bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hemoglobin as a Nitrite Anhydrase: Modeling Methemoglobin‐Mediated N2O3 Formation
Authors: Hopmann Kathrin H. , Cardey Bruno , Gladwin Mark T. , Kim‐Shapiro Daniel B. , Ghosh Abhik 
Published: May 2011

AbstractNitrite has recently been recognized as a storage form of NO in blood and as playing a key role in hypoxic vasodilation. The nitrite ion is readily reduced to NO by hemoglobin in red blood cells, which, as it happens, also presents a conundrum. Given NO’s enormous affinity for ferrous heme, a key question concerns how it escapes capture by hemoglobin as it diffuses out of the red cells and to the endothelium, where vasodilation takes place. Dinitrogen trioxide (N2O3) has been proposed as a vehicle that transports NO to the endothelium, where it dissociates to NO and NO2. Although N2O3 formation might be readily explained by the reaction Hb‐Fe3++NO2−+NO⇌Hb‐Fe2++N2O3, the exact manner in which methemoglobin (Hb‐Fe3+), nitrite and NO interact with one another is unclear. Both an “Hb‐Fe3+‐NO2−+NO” pathway and an “Hb‐Fe3+‐NO+NO2−” pathway have been proposed. Neither pathway has been established experimentally. Nor has there been any attempt until now to theoretically model N2O3 formation, the so‐called nitrite anhydrase reaction. Both pathways have been examined here in a detailed density functional theory (DFT, B3LYP/TZP) study and both have been found to be feasible based on energetics criteria. Modeling the “Hb‐Fe3+‐NO2−+NO” pathway proved complex. Not only are multiple linkage‐isomeric (N‐ and O‐coordinated) structures conceivable for methemoglobin–nitrite, multiple isomeric forms are also possible for N2O3 (the lowest‐energy state has an NN‐bonded nitronitrosyl structure, O2NNO). We considered multiple spin states of methemoglobin–nitrite as well as ferromagnetic and antiferromagnetic coupling of the Fe3+ and NO spins. Together, the isomerism and spin variables result in a diabolically complex combinatorial space of reaction pathways. Fortunately, transition states could be successfully calculated for the vast majority of these reaction channels, both MS=0 and MS=1. For a six‐coordinate Fe3+‐O‐nitrito starting geometry, which is plausible for methemoglobin–nitrite, we found that N2O3 formation entails barriers of about 17–20 kcal mol−1, which is reasonable for a physiologically relevant reaction. For the “Hb‐Fe3+‐NO+NO2−” pathway, which was also found to be energetically reasonable, our calculations indicate a two‐step mechanism. The first step involves transfer of an electron from NO2− to the Fe3+–heme–NO center ({FeNO}6) , resulting in formation of nitrogen dioxide and an Fe2+–heme–NO center ({FeNO}7). Subsequent formation of N2O3 entails a barrier of only 8.1 kcal mol−1. From an energetics point of view, the nitrite anhydrase reaction thus is a reasonable proposition. Although it is tempting to interpret our results as favoring the “{FeNO}6+NO2−” pathway over the “Fe3+‐nitrite+NO” pathway, both pathways should be considered energetically reasonable for a biological reaction and it seems inadvisable to favor a unique reaction channel based solely on quantum chemical modeling.
Squaramides: Bridging from Molecular Recognition to Bifunctional Organocatalysis
Authors: Alemán José , Parra Alejandro , Jiang Hao , Jørgensen Karl Anker 
Published: May 2011

AbstractIn this minireview, squaramides are presented from their roots as artificial anion receptors in molecular recognition studies to their recent advances as powerful bifunctional hydrogen‐bonding catalysts in asymmetric organocatalysis. The main features of the squaramido functionality and the direct comparison with the analogous ureas and thioureas are also discussed.
Proton‐Induced Tuning of Metal–Metal Communication in Rack‐Type Dinuclear Ru Complexes Containing Benzimidazolyl Moieties
Authors: Kobayashi Katsuaki , Ishikubo Masamichi , Kanaizuka Katsuhiko , Kosuge Keiko , Masaoka Shigeyuki , Sakai Ken , Nozaki Koichi , Haga Masa‐aki 
Published: May 2011

