio is lower than that in saturated systems, an AAC2 mechanism cannot be unequivocally excluded. The effect of the leaving group in the vinylic SN1 reaction is discussed.
A Thermostat with Short‐ and Long‐Term Stability of ± 1.5×10−4°C
Authors: Priel Z. , Silberberg A.
Published: November 2013

The design of a thermostat which gives a temperature stability of ± 1.5 × 10−4°C over a period of weeks is described. The temperature sensors are thermistors stabilized by heat treatment. Heat input derives mainly from stirring and heat output mainly from losses to the surroundings. Residual heat input is removed by stabilized circulating thermostats. Temperature balance is due to spread out bare wire heaters which carry a current proportional to the state of the control DC Wheatstone bridge. The controlling thermistors are maintained in two oil baths and the state of the current in the control heaters is transmitted to the thermistors by a thermal feedback system involving small heating coils which are placed in the oil baths around the thermistors and which carry a current proportional to the heating current.
Kinetic Study of the Photoexcited Triplet State of Free Base Porphyrins by EPR
Authors: Scherz A. , Orbach N. , Levanon H.
Published: November 2013

An electron paramagnetic resonance (EPR) study of the photoexcited triplet state of four free base porphyrins is presented. The zero field splitting parameters (ZFS) |D| and |E| were calculated from the EPR spectra of the porphyrins dissolved in n‐octane matrices at 80°K. |D| = 0.0359 cm−1, |E| = 0.0079 cm−1 for tetra phenyl porphyrin (H2 TPP), |D| = 0.0432 cm−1, |E| = 0.0037 cm−1 for tetra (per‐fluoro) phenyl porphyrin H2T (per‐F) PP, |D| = 0.0366 cm−1, |E| = 0.0078 cm−1 for tetra (para‐chloro) phenyl porphyrin H2T(P‐Cl)PP, |D| = 0.0369 cm−1, |E| = 0.0076 cm−1 for tetra (para‐methyl) phenyl porphyrin H2T(P‐Me)PP. The transient behavior of the EPR signal intensities in the last two porphyrins is discussed. The depopulation rate constants of the triplet sublevels kp, the ratio between the population rate constants Ap (at zero field, p = x,y,z), and the spin lattice relaxation rate W within the triplet manifold, were calculated.

kx = (12 ± 2) × 102 sec−1, ky = (0.5 ± 0.1) × 102 sec−1, kz = (1.2 ± 0.4) × 102 sec−1, Ax:Ay:Az ≃ 0.63:0.01:0.33, W = (0.4 ± 0.1) × 104 sec−1 for H2T(P‐Cl)PP, kx = (7 ± 2) × 102 sec−1, ky = (4 ± 1) × 102 sec−1, kz = (1.5 ± 0.5) × 102 sec−1, Ax:Ay:Az ≃ 0.56:0.31:0.13, W = (1.7 ± 0.4) × 103 sec−1 for H2T(P‐Me)PP.
Modification of the Redox‐Properties of Tetraphenylporphyrin‐Complexes by Bases in Methylene‐Chloride Solution. The Equilibrium of Different Oxidation‐States with Added Base as Measured by Cyclic Voltammetry
Authors: Manassen J.
Published: November 2013

The oxidation half‐wave potentials of Co2+ tetraphenylporphyrin, measured by cyclic voltammetry in methylenechloride solution, are changed by the addition of weak bases like methanol, acetone and dimethylformamide. The wave corresponding to the metal‐oxidation Co2+ ⇄ Co3+ is shifted to lower potential, while the wave, corresponding to the ligand oxidation Co3+(TPP) ⇄ Co3+(TPP)+. is shifted to higher potential. It can be shown, that this is due to a preferential interaction of Co3+(TPP) with the bases, which is stronger than that of the Co2+(TPP) as well as that of the Co3+(TPP)+. Because the shifts are proportional to the concentration of added base, they can be followed quantitatively and the equilibrium constants of the interactions between the different oxidation states and the bases can be calculated. The reduction wave of Co2+(TPP), corresponding to the Co3+ ⇄ Co1+ transition is not changed by the weak bases, but is shifted to lower potential by pyridine and the picolines. The shift is again proportional to the concentration of added base. The reduction wave of Fe3−(TPP)Cl− is not changed by the weak bases, but is shifted to lower potential by pyridine. While the reduction wave of the free Fe3+(TPP)Cl− is irreversible, that of the pyridine‐adduct is reversible. In this case the shift is not proportional to the amount of added base. The voltammetric curves of the Cu, Ni, and Zn tetraphenyl‐porphyrins are not changed by the addition of either the weak or the strong bases.
1‐Phenylcycloalkylamine Derivatives. III
Authors: Kalir A. , Sadeh Shoshana , Karoly Hava , Shirin E. , Balderman D. , Edery H. , Porath Gila
Published: November 2013

