bluuebunny/crossref_metadata_2025_split huggingface dataset:
One‐Pot Synthesis of Phenylmethanethiolate‐Protected Au20(SR)16 and Au24(SR)20 Nanoclusters and Insight into the Kinetic Control
Authors: Zhu Xiuyi , Jin Shenshen , Wang Shuxin , Meng Xiangming , Zhu Changwei , Zhu Manzhou , Jin Rongchao 
Published: July 2013

AbstractWe report two synthetic routes for concurrent formation of phenylmethanethiolate (‐SCH2Ph)‐protected Au20(SR)16 and Au24(SR)24 nanoclusters in one‐pot by kinetic control. Unlike the previously reported methods for thiolate‐protected gold nanoclusters, which typically involve rapid reduction of the gold precursor by excess NaBH4 and subsequent size focusing into atomically monodisperse clusters of a specific size, the present work reveals some insight into the kinetic control in gold–thiolate cluster synthesis. We demonstrate that the synthesis of ‐SCH2Ph‐protected Au20 and Au24 nanoclusters can be obtained through two different, kinetically controlled methods. Specifically, route 1 employs slow addition of a relatively large amount of NaBH4 under slow stirring of the reaction mixture, while route 2 employs rapid addition of a small amount of NaBH4 under rapid stirring of the reaction mixture. At first glance, these two methods apparently possess quite different reaction kinetics, but interestingly they give rise to exactly the same product (i.e., the coproduction of Au20(SCH2Ph)16 and Au24(SCH2Ph)20 clusters). Our results explicitly demonstrate the complex interplay between the kinetic factors that include the addition speed and amount of NaBH4 solution as well as the stirring speed of the reaction mixture. Such insight is important for devising synthetic routes for different sized nanoclusters. We also compared the photoluminescence and electrochemical properties of PhCH2S‐protected Au20 and Au24 nanoclusters with the PhC2H4S‐protected counterparts. A surprising 2.5 times photoluminescence enhancement was observed for the PhCH2S‐capped nanoclusters when compared to the PhC2H4S‐capped analogues, thereby indicating a drastic effect of the ligand that is merely one carbon shorter.
Adaptive Dynamic Surface Control with Guaranteed L∞ Tracking Performance for a Class of Uncertain Nonlinear Systems with Unknown Time Delays
Authors: Qu Weiran , Lin Yan , Zhao Qichao 
Published: July 2013

AbstractThis paper is aimed at exploring dynamic surface control (DSC) for a class of uncertain nonlinear systems in strict‐feedback form with time delays. Combining the Finite Covering Lemma (Heine‐Borel Theorem) with neural networks, a novel method is proposed to approximate time delay terms, which leads to the abandonment of traditional Lyapunov‐Krasovskii functionals. Then, a surface error modification and an initialization technique are proposed to guarantee the tracking performance. Moreover, by applying a newly‐developed neural network based adaptive control technique, it is shown that the update law for the proposed DSC scheme is needed only at the last design step with only one parameter being estimated online, which significantly reduces the computational burden, compared with current DSC schemes. Simulation results are presented to illustrate the efficiency of the proposed scheme.
Fifty years of DNA “Breathing”: Reflections on old and new approaches
Authors: von Hippel Peter H. , Johnson Neil P. , Marcus Andrew H. 
Published: July 2013