AbstractRu complexes bearing a bis‐tridentate benzimidazolyl ligand have been synthesized. The dinuclear ones act as a bibasic acid with pKa1=4.36 and pKa2=5.90. The protonated form of the dinuclear complex exhibited two one‐electron oxidations at +0.91 and +1.02 V versus the ferrocenium/ferrocene (Fc/Fc+) couple (the potential difference (ΔE)=0.11 V), but the di‐deprotonated form showed two waves at +0.50 and +0.58 V versus Fc/Fc+ (ΔE=0.08 V). Since the potential difference between two waves reflects the strength of the metal–metal interaction, the deprotonation of the benzimidazole moieties in the complexes weakened the Ru–Ru communication. The degree of electronic coupling between two metal centers, estimated from the intervalence charge transfer (IVCT) band, was greater for the protonated form. DFT calculations for the protonated and deprotonated forms of the dinuclear complex suggest that the RuII–L(H2) π* interaction plays a key role in the Ru–Ru interaction.
Open‐Shell Characters and Second Hyperpolarizabilities of One‐Dimensional Graphene Nanoflakes Composed of Trigonal Graphene Units
Authors: Yoneda Kyohei , Nakano Masayoshi , Fukui Hitoshi , Minami Takuya , Shigeta Yasuteru , Kubo Takashi , Botek Edith , Champagne Benoît 
Published: May 2011

AbstractThe impact of topology on the open‐shell characters and the second hyperpolarizabilities (γ) has been addressed for one‐dimensional graphene nanoflakes (GNFs) composed of the smallest trigonal graphene (phenalenyl) units. The main results are: 1) These GNFs show not only diradical but also multiradical characters when increasing the number of linked units. 2) GNFs composed of an equivalent number of units can exhibit a wide range of open‐shell characters—from nearly closed‐shell to pure multiradical characters—depending on the linking pattern of the trigonal units. 3) This wide variation in open‐shell characters is explained by their resonance structures and/or by their (HOMO−i)−(LUMO+i) gaps deduced from the orbital correlations. 4) The change in the linking structure of the units can effectively control their open‐shell characters as well as their γ values, of which the longitudinal components are significantly enhanced for the singlet GNFs having intermediate open‐shell characters. 5) Singlet alternately linked (AL) systems present intermediate multiradical characters even in the case of a large number of units, which creates a significant enhancement of γ with increasing the size, whereas nonalternately linked (NAL) systems, which present pure multiradical characters, possess much smaller γ values. Finally 6) by switching from the singlet to the highest spin states, the γ values of NAL systems hardly change, whereas those of AL systems exhibit large reductions. These fascinating structure–property relationships between the topology of the GNFs, their open‐shell characters, and their γ values not only deepen the understanding of open‐shell characters of GNFs but aim also at stimulating further design studies to achieve giant NLO responses based on open‐shell graphene‐like materials.
Fine‐Tuning of Triarylamine‐Based Photosensitizers for Dye‐Sensitized Solar Cells
Authors: Olivier Céline , Sauvage Frédéric , Ducasse Laurent , Castet Frédéric , Grätzel Michael , Toupance Thierry 
Published: May 2011

