bluuebunny/crossref_metadata_2025 huggingface dataset:
Loss- and Gain-of-Function Mutations in the F1-HAMP Region of theEscherichia coliAerotaxis Transducer Aer
Authors: del Carmen Burón-Barral Maria , Gosink Khoosheh K. , Parkinson John S.
Published: May 2006

TheEscherichia coliAer protein contains an N-terminal PAS domain that binds flavin adenine dinucleotide (FAD), senses aerotactic stimuli, and communicates with the output signaling domain. To explore the roles of the intervening F1 and HAMP segments in Aer signaling, we isolated plasmid-borne aerotaxis-defective mutations in a host strain lacking all chemoreceptors of the methyl-accepting chemotaxis protein (MCP) family. Under these conditions, Aer alone established the cell's run/tumble swimming pattern and modulated that behavior in response to oxygen gradients. We found two classes of Aer mutants: null and clockwise (CW) biased. Most mutant proteins exhibited the null phenotype: failure to elicit CW flagellar rotation, no aerosensing behavior in MCP-containing hosts, and no apparent FAD-binding ability. However, null mutants had low Aer expression levels caused by rapid degradation of apparently nonnative subunits. Their functional defects probably reflect the absence of a protein product. In contrast, CW-biased mutant proteins exhibited normal expression levels, wild-type FAD binding, and robust aerosensing behavior in MCP-containing hosts. The CW lesions evidently shift unstimulated Aer output to the CW signaling state but do not block the Aer input-output pathway. The distribution and properties of null and CW-biased mutations suggest that the Aer PAS domain may engage in two different interactions with HAMP and the HAMP-proximal signaling domain: one needed for Aer maturation and another for promoting CW output from the Aer signaling domain. Most aerotaxis-defective null mutations in these regions seemed to affect maturation only, indicating that these two interactions involve structurally distinct determinants.
WrbA fromEscherichia coliandArchaeoglobus fulgidusIs an NAD(P)H:Quinone Oxidoreductase
Authors: Patridge Eric V. , Ferry James G.
Published: May 2006

WrbA (tryptophan [W] repressor-binding protein) was discovered inEscherichia coli, where it was proposed to play a role in regulation of the tryptophan operon; however, this has been put in question, leaving the function unknown. Here we report a phylogenetic analysis of 30 sequences which indicated that WrbA is the prototype of a distinct family of flavoproteins which exists in a diversity of cell types across all three domains of life and includes documented NAD(P)H:quinone oxidoreductases (NQOs) from theFungiandViridiplantaekingdoms. Biochemical characterization of the prototypic WrbA protein fromE. coliand WrbA fromArchaeoglobus fulgidus, a hyperthermophilic species from theArchaeadomain, shows that these enzymes have NQO activity, suggesting that this activity is a defining characteristic of the WrbA family that we designate a new type of NQO (type IV). ForE. coliWrbA, theKmNADHwas 14 ± 0.43 μM and theKmbenzoquinonewas 5.8 ± 0.12 μM. ForA. fulgidusWrbA, theKmNADHwas 19 ± 1.7 μM and theKmbenzoquinonewas 37 ± 3.6 μM. Both enzymes were found to be homodimeric by gel filtration chromatography and homotetrameric by dynamic light scattering and to contain one flavin mononucleotide molecule per monomer. The NQO activity of each enzyme is retained over a broad pH range, and apparent initial velocities indicate that maximal activities are comparable to the optimum growth temperature for the respective organisms. The results are discussed and implicate WrbA in the two-electron reduction of quinones, protecting against oxidative stress.
Purification and Characterization of a Hemolysin-Like Protein, Sll1951, a Nontoxic Member of the RTX Protein Family from the Cyanobacterium
Synechocystis
sp. Strain PCC 6803
Authors: Sakiyama Tetsushi , Ueno Hironori , Homma Hideya , Numata Osamu , Kuwabara Tomohiko
Published: May 2006

The hemolysin-like protein (HLP) Sll1951, characterized by the GGXGXDXUX nonapeptide motif implicated in Ca
2+
binding, was purified from the glucose-tolerant strain (GT) of
Synechocystis
sp. strain PCC 6803. HLP was eluted at 560 kDa after gel filtration chromatography. Atomic absorption spectroscopy indicated that the protein bound calcium. The bound Ca
2+
was not chelated with EGTA; however, it was released after being heated at 100°C for 1 min, and it rebound to the Ca
2+
-depleted protein at room temperature. The apparent HLP molecular mass increased to 1,000 kDa and reverted to 560 kDa during the release and rebinding of Ca
2+
, respectively. The monomers of the respective forms appeared at 90 and 200 kDa after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. HLP showed no apparent hemolytic activity against sheep erythrocytes; however, a slight hemolytic activity was detected during the conformational change caused by the rebinding of Ca
2+
. Immunoelectron microscopy using polyclonal antibodies against the 200-kDa monomer revealed that HLP is located in the cell surface layer. The localization and Ca
2+
-induced reversible conformational change suggest that HLP is a member of the repeat in toxin (RTX) protein family despite its latent and low toxicity. In some other cyanobacteria, RTX proteins are reported to be necessary for cell motility. However, the GT was immotile. Moreover, the motile wild-type strain did not express any HLP, suggesting that HLP is one of the factors involved in the elimination of motility in the GT. We concluded that the involvement of RTX protein in cyanobacterial cell motility is not a general feature.
Differential Proteomic Analysis of theBacillus anthracisSecretome: Distinct Plasmid and Chromosome CO2-Dependent Cross Talk Mechanisms Modulate Extracellular Proteolytic Activities
Authors: Chitlaru Theodor , Gat Orit , Gozlan Yael , Ariel Naomi , Shafferman Avigdor
Published: May 2006

