bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ions Can Move a Proton‐Coupled Electron‐Transfer Reaction into Tunneling Regime
Authors: Brala Cvijeta Jakobušić , Pilepić Viktor , Sajenko Ivana , Karković Ana , Uršić Stanko 
Published: September 2011

AbstractThe effects of charged species on proton‐coupled electron‐transfer (PCET) reaction should be of significance for understanding/application of important chemical and biological PCET systems. Such species can be found in proximity of activated complex in a PCET reaction, although they are not involved in the charge transfer process. Reported here is the first study of the above‐mentioned effects. Here, the effects of Na+, K+, Li+, Ca2+, Mg2+, and Me4N+ observed in PCET reaction of ascorbate monoanions with hexacyanoferrate(III) ions in H2O reveal that, in presence of ions, this over‐the‐barrier reaction entered into tunneling regime. The observations are: a) dependence of the rate constant on the cation concentration, where the rate constant is 71 (at I = 0.0023), and 821 (at 0.5M K+), 847 (at 1.0M Na+), and 438 M−1 s−1 (at 0.011M Ca2+); b) changes of kinetic isotope effect (KIE) in the presence of ions, where kH/kD=4.6 (at I = 0.0023), and 3.4 (in the presence of 0.5M K+), 3.3 (at 1.0M Na+), 3.9 (at 0.001M Ca2+), and 3.9 (at 0.001M Mg2+), respectively; c) the isotope effects on Arrhenius pre‐factor where AH/AD=0.97 (0.15) in absence of ions, and 2.29 (0.60) (at 0.5M Na+), 1.77 (0.29) (at 1.0M Na+), 1.61 (0.25) (at 0.5M K+), 0.42 (0.16) (at 0.001M Ca2+) and 0.16 (0.19) (at 0.001M Mg2+); d) isotope differences in the enthalpies of activation in H2O and in D2O, where ΔΔH‡(D,H)=3.9 (0.4) kJ mol−1 in the absence of cations, 1.3 (0.6) at 0.5M Na+, 1.8 (0.4) at 0.5M K+, 1.5 (0.4) at 1.0M Na+, 5.5 (0.9) (at 0.001M Ca2+), and 7.9 (2.8) (at 0.001M Mg2+) kJ mol−1; e) nonlinear proton inventory in reaction. In the H2O/dioxane 1 : 1, the observed KIE is 7.8 and 4.4 in the absence and in the presence of 0.1M K+, respectively, and AH/AD=0.14 (0.03). The changes when cations are present in the reaction are explained in terms of termolecular encounter complex consisting of redox partners, and the cation where the cation can be found in a near proximity of the reaction‐activated complex thus influencing the proton/electron double tunneling event in the PCET process. A molecule of H2O is involved in the transition state. The resulting ‘configuration’ is more ‘rigid’ and more appropriate for efficient tunneling with Na+ or K+ (extensive tunneling observed), i.e., there is more precise organized H transfer coordinate than in the case of Ca2+ and Mg2+ (moderate tunneling observed) in the reaction.
Three New Neolignans and One New Phenylpropanoid from the Leaves and Stems of Toona ciliata var. pubescens
Authors: Liu Yu‐Bo , Qin Jiang‐Jiang , Cheng Xiang‐Rong , Zhu Jia‐Xian , Zhang Fei , Jin Hui‐Zi , Zhang Wei‐Dong 
Published: September 2011

