bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective Catalytic Oxidation of Organosulfur Compounds with tert‐Butyl Hydroperoxide
Authors: Chica Antonio , Gatti Giorgio , Moden Bjorn , Marchese Leonardo , Iglesia Enrique 
Published: December 2005

AbstractRates and selectivities for the oxidation of various organosulfur compounds with tert‐butyl hydroperoxide were measured on CoAPO‐5 (APO=aluminophosphate; Co/P=0.05), Co/H‐Y (Co/Al=0.15), and MoOx/Al2O3 (15 % wt MoO3). Rates increased with increasing electron density at the sulfur atom (methyl phenyl sulfide>diphenyl sulfide>4‐methyldibenzothiophene>2,5‐dimethyl thiophene). Rates (per metal atom) were significantly higher on CoAPO‐5 than on Co/H‐Y, MoOx/Al2O3, or homogeneous Co acetate catalysts. Small amounts of sulfoxides (1‐oxide) were detected on all catalysts at low reactant conversions, together with their corresponding sulfones; at higher conversions, only sulfones (1,1‐dioxide) were detected, indicating that the oxidation of sulfoxides is much faster than for organosulfur reactants in the sequential oxidation pathways prevalent on these catalysts. Framework Co cations were not leached from CoAPO‐5 during the oxidation of 4‐methyldibenzothiophene, but most exchanged Co cations in H‐Y and >20 % of Mo cations in MoOx/Al2O3 were extracted during these reactions. The fraction of redox‐active Co cations in CoAPO‐5 and Co/H‐Y was measured by reduction–oxidation cycles using H2 and O2 and by UV‐visible spectroscopy. This fraction was much larger in CoAPO‐5 (0.35) than in Co/H‐Y (0.01), consistent with the higher oxidation rates measured on CoAPO‐5 and with the involvement of redox‐active species in kinetically‐relevant steps in catalytic oxidation sequences. Redox‐active Co cations at framework positions within accessible channels are required for catalytic activity and structural stability during oxidative desulfurization, whether hydroperoxides are used as reactants or as intermediates (when O2 is used as the oxidant).
Analysis of optical purity and impurity of synthetic d‐phenylalanine products using sulfated β‐cyclodextrin as chiral selector by reversed‐polarity capillary electrophoresis
Authors: Zhao Yan , Yang Xing‐Bin , Jiang Ru , Sun Xiao‐Li , Li Xiao‐Ye , Liu Wen‐Min , Zhang Sheng‐Yong 
Published: December 2005

AbstractA new capillary electrophoresis (CE) method has been achieved for simultaneous separation and quantification of phenylalanine, N‐acetylphenylalanine enantiomers, and prochiral N‐acetylaminocinnamic acid, possibly co‐existent in reaction systems or synthesized products of d‐phenylalanine. The separation was carried out in an uncoated capillary under reversed‐electrophoretic mode. Among the diverse charged cyclodextrins (CDs) examined, highly sulfated (HS)‐β‐CD as the chiral selector exhibited the best enantioselectivity. The complete separation of the analytes was obtained under the optimum conditions of pH 2.5, 35 mM Tris buffer containing 4% HS‐β‐CD, applied voltage −15 kV, and capillary temperature 25°C. Furthermore, the proposed method was applied to the determination of optical purity and trace impurities in three batches of the asymmetric synthetic samples of d‐phenylalanine, and satisfactory results were obtained. The determination recoveries of the samples were in the range of 97.8–103.8%, and precisions fell within 2.3–5.0% (RSD). The results demonstrate that this CE method is a useful, simple technique and is applicable to purity assays of d‐phenylalanine. © 2005 Wiley‐Liss, Inc. Chirality 18:84–90, 2006.
Use of the exciton chirality method in the investigation of ligand‐gated synthetic ion channels
Authors: Sakai Naomi , Talukdar Pinaki , Matile Stefan 
Published: December 2005

AbstractThe objective of this brief highlight is to point out the central role of the exciton chirality method to gain insights on the structural basis of the recently achieved ligand gating of synthetic ion channels. This unprecedented ligand gating was achieved with an equally unprecedented transmembrane rigid‐rod π‐stack architecture that is designed to adopt a closed conformation with helically stacked naphthalenediimide (NDI) acceptors. The intercalation of the complementary electron‐rich dialkoxynaphthalene ligands then stimulates the untwisting of the closed π‐helices into hollow barrel–stave supramolecules. During this helix–barrel transition, the angle between the transition moments of the exciton‐coupled NDI chromophores decreases toward zero. The corresponding disappearance of the split CD provides, according to the exciton chirality method, the otherwise elusive experimental support that ligand‐gated ion channel formation really occurs by this rationally designed helix–barrel transition. © 2005 Wiley‐Liss, Inc. Chirality 18:91–94, 2006.
Circular dichroism of heterochromophoric and partially regenerated purple membrane: Search for exciton coupling
Authors: Karnaukhova Elena , Vasileiou Chrysoula , Wang Andy , Berova Nina , Nakanishi Koji , Borhan Babak 
Published: December 2005