The secretomes of a virulentBacillus anthracisstrain and of avirulent strains (cured of the virulence plasmids pXO1 and pXO2), cultured in rich and minimal media, were studied by a comparative proteomic approach. More than 400 protein spots, representing the products of 64 genes, were identified, and a unique pattern of protein relative abundance with respect to the presence of the virulence plasmids was revealed. In minimal medium under high CO2tension, conditions considered to simulate those encountered in the host, the presence of the plasmids leads to enhanced expression of 12 chromosome-carried genes (10 of which could not be detected in the absence of the plasmids) in addition to expression of 5 pXO1-encoded proteins. Furthermore, under these conditions, the presence of the pXO1 and pXO2 plasmids leads to the repression of 14 chromosomal genes. On the other hand, in minimal aerobic medium not supplemented with CO2, the virulent and avirulentB. anthracisstrains manifest very similar protein signatures, and most strikingly, two proteins (the metalloproteases InhA1 and NprB, orthologs of gene products attributed to theBacillus cereusgroup PlcR regulon) represent over 90% of the total secretome. Interestingly, of the 64 identified gene products, at least 31 harbor features characteristic of virulence determinants (such as toxins, proteases, nucleotidases, sulfatases, transporters, and detoxification factors), 22 of which are differentially regulated in a plasmid-dependent manner. The nature and the expression patterns of proteins in the various secretomes suggest that distinct CO2-responsive chromosome- and plasmid-encoded regulatory factors modulate the secretion of potential novel virulence factors, most of which are associated with extracellular proteolytic activities.
Cation-Induced Transcriptional Regulation of the
dlt
Operon of
Staphylococcus aureus
Authors: Koprivnjak Tomaz , Mlakar Vid , Swanson Lindsey , Fournier Benedicte , Peschel Andreas , Weiss Jerrold P.
Published: May 2006

Lipoteichoic and wall teichoic acids (TA) are highly anionic cell envelope-associated polymers containing repeating polyglycerol/ribitol phosphate moieties. Substitution of TA with
d
-alanine is important for modulation of many cell envelope-dependent processes, such as activity of autolytic enzymes, binding of divalent cations, and susceptibility to innate host defenses.
d
-Alanylation of TA is diminished when bacteria are grown in medium containing increased NaCl concentrations, but the effects of increased salt concentration on expression of the
dlt
operon encoding proteins mediating
d
-alanylation of TA are unknown. We demonstrate that
Staphylococcus aureus
transcriptionally represses
dlt
expression in response to high concentrations of Na
+
and moderate concentrations of Mg
2+
and Ca
2+
but not sucrose. Changes in
dlt
mRNA are induced within 15 min and sustained for several generations of growth. Mg
2+
-induced
dlt
repression depends on the ArlSR two-component system. Northern blotting, reverse transcription-PCR, and SMART-RACE analyses suggest that the
dlt
transcript begins 250 bp upstream of the
dltA
start codon and includes an open reading frame immediately upstream of
dltA
. Chloramphenicol transacetylase transcriptional fusions indicate that a region encompassing the 171 to 325 bp upstream of
dltA
is required for expression and Mg
2+
-induced repression of the
dlt
operon in
S. aureus
.
Living with Genome Instability: the Adaptation of Phytoplasmas to Diverse Environments of Their Insect and Plant Hosts
Authors: Bai Xiaodong , Zhang Jianhua , Ewing Adam , Miller Sally A. , Jancso Radek Agnes , Shevchenko Dmitriy V. , Tsukerman Kiryl , Walunas Theresa , Lapidus Alla , Campbell John W. , Hogenhout Saskia A.
Published: May 2006

Phytoplasmas
(“
Candidatus
Phytoplasma,” class
Mollicutes
) cause disease in hundreds of economically
important plants and are obligately transmitted by sap-feeding insects
of the order Hemiptera, mainly leafhoppers and psyllids. The 706,569-bp
chromosome and four plasmids of aster yellows phytoplasma strain
witches' broom (AY-WB) were sequenced and compared to the onion yellows
phytoplasma strain M (OY-M) genome. The phytoplasmas have small
repeat-rich genomes. This comparative analysis revealed that the
repeated DNAs are organized into large clusters of potential mobile
units (PMUs), which contain
tra5
insertion
sequences (ISs) and genes for specialized sigma factors and membrane
proteins. So far, these PMUs appear to be unique to phytoplasmas.
Compared to mycoplasmas, phytoplasmas lack several recombination and
DNA modification functions, and therefore, phytoplasmas may use
different mechanisms of recombination, likely involving PMUs, for the
creation of variability, allowing phytoplasmas to adjust to the diverse
environments of plants and insects. The irregular GC skews and the
presence of ISs and large repeated sequences in the AY-WB and OY-M
genomes are indicative of high genomic plasticity. Nevertheless,
segments of ∼250 kb located between the
lplA
and
glnQ
genes are syntenic between the two phytoplasmas and
contain the majority of the metabolic genes and no ISs. AY-WB appears
to be further along in the reductive evolution process than OY-M. The
AY-WB genome is ∼154 kb smaller than the OY-M genome, primarily
as a result of fewer multicopy sequences, including PMUs. Furthermore,
AY-WB lacks genes that are truncated and are part of incomplete
pathways in OY-M.
HYDROGENOLYSIS BY AlCl3–LiAlH4 OF ETHER SOLUTIONS OF cis AND trans ISOMERS OF 2,4-DISUBSTITUTED-1,3-DIOXOLANES
Authors: Leggetter B. E. , Brown R. K.
Published: May 2006

Hydrogenolysis by LiAlH4–AlCl3 of ether solutions of the cis and trans isomers of both 2,4-dimethyl-1,3-dioxolane and 2-ethyl-4-methyl-1,3-dioxolane have been carried out.The cis isomers are hydrogenolyzed respectively about 6.8 times and 10 times faster than are the corresponding trans isomers. The ratio of C2—O1 to C2—O3 bond cleavage in the cis isomers is at least 15 to 1 while that for the trans isomers is about 1 to 2. Isomerization during the aluminium chloride catalyzed hydrogenolysis is not detectable for the trans isomers. Slight indications of isomerization are discerned for the cis isomers.
NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULFURIC ACID: V. KETONES, CARBOXYLIC ACIDS, AND SOME OTHER OXYGEN BASES
Authors: Birchall T. , Gillespie R. J.
Published: May 2006

The proton n.m.r. spectra of the conjugate acids of some ketones and carboxylic acids, and of ethyl acetate, nitromesitylene, and ethyl alcohol have been observed. A correlation has been found between the chemical shift of the C=OH+ proton of the conjugate acids of some para-substituted acetophenones and their pKBH + and σ+ values. The rates of proton loss from these conjugate acids have been obtained.
THE STRUCTURE OF HOMOCHASMANINE
Authors: Achmatowicz Jr. O. , Marion Léo
Published: May 2006

