bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the ArsRS Regulon ofHelicobacter pylori, Involved in Acid Adaptation
Authors: Pflock Michael , Finsterer Nadja , Joseph Biju , Mollenkopf Hans , Meyer Thomas F. , Beier Dagmar
Published: May 2006

The human gastric pathogenHelicobacter pyloriis extremely well adapted to the highly acidic conditions encountered in the stomach. The pronounced acid resistance ofH. pylorirelies mainly on the ammonia-producing enzyme urease; however, urease-independent mechanisms are likely to contribute to acid adaptation. Acid-responsive gene regulation is mediated at least in part by the ArsRS two-component system consisting of the essential OmpR-like response regulator ArsR and the nonessential cognate histidine kinase ArsS, whose autophosphorylation is triggered in response to low pH. In this study, by global transcriptional profiling of an ArsS-deficientH. pylorimutant grown at pH 5.0, we define the ArsR∼P-dependent regulon consisting of 109 genes, including the urease gene cluster, the genes encoding the aliphatic amidases AmiE and AmiF, and therocFgene encoding arginase. We show that ArsR∼P controls the acid-induced transcription ofamiEandamiFby binding to extended regions located upstream of the −10 box of the respective promoters. In contrast, transcription ofrocFis repressed by ArsR∼P at neutral, acidic, and mildly alkaline pH via high-affinity binding of the response regulator to a site overlapping the promoter of therocFgene.
Localization of theEscherichia coliRNA Polymerase β′ Subunit Residue Phosphorylated by Bacteriophage T7 Kinase Gp0.7
Authors: Severinova Elena , Severinov Konstantin
Published: May 2006

During bacteriophage T7 infection, theEscherichia coliRNA polymerase β′ subunit is phosphorylated by the phage-encoded kinase Gp0.7. Here, we used proteolytic degradation and mutational analysis to localize the phosphorylation site to a single amino acid, Thr1068, in the evolutionarily hypervariable segment of β′. Using a phosphomimetic substitution of Thr1068, we show that phosphorylation of β′ leads to increased ρ-dependent transcription termination, which may help to switch from host to viral RNA polymerase transcription during phage development.
Multiple
groESL
Operons Are Not Key Targets of RpoH1 and RpoH2 in
Sinorhizobium meliloti
Authors: Bittner Alycia N. , Oke Valerie
Published: May 2006

Among the rhizobia that establish nitrogen-fixing nodules on the roots of host plants, many contain multiple copies of genes encoding the sigma factor RpoH and the chaperone GroEL/GroES. In
Sinorhizobium meliloti
there are two
rpoH
genes, four
groESL
operons, and one
groEL
gene.
rpoH1
mutants are defective for growth at high temperature and form ineffective nodules,
rpoH1 rpoH2
double mutants are unable to form nodules, and
groESL1
mutants form ineffective nodules. To explore the roles of RpoH1 and RpoH2, we identified mutants that suppress both the growth and nodulation defects. These mutants do not suppress the nitrogen fixation defect. This implies that the functions of RpoH1 during growth and RpoH1/RpoH2 during the initiation of symbiosis are similar but that there is a different function of RpoH1 needed later during symbiosis. We showed that, unlike in
Escherichia coli
, overexpression of
groESL
is not sufficient to bypass any of the RpoH defects. Under free-living conditions, we determined that RpoH2 does not control expression of the
groE
genes, and RpoH1 only controls expression of
groESL5
. Finally, we completed the series of
groE
mutants by constructing
groESL3
and
groEL4
mutants and demonstrated that they do not display symbiotic defects. Therefore, the only
groESL
operon required by itself for symbiosis is
groESL1
. Taken together, these results suggest that GroEL/GroES production alone cannot explain the requirements for RpoH1 and RpoH2 in
S. meliloti
and that there must be other crucial targets.
Studies of the CobA-Type ATP:Co(I)rrinoid Adenosyltransferase Enzyme ofMethanosarcina mazeiStrain Gö1
Authors: Buan Nicole R. , Rehfeld Kimberly , Escalante-Semerena Jorge C.
Published: May 2006

Although methanogenic archaea use B12extensively as a methyl carrier for methanogenesis, little is known about B12metabolism in these prokaryotes or any other archaea. To improve our understanding of how B12metabolism differs between bacteria and archaea, the gene encoding the ATP:co(I)rrinoid adenosyltransferase inMethanosarcina mazeistrain Gö1 (open reading frame MM3138, referred to ascobAMmhere) was cloned and used to restore coenzyme B12synthesis in aSalmonella entericastrain lacking the housekeeping CobA enzyme.cobAMmprotein was purified and its initial biochemical analysis performed. In vitro, the activity is enhanced 2.5-fold by the addition of Ca2+ions, but the activity was not enhanced by Mg2+and, unlike theS. entericaCobA enzyme, it was >50% inhibited by Mn2+. The CobAMmenzyme had aKmATPof 3 μM and aKmHOCblof 1 μM. Unlike theS. entericaenzyme, CobAMmused cobalamin (Cbl) as a substrate better than cobinamide (Cbi; a Cbl precursor); the β phosphate of ATP was required for binding to the enzyme. A striking difference between CobASeand CobAMmwas the use of ADP as a substrate by CobAMm, suggesting an important role for the γ phosphate of ATP in binding. The results from31P-nuclear magnetic resonance spectroscopy experiments showed that triphosphate (PPPi) is the reaction by-product; no cleavage of PPPiwas observed, and the enzyme was only slightly inhibited by pyrophosphate (PPi). The data suggested substantial variations in ATP binding and probably corrinoid binding between CobASeand CobAMmenzymes.
In Vitro Biofilm Formation of Commensal and PathogenicEscherichia coliStrains: Impact of Environmental and Genetic Factors
Authors: Reisner Andreas , Krogfelt Karen A. , Klein Bjarke M. , Zechner Ellen L. , Molin Søren
Published: May 2006