A series of phencyclidine analogs has been prepared and subjected to pharmacological screening. None of them surpassed the activity of phencyclidine. It was found that trifluoroacetic acid as a solvent favorably influenced the yield of the Ritter reaction.
Nephelometric Measurements by Use of a Spectrofluorometer. Part II
Authors: Gonen L. , Cogan E.
Published: November 2013

In a previous paper the principle of nephelometric measurement using a spectrofluorometer was described. The method has now been extended and applied for the microdetermination of: (1) Chloride in acid and salt solutions, in clays after acid decomposition, in organic solvents containing hydrocarbons and amines and organic chlorides after combustion; (2) Potassium in acid and salt solutions; (3) Barium in acid and salt solutions; and (4) Sulphate in organic solvents containing hydrocarbons and amines. The method is simple and highly sensitive.
Closing the Bromide Cycle in Magnesium Chloride Thermal Hydrolysis Plants
Authors: Zisner Tuvia
Published: November 2013

A new process is usually tested in the laboratory and pilot plant after being stripped of most of the ancillary equipment associated with it in the full‐scale plant. When such conventional secondary equipment is then coupled to a well‐investigated new process in order to economize on energy consumption, the two may interact to modify the chemistry of the original process. As an example, we demonstrate the creation of a “closed bromide loop” when a fuel‐saving preconcentrator is attached to a MgCl2 to HCl convertor.
Arylmercury Compounds. Part VI. Asymmetric Diarylmercury Compounds
Authors: Halpern Yuval , Garti Nissim
Published: November 2013

Asymmetric diarylmercury compounds were produced together with symmetric products via a symmetrization process. The asymmetric products could not be isolated from the reaction mixture and their existence was indicated through different analyses (mp, IR, PMR, mass spectra, elemental analysis and DTA). The asymmetric products were shown to be unstable and to disproportionate into two symmetric compounds at elevated temperatures, and in organic solvents even at room temperature.
Polymerization of Nitriles by Organotin Catalysts
Authors: Minke Ram , Freireich Shaul , Zilkha Albert
Published: November 2013

The polymerization of the nitrile groups of polyacrylonitrile, polymethacrylonitrile and poly‐α‐cyanoethyl acrylate by organotin compounds was studied. The reaction, which was accompanied by color formation, was found to depend on the concentration and nature of the initiator, temperature, solvent and time of reaction. In the series Pb, Sn and Si, the organometallic derivatives of the former showed the strongest catalyst activity. A series of di‐ and higher nitriles, including benzal malononitrile, 1,1,3,3‐tetracyanopropane, α‐(2‐cyanoethyl) acrylonitrile and Diels Alder adduct of tetracyanoethylene with anthracene, was also polymerized to dark colored polymers. The mechanism of the polymerization is thought to consist of the addition of the organotin compound to the nitrile groups followed by cyclization leading to the formation of conjugated C=N double bonds. Evidence for this mechanism was obtained from the reaction of model compounds, such as 1,3‐dicyanobutane‐1‐carboxylic acid ester, with tributyltin methoxide.
Reactions of Ring C in Glycyrrhetic Acid Derivatives
Authors: Rozen Sh. , Shahak I. , Bergmann E. D.
Published: November 2013

The chemistry of the relatively unreactive glycyrrhetic acid (1) ring C was investigated. The enone group in this ring was reduced by diborane to allylic alcohols (6, 7), which can be readily converted into the corresponding homoannular dienes (2, 5). These dienes were also prepared by NaBH4 reduction of the enone group. The epoxidation of the diene 2 leads to the mono‐(12) and di‐(14) epoxides. A new ring C enone system (13) was also obtained. Treatment of the two different tosylhydrazones derivatives (16, 20) with methyllithium gave the conjugated methylene compounds (17, 21). The NMR spectrum of the latter compound was also studied with a shift reagent — Eu(FOD). The mass spectra of the homoannular dienes (2, 5), allylic alcohols (6, 7) and 11‐methylene compounds (17, 21) were studied and some new types of fragmentation were suggested.
From Quantum Chemistry to Quantum Biochemistry
Authors: Pullman Bernard
Published: November 2013