The structure of homochasmanine, a new alkaloid isolated from Aconitum chasmanthum Stapf, has been determined. Its empirical formula is C26H43O6N and the spectroscopic evidence shows that the base contains five methoxyl and one hydroxyl group. The presence of the hydroxyl group is confirmed by the formation of a monoacetyl derivative. That homochasmanine is 8-O-methylchasmanine has been shown by the synthesis of this substance from the previously known diacetylchasmanine.
THE REACTIVITY OF THE CYCLIC POLYENES TOWARDS FREE RADICALS: III. ADDITION OF THE ETHYL RADICAL
Authors: Brown A. C. R. , James D. G. L.
Published: May 2006

Arrhenius parameters have been measured for the addition of the ethyl radical to cycloheptatriene-1,3,5 and to bicyclo[2.2.1]heptadiene-2,5 in the gas phase; the values for the energy of activation are distinct at 6.4 ± 0.2 and 7.0 ± 0.1 kcal/mole respectively. The addition of the ethyl radical to benzene, cyclohexadiene-1,4, and cyclooctadiene-1,5 proceeds too slowly to be detected. The significance of these results is considered in conjunction with those obtained previously for cyclohexadiene-1,3 and cyclooctatetraene, and the possibility of interpreting the reactivity of the cyclic polyenes in terms of molecular structure is discussed.
LA PYROLYSE DU PROPANE ET DE L'ISOPENTANE: INFLUENCE DE TRACES D'OXYGÈNE ET EFFETS DE PAROIS
Authors: Niclause M. , Martin R. , Combes A. , Dzierzynski M.
Published: May 2006

Results obtained in an analytical and kinetic study of propane or isopentane pyrolysis, either pure or in presence of trace amounts of oxygen, are reported. It is shown particularly, that oxygen accelerates or inhibits the reaction, depending upon wall conditions; an interpretation of this dual effect is proposed. The fact that the pyrolysis of these hydrocarbons can be inhibited almost completely under given conditions proves that any molecular mechanism of decomposition is negligible as compared to the chain reaction.
THE CRYSTAL STRUCTURE AND PHASE TRANSITIONS OF β-Zn2P2O7
Authors: Calvo Crispin
Published: May 2006

β-Zn2P2O7 crystallizes in the C2/m space group with lattice parameters a = 6.61 ± 0.01 Å, b = 8.29 ± 0.01 Å, c = 4.51 ± 0.01 Å, β = 105.4° ± 0.2° and z = 2. The anion, P2O7−4, is centered with its mirror plane coinciding with the mirror plane of the space group. The central oxygen atom, however, shows high anisotropic thermal motion and thus it appears that the P—O—P bond angle is linear only as a result of thermal averaging. The cations are found on twofold axes in irregular sixfold coordination and these ZnO6 groups share three edges with neighboring cations. This cation coordination is, therefore, consistent with that predicted from the red emission of β-Zn2P2O7:Mn++.
APPLICATION OF THE EXTENDED HAMMETT RELATIONSHIP TO THE IONIZATION CONSTANTS OF SUBSTITUTED ANTHRANILIC ACIDS
Authors: Leggate P. , Dunn G. E.
Published: May 2006

The overlapping ionization constants of the carboxyl and amino groups in 14 substituted anthranilic acids have been determined by a spectrophotometric method. The results have been fitted to the extended Hammett relationship log K1K2/K10K20 = ρ1σA + ρ2σB, where A and B refer to ionization of the carboxyl and amino group, respectively. The values of ρ1 and ρ2 so obtained have been used to estimate Kz0, the equilibrium constant for ionization of neutral anthranilic acid to zwitterion.
SPECTRAL PROPERTIES OF p-SUBSTITUTED BENZOYLTRIPHENYLSILANES
Authors: Brook A. G. , Kivisikk Ryan , LeGrow G. E.
Published: May 2006

A series of p-substituted benzoylsilanes have been synthesized and their infrared and ultraviolet spectra determined. Correlations of both the infrared carbonyl stretching frequency and the n–π* ultraviolet absorption with Hammett substituent constants have been found. Benzoylsilanes are generally unstable in ethanol undergoing light-catalyzed decomposition. Benzoyldiphenylphosphine was found to give spectra similar to those of benzoylsilanes.
CYCLOHEXENE-3,3,6,6-d4 A USEFUL COMPOUND FOR THE STUDY OF MECHANISM AND STRUCTURE
Authors: Wolfe Saul , Campbell P. G. C.
Published: May 2006

The title compound (I) was prepared by Diels–Alder reaction of butadiene-1,1,4,4-d4 with ethylene. The considerations which led to the synthesis of I are presented and some examples are then given of how use of I can simplify the study of, and provide new information about, a number of different kinds of problems. In the proton magnetic resonance (n.m.r.) spectra of the products of additions to I, the tertiary protons usually appear as clearly defined quartets. Since |JAB| can be read directly from these spectra, both the stereochemistry of the additions and the conformations of the products can be deduced. Thus, oxymercuration of I is clearly a trans addition and Na/Hg reduction of the mercury takes place with retention of configuration. When the second step is performed in D2O, the oxymercuration–reduction sequence represents a convenient route for the trans addition of DOH to a double bond. Deuteroboration provided an example of cis addition of DOH to I. Acid-catalyzed hydration of I resulted in scrambling of the deuterium atoms. The value of GBr/OH is small; GBr/OHis 600 cal/mol. The position of the double bond in a product resulting from allylic substitution of I is determined by integration of the n.m.r. spectrum. Relative to I, the possibilities are no rearrangement, 50% rearrangement, and 100% rearrangement of the double bond. The first product of allylic substitution by N-bromosuccinimide shows no rearrangement; therefore, this reaction does not require a "free" radical intermediate. The structure of an adduct formed during allylic acetoxylation of I by mercuric acetate (the Treibs reaction) has been determined.
THE ELECTRICAL CONDUCTIVITIES OF SOME TETRA-n-ALKYLAMMONIUM SALTS IN ACETONITRILE
Authors: Harkness A. C. , Daggett Jr. H. M.
Published: May 2006