Our understanding ofEscherichia colibiofilm formation in vitro is based on studies of laboratory K-12 strains grown in standard media. However, pathogenicE. coliisolates differ substantially in their genetic repertoire fromE. coliK-12 and are subject to heterogeneous environmental conditions. In this study, in vitro biofilm formation of 331 nondomesticatedE. colistrains isolated from healthy (n= 105) and diarrhea-afflicted children (n= 68), bacteremia patients (n= 90), and male patients with urinary tract infections (n= 68) was monitored using a variety of growth conditions and compared to in vitro biofilm formation of prototypic pathogenic and laboratory strains. Our results revealed remarkable variation among the capacities of diverseE. coliisolates to form biofilms in vitro. Notably, we could not identify an association of increased biofilm formation in vitro with a specific strain collection that represented pathogenicE. colistrains. Instead, analysis of biofilm data revealed a significant dependence on growth medium composition (P< 0.05). Poor correlation between biofilm formation in the various media suggests that diverseE. coliisolates respond very differently to changing environmental conditions. The data demonstrate that prevalence and expression of three factors known to strongly promote biofilm formation inE. coliK-12 (F-like conjugative pili, aggregative adherence fimbriae, and curli) cannot adequately account for the increased biofilm formation of nondomesticatedE. coliisolates in vitro. This study highlights the complexity of genetic and environmental effectors of the biofilm phenotype within the speciesE. coli.
Structural and Functional Analysis of Rv3214 from
Mycobacterium tuberculosis
, a Protein with Conflicting Functional Annotations, Leads to Its Characterization as a Phosphatase
Authors: Watkins Harriet A. , Baker Edward N.
Published: May 2006

The availability of complete genome sequences has highlighted the problems of functional annotation of the many gene products that have only limited sequence similarity with proteins of known function. The predicted protein encoded by open reading frame Rv3214 from the
Mycobacterium tuberculosis
H37Rv genome was originally annotated as EntD through sequence similarity with the
Escherichia coli
EntD, a 4′-phosphopantetheinyl transferase implicated in siderophore biosynthesis. An alternative annotation, based on slightly higher sequence identity, grouped Rv3214 with proteins of the cofactor-dependent phosphoglycerate mutase (dPGM) family. The crystal structure of this protein has been solved by single-wavelength anomalous dispersion methods and refined at 2.07-Å resolution (R = 0.229; R
free
= 0.245). The protein is dimeric, with a monomer fold corresponding to the classical dPGM α/β structure, albeit with some variations. Closer comparisons of structure and sequence indicate that it most closely corresponds with a broad-spectrum phosphatase subfamily within the dPGM superfamily. This functional annotation has been confirmed by biochemical assays which show negligible mutase activity but acid phosphatase activity with a pH optimum of 5.4 and suggests that Rv3214 may be important for mycobacterial phosphate metabolism in vivo. Despite its weak sequence similarity with the 4′-phosphopantetheinyl transferases (EntD homologues), there is little evidence to support this function.
Role of Conserved Amino Acids in the Catalytic Activity of
Escherichia coli
Primase
Authors: Rodina Anna , Godson G. Nigel
Published: May 2006

The role of conserved amino acid residues in the polymerase domain of
Escherichia coli
primase has been studied by mutagenesis. We demonstrate that each of the conserved amino acids Arg146, Arg221, Tyr230, Gly266, and Asp311 is involved in the process of catalysis. Residues Glu265 and Asp309 are also critical because a substitution of each amino acid irreversibly destroys the catalytic activity. Two K229A and M268A mutant primase proteins synthesize only 2-nucleotide products in de novo synthesis reactions under standard conditions. Y267A mutant primase protein synthesizes both full-size and 2-nucleotide RNA, but with no intermediate-size products. From these data we discuss the significant step of the 2-nucleotide primer RNA synthesis by
E. coli
primase and the role of amino acids Lys229, Tyr267, and Met268 in primase complex stability.
Application of Comparative Phylogenomics To Study the Evolution ofYersinia enterocoliticaand To Identify Genetic Differences Relating to Pathogenicity
Authors: Howard Sarah L. , Gaunt Michael W. , Hinds Jason , Witney Adam A. , Stabler Richard , Wren Brendan W.
Published: May 2006

Yersinia enterocolitica, an important cause of human gastroenteritis generally caused by the consumption of livestock, has traditionally been categorized into three groups with respect to pathogenicity, i.e., nonpathogenic (biotype 1A), low pathogenicity (biotypes 2 to 5), and highly pathogenic (biotype 1B). However, genetic differences that explain variation in pathogenesis and whether different biotypes are associated with specific nonhuman hosts are largely unknown. In this study, we applied comparative phylogenomics (whole-genome comparisons of microbes with DNA microarrays combined with Bayesian phylogenies) to investigate a diverse collection of 94 strains ofY. enterocoliticaconsisting of 35 human, 35 pig, 15 sheep, and 9 cattle isolates from nonpathogenic, low-pathogenicity, and highly pathogenic biotypes. Analysis confirmed three distinct statistically supported clusters composed of a nonpathogenic clade, a low-pathogenicity clade, and a highly pathogenic clade. Genetic differences revealed 125 predicted coding sequences (CDSs) present in all highly pathogenic strains but absent from the other clades. These included several previously uncharacterized CDSs that may encode novel virulence determinants including a hemolysin, a metalloprotease, and a type III secretion effector protein. Additionally, 27 CDSs were identified which were present in all 47 low-pathogenicity strains andY. enterocolitica8081 but absent from all nonpathogenic 1A isolates. Analysis of the core gene set forY. enterocoliticarevealed that 20.8% of the genes were shared by all of the strains, confirming this species as highly heterogeneous, adding to the case for the existence of three subspecies ofY. enterocolitica. Further analysis revealed thatY. enterocoliticadoes not cluster according to source (host).
Role of the Fur Regulon in Iron Transport in
Bacillus subtilis
Authors: Ollinger Juliane , Song Kyung-Bok , Antelmann Haike , Hecker Michael , Helmann John D.
Published: May 2006