AbstractThe synthesis of a series of novel organic photosensitizers based on modified triarylamine motives has been achieved. The new “push‐pull” dyes, bearing one to three naphthyl units in place of phenyl rings, have been successfully obtained following original synthetic routes. The structural, optical and electrochemical properties of these chromophores were studied by combining crystallographic, experimental and theoretical data. We further present a systematic study of this series of dyes. When embedded in dye‐sensitized solar cell devices, the new photosensitizers showed good spectral response with IPCE greater than 85 % from 470 to 580 nm and overall power conversion efficiencies reaching 6.6 %. One of these new sensitizers, containing one naphthyl attached to the π‐conjugated linker and having phenyl rings on the outside, led to the highest molar extinction coefficient and energy conversion efficiency of the series while exhibiting higher electron lifetime.
Cytopathic effects of human papillomavirus infection and the severity of cervical intraepithelial neoplasia : A frequency study
Authors: Alves de Sousa Nadja Lindany , Alves Rosane Ribeiro Figueiredo , Martins Marcelo Rodrigues , Barros Narriman Kennia Da Silva , Ribeiro Andrea Alves , Zeferino Luiz Carlos , Dufloth Rozany Mucha , Rabelo‐Santos Silvia Helena 
Published: May 2011

AbstractCytopathic effects related to the human papillomavirus (HPV) infection are more frequently found in cervical intraepithelial neoplasia (CIN) 1; however, there are indications that at least half the histological diagnoses of CIN2 and CIN3 include koilocytosis areas. The objective of this study was to evaluate the frequency of the cytological criteria suggestive of HPV infection in the cervical smears of women with a histological diagnosis of CIN. One hundred and sixty‐two women with abnormal cervical smears and a diagnosis of CIN confirmed by histopathology were selected, including 46 cases of CIN 1, 42 of CIN 2 and 74 cases of CIN 3. Koilocytosis was found in 63% of the smears from women with a histopathological diagnosis of CIN 1. This sign was observed in 26.2% and 25.7% of smears of women with a diagnosis of CIN 2 and CIN 3, respectively. Cytomegaly also was frequent in cervical smears of women with histopathological diagnosis of CIN 1 (71.8%). On the other hand, spindle cells and atypical metaplasia were more frequent in women with CIN 2 and CIN 3. Atypical parakeratosis showed similar frequency in all grades of CIN diagnosis. Koilocytois and cytomegaly were inversely correlated with the diagnosis of CIN2 or CIN 3, with OR values respectively of 0.30 (95%CI 0.13–0.68) and 0.26 (95%CI 0.11–0.58). The others signs analyzed did not show any significant association. Koilocitosis and cytomegaly can provides good reassurance that a patient with atypical cervical smear have CIN 1. Diagn. Cytopathol. 2012. © 2011 Wiley Periodicals, Inc.
The cytomorphologic spectrum of salivary gland type tumors in the lung and mediastinum: A report of 16 patients
Authors: Monaco Sara E. , Khalbuss Walid E. , Ustinova Elena , Liang Alicia , Cai Guoping 
Published: May 2011

AbstractIn the lung and mediastinum, salivary gland type tumors (SGTTs) can occur as either primary tumors or metastases from tumors arising in the major or minor salivary glands. This study reviewed the cytology cases of SGTTs in the lung and mediastinum diagnosed over a six‐year period at our institution. The specimens included a total of 22 exfoliative or aspiration cytology specimens identified in 16 patients. Two of the cases were primary tumors: adenoid cystic carcinoma (ACC) of the trachea and mucoepidermoid carcinoma (MEC) of the thymus. The remaining 20 tumors were metastases from the parotid, submandibular gland, tongue, nasal cavity, or soft palate. Eight of the 16 patients (50%) had a diagnosis of ACC, four (25%) had salivary duct carcinomas, two (12.5%) had MECs, one (6.25%) was a basaloid tumor, and one (6.25%) was polymorphous low grade adenocarcinoma. In our series, these SGTTs were more commonly metastatic in the lung or mediastinum (87.5% of the patients), and the most common histological subtype was ACC, followed by SDC. This study also illustrates the cytomorphologic features and diagnostic pitfalls of these unusual SGTTs. Diagn. Cytopathol. 2012. © 2011 Wiley Periodicals, Inc.
Effects of different protein content and glycaemic index of ad libitum diets on diabetes risk factors in overweight adults: the DIOGenes multicentre, randomized, dietary intervention trial
Authors: Goyenechea Estibaliz , Holst Claus , van Baak Marleen A. , Saris Wim H. M. , Jebb Susan , Kafatos Anthony , Pfeiffer Andreas , Handjiev Svetoslav , Hlavaty Petr , Stender Steen , Larsen Thomas M. , Astrup Arne , Martinez J. Alfredo ,   on behalf of DIOGenes
Published: May 2011