The conductances of a number of tetra-n-alkylammonium bromides and iodides have been measured in acetonitrile. Limiting equivalent conductances and dissociation constants have been evaluated by two methods. Limiting equivalent ionic conductances have been evaluated from these results. Correlations have been made of the effect of ion size on the ionic conductances and on the relative order of magnitude of the dissociation constants. In an appendix the limiting ionic conductances of a number of other ions have been collected from the existing literature.
THE INFRARED SPECTRUM OF AMMONIA ADSORBED ON CABOSIL SILICA POWDER
Authors: Cant N. W. , Little L. H.
Published: May 2006

not available
PREPARATION AND PROPERTIES OF DIETHYL(DIPHENYLPHOSPHINYL)ALUMINIUM
Authors: Johnson A. William , Larson Willard D. , Dahl Gerd H.
Published: May 2006

Two methods of preparing diethyl(diphenylphosphinyl)aluminium have been investigated. This compound exists as a dimer which can be cleaved to monomeric complexes by a variety of Lewis bases. The structure of the dimer and its chemical transformations are discussed.
THE SOLVOLYSIS OF ARENESULFINATES, SULFUR–OXYGEN VERSUS CARBON–OXYGEN BOND FISSION
Authors: Darwish David , Noreyko John
Published: May 2006

The base-catalyzed solvolysis of p-methoxyneophyl benzenesulfinate and the corresponding 2,6-dimethyl-, 2-methyl-, 4-methyl-, and 2-chloro-benzenesulfinates has been studied in ethanol and aqueous ethanol. The reactions involve sulfur–oxygen bond fission. The rate of sulfur–oxygen bond fission is decreased by the introduction of two methyl groups ortho to the sulfur. The rate decrease may be partly due to steric hindrance to nucleophilic attack on the sulfinate sulfur, but this effect is very small compared to the effect in carboxylate ester hydrolysis. The reactions are catalyzed by ethoxide, acetate, and pyridine. Reaction is very slow in the presence of 2,6-lutidine. With certain arenesulfinate esters one can control the reaction to give sulfur–oxygen or carbon–oxygen bond fission by choice of an appropriate base.
THE REACTION OF UNSATURATED CARBOHYDRATES WITH CARBON MONOXIDE AND HYDROGEN: V. ABSOLUTE STEREOCHEMISTRY OF ANHYDRODEOXYHEPTITOLS FROM 3,4,6-TRI-O-ACETYL-D-GLUCAL. STEREOCHEMISTRY OF HYDROFORMYLATION. CONFORMATIONAL ANALYSIS
Authors: Rosenthal Alex , Koch Hans J.
Published: May 2006

3,4,6-Tri-O-acetyl-D-glucal reacted with carbon monoxide and hydrogen in the presence of dicobalt octacarbonyl to yield a mixture of two epimeric anhydrodeoxyheptitols, namely, 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-D-manno-heptitol (I) and 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-D-gluco-heptitol (II). De-O-acetylation of the mixture, followed by chromatographic separation, yielded crystalline 2,6-anhydro-3-deoxy-D-manno-heptitol (III) and 2,6-anhydro-3-deoxy-D-gluco-heptitol (IV). Reaction of the mixture of heptitols (I) and (II) with p-bromobenzenesulfonyl chloride, followed by fractional crystallization of the brosylates, gave pure 4,5,7-tri-O-acetyl-2,6-anhydro-1-O-(p-bromophenylsulfonyl)-3-deoxy-D-gluco-heptitol (VII). The absolute configuration of (VII) has been previously established by X-ray crystallographic analysis. The absolute configuration of (III) was established by correlation with that of (VII). The conversion of compound (II) into various derivatives is described.Reaction of 3,4,6-tri-O-acetyl-D-glucal with carbon monoxide and deuterium afforded 2,6-anhydro-3-deoxy-D-manno-heptitol-1,1,3-2H3 (XIII) and 2,6-anhydro-3-deoxy-D-gluco-heptitol-1,1,3-2H3 (XIV). Examination of the nuclear magnetic resonance (n.m.r.) spectra of the normal and deuterated anhydrodeoxyheptitols confirmed the structural assignments and showed that cis addition to the double bond took place to give (XIV).Comparison of the exchange reaction of sodium iodide with 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-1-O-tosyl-D-gluco-heptitol (VIII) and with 4,5,7-tri-O-acetyl-2,6-anhydro-3-deoxy-1-O-tosyl-D-manno-heptitol (XV) revealed that the equatorial primary tosyloxy group of (VIII) was exchanged by iodine twice as readily as the axial primary tosyloxy group of (XV).
PYRAZOLINES: VI. THE STEREOCHEMISTRY IN THE PYROLYSIS OF PYRAZOLINES FOR THE C3 AND C5 POSITIONS OF THE PYRAZOLINE MOLECULE
Authors: McGreer Donald E. , Chiu Norman W. K. , Vinje Magnus G. , Wong Ken C. K.
Published: May 2006

cis- and trans-3.5-Dimethyl-3-carbomethoxy-Δ1-pyrazoline (IV and V) have been separated, and product analysis for the pyrolysis and photolysis of these compounds has been completed. The cyclopropane products are formed with some change in the relative configuration of the cis–trans groups in both reactions. The α,β-unsaturated olefin product is formed stereospecifically with IV, yielding methyl 2-methyl-cis-2-pentenoate (XI), and with V, yielding methyl 2-methyl-trans-2-pentenoate (X). The results of the pyrolysis and photolysis of cis,trans-3,4,5-trimethyl-3-carbomethoxy-Δ1-pyrazoline are also described. The product studies and some kinetic studies are the basis of a new mechanism proposed for the pyrolysis of pyrazolines.
THE OXIDATION OF METHYL FUMAROPIMARATE WITH LEAD TETRAACETATE
Authors: Ayer W. A. , McDonald C. E.
Published: May 2006

The oxidation of methyl fumaropimarate (VII) with lead tetraacetate has been found to lead to four different products, two of which have rather novel structures. The results which led to the elucidation of the structures of these products are presented, along with speculation on their mode of formation.
THE METHYLATION OF THE RESORCINOLATE DIANION: I. THE EFFECTS OF SOLVENT AND BASE AND THE ALKYLATION SEQUENCE
Authors: Stein Allan R.
Published: May 2006