AbstractIn order to determine the origin of the bisignate CD spectra of native purple membrane, heterochromophoric analogues containing bacteriorhodopsin regenerated with native all‐trans‐retinal and retinal analogues were investigated. The data collected for the purple membrane samples containing two different chromophores suggest the additive character of the CD spectra. This conclusion was supported by a series of spectra using 5,6‐dihydroretinal and 3‐dehydroretinal and by using 33% regenerated PM in buffer and in presence of osmolytes. Our results support the idea of conformational heterogeneity of the chromophores in the bR in the trimer, suggesting that the three bR subunits in the trimer are not conformationally equal, and therefore, the bisignate CD spectrum of bR in the purple membrane occurs rather due to a superposition of the CD spectra from variously distorted bR subunits in the trimer than interchromophoric exciton‐coupling interactions. © 2005 Wiley‐Liss, Inc. Chirality 18:72–83, 2006.
Design, classification, and strategies of synthesis of modular bidentate ligands based on aryl[2.2]paracyclophane backbone
Authors: Rozenberg Valeria , Zhuravsky Roman , Sergeeva Elena 
Published: December 2005

AbstractThe aryl[2.2]paracyclophane backbone, which is a “hybrid” of a configurationally rigid [2.2]paracyclophanyl unit and a biphenyl unit, is proposed as a new source for the chiral ligands. Classification of such ligands in accordance with mutual arrangement of the functional substituents and their nature is also introduced. Key strategic approaches to the synthesis of regioisomeric biphenols and hydroxyaldehydes, including Suzuki cross‐coupling reaction, lithiation/electrophilic quench, and chiral resolution, are elaborated. Examples of their further modification and application of several O,O‐ and N,O‐ligands as chiral inductors in asymmetric catalysis are described. © 2005 Wiley‐Liss, Inc. Chirality 18:95–102, 2006.
Tracking of enantioselective solubility of rac‐norgestrel in the presence of cyclodextrin by a CD spectroscopic method
Authors: Szegvári Dávid , Zelkó Romána , Horváth Péter , Gergely András 
Published: December 2005

AbstractDissolution of hydrophobic rac‐norgestrel in aqueous γ‐cyclodextrin (γ‐CyD) and hydroxypropyl‐γ‐cyclodextrin (HP‐γ‐CyD) solutions was investigated, and enantioselective dissolution was observed. (−)‐Norgestrel, the eutomer molecule, was dissolved to a greater extent using each of the CyDs, although the effect was more significant in the case of HP‐γ‐CyD. A circular dichroism (CD) spectroscopic method based on measurement of the anisotropy factor was applied for the determination of the enantiomer ratio. The concentration and the enantiomer ratio of norgestrel were determined indirectly in octanol after extraction. Optical rotation dispersion (ORD) measurements could confirm that neither the free CyDs nor their inclusion complexes could get into the organic phase during transport to octanol. Only the norgestrel molecules were able to get into the organic phase, although the enantiomer ratio remained the same as was obtained in the aqueous CyD solution. © 2005 Wiley‐Liss, Inc. Chirality 18:121–126, 2006.
Raman optical activity of proteins, carbohydrates and glycoproteins
Authors: Zhu Fujiang , Isaacs Neil W. , Hecht Lutz , Tranter George E. , Barron Laurence D. 
Published: December 2005

AbstractOn account of its sensitivity to chirality, Raman optical activity (ROA), which may be measured as a small difference in the intensity of vibrational Raman scattering from chiral molecules in right‐ and left‐circularly polarized incident light, or as the intensity of a small circularly polarized component in the scattered light, is a powerful probe of the structure of biomolecules. Protein ROA spectra provide information on secondary and tertiary structures of polypeptide backbones, backbone hydration and side‐chain conformations, and on structural elements present in unfolded states. Carbohydrate ROA spectra provide information on the central features of carbohydrate stereochemistry, especially that of the glycosidic link. Glycoprotein ROA spectra provide information on both the polypeptide and carbohydrate components. This article describes the ROA technique and presents and discusses the ROA spectra of a selection of proteins, carbohydrates, and a glycoprotein. The many structure‐sensitive bands in protein ROA spectra are favorable for applying pattern recognition techniques, illustrated here using nonlinear mapping, to determine structural relationships between different proteins. © 2005 Wiley‐Liss, Inc. Chirality 18:103–115, 2006.
Enantioseparation of secondary alcohols by diastereoisomeric salt formation
Authors: Kiss Violetta , Egri Gabriella , Bálint József , Fogassy Elemér 
Published: December 2005