ABSTRACTThe coding sequences for genes, and much other regulatory information involved in genome expression, are located ‘inside’ the DNA duplex. Thus the “macromolecular machines” that read‐out this information from the base sequence of the DNA must somehow access the DNA “interior.” Double‐stranded (ds) DNA is a highly structured and cooperatively stabilized system at physiological temperatures, but is also only marginally stable and undergoes a cooperative “melting phase transition” at temperatures not far above physiological. Furthermore, due to its length and heterogeneous sequence, with AT‐rich segments being less stable than GC‐rich segments, the DNA genome ‘melts’ in a multistate fashion. Therefore the DNA genome must also manifest thermally driven structural (“breathing”) fluctuations at physiological temperatures that should reflect the heterogeneity of the dsDNA stability near the melting temperature. Thus many of the breathing fluctuations of dsDNA are likely also to be sequence dependent, and could well contain information that should be “readable” and useable by regulatory proteins and protein complexes in site‐specific binding reactions involving dsDNA “opening.” Our laboratory has been involved in studying the breathing fluctuations of duplex DNA for about 50 years. In this “Reflections” article we present a relatively chronological overview of these studies, starting with the use of simple chemical probes (such as hydrogen exchange, formaldehyde, and simple DNA “melting” proteins) to examine the local stability of the dsDNA structure, and culminating in sophisticated spectroscopic approaches that can be used to monitor the breathing‐dependent interactions of regulatory complexes with their duplex DNA targets in “real time.” © 2013 Wiley Periodicals, Inc. Biopolymers 99: 923–954, 2013.
NMR‐profiles of protein solutions
Authors: Pedrini Bill , Serrano Pedro , Mohanty Biswaranjan , Geralt Michael , Wüthrich Kurt 
Published: July 2013

ABSTRACTNMR‐Profiles are quantitative one‐dimensional (1D) presentations of 2D [15N,1H]‐correlation spectra used to monitor the quality of protein solutions prior to and during NMR structure determinations and functional studies. In our current use in structural genomics projects, an NMR‐Profile is recorded at the outset of a structure determination, using a uniformly 15N‐labeled microscale sample of the protein. We thus assess the extent to which polypeptide backbone resonance assignments can be achieved with given NMR techniques, for example, conventional triple resonance experiments or APSY‐NMR. With the availability of sequence‐specific polypeptide backbone resonance assignments in the course of the structure determination, an “Assigned NMR‐Profile” is generated, which visualizes the variation of the 15N–1H correlation cross peak intensities along the sequence and thus maps the sequence locations of polypeptide segments for which the NMR line shapes are affected by conformational exchange or other processes. The Assigned NMR‐Profile provides a guiding reference during later stages of the structure determination, and is of special interest for monitoring the protein during functional studies, where dynamic features may be modulated during physiological processes. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 825–831, 2013.
Randomized clinical trial of angiotensin-converting enzyme inhibitor, ramipril, in patients with intermittent claudication
Authors: Shahin Y , Cockcroft J R , Chetter I C 
Published: July 2013

Abstract

Background
The aim was to investigate the effect of ramipril on clinical parameters in patients with peripheral arterial disease.

Methods
Patients with intermittent claudication were randomized to receive ramipril or placebo for 24 weeks in a double-blind study. Outcome measures were walking distance, arterial stiffness measurement and quality of life (QoL).

Results
A total of 33 patients were included (25 men; mean(s.d.) age 64·6(7.8) years); 14 received ramipril and 19 placebo. After 24 weeks, ramipril improved maximum treadmill walking distance by an adjusted mean (95 per cent confidence interval, c.i.) of 131 (62 to 199) m (P = 0·001), improved treadmill intermittent claudication distance by 122 (56 to 188) m (P = 0·001) and improved patient-reported walking distance by 159 (66 to 313) m (P = 0·043) compared with placebo. Ramipril reduced carotid femoral pulse wave velocity by –1·47 (95 per cent c.i. –2·40 to –0·57) m/s compared with placebo (P = 0·002). Resting ankle : brachial pressure index (ABPI) improved slightly in both ramipril and placebo groups (0·02 (95 per cent c.i. –0·08 to 0·11) versus 0·03 (–0·05 to 0·10); P = 0·830). Ramipril had a slight, non-significant effect on QoL physical domains compared with placebo.

Conclusion
Ramipril improved walking distance in patients with claudication; however, this improvement was not related to improved ABPI but might have been due to ramipril reducing arterial stiffness. Registration number: NCT01037530 (http://www.clinicaltrials.gov).
Economic analysis of a randomized trial of percutaneous angioplasty, supervised exercise or combined treatment for intermittent claudication due to femoropopliteal arterial disease
Authors: Mazari F A K , Khan J A , Carradice D , Samuel N , Gohil R , McCollum P T , Chetter I C 
Published: July 2013