The alkylation of the di-alkali metal salts of resorcinol with methyl iodide under various conditions was examined. Solvent and cation effects on the mode and position of resorcinolate anion methylation are discussed. By examination of the neutral and phenolic fractions and comparison with the alkylation of methoxyphenols and mesorcinol, the principal methylation sequences are determined. The intermediacy of the various hydroxydienones, for example, 2,4,6,6-tetra-and 2,6,6-tri-methyl-1-hydroxycyclohexa-1,4-dien-3-one, in the formation of the principal product, 2,2,4,6,6-pentamethylcyclohex-4-en-1,3-dione, from the methylation of the resorcinolate dianion in nonpolar solvents or water is established by the isolation of such intermediates. The 2,2,4,6,6-pentamethylcyclohex-4-en-1,3-dione itself will be discussed in detail in the second paper in this series.
SYNTHESIS OF ISOTOPICALLY LABELLED OLEFINS VIA THE WITTIG REACTION
Authors: Atkinson J. G. , Fisher M. H. , Horley D. , Morse A. T. , Stuart R. S. , Synnes E.
Published: May 2006

A new application of the Wittig reaction to the preparation of olefins of low molecular weight which allows selective labelling in the vinyl or allyl positions with isotopes of hydrogen and carbon has been developed. Using the modification of the Wittig reaction introduced by E. J. Corey, in which a solution of the methylsulfinyl carbanion in dimethyl sulfoxide serves as the base, a series of olefins from C2 to C8 were synthesized. The synthesis was applied to the preparation of the following labelled compounds: 5-methylene-14C-bicyclo[2.2.1]hept-2-ene; propene-1-14C; 1-butene-1-14C; propene-1-d1; 2-methylpropene-1,1-d2; 2-methyl-d3-propene-3,3,3-d3; 2-methyl-2-butene-4,4,4-d3; 2-methyl-d3-2-butene-1,1,1-d3; methylene-d2-cyclohexane. For the synthesis of carbon-labelled olefins the reaction has few limitations since the intermediates and products are isotopically stable under the reaction conditions. Deuterium-labelled olefins can be obtained from deuterated formaldehyde or β-deuterated phosphonium salts, but α-deuteroketones and aldehydes and α-deuterophosphonium salts lose the isotope to the solvent.In all the Wittig reactions, benzene was formed as a by-product in 10–15% yield. The mechanism of benzene formation is probably analogous to that proposed by Seyferth involving the decomposition of a pentacovalent phosphorous intermediate.
THE SYNTHESIS OF D-glycero-L-altro-HEPTOSE, D-glycero-L-allo-HEPTOSE, AND meso-glycero-altro-HEPTITOL
Authors: Young Robert , Adams G. A.
Published: May 2006

Condensation of D-talose with nitromethane in alkaline methanol gave the corresponding epimeric 1-deoxy-1-nitroheptitols which were converted into D-glycero-L-altro-heptose and D-glycero-L-allo-heptose (1.5:1) in 44% yield. Reduction of D-glycero-L-altro-heptose with sodium borohydride gave the hitherto unknown meso-glycero-altro-heptitol. The gas–liquid chromatography retention times of the 10 geometrically isomeric heptitol heptaacetates were determined. These data provide the necessary information for the key step in a procedure for the rapid identification of an unknown heptose.
NUCLEAR MAGNETIC RESONANCE STUDIES: VIII. DETERMINATION OF THE THERMODYNAMIC PARAMETERS GOVERNING ASSOCIATIONS OF SUBSTITUTED BENZALDEHYDES IN TOLUENE SOLUTION
Authors: Klinck R. E. , Stothers J. B.
Published: May 2006

The temperature dependence of the proton chemical shifts of four substituted benzaldehydes in toluene solution has been measured. From these results, estimates have been made of the enthalpies and entropies of formation of the stereospecific solute–solvent complexes which were previously shown to exist in these systems. These calculations indicate that the ΔH and ΔS values are −0.9 ± 0.2 kcal/mole and −4.9 ± 1.3 e.u., respectively. No correlation with substitution is apparent; the results are compared with other available data.
KINETIC STUDIES OF PROTON TRANSFER FROM PHENOLS TO TRINITROBENZYL ANION
Authors: Blake J. A. , Evans M. J. B. , Russell K. E.
Published: May 2006

The rates of reaction of various phenols with the 2,4,6-trinitrobenzyl anion in the solvent ethanol have been determined by a spectrophotometric method. The rate constants at −40 °C are related to the dissociation constants of the phenols in water at 25 °C and the value of α in the Brönsted relation is 0.84 ± 0.07; α drops to 0.44 ± 0.05 if the results for the substituted acetic acids (1) are included. The rate constants for the phenols are also correlated by the Hammett relationship, the ρ value at −40 °C being 1.82 ± 0.2. The activation energies range from 9.4 to 10.9 kcal/mole.The rate of reaction of trinitrobenzyl anion with 3-methylphenol at −30 °C is reduced by a factor of 12 if the phenol is deuterated at the OH group and the solvent is deuteroethanol. The large isotope effect confirms that the rate-determining step involves proton transfer from the OH group of the phenol. Substitution of lithium or potassium cations for the sodium cation does not affect the rate constant at −10 °C.In the reaction with 3-methylphenol, a measurable concentration of trinitrobenzyl anion remains at equilibrium and the equilibrium constant for the reaction is 1.3 ± 0.2 at 25 °C. The heat and entropy changes are approximately −6.5 kcal/mole and −21 e.u./mole respectively.
PREPARATION OF METAL NITRIDES BY THE EXPLODING WIRE TECHNIQUE
Authors: Joncich Micheal J. , Vaughn Joe W. , Knutsen Byron F.
Published: May 2006