AbstractA general method was found for the resolution of the racemic 1‐phenyl‐1‐propanol (1) and 1‐phenyl‐2‐propanol (2) with various resolving agents. Monoesters of the alcohols were prepared, which were then reacted with different chiral bases. Successful optical resolutions were achieved only with the maleic acid monoesters (3 and 6). Alcohol 1 has been resolved to >99% enantiomeric excess by diastereoisomeric salt formation via its maleic acid monoester (3) using cinchonidine (9) as resolving agent. Alcohol 2 has been obtained in 98% enantiomeric excess by diastereoisomeric salt formation via its the maleic acid monoester (6) using (+)‐dehydroabietylamine (11) as resolving agent. © 2005 Wiley‐Liss, Inc. Chirality 18:116–120, 2006.
Structure and chiroptical properties of supramolecular flower pigments
Authors: Ellestad George A. 
Published: December 2005

AbstractResearch over the last 30 years has shown that at physiological concentrations of ca. 5 × 10−3 M, flower pigments composed of anthocyanins, either alone or complexed with flavone copigments, and frequently with metals, are self‐assembled into non‐covalent, chiral supramolecular complexes. This serves several biological functions including color stability, protection against UV radiation and provision for specific colors to attract insects for pollination. Self‐association of the monomers takes place under conditions of molecular crowding by precise matching of the π–π stacking interactions of the aromatic chromophores and intermolecular hydrogen bonding between the attached sugars. The resulting handedness is controlled by the chiral information provided by the sugars joined glycosidically at certain positions around the periphery of the aromatic nuclei. This review gives an overview of (i) the physicochemical evidence including circular dichroism, 1H NMR, and X‐ray analysis for the structure and supramolecular chirality of these amphiphilic complexes, (ii) the role of the sugars on directing the chirality of the resulting supramolecules, (iii) the energetics of monomer association, and (iv) the possible influence of stacking chirality on insect pollination. © 2005 Wiley‐Liss, Inc. Chirality 18:134–144, 2006.
Robert Boyle's chiral crystal chemistry: Computational re‐evaluation of enantioselective adsorption on quartz
Authors: Kahr Bart , Chittenden Brianne , Rohl Andrew 
Published: December 2005

AbstractWhile searching for early examples of interactions of organic chromophores with minerals in the context of a systematic study of the process of dyeing crystals, we came across Robert Boyle's description of an experiment that may have been evidence of the enantioselective adsorption of a natural product, carminic acid (7‐β‐d‐glucopyranosyl‐9,10‐dihydro‐3,5,6,8‐tetrahydroxy‐1‐methyl‐9,10‐dioxo‐2‐anthracenecarboxylic acid), to the chiral surfaces of α‐quartz, three centuries before such interactions became the subject of active chemical investigations. In order to determine whether Boyle did indeed observe enantioselective adsorption—albeit unbeknownst to him—we attempted to dye quartz with carminic acid according to his recipe. Quartz adsorbs carminic acid only because on heating it develops a network of microfissures that adsorb dye. This process depends on capillarity, not on specific non‐covalent interactions; there is no evidence of enantioselectivity adsorption to heated crystals or enantioselective epitaxy to unheated crystals. These failures changed the focus of our inquiry: Why have almost all attempts to demonstrate the enantioselective adsorption of additives to quartz crystal surfaces been generally confounding and equivocal? In order to answer this question, we complement our experimental historical re‐investigation with contemporary computational techniques for modeling crystal surface structure and the adsorption of additives. Minimizations of the energies associated with the adsorption of carminic acid to relaxed, hydrated d‐ and l‐quartz {10&1macr;0} surfaces are analyzed in light of quartz's abysmal record as an enantioselective stationary phase. © 2005 Wiley‐Liss, Inc. Chirality 18:127–133, 2006.
Incidence of esophageal and gastric carcinomas among American Asians/Pacific Islanders, whites, and blacks
Authors: Wu Xiaocheng , Chen Vivien W. , Ruiz Bernado , Andrews Patricia , Su L. Joseph , Correa Pelayo 
Published: December 2005