AbstractBackgroundDietary regimens providing different levels of protein and glycemic index (GI) foods when prescribed for weight management may also influence insulin sensitivity.Procedures and OutcomesOverweight/obese adults in 8 European countries who lost ≥ 8% of initial body‐weight (BW) after following a low calorie diet (LCD) were later randomly assigned with a 2x2 factorial design into 4 ad libitum dietary groups with two different protein content levels and dissimilar glycemic index, which were compared to a healthy reference diet. Specific markers assessing insulin resistance were measured. The LCD was initially applied to 932 adults and 773 were randomised to the 5 ad libitum diets. The 6‐months programme was completed by 548 participants. The assignment to the Low Protein /High Glycemic Index diet induced a statistically higher HOMA‐IR increase during the 6 months period as compared to the control. Contrariwise, the insulin response was lower in the High Protein/Low Glycemic Index diet after 60 and 90 min of an Oral Glucose Tolerance test subsequently carried out after the 6‐months intervention. The Low Glycemic Index diets (either with high or low protein content) also lead to a decrease in fructosamine levels during the trial.Conclusion/InterpretationAfter a weight loss period, an increase in the dietary protein proportions and a decrease in the consumption of foods with a high Glycemic Index within an ad libitum dietary intervention aiming to weight maintenance produced favorable effects on glycaemic control and insulin sensitivity in overweight/obese subjects. Copyright © 2011 John Wiley & Sons, Ltd.
TCR down‐regulation boosts T‐cell‐mediated cytotoxicity and protection against poxvirus infections
Authors: Hansen Ann K. , Regner Matthias , Bonefeld Charlotte M. , Boding Lasse , Kongsbak Martin , Ødum Niels , Müllbacher Arno , Geisler Carsten , von Essen Marina R. 
Published: May 2011

AbstractCytotoxic T (Tc) cells play a key role in the defense against virus infections. Tc cells recognize infected cells via the T‐cell receptor (TCR) and subsequently kill the target cells by one or more cytotoxic mechanisms. Induction of the cytotoxic mechanisms is finely tuned by the activation signals from the TCR. To determine whether TCR down‐regulation affects the cytotoxicity of Tc cells, we studied TCR down‐regulation‐deficient CD3γLLAA mice. We found that Tc cells from CD3γLLAA mice have reduced cytotoxicity due to a specific deficiency in exocytosis of lytic granules. To determine whether this defect was reflected in an increased susceptibility to virus infections, we studied the course of ectromelia virus (ECTV) infection. We found that the susceptibility to ECTV infection was significantly increased in CD3γLLAA mice with a mortality rate almost as high as in granzyme B knock‐out mice. Finally, we found that TCR signaling in CD3γLLAA Tc cells caused highly increased tyrosine phosphorylation and activation of the c‐Cbl ubiquitin ligase, and that the impaired exocytosis of lytic granules could be rescued by the knockdown of c‐Cbl. Thus, our work demonstrates that TCR down‐regulation critically increases Tc cell cytotoxicity and protection against poxvirus infection.
B lymphocytes acquire and present intracellular antigens that have relocated to the surface of apoptotic target cells
Authors: Ciechomska Marzena , Lennard Thomas W. J. , Kirby John A. , Knight Andrew M. 
Published: May 2011

