bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Physiological and Toxic Conformations in Aβ42 Aggregates
Authors: Masuda Yuichi , Uemura Satoko , Ohashi Ryutaro , Nakanishi Azusa , Takegoshi K. , Shimizu Takahiko , Shirasawa Takuji , Irie Kazuhiro 
Published: December 2008

AbstractAggregation of the 42‐residue amyloid β‐protein (Aβ42) plays a crucial role in the pathogenesis of Alzheimer's disease (AD). Despite numerous structural studies on Aβ aggregates, the relationship between tertiary structure and toxicity remains unclear. Our proline scanning and solid‐state NMR studies suggested that aggregates both of wild‐type Aβ42 and of E22K‐Aβ42 (one of the mutants related to cerebral amyloid angiopathy) contain two conformers: a major one with a turn at positions 25 and 26, and a minor one with a turn at positions 22 and 23. To identify the toxic conformer, the derivative Aβ42‐lactam(22K–23E), in which the side chains at positions 22 and 23 were covalently linked, was synthesized as a minor conformer surrogate, along with Aβ42‐lactam(25K–26E) as a major conformer surrogate. The Aβ42‐lactam(22K–23E) showed stronger aggregation, neurotoxicity, radical generation, and oligomerization than wild‐type Aβ42, whereas in Aβ42‐lactam(25K–26E) were weak. The transition from the physiological conformation with a turn at positions 25 and 26 to the toxic conformation with a turn at positions 22 and 23 might be a key event in the pathogenesis of AD.
Hetero‐Seeding and Solid Mixture to Obtain New Crystalline Forms
Authors: Braga Dario , Grepioni Fabrizia , Maini Lucia , Polito Marco , Rubini Katia , Chierotti Michele R. , Gobetto Roberto 
Published: December 2008

AbstractPara‐methyl benzyl alcohol (p‐MeBA II) and para‐chloro benzyl alcohol (p‐ClBA) are quasi‐isostructural and share the same hydrogen‐bond patterns, but their crystals are not isomorphous. No new polymorphs could be obtained by conventional polymorph screening based on different solvents and different crystallization conditions. Formation of a new polymorph of p‐MeBA named p‐MeBA I, isomorphous with the crystal of p‐ClBA, was induced by hetero‐seeding with a small quantity of powdered p‐ClBA added to a supersaturated solution of p‐MeBA in hexane, while seeding of p‐ClBA with p‐MeBA II failed to give a new phase of p‐ClBA isomorphous with known crystalline p‐MeBA II. Mixed crystals of p‐MeBA and p‐ClBA were also prepared with different p‐MeBA/p‐ClBA ratios to understand the role of the different functional groups in the crystal structure. Crystal phases were characterized by combined use of single‐crystal and powder X‐ray diffraction, differential scanning calorimetry, and solid‐state NMR spectroscopy.
Organic Ligand Binding by a Hydrophobic Cavity in a Designed Tetrameric Coiled‐Coil Protein
Authors: Mizuno Toshihisa , Hasegawa Chinatsu , Tanabe Yoichi , Hamajima Kenta , Muto Takashi , Nishi Yoshinori , Oda Masayuki , Kobayashi Yuji , Tanaka Toshiki 
Published: December 2008

AbstractThe design and characterization of a hydrophobic cavity in de novo designed proteins provides a wide range of information about the functions of de novo proteins. We designed a de novo tetrameric coiled‐coil protein with a hydrophobic pocketlike cavity. Tetrameric coiled coils with hydrophobic cavities have previously been reported. By replacing one Leu residue at the a position with Ala, hydrophobic cavities that did not flatten out due to loose peptide chains were reliably created. To perform a detailed examination of the ligand‐binding characteristics of the cavities, we originally designed two other coiled‐coil proteins: AM2, with eight Ala substitutions at the adjacent a and d positions at the center of a bundled structure, and AM2W, with one Trp and seven Ala substitutions at the same positions. To increase the association of the helical peptides, each helical peptide was connected with flexible linkers, which resulted in a single peptide chain. These proteins exhibited CD spectra corresponding to superhelical structures, despite weakened hydrophobic packing. AM2W exhibited binding affinity for size‐complementary organic compounds. The dissociation constants, Kd, of AM2W were 220 nM for adamantane, 81 μM for 1‐adamantanol, and 294 μM for 1‐adamantaneacetic acid, as measured by fluorescence titration analyses. Although it was contrary to expectations, AM2 did not exhibit any binding affinity, probably due to structural defects around the designed hydrophobic cavity. Interestingly, AM2W exhibited incremental structure stability through ligand binding. Plugging of structural defects with organic ligands would be expected to facilitate protein folding.
Protein Flexibility and Metal Coordination Changes in DHAP‐Dependent Aldolases
Authors: Jiménez Aurora , Clapés Pere , Crehuet Ramon 
Published: December 2008