The
Bacillus subtilis
ferric uptake regulator (Fur) protein mediates the iron-dependent repression of at least 20 operons encoding ∼40 genes. We investigated the physiological roles of Fur-regulated genes by the construction of null mutations in 14 transcription units known or predicted to function in siderophore biosynthesis or iron uptake. We demonstrate that
ywbLMN
, encoding an elemental iron uptake system orthologous to the copper oxidase-dependent Fe(III) uptake system of
Saccharomyces cerevisiae
, is essential for growth in low iron minimal medium lacking citric acid. 2,3-Dihydroxybenzoyl-glycine (Itoic acid), the siderophore precursor produced by laboratory strains of
B. subtilis
, is of secondary importance. In the presence of citrate, the YfmCDEF ABC transporter is required for optimal growth.
B. subtilis
is unable to grow in minimal medium containing the iron chelator EDDHA unless the ability to synthesize the intact bacillibactin siderophore is restored (by the introduction of a functional
sfp
gene) or exogenous siderophores are provided. Utilization of the catecholate siderophores bacillibactin and enterobactin requires the FeuABC importer and the YusV ATPase. Utilization of hydroxamate siderophores requires the FhuBGC ABC transporter together with the FhuD (ferrichrome) or YxeB (ferrioxamine) substrate-binding proteins. Growth with schizokinen or arthrobactin is at least partially dependent on the YfhA YfiYZ importer and the YusV ATPase. We have also investigated the effects of a
fur
mutation on the proteome and documented the derepression of 11 Fur-regulated proteins, including a newly identified thioredoxin reductase homolog, YcgT.
Chemotaxis Is Required for Virulence and Competitive Fitness of the Bacterial Wilt Pathogen
Ralstonia solanacearum
Authors: Yao Jian , Allen Caitilyn
Published: May 2006

Ralstonia solanacearum
, a soilborne plant pathogen of considerable economic importance, invades host plant roots from the soil. Qualitative and quantitative chemotaxis assays revealed that this bacterium is specifically attracted to diverse amino acids and organic acids, and especially to root exudates from the host plant tomato. Exudates from rice, a nonhost plant, were less attractive. Eight different strains from this heterogeneous species complex varied significantly in their attraction to a panel of carbohydrate stimuli, raising the possibility that chemotactic responses may be differentially selected traits that confer adaptation to various hosts or ecological conditions. Previous studies found that an aflagellate mutant lacking swimming motility is significantly reduced in virulence, but the role of directed motility mediated by the chemotaxis system was not known. Two site-directed
R. solanacearum
mutants lacking either CheA or CheW, which are core chemotaxis signal transduction proteins, were completely nonchemotactic but retained normal swimming motility. In biologically realistic soil soak virulence assays on tomato plants, both nonchemotactic mutants had significantly reduced virulence indistinguishable from that of a nonmotile mutant, demonstrating that directed motility, not simply random motion, is required for full virulence. In contrast, nontactic strains were as virulent as the wild-type strain was when bacteria were introduced directly into the plant stem through a cut petiole, indicating that taxis makes its contribution to virulence in the early stages of host invasion and colonization. When inoculated individually by soaking the soil, both nontactic mutants reached the same population sizes as the wild type did in the stems of tomato plants just beginning to wilt. However, when tomato plants were coinoculated with a 1:1 mixture of a nontactic mutant and its wild-type parent, the wild-type strain outcompeted both nontactic mutants by 100-fold. Together, these results indicate that chemotaxis is an important trait for virulence and pathogenic fitness in this plant pathogen.
Epidemiology, Risk Factors, and Prognosis of
Candida parapsilosis
Bloodstream Infections: Case-Control Population-Based Surveillance Study of Patients in Barcelona, Spain, from 2002 to 2003
Authors: Almirante Benito , Rodríguez Dolors , Cuenca-Estrella Manuel , Almela Manel , Sanchez Ferran , Ayats Josefina , Alonso-Tarres Carles , Rodriguez-Tudela Juan L. , Pahissa Albert ,   the Barcelona Candidemia Project Study Group
Published: May 2006

Candida parapsilosis
has emerged as an important yeast species causing fungemia. We describe the incidence and epidemiology of
C. parapsilosis
fungemia. Data from active population-based surveillance in Barcelona, Spain, from January 2002 to December 2003 were analyzed. We focused on 78 episodes of
C. parapsilosis
fungemia, and we compared them with 175
Candida albicans
controls.
C. parapsilosis
accounted for 23% of all fungemias. The annual incidences were 1 episode per 10
5
patients, 1.2 episodes per 10
4
discharges, and 1.7 episodes per 10
5
patient days. All isolates but one (99%) were fluconazole susceptible. Seventy-two isolates (92%) were inpatient candidemias. Forty-two episodes (51%) were considered catheter-related fungemia, 35 (45%) were considered primary fungemia, and 3 (4%) were considered secondary fungemia. Risk factors for candidemia were vascular catheterization (97%), prior antibiotic therapy (91%), parenteral nutrition (54%), prior surgery (46%), prior immunosuppressive therapy (38%), malignancy (27%), prior antifungal infection (26%), transplant recipient (16%), neutropenia (12%), and prior colonization (11%). Multivariate analysis of the differential characteristics showed that the factors that independently predicted the presence of
C. parapsilosis
fungemia were neonate patients (odds ratio [OR], 7.5; 95% confidence interval [CI], 2.1 to 26.8;
P
= 0.002), transplant recipients (OR, 9.2; 95% CI, 1.9 to 43.3;
P
= 0.005), patients with a history of prior antifungal therapy (OR, 5.4; 95% CI, 1.8 to 15.9;
P
= 0.002), and patients who received parenteral nutrition (OR, 2.2; 95% CI, 1.09 to 4.6;
P
= 0.028). The overall mortality rate was lower than that associated with
C. albicans
candidemia (23% versus 43%;
P
< 0.01). In summary,
C. parapsilosis
was responsible for 23% of all candidemias and was more frequent in neonates, in transplant recipients, and in patients who received parenteral nutrition or previous antifungal therapy, mainly fluconazole. The mortality rate was lower than that associated with
C. albicans
fungemia.
HEATS OF MIXING AND HEAT CAPACITIES IN THE SYSTEM: ACETIC ACID–CHLOROFORM–WATER, AT 25°
Authors: Campbell A. N. , Gieskes J. M. T. M.
Published: May 2006