AbstractBackgroundThe aim was to compare costs and utilities of percutaneous transluminal angioplasty (PTA), a supervised exercise programme (SEP) and combined treatment (PTA + SEP) in patients with intermittent claudication (IC) to establish the most cost-effective treatment.MethodsPatients with IC due to femoropopliteal disease were randomized to receive PTA, SEP or PTA + SEP. Assessments were performed before, and at 1, 3, 6 and 12 months postintervention. Clinical and quality-of-life indicators were recorded. The SF-6D Health Utilities index was calculated from the Short Form 36, plotted, and quality-adjusted life-years (QALYs) were generated by calculating the area under the curve. Costs were calculated using National Health Service 2009–2010 payment-by-results tariffs and the National Institute for Health Research Clinical Research Network Investigation pricing index, and adjusted for reinterventions. Cost per QALY and incremental costs were calculated, and sensitivity analyses performed.ResultsA total of 178 patients (PTA, 60; SEP, 60; PTA + SEP, 58) were randomized. All treatments resulted in significant improvement in the SF-6D index (P &lt; 0·001). There was no significant difference between treatments in mean QALYs gained (PTA: 0·620, 95 per cent confidence interval 0·588 to 0·652; SEP: 0·629, 0·597 to 0·660; PTA + SEP: 0·649, 0·622 to 0·675). The adjusted mean cost per procedure was significantly higher for PTA (€7301·74) compared with SEP (€3866·49) and PTA + SEP (€6911·68) (P &lt; 0·001). The cost per QALY was significantly higher for PTA (€11 777·00) compared with SEP (€6147·04) and PTA + SEP (€10 649·74). QALYs were lost when PTA alone was used as first-line treatment in comparison with SEP or PTA + SEP. These results were robust and valid in sensitivity analyses.ConclusionSupervised exercise is the most cost-effective first-line treatment for IC, and when combined with PTA is more cost-effective than PTA alone.
Kinase in Motion: Insights into the Dynamic Nature of p38α by High‐Pressure NMR Spectroscopic Studies
Authors: Nielsen Gerd , Jonker Hendrik R. A. , Vajpai Navratna , Grzesiek Stephan , Schwalbe Harald 
Published: July 2013

AbstractProtein kinases are highly dynamic and complex molecules. Here we present high‐pressure and relaxation studies of the activated p38α mitogen‐activated protein kinase (MAPK). p38α plays a central role in inflammatory diseases such as rheumatoid arthritis and is therefore a highly attractive pharmaceutical target. The combination of high pressure and NMR spectroscopy allowed for a detailed per‐residue based assessment of the structural plasticity of p38α and the accessibility of low‐lying excited‐energy conformations throughout the kinase structure. Such information is uniquely accessible through the combination of liquid‐state NMR and high pressure and is of considerable value for the drug discovery process. The interactions of p38α and DFG‐in and DFG‐out ligands were studied under the application of high pressure, and we demonstrate how we can alter kinase dynamics by pressure in a similar way to what has previously only been observed by ligand binding. Pressure is shown to be a mild and efficient tool for manipulation of intermediate‐timescale dynamics.
Dynamics and Control of Coupled Continuous Chromatography and Crystallization Processes for the Production of Pure Enantiomers
Authors: Swernath S. , Kaspereit M. , Kienle A. 
Published: July 2013

AbstractThe combination of continuous chromatographic processes and subsequent crystallization with a recycle of the mother liquor can improve significantly the efficiency of separation processes for the production of enantiomers if compared to the stand‐alone chromatographic process. For the first time, dynamic operability and plantwide control of such a process combination is investigated. In the first step, the effect of disturbances on the open loop dynamics is evaluated. In a second step, a simple plantwide control strategy is proposed in order to ensure a robust process operation. It is demonstrated that the direct control of the simulated moving bed (SMB) unit is not required to stabilize the process combination while maintaining the desired product specifications. Instead, this can be achieved easily by controlling the amount of solvent removed or added to the system.
Electrochemical and Photoelectrochemical Properties of the Copper Hydroxyphosphate Mineral Libethenite
Authors: Li Man , Cheng Qian , Wittman Reed M. , Peng Xihong , Chan Candace K. 
Published: July 2013