AbstractBACKGROUNDThe authors examined subsite‐specific and histology‐specific esophageal and gastric carcinoma incidence patterns among the Asians/Pacific Islander (API) population in the United States and compared them with those among whites and blacks.METHODSData on newly diagnosed esophageal and gastric carcinomas during 1996–2000 were obtained from 24 population‐based central cancer registries, representing approximately 80% of the API population in the United States. Age‐adjusted rates, using the 2000 United States standard population, and age‐specific rates were computed by anatomic subsite, histology, race, and gender. The difference in the age‐adjusted rates between APIs and other races were examined using the two‐tailed z statistic.RESULTSGreater than 75% of esophageal carcinomas among APIs, both males and females, were squamous cell carcinoma. Adenocarcinoma accounted for < 20% of all esophageal carcinomas. This pattern was similar to that among blacks but was completely opposite to that among whites. The rate of esophageal squamous cell carcinoma was 81% higher among API males compared with white males, but it was 64% less compared with black males. The rates of esophageal adenocarcinoma were significantly lower among APIs than among both whites and blacks both males and females. The majority of gastric carcinomas among APIs were noncardia adenocarcinoma, whereas cardia adenocarcinoma accounted for only 11% of gastric carcinomas among API males and 6% of gastric carcinomas among API females. The age‐adjusted incidence rate of cardia adenocarcinoma was 23% lower among API males compared with white males, but it was 26% higher compared with black males. In contrast, the rates of noncardia adenocarcinoma among APIs were approximately 3.7 times the rate among whites for both males and females and 33% higher than the rate among blacks.CONCLUSIONSSubsite‐specific and histology‐specific incidence patterns of esophagogastric carcinoma among APIs differ from those among whites and blacks. The reasons for significantly higher rates of noncardia adenocarcinoma among APIs compared with whites and blacks need further investigation. Cancer 2006. © 2005 American Cancer Society.
Correlations of telomere length, telomerase activity, and telomeric‐repeat binding factor 1 expression in colorectal carcinoma
Authors: Garcia‐Aranda Cristina , de Juan Carmen , Diaz‐Lopez Antonio , Sanchez‐Pernaute Andres , Torres Antonio‐Jose , Diaz‐Rubio Eduardo , Balibrea Jose‐Luis , Benito Manuel , Iniesta Pilar 
Published: December 2005

AbstractBACKGROUNDTelomere maintenance has been proposed as an essential step for tumor cell immortalization. The objectives of the current study were to investigate the mechanisms implicated in telomere length in colorectal carcinoma (CRC) and to evaluate the prognostic impact of telomere status.METHODSNinety‐one colorectal carcinoma samples that were obtained from patients who underwent surgery were analyzed to investigate the factors related to telomere function. The authors studied telomerase activity, terminal restriction fragment (TRF) length, and telomeric‐repeat binding factor (TRF1) expression and analyzed the prognostic implications of those factors.RESULTSMost tumors (81.3%) displayed telomerase activity. Overall, telomeres in CRC specimens were significantly shorter compared with telomeres in normal, adjacent specimens (P = 0.02). Moreover, tumors that demonstrated shortened telomeres displayed higher TRF1 levels than tumors without telomere shortening. In relation to patient prognosis, a significantly poor clinical course was observed in the group of patients who had tumors with longer telomeres (P = 0.02), and this finding emerged as an independent prognostic factor in a Cox proportional hazards model (P = 0.04; relative risk, 6.48). Among patients with tumors classified as telomerase‐positive, telomere length ratios (the ratio of tumor tissues to normal tissues) ≤ 0.66 or TRF1 over‐expression conferred a favorable outcome (P = 0.03 and P = 0.05, respectively).CONCLUSIONSThe majority of CRC specimens in the current study displayed telomerase reactivation. However, only those tumors that displayed telomere elongation conferred a poor prognosis. Conversely, colorectal tumors that over‐expressed TRF1 demonstrated telomere shortening, and patients with those tumors had a better clinical course. Cancer 2006. © 2005 American Cancer Society.
Molecular mechanism of phenoxodiol‐induced apoptosis in ovarian carcinoma cells
Authors: Alvero Ayesha B. , O'Malley David , Brown David , Kelly Graham , Garg Manish , Chen Wei , Rutherford Thomas , Mor Gil 
Published: December 2005