Three periods may be discerned in the development of quantum biochemistry. In the first, simple Hückel theory was applied to conjugated units of biochemical interest. Despite the simplicity of the method, careful analysis has allowed the interpretation of a considerable number of experimental facts, and also a number of predictions. The second stage is linked to the development of all‐valence‐electron and all‐electron theories and techniques. Now the electronic structure of saturated and partially saturated – biomolecules could be investigated, as well as the large field of conformational problems. The third, and present, period is concerned with the study of environmental effects, in particular solvent effects, on molecular structure and properties. Efforts in this field are developing along two lines: one is the “traditional” continuum model which attempts to account for the bulk effect of the medium; the second employs a model that combines the interacting entities as a “supermolecule”. The “dipeptide” protein model, the backbone of nucleic acids, the polar heads of phospholipids, have been subjected to an analysis of the second type. As for proteins, a conclusion of conceptual significance could be arrived at, namely, that the “protein effect” does not create “extraordinary” conformations. In other words sites of attack on biomolecules can be determined through evaluation of molecular electrostatic potentials.
Molecular Structure Information From X‐Ray Photoelectron Spectroscopy
Authors: Shirley David A.
Published: November 2013

A discussion is given of the types of molecular structure information available from X‐ray photoelectron spectroscopy. A complete set of atomic charges in a molecule can be deduced from core‐level binding energy shifts. Atomic‐orbital composition of molecular orbitals is derived from relative intensities. Correlation peaks yield information about electron correlation. Relaxation energies are related to basicity for certain functional groups.
Chemical Basis of Memory: Approaches Using Molar and Smaller Systems
Authors: Barondes Samuel H.
Published: November 2013

Contemporary assumptions about memory storage in the nervous system are that: (1) it is the expression of a change in the efficacy of synaptic transmission in specific pathways in the central nervous system that mediate the behavior that is remembered; (2) this change is the expression of a biochemical change in the neurons in question. The purpose of this brief paper is to: (1) define the nature of the problems of memory storage in more specific terms based on our knowledge of synaptic transmission and general biochemical regulatory processes; (2) describe two approaches to this problem that will ultimately contribute to its understanding in biochemical terms: (a) a molar approach in which the assay of memory is the behavior of an organism and in which certain types of biochemical and pharmacological studies can point to underlying biochemical mechanisms; (b) an approach using smaller systems in which direct physiological, pharmacological and biochemical measurements can be made of the factors regulating changes in the efficacy of synaptic transmission as a function of repetitive stimulation of a specific synapse.
Is There a Chemical Memory Trace?
Authors: Ungar G.
Published: November 2013

The existence of chemical changes in the brain correlated with acquisition and storage of information, and impairment of learning by inhibitors of RNA and protein synthesis suggest that chemical processes are involved in long‐term memory. The main controversy is over the significance of these processes: whether they are merely concerned with increased metabolic needs or represent a molecular code in which neural information would be processed and preserved. The molecular coding hypothesis can neither be proved nor disproved by a purely chemical approach; additional means are necessary for revealing the presence of minute amounts of specific substances. One of these means is the behavioral bioassay which, in the last ten years, has guided the detection of eight learning‐induced substances, all peptides, in the brain. Two of them (scotophobin, ameletin) have been fully identified and synthesized; they can now be determined and studied by chemical methods. Three other peptides have been purified and their structure is being elucidated. Although good correlation has been found between scotophobin and dark avoidance, specificity of each peptide for a given learned behavior requires further study. The nature of the hypothetical coding system is unknown but it operates probably within the framework of neural circuits: it could create new synaptic junctions, mark them and guide the flow of nerve impulses along the new channels induced by learning. This reprogramming may be based on the chemical recognition system that is believed to direct the formation of the genetically programmed pathways.
Dewatering of Dead Sea Brine by Osmosis
Authors: Loeb Sidney , Weintraub Melvin , van Hezel Johanna
Published: November 2013

The first stage in the production of potash from the Dead Sea involves removal of water from Dead Sea Brine by solar evaporation. The pond function can be supplemented by osmosis, utilizing as a dewatering agent End Brine, a high osmotic pressure solution, available in large quantities as a waste stream from the solar evaporation process. For this osmosis service, asymmetric membranes, i.e. those possessing a dense skin surmounting a porous substructure, were examined. These were tubular membranes 16 mm in diameter. The membranes were of cellulose acetate, fabricated by the Loeb‐Sourirajan technique. The principle objective was to obtain a water permeation flux (permeation rate per unit area) sufficiently high for economic operation. Parameters examined included (1) casting solution composition; (2) temperature to which the membrane was heated in the casting process; (3) circulating brine flow characteristics; (4) effect of using diluted End Brine; (5) influence of reinforcing sleeve; (6) total membrane thickness. Of these parameters the last was found to be most important. At 70 microns, the minimum practical thickness, the flux was still too low. The experimental results were supported by a transport analysis of osmotic flow through an asymmetric membrane. This analysis indicated that any asymmetric membrane of the same thickness, regardless of its chemical composition would also have such low flux because flux is limited by the necessary back diffusion rate of dissolved salt in the porous substructure and by the high salt concentrations within it.
New Techniques in Solvent Extraction and in ION‐Exchange
Authors: Baniel A.
Published: November 2013