An exploratory research program investigated the possibility of preparing metal nitrides by electrically exploding metal wires and foils in an atmsophere of (a) nitrogen, (b) ammonia, or (c) nitrogen and hydrogen. The explosions were carried out in an enclosed stainless steel pressure vessel. In a few cases, the wire was exploded while covered with liquid nitrogen in a stainless steel container maintained at liquid nitrogen temperatures.The samples were analyzed using a modified Kjeldahl method for nitrogen. Greater yields of nitrides were obtained when a greater charge was given the oil-filled condensers used to supply the current, and when the pressure of gas surrounding the wire was increased. Yields as high as 50% were obtained in some cases. Clearly defined nitrides were obtained with magnesium, titanium, zirconium, tantalum, zinc, and aluminium. The metals iron, rhodium, platinum, copper, and cadmium did not appear to form stable nitrides under the experimental conditions.A brief discussion of a mechanism by which a wire may explode is given.
SOME HYDROGEN ABSTRACTION REACTIONS OF PERFLUOROETHYL RADICALS
Authors: Pritchard G. O. , Dacey J. R. , Kent W. C. , Simonds C. R.
Published: May 2006

With perfluoroazoethane as a photolytic source of C2F5 radicals, the hydrogen abstraction reactions of C2F5 with deuterium, ethane, cyclohexane, acetone, and trifluoroacetaldehyde have been studied, and the Arrhenius parameters derived. The H-atom abstraction reactions of the three perfluoroalkyl radicals, CF3, C2F5, and C3F7, are discussed.
THEORIES OF INHIBITION BY NITRIC OXIDE
Authors: Back Margaret H. , Laidler Keith J.
Published: May 2006

Theories of the inhibition by nitric oxide of pyrolysis and other reactions, proposed by Voevodsky, by Wojciechowski and Laidler, and by Norrish and Pratt, are critically discussed in this paper with reference to the experimental results. The Voevodsky scheme, involving the suppression by nitric oxide of a heteorgeneous initiation process, is shown to be inconsistent with the observed results for ethane pyrolysis. The Norrish–Pratt scheme, involving oxime formation and NO-induced oxime decomposition, is shown to be unsatisfactory in failing to predict nonintegral orders and in leading to activation energies that are much too high. It is concluded that it is necessary to postulate H abstraction by NO, as in the Wojciechowski–Laidler mechanisms.
THE PROTON MAGNETIC RESONANCE SPECTRA AND TAUTOMERIC EQUILIBRIA OF ALDOSES IN DEUTERIUM OXIDE
Authors: Lemieux R. U. , Stevens J. D.
Published: May 2006

The proton magnetic resonance spectra of D-xylose, D-lyxose, D-arabinose, D-ribose, D-glucose, D-mannose, and D-galactose were determined at 100 Mc.p.s. in deuterium oxide. The chemical shifts and structures of a number of ring protons in these compounds were determined either by spin-decoupling experiments or by synthesis of specifically deuterated compounds. The proton magnetic resonance parameters are shown to provide considerable information on the conformations and tautomeric equilibria for the sugars in aqueous solution. It is concluded that, for aldopyranoses in a chair conformation, the chemical shift of equatorial protons at a given position is virtually independent of configurational changes at other positions. However, an axial proton is shielded about 0.3 p.p.m. less by an axial hydroxyl group at a neighboring position than when the hydroxyl group is in an equatorial orientation. An axial hydroxyl group leads to deshielding of an opposing axial proton by about 0.35 p.p.m. By using the chemical shifts of the ring protons of β-D-xylopyranose and β-D-glucopyranose as reference point, the chemical shifts of protons in other pyranose structures could be anticipated to within a useful degree of accuracy.Evidence was obtained that D-ribose and 2-deoxy-D-ribose exist in aqueous solution both in the pyranose and in the furanose forms. None of the other pentoses showed readily detectable amounts of the furanose forms at equilibrium. Although D-allose does not give readily detectable amounts of the furanose forms when at equilibrium in aqueous solutions, D-altrose does. D-Talose showed only two forms, one of which was the β-pyranose structure.
THE PREPARATION OF 5-ALKYLTHIO, BRANCHED TRYPTAMINES
Authors: Horner J. Kenneth , DeGraw J. I. , Skinner W. A.
Published: May 2006

The Japp–Klingemann reaction has been employed to prepare six new tryptamines. Data on the intermediate phenylhydrazones, β-carbolines, and tryptamine carboxylic acids are presented. Syntheses of 5-methyl-, 6-methyl-, 5,5-dimethyl-, and 5,6-dimethyl-2-oxopiperidine-3-carboxylates are described.
THE NUCLEAR MAGNETIC RESONANCE SPECTRUM OF VINYLENE CARBONATE
Authors: McLauchlan K. A. , Schaefer T.
Published: May 2006

The H and 13C spectra of vinylene carbonate have been studied by double-resonance techniques. It was found that J(13C—H) = ±220.15 ± 0.15 c/s, J(13C—C—H) = ±17.47 ± 0.12 c/s, and J(H—C—C′—H′) = ±1.47 ± 0.03 c/s. A long-range coupling of 9.26 ± 0.10 c/s was observed between the carbon nucleus of the carbonate group and the vinyl protons. The magnitudes and signs of the geminal 13C—C—H couplings are discussed in terms of the molecular orbital theory of Pople and Bothner-By.
SELENIUM ISOTOPE EFFECTS IN THE REDUCTION OF SODIUM SELENITE AND OF SODIUM SELENATE
Authors: Rees C. E. , Thode H. G.
Published: May 2006

Selenium isotope effects in the reduction of sodium selenite and of sodium selenate have been studied. Rate constant ratios for the 76Se and 82Se species have been determined for the reactions Seiv → Se0 (1.017), Sevi → Seiv (1.018), and Se0 → Seiv (1.010) at room temperature. Theoretical predictions of the first two ratios, from the use of models in which the rate-controlling steps are assumed to be Se—O bond cleavages in SeO32− and SeO42−, respectively, lead to predictions in good agreement with experiment.
THE Hg 6(3P1) PHOTOSENSITIZATION OF SPIROPENTANE
Authors: Maré G. R. De , Walker L. G. , Strausz O. P. , Gunning H. E.
Published: May 2006

The triplet mercury photosensitization of spiropentane affords ethylene, allene, and methylenecyclobutane as major reaction products. This indicates an olefinic-type interaction with the quaternary C—C σ-bond of spiropentane, the cleavage of which results in a triplet state diradical. The initially formed diradical may undergo isomerization through ring cleavage or deactivation by collision. The open chain diradical then either decomposes unimolecularly into C2H4 + C3H4 or on collisional relaxation isomerizes to methylenecyclobutane.The paraffinic-type interaction between Hg* and spiropentane which would lead to C—H bond scission appears to have minor significance.
ELECTRON SPIN RESONANCE STUDIES OF PHOTOLYTICALLY GENERATED AROMATIC KETYLS
Authors: Wilson Raymond
Published: May 2006

