bluuebunny/crossref_metadata_2025_split huggingface dataset:
Positive ion chemistry of esters of carboxylic acids in air plasma at atmospheric pressure
Authors: Marotta Ester , Paradisi Cristina 
Published: November 2005

AbstractIonization of esters of carboxylic acids RCOOR′ (R = H, alkyl; R′ = alkyl) within the air plasma of the Atmospheric Pressure Chemical Ionization (APCI) source occurs largely via H+‐transfer and, to a minor extent, via NO+ association. The protonated ester MH+ is normally observed as M2H+ and as higher aggregates (M3H+, M3H+(H2O)) also at high source temperature. The behavior of M2H+ upon collisional activation is consistent with the reported dissociation of proton‐bound dimers to MH+ species that, in turn, fragment according to the known paths of lowest energy. In addition, other important product ions form within the plasma, some in very high relative abundance, which are attributed to ion‐molecule condensation reactions between neutral M and either MH+ or M2H+ resulting in the elimination of CO, R′OH, alkene from the alkoxy moiety of the ester and HCOOH. A general scheme is proposed to account for the experimental observations, which suggest that the encounter complex formed between MH+ and M or between M2H+ and M may either collisionally relax to the protonated dimer or trimer, respectively, or react via covalent bond forming and cleaving steps to eliminate stable neutral molecules. The proposed scheme is supported by both the observed concentration dependence and the temperature dependence of the products relative abundances within the plasma. Such reactions can be the dominant process, as in the case of formate esters. A second significant ionization route involves addition of NO+ to form MnNO+ (n = 1, 2, 3). An additional product corresponding to [M2NO+ − CO2] is also observed with iso‐ and n‐butyl formate esters. Copyright © 2005 John Wiley & Sons, Ltd.
Identification and composition of cuticular hydrocarbons of the major Afrotropical malaria vector Anopheles gambiae s.s. (Diptera: Culicidae): analysis of sexual dimorphism and age‐related changes
Authors: Caputo Beniamino , Dani Francesca R. , Horne Gill L. , Petrarca Vincenzo , Turillazzi Stefano , Coluzzi Mario , Priestman Angela A. , della Torre Alessandra 
Published: November 2005

AbstractForty‐eight cuticular hydrocarbons (CHCs) were characterized by gas chromatography‐mass spectrometry from the epicuticular surface of the major Afrotropical malaria vector Anopheles gambiae. The hydrocarbons identified were 14 n‐alkanes, 16 monomethyl alkanes, 13 dimethyl alkanes, 5 alkenes, with main‐chain lengths ranging from C17 to C47, and the results are consistent with those from other Culicidae species. Qualitative differences were not observed between laboratory pools of three females and males, between different age‐groups (0–16 days) and between single field specimens, whereas quantitative differences in CHC profiles were observed. Differences between sexes were more marked in individuals aged 0–2 days than in older ones. Both sexes undergo strong CHC profile changes with age, and individuals aged 0–2 days differ remarkably from the older ones. The possibility of exploiting these changes for estimating the age of mosquito was explored through multivariate analyses of the relative abundance of the compounds, using either the whole CHC profile or a subset of CHCs. Such a method allows us to assign more than 85% of females and 75% of males to the correct age‐group. Although preliminary, these results show that the method is promising, as it has already been shown in Aedes aegypti and An. stephensi. The correct determination of the vector age (particularly in the case of the An. gambiae complex of sibling species) provides valuable information in malaria epidemiology and in evaluation of the effectiveness of vector control strategies. Further efforts will be made to validate this method on single specimens reared in seminatural conditions before being proposed to medical entomologists working in the Afrotropical region. Copyright © 2005 John Wiley & Sons, Ltd.
Marine macroalgae analyzed by mass spectrometry are rich sources of polyunsaturated fatty acids
Authors: De Angelis L. , Risé P. , Giavarini F. , Galli C. , Bolis C. L. , Colombo M. L. 
Published: November 2005

AbstractAlgae from cold water (Canada) and warm water (China) were analyzed for their total lipid content, and for their fatty acid (FA) composition and content. The major findings are that FA from Canadian algae are generally richer in polyunsaturated FA (PUFA), with a higher n‐3/n‐6 FA ratio, and a higher degree of total unsaturation. The 18 C, 4 double bonds FA (18 : 4 stearidonic acid, morotic acid as synonym) was detected in greater amounts in cold water samples. The high levels of total PUFA, and especially of n‐3 FA in Canadian algae, suggests their possible utilizations for nutritional purposes. Copyright © 2005 John Wiley & Sons, Ltd.
Surfactant self‐assembling in gas phase: electrospray ionization‐ and matrix‐assisted laser desorption/ionization‐mass spectrometry of singly charged AOT clusters
Authors: Bongiorno D. , Ceraulo L. , Ruggirello A. , Turco Liveri V. , Basso E. , Seraglia R. , Traldi P. 
Published: November 2005