Separations and reactions achieved through redistribution between a stationary phase and a liquid phase or between two liquid phases pertain to the disciplines of “ion‐exchange” and “solvent extraction” and also to various membrane separations as well as chromatographic techniques involving a stationary phase and a moving liquid phase. A unified view of all techniques and disciplines involved is presented and operationally applicable definitions of ion‐exchange and of solvent extraction proposed. Likely and possible innovations are discussed, in particular: (a) new types of solvent systems with special reference to systems that respond strongly to imposed composition parameters and to temperature changes; (b) solid ion‐exchangers structured on the molecular level so as to separate ion‐exchange from solvent or membrane functions; (c) liquid‐phase to liquid‐phase transfer with the interposition of membranes between the phases.
Hydroboration. 44. Diisopinocampheylborane of High Optical Purity. Asymmetric Synthesis via Hydroboration with Essentially Complete Asymmetric Induction
Authors: Brown Herbert C. , Yoon Nung Min
Published: November 2013

The reaction of borane with α‐pinene in tetrahydrofuran attains equilibrium in 3 days at 0°. With 15% excess (+)‐α‐pinene ([α]D26.5 + 47.99°), the formation of diisopinocampheylborane is essentially quantitative (‐99.5%). The longer reaction time is accompanied by a selective incorporation of the major isomer into the reagent. Thus, (+)‐α‐pinene, dehydroborated from diisopinocampheylborane with triethylamine, exhibits an optical rotation of [α]D23.5 + 51.0°, indicating an optical purity of 99.8%, and the isopinocampheol, obtained following the oxidation of the reagent, showed [α]D23 −35.1° (c 10, benzene), a higher rotation than any realized previously. The hydroboration of cis‐2‐butene with this diisopinocampheylborane in tetrahydrofuran at −25° provided 2‐butanol of high optical purity, [α]D22.5 −13.29°, an optical purity of 98.4%. Thus this reaction proceeds with nearly complete asymmetric induction.
Polarized Electrons and the Origin of Optical Activity
Authors: Bonner William A. , van Dort Mark A. , Yearian Mason R. , Zeman Herbert D. , Li Gloria C.
Published: November 2013

The history of experiments bearing on the origin of optical activity in nature by parity non‐conservation during the β‐decay of radioactive isotopes is briefly reviewed. Following this, we present a more detailed description of our recent published and unpublished data and calculations regarding the generation of optical activity in DL‐leucine by means of artificially produced longitudinally polarized electrons from a linear accelerator.
Transition Metal Carbyne Complexes, XXIX. Metal Carbon Triple Bonds: X‐Ray Studies on Group VIa Metal Carbyne Complexes
Authors: Huttner G. , Frank A. , Fischer E. O.
Published: November 2013

Structural results of X‐ray investigations on group VIa metal carbyne complexes are described and the influences of different substituents on the metal carbon triple bond are discussed. From the M‐Ccarbyne distances metal triple bond radii are derived.
The Elplacarnet Tree: A Complement to the Periodic Table for the Organometallic Chemist
Authors: King R. B.
Published: November 2013

Only a limited number of the many possible networks of planar sp2 carbon atoms are sufficiently compact to bond entirely to a single transition metal atom as perhapto ligands. These networks, which are conveniently called elplacarnets, correspond to the vertices of a tree. The edges of this elplacarnet tree correspond to four different types of growth processes which occur at vertices of degree 1, at vertices of degree 2, in rings, and across an edge connecting two vertices of degree 1. For the middle transition metals (e.g. chromium through cobalt) the elplacarnet tree contains 13 vertices and 12 edges. Some applications of the elplacarnet tree in understanding the extensive varieties of structures of transition metal organometallic complexes containing unsaturated hydrocarbon ligands are summarized.
Photonitrosylation of Carbonylmetal Complexes in Chloroform and Carbon Tetrachloride Solution
Authors: Herberhold Max , Klein Reinhard , Alt Helmut G.
Published: November 2013

The photo‐induced reaction of carbonylmetal complexes with gaseous nitric oxide (“photonitrosylation”) in either chloroform or carbon tetrachloride solution is recommended as a synthetic method to prepare nitrosylmetal chlorides. Binary carbonyliron compounds (Fe(CO)5, Fe2(CO)9, Fe3(CO)12) are converted into Fe(NO)3Cl which is also accessible by the cleavage of binuclear [Fe(NO)2Cl]2 with NO in non‐coordinating solvents. Carbonylcobalt complexes (Co2(CO)M, Co(CO)3NO) are photonitrosylated to give binuclear [Co(NO)2Cl]2, while cyclopentadienylcarbonyl‐chormium compounds ([CpCr(CO)3]2, [CpCr(CO)2]2, CpCr(CO)2NO) lead to mononuclear CpCr(NO)2Cl in excellent yields.