AbstractThe mobility of rhamnulose‐1‐phosphate aldolase (RhuA) was analysed with a normal mode description and high level calculations on models of the active site. We report the connection between the mobility and the chemical properties of the active site, and compare them to a closely related enzyme, fuculose‐1‐phosphate aldolase (FucA). Calculations show that the different coordination number for the zinc ion, reported in the crystal structures of RhuA and FucA, was due to a different spatial arrangement of the residues, not to their different chemical nature. Moreover, the metal coordination change is correlated with activity. The domain mobility of the enzyme can reshape the active site of RhuA into the arrangement found in the FucA structure, and vice‐versa. This has a direct influence on the energy barrier for the aldol reaction catalyzed by these enzymes, thus showing a coupling of the domain movements and the catalytic effects. Hence domain movements and the coordination chemistry of the active site metal suggest an explanation of why these enzymes have similar experimental turnover rates.
Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water
Authors: Gómez‐Hortigüela Luis , Pérez‐Pariente Joaquín , Corà Furio 
Published: December 2008

AbstractA combination of experimental characterisation techniques and computational modelling has allowed us to gain insight into the molecular features governing structure direction in the synthesis of microporous aluminophosphates. The occlusion of three different structure‐directing agents (SDAs), triethylamine (TEA), benzylpyrrolidine (BP) and (S)‐(−)‐N‐benzylpyrrolidine‐2‐methanol (BPM), within the AFI structure during its crystallisation, together with the simultaneous incorporation of water, has been experimentally measured. We found a higher incorporation of organic molecules in the structure obtained with BPM, while a higher water (and lower organic) content is found for the ones obtained with TEA and BP as SDAs. The computational study provides a thermodynamic explanation for the observed behaviour in terms of the relative stabilisation energy of the SDAs and water molecules within the AFI framework compared with when they are in aqueous solution, and demonstrates that a competition for preferential occupation exists between water and organic SDAs, which is a function of the interaction with the inorganic framework. The lower interaction of TEA and BP molecules with the AFI structure promotes the simultaneous incorporation of water molecules in the 12‐membered‐ring (MR) channel, to increase the host–guest interaction energy and thus the thermodynamic stability. The presence of strongly interacting methanol groups in the BPM molecules leads to the incorporation of only organic molecules within the 12‐MR channels. Our results demonstrate the essential role that water molecules play in the stabilisation of hydrophilic microporous aluminophosphates; a minimum amount of organic SDA is, however, essential for a templating role of the microporous architecture.
Facile Functionalization of Multilayer Fullerenes (Carbon Nano‐Onions) by Nitrene Chemistry and “Grafting from” Strategy
Authors: Zhou Li , Gao Chao , Zhu Dandan , Xu Weijian , Chen Fanqing Frank , Palkar Amit , Echegoyen Luis , Kong Eric Siu‐Wai 
Published: December 2008

AbstractFacile functionalization of multilayer fullerenes (carbon nano‐onions, CNOs) was carried out by [2+1] cycloaddition of nitrenes. The products were further derivatized by using the “grafting from” strategy of in situ ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Using one‐step nitrene chemistry with high‐energy reagents, such as azidoethanol and azidoethyl 2‐bromo‐2‐methyl propanoate, in N‐methyl‐2‐pyrrolidone at 160°C for 16 h, hydroxyl and bromide functionalities were introduced onto the surfaces of CNOs. These hydroxyl CNOs (CNO‐OH) and bromic CNOs (CNO‐Br) were extensively characterized by various techniques such as thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), Raman spectroscopy and X‐ray photo electron spectroscopy (XPS). TGA measurements indicated that the surface hydroxyl and bromide group density reached 1.49 and 0.49 mmol g−1, respectively. The as‐functionalized CNOs showed much better solubility in solvents than pristine CNOs. The CNO‐OH were also observed to fluoresce at λ=453 nm in water. The CNO‐OH and CNO‐Br can be conveniently utilized as macroinitiators to conduct surface‐initiated in‐situ polymerizations. Poly(ε‐caprolactone) (PCL, 45wt %) and polystyrene (PS, 60 wt%) were then grafted from surfaces of CNOs through the ROP of ε‐caprolactone with the macroinitiator CNO‐OH and the ATRP of styrene with the macroinitiator CNO‐Br, respectively. The structures and morphology of the resulting products were characterized by 1H NMR, scanning electron microscopy (SEM), TEM, and atomic force microscopy (AFM). The polymer functionalized CNOs have good solubility/dispersibility in common organic solvents. The facile and scalable functionalization approaches can pave the way for the comprehensive investigation of chemistry of CNOs and fabrication of novel CNO‐based nanomaterials and nanodevices.
C80Cl12: A Chlorine Derivative of the Chiral D2‐C80 Isomer—Empirical Rationale of Halogen‐Atom Addition Pattern
Authors: Simeonov Kalin S. , Amsharov Konstantin Yu , Jansen Martin 
Published: December 2008