AbstractThe induction of an effective immune response requires the activation of CD4+ T lymphocytes by APCs. While DCs have been shown to be pivotal in this process, it is now apparent that optimal CD4+ T‐cell activation also requires B‐lymphocyte APC function. Along with the acquisition of soluble antigens, it is known that B cells also acquire membrane‐tethered antigens. Recent reports have described the relocation of intracellular antigens to the cell surface following immunogenic apoptosis. This study was designed to determine whether B cells can acquire and present such antigens to CD4+ T cells. By targeting the model antigen tetanus toxin C fragment to various cellular locations, we show that antigen‐specific B cells acquire intracellular antigens that have relocated to the surface of cells undergoing immunogenic apoptosis. Crucially, we also demonstrate that antigen‐specific B cells acquiring relocated antigen from apoptotic targets are capable of efficiently inducing CD4+ T‐cell activation. We propose that the acquisition and presentation of intracellular antigens that have relocated to the cell surface during immunogenic apoptosis represents a novel means by which antigen‐specific B cells contribute to the generation of immunity.
T‐cell help permits memory CD8+ T‐cell inflation during cytomegalovirus latency
Authors: Walton Senta M. , Torti Nicole , Mandaric Sanja , Oxenius Annette 
Published: May 2011

AbstractCD4+ T cells are implied to sustain CD8+ T‐cell responses during persistent infections. As CD4+ T cells are often themselves antiviral effectors, they might shape CD8+ T‐cell responses via help or via controlling antigen load. We used persistent murine CMV (MCMV) infection to dissect the impact of CD4+ T cells on virus‐specific CD8+ T cells, distinguishing between increased viral load in the absence of CD4+ T cells and CD4+ T‐cell‐mediated helper mechanisms. Absence of T‐helper cells was associated with sustained lytic MCMV replication and led to a slow and gradual reduction of the size and function of the MCMV‐specific CD8+ T‐cell pool. However, when virus replication was controlled in the absence of CD4+ T cells, CD8+ T‐cell function was comparably impaired, but in addition CD8+ T‐cell inflation, a hallmark of CMV infection, was completely abolished. Thus, CD8+ T‐cell inflation during latent CMV infection is strongly dependent on CD4+ T‐cell helper functions, which can partially be compensated by ongoing lytic viral replication in the absence of CD4+ T cells.
Single‐Step Synthesis of Ruthenium Catalytic Nanocrystallites in a Stable Carbon Support
Authors: Calderon‐Moreno Jose M. , Pol Vilas G. , Popa Monica 
Published: May 2011

AbstractMetallic Ru nanoparticles have been prepared and incorporated in a protective carbon support by the decomposition of a single organometallic precursor, RuIII acetylacetonate, under autogenic conditions in a single‐step process in the absence of any solvents or stabilizers. The product structure was confirmed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, scanning transmission electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. Measurements demonstrated the exclusive presence of hexagonal metallic ruthenium nanoparticles with a homogeneous size of 2–4 nm in a carbon supporting matrix, forming a high loading Ru catalyst with a muffin cookie like structure. The mechanism of the process is explained by the nucleation of Ru crystalline nuclei before carbon deposits on the Ru nanocrystallites, in an early stage of nanoparticle growth, during the single precursor decomposition. The carbon acts as a protective support, preventing further Ru nanoparticle growth, agglomeration or sintering. The catalytic properties have been tested by the hydrogenation of benzene to cyclohexane, and show high activity, full conversion of benzene, 100 % selectivity for cyclohexane and good recyclability.
Synthesis, Structures, and Unique Luminescent Properties of Tridentate C∧C∧N Cyclometalated Complexes of Iridium
Authors: Koga Yuji , Kamo Marina , Yamada Yuji , Matsumoto Taisuke , Matsubara Kouki 
Published: May 2011