The heats of mixing, HE, and heat capacities, at 25 °C, have been determined both for the ternary system: acetic acid–chloroform–water, and for the component binary systems: acetic acid–chloroform and acetic acid–water. The results are discussed in their bearing on the equilibria existing in these systems.
ELECTRON SPIN RESONANCE SPECTRA OF 15N-CENTERED RADICALS AT LOW TEMPERATURES: I. THE RADICAL NH3+ TRAPPED IN NH4ClO4
Authors: Fujimoto M. , Morton J. R.
Published: May 2006

The electron spin resonance spectrum of NH3+ trapped in ammonium perchlorate (95% 15N) was examined at 300 °K, 77 °K, and 4 °K. The spectra are interpreted in terms of π-radical theory, and demonstrate the different stages in the freezing-out of the rotational motion of the ion.
SUBSOLUTIONS IN MULTICOMPONENT SYSTEMS: APPLICATIONS TO SOME TERNARY AQUEOUS ACID SULFATE SYSTEMS AT UNIVARIANCE
Authors: Sukava A. J.
Published: May 2006

A method is described by which univariant composition data for multicomponent solutions may be tested for consistency or accuracy, and used to estimate or verify invariant points, by reference to the vapor pressure data for an appropriate binary subsolution derived from the system. A subsolution is defined as any homogeneous part of a multicomponent solution, such that it is composed of a smaller number of the components than the total but in which the relative masses of these components are the same as in the parent solution.Published data for ternary systems containing sulfuric acid, water, and the metal sulfates MnSO4, FeSO4, ZnSO4, BeSO4, Na2SO4, and CuSO4 are examined. Some new data for the CuSO4 system are also presented. The subsolution in each case is the binary H2SO4–H2O solution, for which adequate vapor pressure data are available.
REACTIONS OF THE ETHYL RADICAL: VI. ADDITION TO CONJUGATED DIENES
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 the conjugated diene system in three representative molecular environments. Significant differences are found among the values of the energy of activation for addition, which are: 4.5 ± 0.2 kcal/mole for 2,3-dimethylbutadiene-1,3, 5.2 ± 0.3 kcal/mole for cyclohexadiene-1,3, and 6.6 ± 0.3 kcal/mole for 2,5-dimethylhexadiene-2,4. The increase in the energy of activation in this series is paralleled by an increase in the degree of shielding of the terminal carbon atoms of the conjugated system by substituent groups. The energy of activation for metathesis is significantly lower for cyclohexadiene-1,3 (5.4 ± 0.5 kcal/mole) than for 2,5-dimethylhexadiene-2,4 (7.6 ± 0.4 kcal/mole); the activated hydrogen atoms of the former are all secondary, whereas those of the latter are all primary. The ratio of the rate constants for addition and metathesis at 60° indicate that the radical homopolymerization of cyclohexadiene-1,3 and 2,5-dimethylhexadiene-2,4 should be subject to extensive degradative chain transfer.
SPECTRES INFRAROUGES DE COMPOSÉS RICHES EN AZOTE
Authors: Tremblay Méüde
Published: May 2006

not available
A PROTON MAGNETIC RESONANCE STUDY OF SODIUM 3,5,5-TRIMETHYL HEXANOATE
Authors: Cyr T. J. R. , Dunell B. A.
Published: May 2006

not available
HETEROCYCLONIUMYL ZWITTERIONS. PART I. THE ALKALI-CATALYZED CLEAVAGE OF 2-HYDROXYMETHYL- AND 2-FORMYL-PYRIDINIUM CATIONS
Authors: Golding S. , Katritzky A. R.
Published: May 2006

not available
COMPLEXES OF STANNIC IODIDE WITH AROMATIC HYDROCARBONS
Authors: Murphy J. F. , Baker D. E.
Published: May 2006

Spectrophotometric measurements on solutions of stannic iodide were found to provide evidence for complex formation with aromatic hydrocarbons. Calculations, based on spectra for mixed solutions of benzene and stannic iodide in carbon tetrachloride, yield values of 0.26 for the equilibrium constant (mole fraction), 28 400 1/mole cm for the molar extinction coefficient of the benzene – stannic iodide complex. Kinetic evidence indicates that the order of decreasing complex stabilities is from xylene to toluene to benzene. The formation of stannic iodide – aromatic hydrocarbon complexes provides an explanation for the discrepancy between measured solubilities of stannic iodide in benzene, toluene, and xylene, and the solubilities predicted by the Hildebrand theory of regular solutions.
AUTOXIDATION REACTIONS CATALYZED BY COBALT ACETATE BROMIDE
Authors: Hay Allan S. , Blanchard Harry S.
Published: May 2006

Cobalt acetate bromide in acetic acid solution is an extraordinarily active catalyst for the autoxidation of hydrocarbons. Carboxylic acids and ketones are readily prepared in high yields at moderate temperatures and at atmospheric pressure. In addition, benzylic and allylic groups can be converted to esters of the corresponding alcohols, and the oxidation of tetralin can be controlled to give either α-tetralone or 1,2-dihydronaphthalene as the major product. A mechanism for these reactions is postulated.
SYNTHESIS OF ANHYDRODIDEOXYHEXITOLS RELATED TO ANHYDRODEOXYHEXITOLS FROM OXO REACTION OF 3,4-DI-O-ACETYL-D-XYLAL
Authors: Rosenthal Alex , Abson D.
Published: May 2006

2,3-Di-O-acetyl-1,5-anhydro-4,6-dideoxy-D-arabino-hexitol (VI) and 2,3-di-O-acetyl-1,5-an-hydro-4,6-dideoxy-L-xylo-hexitol (VII) were prepared by reaction of methyl magnesium bromide with 3,4-di-O-acetyl-D-xylo-pyranosyl chloride. An independent synthesis of compounds (VI) and (VII) was also achieved from the 6-O-tosyl derivatives of the oxo products from 3,4-di-O-acetyl-D-xylal, thus confirming that the configuration of the secondary hydroxyls of glycals is not inverted during the oxo reaction.
PHOTOREARRANGEMENT OF 2,3-DIMETHYL-4,5-DIHYDROFURAN AND 2-METHYL-4,5-DIHYDROFURAN
Authors: McGreer Donald E. , Vinje Magnus G. , McDaniel Robert S.
Published: May 2006