AbstractWelcome to the family! The constitution of the chiral D2‐C80 fullerene has been confirmed through single‐crystal X‐ray analysis of the chlorinated C80Cl12. The addition pattern of the chlorine atoms in the structure of C80Cl12 together with other structures of halogenated higher fullerenes is discussed. A stepwise principle of higher fullerene reactivity is proposed. Unusual short intermolecular chlorine–chlorine contacts are reported.magnified image
Mathematical modelling of CO2 facilitated transport through liquid membranes containing amines as carrier
Authors: Gorji Aliakbar Heydari , Kaghazchi Tahereh 
Published: December 2008

AbstractAn approximate analytical solution for the facilitated transport of carbon dioxide across a liquid membrane containing aqueous primary and secondary amine solutions has been developed in which the reversible reaction A(CO2) + 2B(amine) $\Leftrightarrow$ AB(carbamate) + BH(protonated amine) occurs inside the liquid membranes. The current approximate analytical solution predicts the facilitated factor of CO2 through the membrane and is based on the dimensionless, nonlinear diffusion‐reaction transport problem. The approximate analytical solution predicts the facilitation factors for the range from the moderate reaction rate to the equilibrium chemical reaction regime, allowing unequal diffusivities of complexes and carrier and cases of zero and nonzero permeate side solute concentrations. In the present mathematical model, a constant free carrier concentration is assumed throughout the membrane phase. In comparison with the numerically calculated results, the results obtained were found to be in well agreement.
Oil–water two‐phase flow in microchannels: Flow patterns and pressure drop measurements
Authors: Salim Abdelkader , Fourar Mostafa , Pironon Jacques , Sausse Judith 
Published: December 2008

AbstractThis paper investigates oil–water two‐phase flows in microchannels of 793 and 667 µm hydraulic diameters made of quartz and glass, respectively. By injecting one fluid at a constant flow rate and the second at variable flow rate, different flow patterns were identified and mapped and the corresponding two‐phase pressure drops were measured. Measurements of the pressure drops were interpreted using the homogeneous and Lockhart–Martinelli models developed for two‐phase flows in pipes. The results show similarity to both liquid–liquid flow in pipes and to gas–liquid flow in microchannels. We find a strong dependence of pressure drop on flow rates, microchannel material, and the first fluid injected into the microchannel.
Flow regime determination in horizontal hydrotransport using non‐intrusive acoustic probes
Authors: Albion Katherine , Briens Lauren , Briens Cedric , Berruti Franco 
Published: December 2008

AbstractA variety of flow regimes may be observed in the hydrotransport of solids. Maintaining a consistent operation requires rapid detection of any change in flow regime. The objective of this study was to develop reliable, non‐intrusive, and on‐line methods for flow regime detection in a hydrotransport pipe based on acoustic measurements.Slurries were transported in a 0.05 m diameter stainless steel hydrotransport pipe. Acoustic measurements were recorded by microphones along the length of the horizontal pipe. Two flow regimes were observed: suspended solids flow and flow over settled solids. Cycle and frequency analyses of the acoustic signals provided reliable identification of these flow regimes.
A particle filter approach to identification of nonlinear processes under missing observations
Authors: Gopaluni R. B. 
Published: December 2008

AbstractA novel maximum likelihood solution to the problem of identifying parameters of a nonlinear model under missing observations is presented. If the observations are missing, then it is difficult to build a partial likelihood function consisting of only the available observations. Hence, an expectation–maximization (EM) algorithm, which uses the expected value of the complete log‐likelihood function including the missing observations, is developed. The expected value of the complete log‐likelihood (E‐step) in the EM algorithm is approximated using particle filters and smoothers. New expressions for particle filters and smoothers under missing observations are derived. In order to reduce the variance on the smoothed states, a point‐wise (as opposed to path‐based) state estimation procedure is used. The maximization step (M‐step) in the EM algorithm is performed using standard optimization routines. The proposed nonlinear identification approach is illustrated through numerical examples.
Optimization by response surface methodology (RSM) for toluene adsorption onto prepared acid activated clay
Authors: Amari Abdelfattah , Gannouni Abdelaziz , Chlendi Mohamed , Bellagi Ahmed 
Published: December 2008