AbstractThe self‐assembling of sodium bis (2‐ethylhexyl) sulfosuccinate (AOT) in gas phase has been investigated by electrospray ionization‐ and matrix‐assisted laser desorption/ionization mass spectrometry. Large surfactant clusters with an aggregation number close to that found in apolar media have been observed either as positive or negative ions. Moreover, the marked predominance of singly charged species as well as preliminary theoretical calculations strongly suggest an aggregate structure characterized by an internal hydrophilic core hosting the extra charge surrounded by an apolar shell constituted by the surfactant alkyl chains. This structure is similar to that of the more familiar reversed micelles formed when an appropriate surfactant is solubilized in apolar solvents. Finally, similar trends are observed independently either on the ionization technique or the polarity of the solvent used. This, together with the large dependence of the aggregation number on the flow rates, strongly indicates that self‐assembling of the surfactant molecules occurs during the evaporation step. Copyright © 2005 John Wiley & Sons, Ltd.
Generation of high O2 (a1Δg) concentrations in O2/H2 mixtures
Authors: Du Kangyan , Krogh Ole , Setser D. W. 
Published: November 2005

AbstractThe effect of hydrogen on the concentration of singlet oxygen in the a1Δg and b1Σ states, generated from a microwave discharge in O2 and in an O2/Ar mixture, was studied in flow reactors. The addition of hydrogen, in a range of 0.01–1 of concentration of the O2, increased the yields of singlet oxygen by factor of 5–20. In addition to the higher O2 (a and b) concentrations, the addition of hydrogen removed the usual NO2 fluorescence, making observation of the O2(b → X) transition at 762 nm much easier in the flow reactor. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 12–17, 2006
Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine
Authors: Bahrami Homayoon , Zahedi Mansour 
Published: November 2005

AbstractThe kinetics of the permanganic oxidation process of L‐norleucine, L‐leucine, L‐iso‐leucine, and L‐tert‐leucine in strong acid medium has been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions in strong acid medium analogous to weak acid medium, but in the former, ratio of Mn(II) to amino acid concentration must reach a certain amount for autocatalytic phenomenon to emerge, which we call “critical ratio.” This critical ratio depends on the nature of the amino acid employed. Thus considering “delayed autocatalytic behavior” of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. Kinetic data in a noncatalytic pathway have been fitted to a biparametric equation including inductive, steric, and hyperconjugation correction effects, and it is determined that by shifting the side branch on a carbon chain toward an α‐carbon atom (adjacent to amino acid's functional group) and also adding branches to the α‐carbon atom, the reaction rate in the noncatalytic pathway decreases. Inductive and steric hindrance factors in amino acid's carbon chain are effective on processes' rate both in catalytic and noncatalytic pathways. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 1–11, 2006
Classic and multivariate modeling treatment of the kinetics and mechanism of isomerization of 5‐cholesten‐3‐one catalyzed by sodium ethoxide
Authors: González‐Hernández J. L. , Canedo M. M. , Grande C. 
Published: November 2005

AbstractA classic kinetic methodology including the treatment of the steady‐state method and a multivariate modeling kinetic treatment were applied to the kinetics and mechanism of the isomerization reaction of 5‐cholesten‐3‐one to 4‐cholesten‐3‐one catalyzed by EtO− in ethanol absolute. The rate constants, thermodynamic parameters of activation, equilibrium constant, and the isomerization enthalpy were determined. The multivariate modeling kinetic treatment allows us to calculate the concentrations of the species, in which the 3,5‐dienolate is included as a highly reactive intermediate species and was able to discriminate among several applicable mechanisms validating the one comprising two reversible steps. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 38–47, 2006
Chloraminometric and bromaminometric oxidation of sulfanilic acid in alkaline medium: A comparative kinetic and mechanistic study
Authors: Puttaswamy  , Jagadeesh R. V. 
Published: November 2005