Electron spin resonance observations on the photolytically generated ketyls of benzaldehyde, acetophenone, and benzophenone in protic solvents are reported. Proton coupling constants differ considerably from those reported by other workers for the same ketyls generated by other methods in aprotic solvents.Molecular orbital calculations of unpaired electron spin densities, in which the effective electronegativities of the oxygen atoms on the ketyls are assumed to be increased by hydrogen bonding in protic solvents, are reported. The calculated changes in spin densities agree qualitatively with the semi-empirical changes calculated by the McConnell relationship.Observations on the dynamics of solvation of the benzaldehyde ketyl in a mixture of a protic and an aprotic solvent are reported and discussed.
THE SYSTEM: ALUMINIUM–INDIUM–SILVER: PART I. THE BINARY AND TERNARY MISCIBILITY GAPS
Authors: Campbell A. N. , Wagemann R.
Published: May 2006

The miscibility gap in the binary system: Al–In has been investigated and the critical temperature and composition estimated as 945 °C and 68.8% In, 31.2% Al (by weight).The liquid–liquid partial miscibility region of the ternary system has also been determined. The lowest temperature at which two liquids can exist in equilibrium before a third (solid) phase appears was found to be approximately 590°. At this temperature, the ternary gap extends to 30.5% Ag, 34.7% Al, and 34.8 In. Isotherms of the ternary gap are given for 50° intervals between 650° and 900°. A true ternary critical point does not exist, i.e. the binary critical temperature is lowered continuously by addition of silver.
HOMOGENEOUS CATALYSIS OF D2–H2O EXCHANGE BY RUTHENIUM (III) CHLORIDE: EVIDENCE FOR THE HETEROLYTIC SPLITTING OF HYDROGEN
Authors: Halpern Jack , James Brian R.
Published: May 2006

The prediction, based on earlier studies of the ruthenium(III) chloride catalyzed oxidation of H2 by iron(III), that in the absence of iron(III) or other oxidants ruthenium(III) chloride should catalyze homogeneously the isotopic exchange between D2 and H2O has been confirmed. A kinetic study was made of this exchange reaction in which the dependence of the exchange rate and of the exchange product distribution (HD:H2 ratio) on the concentrations of ruthenium(III), hydrogen ion, and chloride ion were determined. The results, and in particular the observation that the HD:H2 ratio of the exchange product increases with the concentrations cf H+ and Cl−, support the view that the ruthenium (III)-catalyzed oxidation of D2 by iron(III) and the D2–H2O exchange reaction proceed through related mechanisms involving a common rate-determining step in which D2 is split heterolytically and a deuteridoruthenium(III) complex is formed.
ELECTROLYTIC FORMATION OF LIVING POLYMERS FROM STYRENE
Authors: Funt B. L. , Richardson D. , Bhadani S. N.
Published: May 2006

Electrolysis of solutions of styrene in tetrahydrofuran produced living polymers and the typical colors of the living anions were observed. NaAl(C2H5)4 and NaB(C6H5)4 were each found suitable as conducting electrolytes.When naphthalene was added to the solution in the absence of monomer the green sodium naphthalene complex was produced by electrolysis. Upon the addition of styrene monomer the orange living polystyryl anions were formed immediately. These changes were followed spectrophotometrically.At the anode a terminating species was formed in a corresponding ratio to the living ions generated at the cathode. A mixing of the anode and cathode solutions resulted in a destruction of the living species and decolorization of the solution. The substances responsible were believed to be Al(C2H5)3 and B(C6H5)3 for the corresponding salts.Possible mechanisms for the electro-polymerization reaction are proposed and discussed.
THE INFRARED SPECTRA OF SOME MIXED ALKYLARYLARSONIUM SALTS
Authors: Cullen W. R. , Deacon G. B. , Green J. H. S.
Published: May 2006

The infrared spectra (4000 to 200 cm−1) of some trimethylphenyl-, dimethyldiphenyl-, methyltriphenyl-, triethylphenyl-, and diethyldiphenyl-arsonium salts have been recorded. Vibrational assignments have been made for the quaternary onium cations and have been compared with those for related compounds including one alkylarylgermane.
ORGANIC AND BIOLOGICAL SPECTROCHEMICAL STUDIES: XXII. THE INFRARED, ULTRAVIOLET, AND NUCLEAR MAGNETIC RESONANCE SPECTRA OF SOME SUBSTITUTED 2-INDANONES AND REFERENCE COMPOUNDS
Authors: Moriconi Emil J. , St. George John P. , Forbes W. F.
Published: May 2006

Infrared, ultraviolet, and nuclear magnetic resonance spectra of the following compounds are reported: 2-indanone (I), trans- and cis-hexahydro-2-indanone (V and XI), 1-chloro-2-indanone-1,3,3-d3 (III), 1-bromo-2-indanone-1,3,3-d3 (IV), 1-chloro-trans-hexahydro-2-indanone (VII), 1-bromo-trans-hexahydro-2-indanone (VIII), some deuterated forms of these compounds, 2-chlorocyclohexanone-2,6,6-d3, and 2-bromocyclohexanone-2,6,6-d3.2-Indanone and trans-hexahydro-2-indanone each display two peaks in the carbonyl infrared region with intensity ratios of approximately 40:1. The origin of these doublets is discussed.Nuclear magnetic resonance spectra were determined to indicate the presence or absence of ring mobility, and spin–spin coupling data were used to support some of the conclusions deduced from the infrared data for some of the compounds.
MASS SPECTRA AND REACTION MECHANISM STUDIES: THE FAVORSKY–MARKER REARRANGEMENT OF 17α-BROMOPREGNENOLONES IN DEUTERATED METHANOL
Authors: Deghenghi R. , Schilling G. , Papineau-Couture G.
Published: May 2006