Irradiation of an ether solution of the title compounds with a medium-pressure mercury are gave in each case a rearrangement reaction, with formation of an acetyl cyclopropane isomer as the major product. This reaction is similar to that induced thermally at 450°.
SUBSTITUENT EFFECTS IN THE FLUORENE SERIES: I. SYNTHESIS AND ACETOLYSIS OF SOME DINITRO-9-FLUORENYLp-TOLUENESULFONATES
Authors: Guzik Frederick F. , Colter Allan K.
Published: May 2006

2,4-, 2,5-, and 2,7-Dinitrofluorenones (Ia, Ib, and Ic) were converted to 2,4-, 2,5-, and 2,7-dinitro-9-fluorenyl p-toluenesulfonates (IVa, IVb, and IVc) through the corresponding 9-diazo compounds (IIIa, IIIb, and IIIc). These diazo compounds were converted directly to the three dinitro-9-fluorenols (VIa, VIb, and VIc) and 9-fluorenyl acetates (Va, Vb, and Vc).Rates of acetolysis of the three p-toluenesulfonates (IVa, IVb, and IVc) were measured in glacial acetic acid at 50.17° and 70.07°. The results are discussed.
THE MECHANISMS OF THE HALOGENATIONS AND HALOGENOMETHOXYLATIONS OF D-GLUCAL TRIACETATE, D-GALACTAL TRIACETATE, AND 3,4-DIHYDROPYRAN
Authors: Lemieux R. U. , Fraser-Reid B.
Published: May 2006

The stereochemical routes of the reactions showed trends, when the halogen, the olefin, and the solvent were changed, which can be accounted for on the basis of (a) the relative stabilities of the halonium and oxocarbonium ions formed as intermediates, (b) the effect of ring conformation on the ease of formation of oxocarbonium ions involving the ring-oxygen of the pyranose ring, (c) the role of the anomeric effect in determining the stability of the transition state, and (d) the influence on the route of reaction of whether or not the intermediate cations are solvated by a nucleophile as they are formed. Proton magnetic resonance spectroscopy was extensively used to determine the compositions of products and the configurations and conformations of the compounds obtained.
KETO–ENOL TAUTOMERISM IN β-DICARBONYLS STUDIED BY NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY: II. SOLVENT EFFECTS ON PROTON CHEMICAL SHIFTS AND ON EQUILIBRIUM CONSTANTS
Authors: Rogers Max T. , Burdett Jane L.
Published: May 2006

The effect of various solvents on the proton chemical shifts of a number of acyclic β-di-ketones and β-ketoesters has been observed by nuclear magnetic resonance spectroscopy. These shifts are discussed in terms of the dissociation of intramolecular and intermolecular hydrogen bonds on dilution. A complex of benzene with the enol tautomer of the β-dicarbonyl molecule is proposed. The effect of solvents on the position of the tautomeric equilibrium is discussed.
SAMPLE INJECTION IN PROGRAMMED TEMPERATURE GAS CHROMATOGRAPHY AND ITS SIGNIFICANCE FOR TRACE ANALYSIS
Authors: Hollingshead L. W. , Habgood H. W. , Harris W. E.
Published: May 2006

The measurement of apparent plate heights resulting from various values of the total sample volume has been carried out for C5 to C8n-alkanes on Apiezon L under both isothermal and p.t.g.c. conditions. Plug injection of samples was achieved through the use of a syringe plunger driven at constant speed by a motor. The time for injection of gas samples ranged from 1 to 300 s. All of the results, both isothermal and p.t.g.c, could be correlated to the same plot of Happ/Hc against √nΔVs/VT0 where Happ is the observed plate height, Hc the limiting plate height at low sample volumes, n the true plate number, ΔVs the sample volume, and VT0 the isothermal retention volume at the initial temperature. The experimental values lie somewhat above the theoretical curve calculated by van Deemter et al. It is confirmed that sample volumes less than [Formula: see text] give negligible excess peak broadening. Applying these concepts to trace analysis, very large samples may be used in p.t.g.c. under such initial temperature conditions that the major component is only weakly retained, while traces of heavier components are concentrated into narrow bands and eluted as sharp peaks with the increased sensitivity provided by the large sample. As an example, chromatograms are presented for the p.t.g.c. analysis of natural gas on deactivated alumina, using sample volumes ranging from 2 to 500 ml.
INVESTIGATION OF THE STRUCTURE OF 1,5-METHYLENE-QUINOLIZIDINIUM ION
Authors: Edwards O. E. , Fodor Gábor , Marion Léo
Published: May 2006

Galinovsky observed that O-tosyllupinine (II) readily isomerized to a quaternary tosylate. Without rigorous proof he assigned to this a monomeric azetidinium salt structure. A study of the infrared and nuclear magnetic resonance spectra and molecular weight of the compound confirms the 1,5-methylene-quinolizidinium salt structure III.
THE ROLE OF ASPARTIC ACID IN THE BIOSYNTHESIS OF RICININE1
Authors: Johns S. R. , Marion Léo
Published: May 2006

Ricinine, isolated from Ricinuscommunis L. fed aspartic acid-3-14C and aspartic acid-4-14C, was degraded, and in each case the activity of all the carbon atoms was determined. The results obtained indicate that aspartic acid is incorporated into ricinine via the Krebs tricarboxylic acid cycle rather than directly as aspartic acid. Experiments with aspartic acid-13N support this suggestion; they indicate that the ring nitrogen from ricinine is not derived directly from the nitrogen of aspartic acid, since both it and the nitrile nitrogen contain essentially the same abundance of 15N.
ALKALOIDS OF THE SEEDS OF ASPIDOSPERMA FENDLERI WOODSON
Authors: Burnell R. H. , Medina J. D. , Ayer W. A.
Published: May 2006

The structures of three new alkaloids from the seeds of A. fendleri have been elucidated and two of the bases have been converted into aspidolimidine. A fourth base has been shown to be present in small amounts but its nature remains unknown.
THE OCCURRENCE OF 2,3-DIBROMOBENZYL ALCOHOL 4,5-DISULFATE, DIPOTASSIUM SALT, IN POLYSIPHONIA LANOSA
Authors: Hodgkin J. H. , Craigie J. S. , McInnes A. G.
Published: May 2006