AbstractThe kinetics of oxidation of sulfanilic acid (SAA) by chloramine‐B (CAB) and bromamine‐B (BAB) has been investigated in alkaline medium at 35 ± 0.1°C. The oxidation reaction follows identical kinetics in the case of both the oxidants with first‐order dependence on each [oxidant]o and [SAA]o and an inverse first‐order dependence on [OH−]. The variation of ionic strength, dielectric constant of the medium, addition of the reaction product (benzenesulfonamide), and halide ions showed no significant influence on the reaction rate. Proton inventory studies made in H2O–D2O mixtures for CAB and BAB have been utilized to calculate the isotopic fractionation factor. The reaction has been studied at different temperatures, and activation parameters for the composite reaction have been computed from the Arrhenius plots. N‐Hydroxylaminobenzene‐4‐sulfonic acid was identified as the oxidation product of SAA from IR and GC‐MS analysis. A mechanism consistent with the kinetic results is proposed in which PhSO2NHX (X = Cl or Br) interact with the substrate in the rate‐limiting step. A suitable rate law is derived. The rate of oxidation of sulfanilic acid is about fourfold faster in BAB compared to CAB. The oxidation of SAA brought about by CAT and BAT was also investigated under identical experimental conditions, and the overall rate of oxidation of SAA increases in the order: BAB > BAT > CAB > CAT. This may be attributed to the difference in electrophilicities of Cl+ and Br+ ions and also the van der Waal's radii of chlorine and bromine. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 48–56, 2006
Use of the pig caecum model to mimic the human intestinal metabolism of hispidulin and related compounds
Authors: Labib Samira , Hummel Sylvia , Richling Elke , Humpf Hans‐Ulrich , Schreier Peter 
Published: November 2005

AbstractUp to now, the metabolism of hispidulin (5,7,4′‐trihydroxy‐6‐methoxyflavone), a potent ligand of the central human benzodiazepine receptor, has not been investigated. To elucidate the metabolism of hispidulin in the large intestine, its biotransformation by the pig caecal microflora was studied. In addition, the efficiency of the pig caecal microflora to degrade galangin (3,5,7‐trihydroxyflavone), kaempferol (3,5,7,4′‐tetrahydroxyflavone), apigenin (5,7,4′‐trihydroxyflavone), and luteolin (5,7,3′,4′‐tetrahydroxyflavone) was investigated. Identification of the formed metabolites was performed by high‐performance liquid chromatography (HPLC)‐diode array detection, HPLC‐electrospray ionization‐tandem mass spectrometry, and high‐resolution gas chromatography‐mass spectrometry. The caecal microflora transformed hispidulin to scutellarein (5,6,7,4′‐tetrahydroxyflavone), an effective α‐glucosidase inhibitor, and 3‐(4‐hydroxyphenyl)‐propionic acid; galangin to phenylacetic acid and phloroglucinol; kaempferol to 4‐hydroxyphenylacetic acid, phloroglucinol, and 4‐methylphenol; apigenin to 3‐(4‐hydroxyphenyl)‐propionic acid and 3‐phenylpropionic acid, and luteolin to 3‐(3‐hydroxyphenyl)‐propionic acid, respectively. To elucidate to what extent different hydroxylation patterns on the B‐ring influence the degradation degree of flavonoids, the conversions of galangin and kaempferol as well as that of apigenin and luteolin were compared with those of quercetin (3,5,7,3′,4′‐pentahydroxyflavone) and chrysin (5,7‐dihydroxyflavone), respectively. Regardless of the flavonoid subclass, the presence of a hydroxy group at the 4′‐position seems to be a prerequisite for fast breakdown. An additional hydroxy group at the B‐ring did not affect the degradation degree.
Pyrolytic acrylamide formation from purified wheat gluten and gluten‐supplemented wheat bread rolls
Authors: Claus Achim , Weisz Georg M. , Schieber Andreas , Carle Reinhold 
Published: November 2005

AbstractRecent studies have revealed different acrylamide formation mechanisms, e. g. from carnosine (N‐β‐alanyl‐L‐histidine) and aminopropionamide as additional precursors. The occurrence of acrylamide in food matrices devoid of common precursors such as meat supports an additional formation pathway. Gluten was recovered from wheat flour by water extraction. Starch, reducing sugars and amino acids were removed using α‐amylase and NaCl solution and were completely absent in the purified gluten fraction. The gluten was dry heated at temperatures ranging from 160 to 240°C for 8 to 12 min and analyzed for acrylamide and cinnamic amide using liquid chromatography‐tandem mass spectrometry. Acrylamide could be detected up to 3997 μg/kg gluten dry weight. Cinnamic amide was detected and unambiguously identified in the gluten samples, thus confirming the proposed formation of acrylamide from proteins. After gluten addition to bread roll dough, protein pyrolysis to form acrylamide in the complex food matrix was assessed. Contents of asparagine and reducing sugars were diminished due to the addition of the gluten. In contrast to the expectation with respect to the well‐established common formation mechanism of acrylamide, it increased from 53.4 to 63.9 μg/kg (+20%), which was in good correlation with the higher proportion of gluten. As demonstrated by the t‐test, the increase in acrylamide was significant when comparing 0 and 15% gluten addition. Additionally, cinnamic amide could be found in crusts of bread rolls. Thus, evidence for pyrolytic formation of acrylamide from wheat gluten was provided.
Natural flavonoids are potent inhibitors of glycogen phosphorylase
Authors: Jakobs Sandra , Fridrich Diana , Hofem Sabine , Pahlke Gudrun , Eisenbrand Gerhard 
Published: November 2005