AbstractThree new neolignans, (7S,8S,7′E)‐4,9‐dihydroxy‐3,7,3′,9′‐tetramethoxy‐8,4′‐oxyneolign‐7′‐ene (1), (7R,8S,7′E)‐4, 9‐dihydroxy‐3,7,3′,9′‐tetramethoxy‐8,4′‐oxyneolign‐7′‐ene (2), (7S,8S,7′E)‐5, 9‐dihydroxy‐3,7,3′,5′,9′‐pentamethoxy‐8,4′‐oxyneolign‐7′‐ene (3), and one new phenylpropanoid, threo‐5‐hydroxy‐3,7‐dimethoxyphenylpropane‐8,9‐diol (4), were isolated from the leaves and stems of Toona ciliata var. pubescens. Their structures were determined on the basis of spectroscopic analysis, especially 2D‐NMR, HR‐ESI‐MS, and CD data. The antiproliferative activities of these compounds against four tumor cell lines (A549, Colo 205, QGY‐7703, and LOVO) were also evaluated by MTT (=(3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) method.
Stepwise Mechanism of Hydroxide Ion Catalyzed Cyclization of Uridine 3′‐Thiophosphates
Authors: Ora Mikko , Hanski Anne 
Published: September 2011

AbstractDiastereoisomeric isopropyl‐, 2‐ethoxyethyl‐, 2,2‐dichloroethyl‐ and 2,2,2‐trichloroethyl uridine 3′‐thiomonophosphates, 1a–1d, respectively, have been synthesized, and their hydrolyses in aqueous alkali at 25° have been followed by HPLC. According to the time‐dependent product distributions obtained, the alkyl phosphorothioates 1a–1d undergo cleavage to uridine 2′‐ and 3′‐thiophosphates, 7a and 7b, respectively, via a uridine 2′,3′‐cyclic thiophosphate (6). The rate of the hydroxide ion‐catalyzed cyclization of both (RP)‐ and (SP)‐diastereoisomer is highly dependent on the polar nature of the leaving group, the βlg values being −1.23±0.03 and −1.24±0.03, respectively. Brønsted dependence of the second‐order rate constants (kOH [dm3 mol−1 s−1]) on the pKa values of the leaving alcohols shows a convex breakpoint on going from alkyl esters 1a–1d to aryl esters studied earlier. This may be considered as a strong evidence for a stepwise mechanism, where the formation and breakdown of the phosphorane intermediate is the rate‐limiting step with aryl and alkyl esters, respectively.
Three New Peroxy Triterpene Lactones from Pseudolarix kaempferi
Authors: Tan Jun‐Ming , Qiu Yi‐Hua , Tan Xin‐Qi , Tan Chang‐Heng 
Published: September 2011

AbstractThree new 3(4),9(10)‐disecocycloartane peroxy triterpene lactones, named as pseudolarolides Q2, T1, and T2 (1–3, resp.), along with five known triterpenoids, were isolated from the seeds of Pseudolarix kaempferi Gord. Their structures were elucidated to be (9R,10R,16R,23R,25R)‐16,23‐epoxy‐9,10‐epidioxy‐3,4:9,10‐disecocycloart‐1(2)‐ene‐3,4:26,23‐diolide (1), (1R,9R,10S,16R,23S,25R)‐1,4:16,23‐diepoxy‐9,10‐epidioxy‐3,4;9,10‐disecocycloartan‐26(23)‐olid‐3‐oic acid methyl ester (2), and (1R,9R,10S,16R,23R,25R)‐1,4:16,23‐diepoxy‐9,10‐epidioxy‐3,4;9,10‐disecocycloartan‐26(23)‐olid‐3‐oic acid methyl ester (3) on the basis of spectroscopic analysis.
Detection of familial adenomatous polyposis with orthogonal polarized spectroscopy of the oral mucosa vasculature
Authors: Basiri Ali , Edelstein Daniel L. , Graham Jenna , Nabili Afshin , Giardiello Francis M. , Ramella‐Roman Jessica C. 
Published: September 2011

AbstractFamilial Adenomatous Polyposis (FAP) is an autosomal dominant disease characterized by the development of multiple colonic polyps at younger age with a near 100% lifetime risk of colorectal cancer. The determination of FAP is made after extensive clinical evaluation and genetic testing of at risk individuals. We investigated a novel spectro‐polarimetric imaging system capable of capturing high‐resolution images of the oral mucosa at different wavelengths in an attempt to distinguish patients with FAP from controls. Results of a clinical trial show that the system is capable of separating FAP positive individuals from controls by measuring the individuals' oral vascular density and complexity. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge‐transfer processes in the assembly of SinOm neutral clusters
Authors: Jadraque Maria , Martin Margarita 
Published: September 2011