AbstractAdsorption of toluene onto acid activated clay was carried out. Modified clay was prepared by acid attack (H2SO4) on raw material. Response surface methodology based on a 2‐level, 4‐variables central composite orthogonal design was used to evaluate the effects of important parameters on the adsorption of toluene on to activated clay. Temperature (53.8–96.2°C), contact time (0.57–6.93 h), mass ratio of liquid/solid (3.38–7.62) and strength of acid (7.75–57.24%) were chosen as process variables for the optimization. Of these parameters, temperature reaction and time had greater impact on toluene adsorption than did the other parameters. Analysis of variance (ANOVA) shows a good agreement between theoretical analysis and experimental data. The validity of model is verified by an experiment at the optimum conditions. The optimum conditions for the maximum adsorption of toluene onto activated clay are: temperature of 96.2°C, a contact time of 6.93 h, a liquid/solid ratio of 5.98 and strength of acid of 32.94%. Since the predicted values and the actual experimental value obtained for the maximum adsorption of toluene are within 95% confidence intervals, the final model is considered valid and has satisfactory predictive ability.
Synthesis of Bicyclic N‐Arylmethyl‐Substituted Iminoribitol Derivatives as Selective Nucleoside Hydrolase Inhibitors
Authors: Berg Maya , Bal Gunther , Goeminne Annelies , Van der Veken Pieter , Versées Wim , Steyaert Jan , Haemers Achiel , Augustyns Koen 
Published: December 2008

AbstractA series of bicyclic N‐arylmethyl‐substituted iminoribitols were synthesised and evaluated in vitro against T. vivax nucleoside hydrolase. The importance of the N–Asp40 interaction was confirmed and depends on an optimal pKa value, which can be influenced by substituents. The compounds were active inhibitors of nucleoside hydrolase (IAG‐NH) and are inactive against human purine nucleoside phosphorylase.magnified imageThe purine metabolism of Trypanosoma and Leishmania spp. provides a good target in the search for new selective drugs. Bicyclic N‐arylmethyl‐substituted iminoribitols were developed as inhibitors of T. vivax nucleoside hydrolase, a key enzyme of the purine salvage pathway. The obtained results and structure–activity data confirmed our model for inhibitor binding with a hydrogen bond between a nitrogen atom of the nucleobase mimetic and the protonated Asp40 from the enzyme. This interaction depends on an optimal pKa value, which can be influenced by the electronic properties of the substituents. These compounds are potent, selective inhibitors of nucleoside hydrolase and are inactive toward human nucleoside phosphorylase.
Chemoimmunotherapy may overcome the adverse prognostic significance of 11q deletion in previously untreated patients with chronic lymphocytic leukemia
Authors: Tsimberidou Apostolia‐Maria , Tam Constantine , Abruzzo Lynne V. , O'Brien Susan , Wierda William G. , Lerner Susan , Kantarjian Hagop M. , Keating Michael J. 
Published: December 2008

AbstractBACKGROUND:An 11q22 deletion is considered an independent factor predicting poor survival in chronic lymphocytic leukemia (CLL).METHODS:We searched the electronic CLL database for consecutive patients who presented to the M. D. Anderson Cancer Center Department of Leukemia from October 2003 to April 2007 with untreated CLL and who had an 11q22 deletion, detected by fluorescence in situ hybridization (FISH) analysis of bone marrow samples. FISH analysis was performed using the following probes: trisomy 12 (12p11.1‐q11), TP53 (17p13.1), ATM (11q22.3), LAMP1 (13q34), and D13S319 loci (13q14.3).RESULTS:Sixty‐nine patients with untreated CLL with an 11q22 deletion were identified. The median patient age was 59 years (range, 26–81 years); 80% were men, 53% had Zubrod performance status >0, and 13% had Rai stage III to IV disease. Lymphadenopathy (massive), splenomegaly, anemia, and thrombocytopenia were present in 96% (12%), 19%, 9%, and 4%, respectively. In addition, 62% of patients had deletions in 13q, and 3% had trisomy 12. Forty patients required therapy for progressive disease. The overall response rates for FCR (fludarabine, cyclophosphamide, and rituximab), CFAR (FCR plus alemtuzumab), and rituximab plus granulocyte‐macrophage colony‐stimulating factor were 100%, 100%, and 33%, respectively. The 11q22 deletion was undetectable in 25 of 27 patients monitored after treatment using FISH analysis. The median follow‐up was 17 months. At 1 and 3 years, the survival rates were 97% and 91%, respectively, and the relapse‐free survival rates were 100% and 77%, respectively.CONCLUSIONS:CLL with an 11q22 deletion was associated with high rates of response, survival, and relapse‐free survival when treated with chemoimmunotherapy. Cancer 2009. © 2009 American Cancer Society.
Reconfigurable Logic Devices on a Single Dopant Atom—Operation up to a Full Adder by Using Electrical Spectroscopy
Authors: Klein Michael , Lansbergen Gabriel P. , Mol Jan A. , Rogge Sven , Levine Raphael D. , Remacle Francoise 
Published: December 2008