A new brominated phenolic compound, isolated in 5% yield from the red alga Polysiphonialanosa, has been characterized as 2,3-dibromobenzyl alcohol 4,5-disulfate, dipotassium salt. The structural determination, synthesis, and properties of this compound and its derivatives are described.
SYNTHESIS AND NUCLEAR MAGNETIC RESONANCE SPECTRUM OF 3′,4′,6′-TRI-O-ACETYL-2-(METHYLTHIO)-D-GLUCOPYRANO[2′,1′:4,5]-2- THIAZOLINE
Authors: Ito Teiichiro
Published: May 2006

1,3,4,6-Tetra-O-acetyl-2-deoxy-2-(dithiocarbomethoxy)-2-amino-β-D-glucopyranose, when it was treated with trifluoroacetic acid, gave 3′,4′,6′-tri-O-acetyl-2-(methylthio)-D-glucopyrano-[2′,1′:4,5]-2-thiazoline (III). Compound III showed a nuclear magnetic resonance spectrum capable of full interpretation. Long-range coupling between H2 and H4 was observed. The conformation of this compound in solution was discussed on the basis of the coupling constants for ring hydrogens.
REACTIONS OF AMIDES AND RELATED COMPOUNDS: III. N.M.R. INVESTIGATION OF THE PROTONATION OF N,N-DIMETHYLNITROSOAMINE, N,N-DIETHYLNITROSOAMINE, AND N-NITROSOPIPERIDINE
Authors: Kuhn Stephen J. , McIntyre John S.
Published: May 2006

Protonation of N,N-dimethylnitrosoamine has been investigated by dissolving the nitrosoamine in different acids and recording the proton magnetic resonance spectra of these solutions. Concentrated sulfuric acid, sulfuric acid monohydrate, perchloric acid (72%), trifluoroacetic acid, and fluorosulfuric acid have been used in this study. Only in fluorosulfuric acid near 0 °C and lower was a new signal observed for the protonated nitrosoamine molecule. Integration of the peaks has shown that only one proton is captured by the nitrosoamine. The following structure is suggested for the protonated nitrosoamine.[Formula: see text]The n.m.r. spectra of fluorosulfuric acid solutions of N,N-diethylnitrosoamine and N-nitrosopiperidine also show separate signals for the captured proton.The n.m.r. spectrum of an equimolar solution of N,N-dimethylnitrosoamine, N,N-dimethylformamide, and trifluoroacetic acid in 2-nitropropane indicates that N,N-dimethylnitrosoamine is a weaker base.
EFFECT OF CO AND N2 ON MERCURY-PHOTOSENSITIZED REACTIONS
Authors: Homer J. B. , Lossing F. P.
Published: May 2006

The addition of CO is found to increase the rate of the mercury-photosensitized decomposition of certain compounds (ethylene, acetone, anisole) by a factor in excess of 2.5, but does not affect the rate with paraffin hydrocarbons. The addition of N2, known to quench Hg(3P1) to the metastable Hg(3P0) state, does not produce an increase in rate. The results are discussed with reference to a possible HgCO* complex which contains most of the original excitation energy of Hg(3Pi) atom.
60Co γ-RADIOLYSIS OF HYDROGEN HALIDES AT 77 °K
Authors: Rumfeldt R. C. , Armstrong D. A.
Published: May 2006

Yields of hydrogen formed in the 60Co γ-radiolyses of pure polycrystalline samples of HBr and HCl at 77 °K decrease with increasing dose in the range 0 to 1 × 1018 eV per g. The true initial yields are G(H2)solidHClat77°K = 6.3 ± 0.2 and G(H2)solidHBrat77°K = 12.3 ± 0.3. Within experimental error these are the same as the respective liquid-phase yields at −79 °C. For doses in excess of 2 × 1018 eV per g the dose dependence is no longer significant and the yields tend toward plateau values of 3.2 ± 0.1 and 10.3 ± 0.1 for HCl and HBr respectively. The dose dependence of the hydrogen yields is attributed to the scavenging of a reactive intermediate by the halogen atoms and molecules which accumulate in the solid matrix as the dose increases.In independent experiments with an apparatus of the Klein–Scheer type it was shown that hydrogen atoms react readily with films of HBr at 77 °K. There is, however, no evidence of a significant reaction with HCl at this temperature. The difference in behavior of the two hydrogen halides may be explained by their different activation energies for reaction with hydrogen atoms. The results of the γ-radiolyses are discussed in the light of these experiments and it is suggested that the dose dependence may be a result of the scavenging of an ionic intermediate rather than a thermal hydrogen atom.
THERMODYNAMIC AND ELECTROCHEMICAL PROPERTIES OF ZIRCONIUM CHLORIDES IN ALKALI CHLORIDE MELTS
Authors: Swaroop B. , Flengas S. N.
Published: May 2006

The liquidus curves in the binary equilibrium phase diagrams of the systems, ZrCl2–MCl, and ZrCl3–MCl, where M is potassium or sodium, have been determined where possible. The electrochemical properties of the dilute solutions of zirconium di-, tri-, and tetra-chlorides, in the temperature range 670 °C to 750 °C, were investigated by reversible electromotive force measurements. From the results various equilibria between zirconium metal and the solutions of zirconium tri- and tetra-chlorides, respectively, were determined. Activity calculations indicate that zirconium tetrachloride is heavily complexed in these melts.
CHOLLA GUM: I. STRUCTURE OF THE DEGRADED CHOLLA GUM
Authors: Parikh V. M. , Jones J. K. N.
Published: May 2006