AbstractThe chemical bond formation in oxygen‐rich SinOm clusters was investigated by sampling the potential energy surface of the model systems SiO + SiO2 → Si2O3 and (SiO)2 + SiO2 → Si3O4 along a two‐dimensional reaction coordinate, by density functional theory calculations. Evidence for crossing between the weakly bound neutral–neutral (SiO)n + SiO2 and the highly attractive ion‐pair (SiO) + SiO surfaces was found. Analysis of frontier molecular orbitals and charge distribution showed that surface crossing involves transfer of valence electron charge from (SiO)2 to SiO2. The sum of the natural atomic charges over the (SiO)n and (SiO2) groups of the SinOm cluster products, gave a net positive charge on the (SiO)n “core” and a net negative charge on the (SiO2) groups. This is interpreted as the “ion‐pair memory” left on the SinOm products by the charge‐transfer mechanism and may provide a way to assess the role of charge‐transfer processes in the assembly of larger SinOm neutral clusters. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011
Reference interval and determinants of the serum homocysteine level in a Korean population
Authors: Moon Hee‐Won , Whang Dong Hee , Ko Young Jin , Joo Shin Young , Yun Yeo‐Min , Hur Mina , Kim Jin Q 
Published: September 2011

AbstractIn this study, we estimated the reference intervals of the serum homocysteine (Hcy) level using two automated immunoassays, and we demonstrated the effects of various factors on the Hcy level in a Korean population. We calculated the gender‐ and assay‐specific reference intervals using the data from 809 healthy Koreans, and we assessed the effects of physiologic and lifestyle factors on the Hcy level. The upper limit was higher in males (19.21 and 19.76 μmol/l) than that in females (14.99 μmol/l and 15.16 μmol/l, AxSym and ADVIA centaur, respectively); the upper limits were comparable between the two assays. Smokers, vitamin nonusers, and persons without regular exercise showed a lower folate level and a higher Hcy level. The risk of hyperhomocysteinemia was significantly associated with the male gender (adjusted OR: 5.705, P‐value: 0.008) and with the low folate level group (adjusted OR: 10.412, P‐value: 0.002) on the multivariate analysis. The Hcy level was significantly different according to various factors, especially in the gender and folate level. The reference interval should be determined for each ethnic population and for each assay. The appropriate cutoff for assessing the risk for cardiovascular disease or stroke should also be validated in each population. J. Clin. Lab. Anal. 25:317–323, 2011. © 2011 Wiley‐Liss, Inc.
Urinary biomarkers for secondhand smoke
Authors: Ino Toshihiro , Ohtani Tetsuya , Yoshimi Itsuro 
Published: September 2011

AbstractThe use of a biomarker is mandatory for quantitative analysis of exposure to secondhand smoke (SHS). This article summarizes urinary biomarkers of smoke exposure which can be now quantified. The most reliable urinary biomarkers to assess the exposure to SHS are NNAL 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanol and NNAL‐Glucuronides, which is metabolites of tobacco‐specific nitrosamine. These substances were detected even in 50% of children who had undetectable level of cotinine (<0.5 ng/ml). Urinary cotinine, which is determined by a highly sensitive competing enzyme immunoassay, is also a useful biomarker. However, individual variability of CYP2A6 allele,in which nicotine is catalyzed to cotinine, affects the level of urinary cotinine. Approximately 20% of Japanese subjects have homozygotes or heterozygotes of the CYP2A6*4 allele, which has impaired nicotine metabolism and subsequently may underestimate the actual exposure to SHS. In assessing the exposure to SHS, therefore, individual variability of CYP2A6 gene polymorphism should be taken into consideration. The combination of urinary cotinine measurement and self‐report of parents' smoking seems to be accurate to assess the exposure to SHS in mass screening. J. Clin. Lab. Anal. 25:354–358, 2011. © 2011 Wiley‐Liss, Inc.
Altered sciatic nerve fiber morphology and endoneural microvessels in mouse models relevant for obesity, peripheral diabetic polyneuropathy, and the metabolic syndrome
Authors: Nowicki Marcin , Kosacka Joanna , Serke Heike , Blüher Matthias , Spanel‐Borowski Katharina 
Published: September 2011