AbstractBACKGROUNDPreviously, it was demonstrated that phenoxodiol induces apoptosis in epithelial ovarian carcinoma (EOC) cells and that it is capable of sensitizing these cells to Fas‐mediated apoptosis. The objectives of this study were to determine whether phenoxodiol can also act as chemosensitizer to chemotherapeutic agents and to characterize the molecular mechanism behind its sensitizing effect.METHODSTen EOC cell lines were used in this study. The effect of phenoxodiol on the inhibitory concentration 50% (IC50) of carboplatin, paclitaxel, and gemcitabine was determined by the CellTiter 96 Assay. The in vivo effect of combination treatments with phenoxodiol and the above‐mentioned agents was determined in animal xenograft models. Apoptosis was measured using the Caspase‐Glo Assay and the apoptotic cascade was characterized by Western blot analyses.RESULTSThe results showed that phenoxodiol is able to sensitize EOC cells to carboplatin, paclitaxel, and gemcitabine both in vitro and in vivo. In addition, it was demonstrated that phenoxodiol is capable of inducing apoptosis by: 1) the activation of the mitochondrial pathway through caspase‐2 and Bid signaling, and 2) the proteasomal degradation of the anti‐apoptotic protein XIAP.CONCLUSIONUnderstanding the components of the apoptotic pathway activated by phenoxodiol, which allows it to sensitize EOC cells to chemotherapeutic agents, will provide valuable information on the characteristic mode of action of a chemosensitizer. This will help in the identification of novel drugs and in the design of better strategies for combination therapy in patients with recurrent ovarian carcinoma. Cancer 2006. © 2005 American Cancer Society.
Hyperglycemia and insulin resistance in men with prostate carcinoma who receive androgen‐deprivation therapy
Authors: Basaria Shehzad , Muller Denis C. , Carducci Michael A. , Egan Josephine , Dobs Adrian S. 
Published: December 2005

AbstractBACKGROUNDProstate carcinoma (PCa) is one of the most common malignancies in men. Androgen‐deprivation therapy (ADT) is used frequently in the treatment of recurrent and metastatic PCa, rendering these men hypogonadal. Because male hypogonadism is associated with an unfavorable metabolic profile, and men with PCa have high cardiovascular mortality, the authors evaluated the effects of long‐term ADT on fasting glucose levels, insulin levels, and insulin resistance.METHODSTo evaluate the long‐term effects of ADT on fasting glucose and insulin resistance in men with PCa who received ADT and to determine whether these metabolic alterations are a result of hypogonadism, the authors conducted a cross‐sectional study at a university‐based research institution in the United States. In total, 53 men were evaluated, including 18 men with PCa who received ADT for at least 12 months prior to the onset of the study (the ADT group), 17 age‐matched men with nonmetastatic PCa who had undergone prostatectomy and/or received radiotherapy and who were not receiving ADT (the non‐ADT group), and 18 age‐matched controls (the control group). None of the men had a known history of diabetes mellitus.RESULTSThe mean age was similar in all 3 groups (P = 0.33). Serum total testosterone levels (P < 0.0001) and free testosterone levels (P < 0.0001) were significantly lower in the ADT group compared with the other groups. Men in the ADT group had a higher BMI compared with the other groups (overall P = 0.005). After adjustment for age and BMI, men in the ADT group had significantly higher fasting levels of the following parameters: 1) Glucose levels were 131.0 ± 7.43 mg/dL in the ADT group compared with 103.0 ± 7.42 mg/dL in the non‐ADT group (P = 0.01) and 99.0 ± 7.58 mg/dL in the control group (P < 0.01). 2) Insulin levels were 45.0 ± 7.25 uU/mL in the ADT group compared with 24.0 ± 7.24 uU/mL in the non‐ADT group (P = 0.05) and 19.0 ± 7.39 uU/mL in the control group (P = 0.02). 3) Leptin levels were 25.0 ± 2.57 ng/mL in the ADT group compared with 12.0 ± 2.56 ng/mL in the non‐ADT group (P < 0.01) and 6.0 ± 2.62 ng/mL in the control group (P < 0.01). 4) The homeostatic model assessment for insulin resistance (HOMAIR) = 17.0 ± 2.78 in the ADT group compared with HOMAIR = 6.0 ± 2.77 in the non‐ADT group (P < 0.01) and HOMAIR = 5.0 ± 2.83 in the control group (P = 0.01). There was a significant negative correlation between total and free testosterone levels with fasting glucose, insulin, leptin, and HOMAIR.CONCLUSIONSThe current data suggested that men with PCa who are receiving long‐term ADT are at risk for developing insulin resistance and hyperglycemia, thus leading to their increased risk of cardiovascular disease. This adverse metabolic profile developed independent of age and BMI and appeared to be a direct result of androgen deprivation. Cancer 2006. © 2005 American Cancer Society.