Purified cholla gum (Opuntiafulgida) contains L-arabinose (51.6%), D-galactose (31.7%), D-xylose (15.0%), L-rhamnose (2-3%), and D-galacturonic acid (11.2%). Partial hydrolysis of the gum by cold acid produced a polymer which contained only D-galactose and D-galacturonic acid in the proportion 9:2. Methylation and hydrolysis of the degraded gum produced 2,3,4,6-tetra-O-methyl-D-galactose (2 moles), 2,3,4-tri-O-methyl-D-galactose (1 mole), 2,4,6-tri-O-methyl-D-galactose (2 moles), 2,4-di-O-methyl-D-galactose (4 moles), and 2,3,4-tri-O-methyl-D-galacturonic acid (2 moles). Smith-type degradation of the degraded gum produced D-galactose (6 moles), glycolaldehyde (? moles), glycerol (2.5 moles), and glyceronic acid (2.5 moles).Hydrolysis of the undegraded gum produced an aldobiouronic acid, which was proved to be 3-O-(β-D-galactopyranosyl uronic acid)-D-galactose by its reduction, methylation, and the identification of the methylated sugars obtained by the hydrolysis of the octamethyl galactobioside.Based on these results, a possible structure for the average chain length of the degraded gum has been proposed.
ÉTUDES SUR LES PHÉNYL-5 CYCLOHEXANEDIOLS-1,3 ISOMÈRES
Authors: Richer Jean-Claude , -Thanh-Hoa Nguyen-Thi
Published: May 2006

not available
ION PAIR EFFECTS IN THE REACTION BETWEEN POTASSIUM FERROCYANIDE AND POTASSIUM PERSULFATE
Authors: Chlebek R. W. , Lister M. W.
Published: May 2006

The rate of the reaction between potassium ferrocyanide and potassium persulfate has been measured over a range of conditions. The rate is dependent on the potassium ion concentration, and it is shown that this is explained if it is assumed that KFe(CN)63−and KS2O8−are the reacting species. The equilibrium constants governing the formation of these ion pairs were measured with a cation-sensitive glass electrode. Similar constants for the products KFeCCN6)2−and KSO4−, and also for KNO3, were measured. From these equilibrium constants, the true rate constants of the reaction can be obtained, and it is shown that these vary with ionic strength in the manner predicted by Brönsted's equation.
THE THERMODYNAMIC PROPERTIES OF HYDROGEN SELENIDE
Authors: Rawling J. R. , Toguri J. M.
Published: May 2006

Hydrogen selenide may be generated by the reaction of hydrogen gas with liquid selenium according to the reaction[Formula: see text]where[Formula: see text]The equilibrium constant K of this reaction was measured by passing hydrogen over liquid selenium at controlled rates of flow over the temperature range 525–625 °C. The equilibrium ratio of hydrogen to hydrogen selenide was determined by gas analysis. Over the temperature range 525–625 °C, the equilibrium constant can be expressed by the equation[Formula: see text]This expression leads to ΔH298° = 9 174 ± 107 cal mole−1, ΔF298° = 5 132 cal mole−1, and ΔS298° = 13.56 e.u. (entropy units) for the respective heat, free energy, and entropy of formation of hydrogen selenide from hydrogen and crystalline selenium.
KINETICS AND MECHANISM OF COMPLEX FORMATION BETWEEN ETHYLENE AND RUTHENIUM(II) CHLORIDE IN AQUEOUS SOLUTION
Authors: Halpern Jack , James Brian R.
Published: May 2006

The formation of a 1:1 π-complex between ethylene and ruthenium(II) in aqueous hydrochloric acid solution is described. The kinetics of the reaction were examined over a range of temperatures and of concentrations of ruthenium(II), ethylene, hydrogen ion, and chloride ion. The results suggest that complex formation proceeds through a stepwise (SN1) mechanism in which the initial step involves the dissociation of a chlororuthenate(II) complex.
THE CLEAVAGE OF PHOSPHORUS TO NITROGEN BONDS WITH HYDROGEN FLUORIDE
Authors: Greenhalgh R. , Blanchfield J. R.
Published: May 2006

Dialkyl phosphoramidates and alkyl P–alkylphosphonamidates react with hydrogen fluoride breaking the P—N bond to yield the corresponding fluoridates. This cleavage occurred when the nitrogen was unsubstituted, but the yield of product was increased by methyl substitution on the nitrogen. The reaction with diphenyl N,N-dimethylphosphoramidate was not restricted to the P—N bond, since cleavage of the CO—P bonds took place giving, as the ultimate product, hexafluorophosphoric acid. The results obtained indicate that hydrogen fluoride is the most efficient of the hydrogen halides in cleaving P—N bonds.
REACTIONS OF HYDRAZINE WITH ALKOXIDES
Authors: Bains M. S.
Published: May 2006

not available
THE REACTION OF CARYOPHYLLENE AND DIAZOACETIC ESTER; SOME OBSERVATIONS ON CYCLOPROPANES
Authors: Warnhoff E. W. , Dave V.
Published: May 2006

The crystalline acid obtained in 1928 from saponification of the caryophyllene – diazoacetic ester reaction product has been found to be a 1:1 mixture of the stereoisomers V and VII. Compound III is an exception to the observation that cyclopropane CH bonds absorb in the 1.55–1.70 μ near-infrared region.
ON THE CONDENSATION OF p-CRESOL WITH GLYOXAL
Authors: Thyagarajan B. S. , Balasubramanian K. K. , Rao R. Bhima
Published: May 2006

not available
THE PREPARATION AND CHARACTERIZATION OF cis- AND trans-2-HYDRO-3-CHLOROHEXAFLUORO-2-BUTENE
Authors: Burton Donald J. , Johnson Richard L. , Bogan Richard T.
Published: May 2006

not available
ANODIC OXIDE FILMS ON INDIUM ANTIMONIDE
Authors: Harkness A. C. , Young L.
Published: May 2006

The kinetics of formation of anodic oxide films on different crystal faces of single crystal indium antimonide have been investigated by measurements of charge passed, capacitance, and optical properties. Below a transition or breakdown region of voltage no difference in kinetics was found. Above this voltage a marked difference appeared. The transition voltage was found to depend on both the crystal face and the current density at which the film was formed.
LA SOLUBILITÉ DANS LES MÉLANGES ÉTHER ÉTHYLIQUE - ACIDES INORGANIQUES DE CERTAINS SELS DE FER, COBALT ET MANGANÈSE
Authors: Muzzarelli R. A. A.
Published: May 2006

not available
STEROIDS AND RELATED NATURAL PRODUCTS: XXVIII. STEREOCHEMISTRY OF 3-HYDROXY-4-OXA-5α-CHOLESTANE AND RELATED HEMIACETALS
Authors: Pettit George R. , Knight John C. , Evers William J.
Published: May 2006