AbstractThe morphology of sciatic nerves from leptin‐deficient ob/ob mice and leptin receptor‐deficient db/db mice, both models for obesity, peripheral diabetic neuropathy, and the metabolic syndrome, has yet to be examined for changes in nerve fibers and in endoneural microvessels. Sciatic nerves from three groups of 4‐month‐old mice (WT C57BL6, ob/ob, and db/db) were investigated. In ultrathin sections, the thickness of myelin sheaths was significantly reduced in small, medium‐sized, and large axons of db/db mice compared with WT mice. In ob/ob mice, only large fibers showed a decrease in myelin sheath thickness. The number of nonmyelinated nerve fibers was lower in ob/ob mice than in the db/db group. A thickened basal lamina of Schwann cells occurred in the ob/ob group only. In contrast, the basement membrane of endoneural microvessels was thickened in both obese groups. For this reason, laminin expression in Western blot analysis was lower in the db/db group than in the ob/ob one. Endoneural microvessels, which had been injected with fluorescein isothiocyanate, depicted signs of vasodilatation in the ob/ob and vasoconstriction in db/db mice. Endoneural vessels displayed two receptors of oxLDL. LOX‐1 was strongly expressed in db/db mice, whereas TLR4 was at its maximum in the ob/ob group. We conclude that changes in nerve fibers and in endoneural microvessels are present in sciatic nerve of both mouse models of type 2 diabetes. Upregulation of oxLDL‐dependent receptors in endoneural microvessels might be connected to different degrees of oxidative stress in severe diabetic db/db mice and in the mild diabetic ob/ob group. © 2011 Wiley Periodicals, Inc.
Classification and differential metabolite discovery of liver diseases based on plasma metabolic profiling and support vector machines
Authors: Lin Xiaohui , Zhang Yang , Ye Guozhu , Li Xiang , Yin Peiyuan , Ruan Qiang , Xu Guowang 
Published: September 2011

AbstractDiscovery of differential metabolites is the focus of metabonomics study. It has very important applications in pathogenesis and disease classification. The aim of this work is to identify differential metabolites for classifying the patients with hepatocellular carcinoma, cirrhosis and hepatitis based on metabolic profiling data analyzed by gas chromatography‐time of flight mass spectrometry. A two‐stage feature selection algorithm, F‐SVM, combining F‐score in analysis of variance and support vector machine (SVM), was applied in discovering discriminative metabolites for three different types of liver diseases. The results show that the accuracy rate of the double cross‐validation was 73.68±2.98%. 22 important differential metabolites selected by F‐SVM were identified and related pathophysiological process of liver diseases was set forth. We conclude that F‐SVM is quite feasible to be applied in the selection of biologically relevant features in metabonomics.
Silica‐coated La0.75Sr0.25MnO3 nanoparticles for magnetically driven DNA isolation
Authors: Trachtová Štěpánka , Kaman Ondřej , Španová Alena , Veverka Pavel , Pollert Emil , Rittich Bohuslav 
Published: September 2011

AbstractMagnetic La0.75Sr0.25MnO3 nanoparticles possessing an approximately 20‐nm‐thick silica shell (LSMO(0.25)@SiO2) were characterised and tested for the isolation of PCR‐ready bacterial DNA. The results presented here show that the nanoparticles do not interfere in PCR. DNA was apparently reversibly adsorbed on their silica shell from the aqueous phase system (16% PEG 6000–2 M NaCl). The method proposed was used for DNA isolation from complex food samples (dairy products and probiotic food supplements). The isolated DNA was compatible with PCR. The main advantages of the nanoparticles tested for routine use were their high colloidal stability allowing a more precise dosage and therefore high reproducibility of DNA isolation.
NMR quantitation: influence of RF inhomogeneity
Authors: Mo Huaping , Harwood John , Raftery Daniel 
Published: September 2011