AbstractA silicon field‐effect transistor is operated as a logic circuit by electrically addressing the ground and excited electronic states of an embedded single dopant atom. Experimental results—complemented by analytical and computational calculations—are presented. First, we show how a complete set of binary logic gates can be realized on the same hardware. Then, we show that these gates can be operated in parallel on the very same dopant up to the logic level of a full adder. To use the device not as a switch but as a full logic circuit, we make essential use of the excited electronic states of the dopant and of the ability to shift their energy by gating. The experimental ability to use two channels to measure the current flowing through the device and the conductance (dI/dV) allows for a robust reading of the output of the logic operations.
Progress in Mimetic Studies of Cell Adhesion and the Mechanosensing
Authors: Smith Ana‐Sunčana , Sackmann Erich 
Published: December 2008

AbstractVesicle–substrate adhesion has been studied for over two decades with the motivation to understand and mimic cell adhesion. In recent years, with progress in theoretical modelling, the development of experimental techniques, and improved data‐analysis procedures, considerable advances have been made in the understanding of the adhesion process. It is this progress which constitutes the focus of this review.
Kelleraußenwände
Authors: Prepens Manfred 
Published: December 2008

AbstractKellermauerwerk lässt sich rationell und sehr wirtschaftlich aus KS‐Plansteinen oder großformatigen Kalksandsteinen (KS XL) erstellen. Durch die glatte Oberfläche der Kalksandsteine brauchen die Kelleraußenwände weder innen noch außen mit einem Putz oder Rappputz versehen zu werden. Sie werden innen zum Beispiel weiß gestrichen. Außenseitig wird die Abdichtung direkt auf dem ebenen und tragfähigen KS‐Mauerwerk aufgebracht (Bild 1).Kelleraußenwände werden hoch beansprucht und müssen diesen Beanspruchungen standhalten. Sie tragen vertikale Lasten aus den Geschossdecken und den aufgehenden Wänden über die Fundamente in den Baugrund ab. Zusätzlich werden sie horizontal durch die Erdanschüttung, durch Bodenfeuchtigkeit und gegebenenfalls durch aufstauendes Sickerwasser belastet.Die heutigen Abdichtungen bieten hohe Sicherheit vor Durchfeuchtung der Wände und gewährleisten damit trockene Kellerräume – eine Voraussetzung für den hochwertigen Kellerausbau (Bild 2). Die Abdichtung der Kelleraußenwände erfolgt nach DIN 18195 [1] mit kunststoffmodifizierten Bitumendickbeschichtungen (KMB), Bitumen‐, Kunststoff‐ oder Elastomer‐Dichtungsbahnen.
Scherfestigkeit, Haftscherfestigkeit und Fugendruckfestigkeit
Authors: Siech Hans Joachim 
Published: December 2008

AbstractFür die Bewertung und Zuordnung von Mauer‐ und Putzmörteln gelten einschlägige Normen. Diese beinhalten u.a. die Vorgaben zur Herstellung von Prüfkörpern, die Art und Anzahl sowie deren Lagerung und Prüfung. Für die Gewerke Mauern und Putzen, für die gesicherte funktionelle Eigenschaften in Verbindung des Mörtels mit den entsprechenden Wandbildnern zu erfüllen sind (wie Verbundfestigkeit, Erhärtungsverhalten), sind weitere Prüfkriterien zu erfüllen. Zu diesen zählen für den Mauerwerksbau der prüftechnische Nachweis für die Haftscherfestigkeit und die Fugendruckfestigkeit.Für die Prüfungen ist ein bestimmter Kalksand‐Vollstein NF als Referenzstein zu verwenden. Den materialspezifischen Eigenschaften der Mauermörtel und insbesondere denen der Wandbaustoffe (Referenzsteine) ist Rechnung zu tragen. Es gilt, sie in ihren Eigenschaften bestmöglich und für die gestellten Anforderungen aufeinander abzustimmen.