AbstractThere has been much interest recently in the discovery of new, non‐oxide materials for photoelectrochemical applications. The copper hydroxyphosphate mineral libethenite, Cu2(OH)PO4 (CHP), which has a Jahn–Teller distorted structure and d9 electron configuration, has recently been reported to display photocatalytic activity. To better understand the properties of this material, a detailed investigation of the relevant fundamental characteristics such as the flatband potential, conduction type, and band diagram was performed using electrochemical and photoelectrochemical methods on CHP thin films deposited onto fluorine‐doped tin oxide (FTO) substrates. Density functional theory was used to calculate the band structure, effective mass of electrons and holes, and vacancy formation energies in CHP. CHP was found to be active for electrochemical water oxidation, as confirmed by quantitative O2 measurements. Possible factors behind the low photocurrents observed in linear scanning voltammetry are discussed. Better understanding of this material may lead to the development of improved catalysts and photocatalysts from natural mineral sources.
Theory of Kinetically Controlled Electrode Reaction Coupled to Ion Transfer across the Liquid/Liquid Interface
Authors: Komorsky‐Lovrić Šebojka , Lovrić Milivoj 
Published: July 2013

AbstractAn electron‐transfer reaction at a graphite electrode covered by a thin film of an organic solvent that is immiscible with water, immersed into an aqueous electrolyte solution, is studied theoretically. The redox couple is confined within the film, and conductivity is achieved by the transfer of an anion of supporting electrolyte across the organic solvent/water interface. In linear scan voltammetry, the peak potential depends on the initial concentration of either the reactant or the anion of supporting electrolyte in the film. A critical value of the dimensionless kinetic parameter κ, which can be used to determine the standard rate constant, is calculated.
Fibrous Networks with Incorporated Macrocycles: A Chiral Stimuli‐Responsive Supramolecular Supergelator and Its Application to Biocatalysis in Organic Media
Authors: Qi Zhenhui , Wu Changzhu , Malo de Molina Paula , Sun Han , Schulz Andrea , Griesinger Christian , Gradzielski Michael , Haag Rainer , Ansorge‐Schumacher Marion B. , Schalley Christoph A. 
Published: July 2013

AbstractA new and versatile, crown ether appended, chiral supergelator has been designed and synthesized based on the bis‐urea motif. The introduction of a stereogenic center improved its gelation ability significantly relative to its achiral analogue. This low‐molecular‐weight gelator forms supramolecular gels in a variety of organic solvents. It is sensitive to multiple chemical stimuli and the sol–gel phase transitions can be reversibly triggered by host–guest interactions. The gel can be used to trap enzymes and release them on demand by chemical stimuli. It stabilizes the microparticles in Pickering emulsions so that enzyme‐catalyzed organic reactions can take place in the polar phase inside the microparticles, the organic reactants diffusing through the biphasic interface from the surrounding organic phase. Because of the higher interface area between the organic and polar phases, enzyme activity is enhanced in comparison with simple biphasic systems.
Phototriggered Release of a Leaving Group in Ketoprofen Derivatives via a Benzylic Carbanion Pathway, But not via a Biradical Pathway
Authors: Li Ming‐De , Su Tao , Ma Jiani , Liu Mingyue , Liu Han , Li Xuechen , Phillips David Lee 
Published: July 2013

Abstract2‐Acetoxymethyl‐2‐(3‐benzoylphenyl)propionic acid (KP‐OAc) was used as a model to elucidate the solvent‐mediated photochemistry mechanism of Ketoprofen (KP). In solutions with a low concentration of water, KP‐OAc exhibits a benzophenone‐like photochemistry, reacting with water molecules through some reaction to form a ketyl radical intermediate. In neutral solutions with a high concentration of water or acidic solutions, KP‐OAc undergoes a photodecarboxylation reaction with the assistance of water molecules or with the catalysis of perchloric acid to directly generate a biradical intermediate that cannot induce the phototrigger reaction to release the AcO− group. Therefore, the lifetime of the biradical intermediate of KP‐OAc is almost same as that of the biradical intermediate formed from KP in the same kinds of solutions. However, the photodecarboxylation of KP‐OAc in phosphate buffer solution directly produces the benzylic carbanion intermediate, which can induce the phototrigger reaction to release the AcO− group. Therefore, the lifetime of the biradical intermediate of KP‐OAc is significantly shorter than the lifetime of the biradical intermediate of KP in phosphate buffer solution. Interestingly, the investigation of the photochemistry of KP‐OAc not only verifies the solvent‐mediated photochemistry mechanism of KP but also provides some new insight into the potential of using this kind of platform for phototrigger applications. The biradical intermediate is not the key species leading to the phototrigger reaction but the benzylic carbanion species is the key reactive intermediate that can mediate the phototrigger reaction of KP‐OAc. Therefore, a change in the pH of the solutions can be utilized to switch on and switch off the photorelease reactions of KP derivative phototrigger compounds.
Photosynthetic Antenna‐Reaction Center Mimicry with a Covalently Linked Monostyryl Boron‐Dipyrromethene–Aza‐Boron‐Dipyrromethene–C60 Triad
Authors: Shi Wen‐Jing , El‐Khouly Mohamed E. , Ohkubo Kei , Fukuzumi Shunichi , Ng Dennis K. P. 
Published: July 2013