AbstractThe first C∧C∧N cyclometalated complexes of iridium that bear tridentate pyridylbiphenylene ligands are reported herein. These complexes were synthesized in good yields by means of the directed C–C bond activation of biphenylene with the assistance of pyridyl group precoordination. Their photoluminescent performances were also studied and show unique luminescent properties at longer wavelengths in the near‐infrared range than that of previously synthesized C∧N∧C cyclometalated iridium complexes.
Non‐Aqueous Preparation of High‐Crystallinity Hierarchical TiO2 Hollow Spheres with Excellent Photocatalytic Efficiency
Authors: Lü Xujie , Ding Shangjun , Xie Yian , Huang Fuqiang 
Published: May 2011

AbstractHigh‐crystallinity hierarchical anatase TiO2 hollow spheres were prepared by a high‐temperature (350 °C) and non‐aqueous solvothermal method in the absence of water, templates, or additives. The hollow structures were assembled from highly crystallized TiO2 nanoparticles and exhibit superior photocatalytic properties relative to those of Degussa P25 TiO2 under irradiation with UV light. The influence of reaction temperature on the crystallinity, morphology, crystallite shape and size, band gap, specific surface area, and pore size distribution of TiO2 has been studied in detail. It is evident that reaction temperature is the most important factor to increase the crystallinity of TiO2 in order to improve its charge transfer and transport properties, which are important in photocatalysis.
Reactivity of a 16‐Electron CpCo Half‐Sandwich Complex Containing a Chelating 1,2‐Dicarba‐closo‐dodecaborane‐1,2‐diselenolate Ligand towards FcC(O)C≡CH
Authors: Ye Hongde , Bai Wenjun , Xie Mingshi , Li Yizhi , Yan Hong 
Published: May 2011

AbstractThe 16‐electron half‐sandwich complex CpCo(Se2C2B10H10) (1, Cp = cyclopentadienyl) reacts with FcC(O)C≡CH in CH2Cl2 at ambient temperature to give [{FcC(O)CCH}(Se2C2B10H10)] (3) and [CpCo(Se2C2B10H9){CH2CC(O)Fc}] (4). Complex 3 is generated by the alkyne addition to the 1,2‐dicarba‐closo‐dodecaborane‐1,2‐diselenolate ligand in 1 with the loss of the CpCo unit. In 4, metal‐induced B–H activation occurs in the B(3)/B(6) position of carborane followed by the formation of a C–B bond. In MeOH the reaction leads to an unexpected product, [{FcC(O)CHCH}CpCo(Se2C2B9H9){CH2CC(O)Fc}] (5), which contains two alkynes and a nido‐C2B9 cage. In MeOH, 4 can further react with the alkyne to give 5. In the presence of silica, 4 loses the CpCo unit to afford [{FcC(O)CCH2}(Se2C2B10H9)] (6), which is a symmetrical molecule with the B–CH2 unit retained. All of these complexes have been characterized by IR, NMR, elemental analysis, mass spectrum, and single‐crystal X‐ray diffraction analysis.
Biocatalytic Promiscuity
Authors: Humble Maria Svedendahl , Berglund Per 
Published: May 2011

AbstractEnzymes are attractive catalysts because of their promiscuity and their ability to perform highly regio‐, chemo‐ and stereoselective transformations. Enzyme promiscuity allows optimisation of industrial processes that require reaction conditions different from those in nature. Many enzymes can be used in reactions completely different from the reaction the enzyme originally evolved to perform. Such catalytically promiscuous reactions can be secondary activities hidden behind a native activity and might be discovered either in screening for that particular activity or, alternatively, by chance. Recently, researchers have designed enzymes to show catalytic promiscuity. It is also possible to design new enzymes from scratch by computer modelling (de novo design), but most work published to date starts from a known enzyme backbone. Promiscuous activity might also be induced or enhanced by rational design or directed evolution (or combinations thereof). Enzyme catalytic promiscuity provides fundamental knowledge about enzyme/substrate interactions and the evolution of new enzymes. New enzymes are required by industry, which needs to optimise chemical processes in an environmentally sustainable way. In this review various aspects of enzyme catalytic promiscuity are considered from a biocatalytic perspective.