Several new 3-hydroxy-4-oxa type steroidal hemiacetals (V and VII) have been prepared by diborane reduction of the corresponding δ-lactones. A detailed proton magnetic resonance study of the hemiacetal (IXa) derived from 3-oxo-4-oxa-5α-cholestane (VIII) indicated that diborane reduction led in each case to an epimeric mixture. Treating hemiacetal IXa with methanol – hydrochloric acid gave a mixture of acetals IXb and IXc. Pure specimens of the epimeric acetals were obtained by preparative thin-layer chromatography, and configurational assignments based on proton magnetic resonance studies were provided for each isomer. Allowing lactone VIII (in tetrahydrofuran solution) to react with 1 equivalent of diborane during 4 min resulted in approximately 80% conversion into hemiacetal IXa, and provided an illustration of the potential utility of the reduction reaction.
ELECTRICAL PROPERTIES AND STRUCTURES OF SOLID AND LIQUID GeS, SnS, AND PbS
Authors: Handfield G. , D'Amboise M. , Bourgon M.
Published: May 2006

The electrical conductivity of germanium(II) sulfide in the liquid state has been measured with a capillary-type cell. Both a-c. and d-c. methods were used. The conductivity of liquid GeS increases regularly with tempersature from 1.33 Ω−1 cm−1 at 664 °C to 2.52 Ω−1 cm−1 at 705 °C. The experimental facts lead to the conclusion that GeS remains a semiconductor in the liquid state with a conduction band situated at 2.5 eV above the valence band.The energy gaps of GeS, SnS, and PbS in the solid state are compared with those of the corresponding liquids. It is concluded that these sulfides, in the liquid state, have structures very similar to that of the solids. Liquid PbS has a structure somewhat similar to that of metals. In the case of SnS and GeS, heating and melting are accompanied by a gradual loosening of the double layers which constitute the crystals. Accumulated evidence indicates that the molecular character of SnS and GeS is increased on going from the solid to the liquid state.
ADSORPTION OF CYCLOHEXANE AND BENZENE ON MIXED HYDROXIDES AND OXIDES OF MAGNESIUM AND ALUMINIUM
Authors: Razouk R. I. , Nashed Sh. , Antonious F. N.
Published: May 2006

Seven mixed hydroxides of magnesium and aluminium were prepared, and phase and structural changes accompanying their dehydration were investigated by differential thermal analysis, thermogravimetric analysis, and X-ray diffraction techniques. The differential thermal analysis curves possess 2 peaks corresponding to those of parent hydroxides together with a new peak, and the thermogravimetric analysis curves show slight inflections. X-ray diffraction patterns of the mixed hydroxides possess the characteristic lines of the parent hydroxides together with three to five new intense lines which might indicate the formation of a double hydroxide. When the mixed hydroxides are progressively heated they give rise to products possessing patterns which first become diffuse and ultimately pass mainly into the spinel pattern.Adsorption isotherms of cyclohexane and benzene were measured on the mixed hydroxides and their dehydration products. Specific surface areas calculated by the application of the Brunauer, Emmett, Teller (B.E.T.) equation are in general in good agreement for the two adsorbates. The surface area increases with rise of dehydration temperature to a maximum at 500–600 °C and then decreases with further rise in temperature. This behavior is common to crystalline oxide systems and may be ascribed to the intermingling of decomposition, re-crystallization, and sintering processes. Variations in the molecular ratio of the mixed oxides (as much as 20-fold), and in the method of preparation, do not much alter the surface area.
THE ELECTROLYTIC CONDUCTANCES OF SODIUM CHLORATE AND OF LITHIUM CHLORATE IN WATER AND IN WATER–DIOXANE
Authors: Campbell A. N. , Kartzmark E. M. , Oliver B. G.
Published: May 2006

The conductances, densities, and viscosities of aqueous solutions of sodium chlorate were determined over the complete range of concentration at 25 °C and at 35 °C. An attempt was made to reproduce the results at 25 °C with the viscosity-corrected Falkenhagen–Leist and Wishaw–Stokes equations. The limiting equivalent conductances of sodium chlorate at 25 °C and 35 °C in water were also determined.The conductances, densities, and viscosities of sodium chlorate at 25 °C and 35 °C were determined in a solvent consisting of 64.5% dioxane, 35.5% water. The limiting equivalent conductances of sodium chlorate at 25 °C and 35 °C and of lithium chlorate at 25 °C in this solvent were determined by analyzing the data with the Fuoss–Onsager equation for associated electrolytes.Finally, conductances of sodium chlorate and lithium chlorate at 25 °C were determined in a solvent consisting of 90% dioxane, 10% water.
THE Hg 6(3P1) PHOTOSENSITIZED DECOMPOSITION OF METHYLENECYCLOBUTANE VAPOR
Authors: Maré G. R. De , Strausz O. P. , Gunning H. E.
Published: May 2006

The main mode of decomposition, in which at least two biradicals are involved, is a molecular split into ethylene and allene. The pressure dependence of the reaction exhibits some unusual features which may be interpreted by a stepwise collisional removal of vibrational energy from one of the transient biradicals.
OUINOLINE N-OXIDE COMPLEXES OF TITANYL, ZIRCONYL, AND THORIUM PERCHLORATES
Authors: Krishnan V. , Patel C. C.
Published: May 2006

not available
INVESTIGATIONS ON SOME AMINE COMPLEXES OF IRON(III) PHTHALIMIDE. INFRARED SPECTROSCOPIC MEASUREMENTS
Authors: Narain Gopal
Published: May 2006

not available
EXOCELLULAR ALGINIC ACID FROM AZOTOBACTER VINELANDII
Authors: Gorin P. A. J. , Spencer J. F. T.
Published: May 2006

Azotobactervinelandii produces a partly acetylated exocellular polysaccharide which consists mainly of D-mannuronic acid units and a small proportion of L-guluronic acid units. It resembles alginic acid since it contains 4-O-linked mannuronosyl residues and guluronosyl residues which are 4-O- and (or) 5-O-linked. The specific rotation of bacterial sodium alginate is close to that of its algal counterpart, thus suggesting that the glycosidic configurations are similar.