AbstractThe NMR peak integral is ideally linearly dependent on the sine of excitation angle (θ), which has provided unsurpassed flexibility in quantitative NMR by allowing the use of a signal of any concentration as the internal concentration reference. Controlling the excitation angle is particularly critical for solvent proton concentration referencing to minimize the negative impact of radiation damping, and to reduce the risk of receiver gain compression. In practice, due to the influence of RF inhomogeneity for any given probe, the observed peak integral is not exactly proportional to sin θ. To evaluate the impact quantitatively, we introduce a RF inhomogeneity factor I(θ) as a function of the nominal pulse excitation angle and propose a simple calibration procedure. Alternatively, I(θ) can be calculated from the probe's RF profile, which can be readily obtained as a gradient image of an aqueous sample. Our results show that without consideration of I(θ), even for a probe with good RF homogeneity, up to 5% error can be introduced due to different excitation pulse angles used for the analyte and the reference. Hence, a simple calibration of I(θ) can eliminate such errors and allow an accurate description of the observed NMR signal's dependence on the excitation angle in quantitative analysis. Copyright © 2011 John Wiley & Sons, Ltd.
A Case of Dwarfism from the Byzantine City Rehovot‐in‐the‐Negev, Israel
Authors: Slon V. , Nagar Y. , Kuperman T. , Hershkovitz I. 
Published: September 2011

ABSTRACTSkeletons of dwarfs have been found in many archaeological sites from around the world. Nevertheless, their descriptions (morphologically and metrically) are very limited. We describe herein the skeleton of a male dwarf, approximately 35–50 years old, found in the Byzantine cemetery (5th–8th century CE) of Rehovot‐in‐the‐Negev, southern Israel. Living stature was estimated at 120–125 cm. Detailed morphological skeletal descriptions and morphometric analysis, together with computed tomography (CT) observations, suggest a diagnosis of achondroplasia. The long bones anomalies, in tandem with other features such as hydrocephalus and spinal stenosis, are discussed in regard to their effect on the dwarf's daily life. The putative place of dwarfs in early Christian communities, compared with dwarfs from other times and places, will be addressed. Copyright © 2011 John Wiley & Sons, Ltd.
Flexible polybenzoxazine thermosets containing pendent aliphatic chains
Authors: Agag Tarek , Akelah Ahmed , Rehab Ahmed , Mostafa Salwa 
Published: September 2011

AbstractThe rich chemistry of polybenzoxazines allows a wide range of molecular structure design by using appropriate starting materials. A new class of polybenzoxazines has been developed from benzoxazine monomers containing pendent long aliphatic chains. The monomers have been synthesized by the reaction of phenol or bisphenol A with two different long‐chain aliphatic amines. The chemical structure of the monomers was confirmed by 1H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The polymerization behavior of the monomers studied by differential scanning calorimetry shows exothermic peaks due to the ring‐opening polymerization of benzoxazine monomers centered at 247–255 °C. Dynamic mechanical analysis indicated that the glass transition temperatures Tg were in the range 81–92 °C. The thermal stability of the polymers was also examined by thermogravimetric analysis, demonstrating that the weight loss temperatures decreased in comparison with that of traditional polybenzoxazine. Copyright © 2011 Society of Chemical Industry
Effect of crystallization on barrier properties of formulated polylactide
Authors: Courgneau Cécile , Domenek, Sandra , Lebossé Régis , Guinault Alain , Avérous Luc , Ducruet Violette 
Published: September 2011