AbstractThere is little known about effects to be expected from high intake of flavonoids with respect to regulation of glucose/glycogen homeostasis. Glucose/glycogen homeostasis is mainly regulated by glycogen synthase (GS) and glycogen phosphorylase (GP). We investigated effects of naturally occurring flavonoids with varying substitution pattern on the activity of isolated muscle GP. Almost all flavonoids tested inhibited phosphorylated, active GPa, as well as unphosphorylated, adenosine monophosphate‐activated GPb. However, inhibition of GPa was two‐to‐fourfold stronger than that of GPb. The flavonol quercetin and the anthocyanidins cyanidin and delphinidin turned out to be the most potent inhibitors of GPa, with concentration values where enzymatic activity is 50% of the respective control in the low micromolar range (< 5 μM). Furthermore, by comparing GPa inhibitory activity of typical representatives from all known flavonoid classes, structural elements of flavonoids required for effective GP inhibition could be identified.
Photodegradation mechanism and stabilization of polyphenylene oxide and rigid‐rod polymers
Authors: So Ying‐Hung 
Published: November 2005

AbstractPoly(2,4‐dimethyl‐1,4‐phenylene oxide) (PPO), poly(benzo[1,2‐d:5,4‐d′]bisoxazole‐2,6‐diyl‐1,4‐phenylene) (PBO) and poly(benzo[1,2‐d:4,5‐d′]bisthiazole‐2,6‐diyl‐1,4‐phenylene) (PBZT), which are polymers with extended conjugated structures, undergo a self‐sensitized photo‐induced electron‐transfer reaction. A second component is not required. This article presents many similar observations on these polymers when they are exposed to light and evidence to support the proposed photo‐induced electron‐transfer mechanism. Methods to stabilize these polymers against photo‐oxidation are also described. Workers investigating other conjugated polymeric systems may find the experimental methods, observations and polymer stabilization approaches discussed in this review useful. Copyright © 2005 Society of Chemical Industry
Proteome analysis of combined effects of androgen and estrogen on the mouse mammary gland
Authors: Zhang Lijun , Liu Xin , Zhang Jian , Cao Rui , Lin Ying , Xie Jinyun , Chen Ping , Sun Yi , Li Daiqiang , Liang Songping 
Published: November 2005

AbstractWe and other investigators have previously shown that estrogen and androgen have synergistic effects on the growth of mammary epithelial ducts and alveoli in the Noble mouse. However, the molecular mechanisms behind the synergy are unknown. In the present study, we treated female FVB mice with 17‐estrodial (E2) and 5‐dihydrotestosterone‐bezonate (DHT‐B) using slow‐releasing hormone pellets for 7 months. Dissection showed that hormone treatment caused atypical hyperplasia of mammary ducts and alveoli. A functional proteomic approach was used to study the holistic protein changes in mammary glands. 2‐DE was used to separate proteins. Twenty‐five protein spots that were differentially expressed in hormone‐treated tissues compared to the control were identified by MALDI‐TOF‐MS, and ESI‐quadrupole‐TOF‐MS, which include some proteins that are correlative with response to estrogen and androgen stimulation, cells differentiation and growth, signal transduction, metabolism, etc. Real‐time RT‐PCR was carried out to verify the different expression. These results offered some clues to understand the function of E2 and DHT‐B.
Ligand‐independent orphan receptor TR2 activation by phosphorylation at the DNA‐binding domain
Authors: Khan Shaukat Ali , Park Sung Wook , Huq M. D. Mostaqul , Wei Li‐Na 
Published: November 2005