An examination of the mass spectra of the products isolated from a Favorsky rearrangement of 17α-bromopregnenolone acetate (Marker's conditions) in deuterated solvents offers a clue to the reaction mechanism. The stereochemical implications and the mass fragmentation pattern of the products examined are discussed.
THE REACTION OF SOME COMPOUNDS CONTAINING THIOAMIDE GROUPS WITH 2,4,6-TRICHLORO-1,3,5-TRIAZINE
Authors: Pollak A. , Stanovnik B. , Tišler M.
Published: May 2006

The reaction between some compounds containing thioamide groups and cyanuric chloride was investigated. Evidence is presented that the reaction proceeds on the thioamide sulfur and not on the nitrogen as postulated earlier. The reaction with thiourea was used for the preparation of trithiocyanuric acid, as well as for the preparation of 3-chloro-6(1H)-pyridazinethione or 3-mercapto-6(1H)-pyridazinethione, and presents a new and convenient method for the synthesis of these compounds.
PROTON MAGNETIC RESONANCE SPECTRA OF D-GLUCOPYRANOSE POLYMERS
Authors: Glass C. A.
Published: May 2006

not available
THE INHIBITED AUTOXIDATION OF STYRENE: PART V. THE KINETICS AND DEUTERIUM ISOTOPE EFFECT FOR INHIBITION BY DIPHENYLAMINE, PHENYL-α-NAPHTHYLAMINE, AND PHENYL-β-NAPHTHYLAMINE
Authors: Brownlie I. T. , Ingold K. U.
Published: May 2006

The thermal oxidation of styrene inhibited by diphenylamine, phenyl-α-naphthylamine, and phenyl-β-naphthylamine has been examined. It has been shown that the autocatalysis of the diphenylamine- and phenyl-β-naphthylamine-inhibited oxidations is probably due to a reaction between the inhibitor radical and the hydroperoxide formed in the primary step of inhibition. This reaction is too slow to produce significant autocatalysis with phenyl-α:-naphthylamine under the present experimental conditions.The primary inhibition reaction involves abstraction of the amino hydrogen since its replacement by deuterium leads to a fairly large kinetic isotope effect (kH/kD ~ 3–4).
THE REACTIVITY OF METAL–METAL BONDS: I. THE Sn–Sn BOND
Authors: Clark H. C. , Cotton J. D. , Tsai J. H.
Published: May 2006

The reactions of a series of fluorinated olefins with hexamethylditin have been investigated, under conditions which favor the formation of (CH3)3Sn• radicals. Two principal types of products have been isolated, namely (polyfluoroalkyl)trimethyltin compounds, e.g. (CH3)3 SnCF2CF(R)H, and insertion products of the type (CH3)3SnCF2CF(R)Sn(CH3)3, where R = F or CF3. These results are consistent with the formation of intermediate radicals such as (CH3)3SnCF2C(R)F• which then participate either in hydrogen abstraction or in the formation of the insertion products. Reactions of hexamethylditin with CF2=CFH, CF2=CH2, CF2=CFCl, CF2=CFBr, and C2H4 are also discussed. The direction of attack of the (CH3)3Sn• radical on the olefins indicates that the former has a high degree of nucleophilic character. A more detailed study of the reactions of the cyclic hexamers of dimethyltin and diphenyltin with tetrafluoroethylene shows that some addition does occur, but that the products are of indeterminate composition. The reaction of hexameric dimethyltin with trifluoroiodomethane has also been examined.
A REFINEMENT OF THE CRYSTAL STRUCTURES OF (NH4)2TeBr6 AND Cs2TeBr6
Authors: Das A. K. , Brown I. D.
Published: May 2006

(NH4)2TeBr6 and Cs2TeBr6 crystals have the cubic K2PtCl6 structure with space group: [Formula: see text] with a0 = 10.728 ± 0.003 Å and 10.918 ± 0.002 Å respectively. The positional coordinate of the bromine atom, and the anisotropic temperature factors of all atoms in the unit cell, have been refined for both crystals by a full matrix least-squares analysis of the three dimensional X-ray diffraction data (R = 0.08). The Te—Br distance, corrected for probable thermal motions of atoms forming the bond, is 2.70 ± 0.01 Å in both crystals.
STRUCTURAL COMPONENTS IN METHYL VINYL SULFONE MODIFIED COTTON CELLULOSE
Authors: Rowland S. P. , Cirino V. O. , Bullock A. L.
Published: May 2006

Methylsulfonylethyl cellulose was prepared at a low degree of substitution (0.11), which is conventional for the chemical modification of cotton, by the Michael addition of methyl vinyl sulfone to cotton fabric. The distribution of substituents in the anhydroglucose units was determined by hydrolysis of the molecular chain to glucose units, selective concentration of the substituted glucose components, gas-liquid chromatographic analyses of the methylsulfonylethylglucoses, and comparison with authentic samples of 2-O-, 3-O-, and 6-O-methylsulfonylethylglucoses in the form of trimethylsilyl ethers. The validity of each of these steps for quantitative analyses has been examined. The ratio of the 2-O-, 3-O-, and 6-O-monomethylsulfonylethylglucoses was found to be 0.20:0.03:1.0. No evidence was found for the presence of di- or tri-substituted glucoses.
CARCINOGENICITY OF LACTONES: I. THE REACTION OF 4-METHYLBUTENO- AND 4-METHYLBUTANO-γ-LACTONES WITH PRIMARY AMINES
Authors: Jones J. Bryan , Young John M.
Published: May 2006

As the first stage in the investigations of the mechanisms of action of carcinogenic lactones, the reactions of 4-hydroxypent-2-enoic acid lactone (II, R = CH3), which is a carcinogen, and of the non-carcinogenic 4-hydroxypent-3-enoic (III, R = CH3) and 4-hydroxypentanoic (IV, R = CH3) acid lactones with methylamine and benzylamine have been studied. As expected, the carcinogenic lactone reacts to give the Michael addition products, whereas both inactive lactones undergo ring opening by nucleophilic attack at the carbonyl group. From the relative rates of reaction of the amines with the lactones it is concluded that the induction of tumors by II (R = CH3) does not involve alkylation of biological primary alkylamino groups. The proton magnetic resonance spectra of the products enable the different reaction pathways to be distinguished readily, and may provide the basis for rapid physicochemical screening of alkylation agents that are potential carcinogens.