AbstractPolylactide (PLA), a biodegradable polymer obtained from biomass, was formulated with a nucleating agent, talc, and a plasticizer, acetyl tributyl citrate, and cold crystallized in α and α′ form. The barrier properties of crystallized PLA were investigated as a function of the formulation and the crystalline form, thanks to three molecules with increasing polymer interactions, i.e. helium, oxygen and ethyl acetate (EA). Contrary to expectation, the oxygen diffusion coefficient in neat and formulated PLA did not decrease with crystallization. Even an increase of the diffusion coefficient was noticed for the most interacting probe, EA, in formulated PLA. Conditioning of neat and formulated PLA in an atmosphere containing EA vapour caused a modification of the material structure by plasticization and induced crystallization even at small EA activities. The plasticizing effect caused the glass transition temperature Tg to shift to below ambient temperature. In the case of neat PLA induced crystallization in solely the α form was obtained, and in the case of formulated PLA a blend of α and α′ forms was observed. Copyright © 2011 Society of Chemical Industry
Single electron transfer‐living radical polymerization of methyl methacrylate catalyzed by ytterbium powder
Authors: Liu Delong , Ma Jing , Chen Hou , Yin Ping , Ji Naiyi , Zong Guangxi 
Published: September 2011

AbstractZerovalent ytterbium (Yb) powder is firstly used as a catalyst in single electron transfer‐living radical polymerization of methyl methacrylate initiated by carbon tetrachloride in N, N‐dimethylformamide (DMF) and dimethyl sulfoxide, respectively. Polymerization proceeds in a “living”/controlled way as evidenced by kinetic studies and chain extension results, producing well‐defined polymers with controlled degree of polymerization and narrow molecular weight distribution. The apparent activation energy of polymerization in DMF is accounted to be 36.2 kJ/mol, and the energy of equilibrium state is calculated to be 13.9 kJ/mol. An increase in the concentration of Yb(0) yields a higher monomer conversion. It is observed that polymerization rate experiments a rapid increase in the presence of more polar solvent water, and increasing in the content of H2O results in an increase in the apparent rate constant of polymerization, and a decrease in the molecular weight distribution. The reaction rate and molecular weight increase along with the decrease of DMF content. The effect of Yb(0) powder content, different ligands and concentration of initiator on the polymerization is also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
A couple‐based intervention for patients and caregivers facing end‐stage cancer: outcomes of a randomized controlled trial
Authors: McLean Linda M. , Walton Tara , Rodin Gary , Esplen Mary Jane , Jones Jennifer M. 
Published: September 2011

AbstractBackgroundWe evaluated the effect of Emotionally Focused Therapy (EFT) [intervention (INT)], modified for the advanced cancer population versus standard care [control (CTL)], on marital functioning and psychosocial outcomes among distressed couples. EFT examines the ways couples process patterns of interaction, facilitating change.MethodsForty‐two patients with metastatic cancer and their caregivers were assigned randomly to receive eight sessions of EFT delivered by one EFT‐trained psychologist or standard care provided by multidisciplinary clinicians. Partners completed measures of marital functioning, depression, hopelessness, empathic caregiving (patient), and caregiver burden (caregiver) before randomization at baseline (T0), post‐intervention (T1), and 3‐month post‐intervention (T2). Data were analyzed using three‐way analyses of covariance; main effects were treatment, patient status, and sex. Multilevel modeling was also employed.ResultsAt T1, INT group led to significant improvement in marital functioning (p ≤ 0.0001) and patients' experience of caregiver empathic care (p = 0.02) versus CTL group. Effect sizes for these differences were in the large range (d = 1.00). In both groups, patients showed a marginally higher mean score for marital functioning compared with caregivers [INT: M = 56.3, standard deviation (SD) = 4.6 vs M = 54.3, SD = 4.5; CTL group: M = 43.4, SD = 10.3 vs M = 42.4, SD = 6.8, respectively]. At T2, results were maintained.ConclusionsThe effectiveness of and adherence to the EFT couple intervention for patients facing advanced cancer were demonstrated in this study. Larger randomized control trials are needed to confirm these findings. Qualitative studies may help to further understand the mechanism by which such an intervention may act. Copyright © 2011 John Wiley & Sons, Ltd.