AbstractIn a previous report we demonstrated protein kinase C (PKC)‐mediated phosphorylation of the ligand‐binding domain (LBD) of orphan nuclear receptor TR2. In this report, we provide the evidence of PKC‐mediated phosphorylation of the DNA‐binding domain (DBD) of TR2. Two PKC target sites were predicted within the DBD, at Ser‐170 and Ser‐185, but only Ser‐185 was confirmed by MS. Phosphorylation of DBD facilitated DNA binding of the TR2 receptor and its recruiting of coactivator p300/CBP‐associated factor (P/CAF). Ser‐185 was required for DNA binding, whereas both Ser‐170 and Ser‐185 were necessary for receptor interaction with P/CAF. The P/CAF‐interacting domain of TR2 was located in its DBD. A double mutant (Ser‐170 and Ser‐185) of TR2 significantly lowered the activation of its target gene RARβ2. This study provides the first evidence for ligand‐independent activation of TR2 orphan receptor through PTM at the DBD, which enhanced its DNA‐binding ability and interaction with coactivator P/CAF.
Ubiquitous cancer genes: Multipurpose molecules for protein micro‐arrays
Authors: Altenberg Brigitte , Gemuend Christine , Greulich Karl Otto 
Published: November 2005

AbstractMultipurpose genes in the human genome which are over‐expressed in a large variety of different cancers have been identified. Forty‐two of the 19,016 human genes annotated to date (0.2%) are ubiquitously over‐expressed in half or more of the 36 investigated human cancers. Of these genes, 15 are involved in protein biosynthesis and folding, six of them in glycolysis. A group of 13 solid tumours over‐express almost all (39–42 of 42) ubiquitous cancer genes, suggesting a common mechanism underlying these cancers. Others, such as endocrine cancers, have only a few over‐expressed ubiquitous cancer genes. The proteins for which these genes code or the corresponding antibodies are candidates for small protein microarrays aiming at maximum information with only a limited number of proteins. Since the over‐expression pattern varies from cancer to cancer, distinction between different cancer classes is possible using one single set of protein or antibody molecules.
The up‐regulation of proteasome subunits and lysosomal proteases in hepatocellular carcinomas of the HBx gene knockin transgenic mice
Authors: Cui Fang , Wang Youliang , Wang Jie , Wei Kaihua , Hu Jingqun , Liu Fang , Wang Hongli , Zhao Xiaohang , Zhang Xuemin , Yang Xiao 
Published: November 2005

AbstractChronic infection of hepatitis virus B (HBV) has been proven to be one of the most important risk factors of hepatocellular carcinoma (HCC). HBx has been shown to function in the viral life cycle and the development of HCC. Recently, we have reported that HBx transgenic mice (p21‐HBx), generated by gene knockin, develop HCC at the age of 18 months. To further study the function of HBx during the development of HCC in vivo, we performed proteomic analysis of the transgenic and wild‐type control mice. The combination of 2‐DE and MALDI‐TOF MS revealed that proteasome subunits (PSMA6, PSMB4, PSMC2 and PSMD12) were up‐regulated in tumor tissues of the p21‐HBx transgenic mice. Cathepsin B, ubiquinol‐cytochrome C reductase core protein 1 and an ATP‐dependent caseinolytic protease, which were involved in the cellular proteolytic process, were also found increased in tumors. The results were confirmed in tumors of transgenic mice and HCCs of human using RT‐PCR. All these results suggested that the strengthened ubiquitin‐proteasome and lysosomal pathway might contribute to the development of HBx‐related HCC.
Array based capillary IEF with a whole column image of laser‐induced fluorescence in coupling to capillary RPLC as a comprehensive 2‐D separation system for proteome analysis
Authors: Mao Yu , Li Yan , Zhang Xiangmin 
Published: November 2005

AbstractBased on array CIEF (ACIEF) and a novel whole column imaging detection (WCID), a comprehensive 2‐D system with laser‐induced fluorescence was developed for protein mapping. By coupling capillary RPLC (CRPLC) as the first dimension and ACIEF as the second dimension, a high‐throughput and high‐resolution proteomic expression profiling was obtained. An array of up to 60 capillaries was assembled, with electrical connections made through filling small breaks, created on each capillary at positions of buffer reservoirs, with a porous polymer. A whole column image system with laser‐induced fluorescence (LIF) was devised. Spot excitation was performed with a laser converted to produce linear light, and a CCD camera was employed to take images of the protein fluorescence during line laser scanning of the capillary array. Quantitative detection of thousands of focusing protein bands in the capillary array was achieved. Details on the capillary array fabrication and scanning LIF detection system devices are discussed. The efficiency of this CRPLC‐ACIEF‐LIF‐WCID system was further demonstrated using samples of soluble proteins extracted from liver cancer tissue. The overall peak capacity was estimated to be around 18 000 in an analysis time of less than 3 h. The reproducibility of consecutive runs and different columns were assessed as having an RSD of 1.5% and 2.2% in focusing positions, respectively.