AbstractAn efficient functional mimic of the photosynthetic antenna‐reaction center has been designed and synthesized. The model contains a near‐infrared‐absorbing aza‐boron‐dipyrromethene (ADP) that is connected to a monostyryl boron‐dipyrromethene (BDP) by a click reaction and to a fullerene (C60) using the Prato reaction. The intramolecular photoinduced energy and electron‐transfer processes of this triad as well as the corresponding dyads BDP‐ADP and ADP‐C60 have been studied with steady‐state and time‐resolved absorption and fluorescence spectroscopic methods in benzonitrile. Upon excitation, the BDP moiety of the triad is significantly quenched due to energy transfer to the ADP core, which subsequently transfers an electron to the fullerene unit. Cyclic and differential pulse voltammetric studies have revealed the redox states of the components, which allow estimation of the energies of the charge‐separated states. Such calculations show that electron transfer from the singlet excited ADP (1ADP*) to C60 yielding ADP.+‐C60.− is energetically favorable. By using femtosecond laser flash photolysis, concrete evidence has been obtained for the occurrence of energy transfer from 1BDP* to ADP in the dyad BDP‐ADP and electron transfer from 1ADP* to C60 in the dyad ADP‐C60. Sequential energy and electron transfer have also been clearly observed in the triad BDP‐ADP‐C60. By monitoring the rise of ADP emission, it has been found that the rate of energy transfer is fast (≈1011 s−1). The dynamics of electron transfer through 1ADP* has also been studied by monitoring the formation of C60 radical anion at 1000 nm. A fast charge‐separation process from 1ADP* to C60 has been detected, which gives the relatively long‐lived BDP‐ADP.+C60.− with a lifetime of 1.47 ns. As shown by nanosecond transient absorption measurements, the charge‐separated state decays slowly to populate mainly the triplet state of ADP before returning to the ground state. These findings show that the dyads BDP‐ADP and ADP‐C60, and the triad BDP‐ADP‐C60 are interesting artificial analogues that can mimic the antenna and reaction center of the natural photosynthetic systems.
Ionic Aggregates of Lithium Organocuprates
Authors: Putau Aliaksei , Wilken Mona , Koszinowski Konrad 
Published: July 2013

AbstractWe have used a combination of electrospray ionization mass spectrometry and electrical conductivity measurements to analyze solutions of the Gilman cuprates LiCuR2⋅LiX, with R=Ph, Bu and X=Cl, Br, I, in tetrahydrofuran and have compared our findings with previous results on cyanocuprates LiCuR2⋅LiCN. Among the various polynuclear organocuprate ions observed, Li2Cu3Ph6−, LiCu4Ph6−, and Cu5Ph6− are of particular interest because aggregates of the same composition are known from X‐ray crystal structures. Control experiments have indicated that the polynuclear organocuprate anions detected in solution are indeed identical to those formed in the solid state. As abundant ions of the type Li2Cu3R6− are found in solutions of Gilman cuprates and cyanocuprates alike, their possible involvement in organocuprate reactions should be considered. For comparison, we have also included solutions of LiCu(R)I, LiCuX2⋅LiX, LiCuX2, and CuCN⋅2 LiX in the present study.