bluuebunny/crossref_metadata_2025 huggingface dataset:
Directed evolution: Past, present, and future
Authors: Cobb Ryan E. , Chao Ran , Zhao Huimin
Published: December 2012

Directed evolution, the laboratory process by which biological entities with desired traits are created through iterative rounds of genetic diversification and library screening or selection, has become one of the most useful and widespread tools in basic and applied biology. From its roots in classical strain engineering and adaptive evolution, modern directed evolution came of age 20 years ago with the demonstration of repeated rounds of polymerase chain reaction (PCR)‐driven random mutagenesis and activity screening to improve protein properties. Since then, numerous techniques have been developed that have enabled the evolution of virtually any protein, pathway, network, or entire organism of interest. Here, we recount some of the major milestones in the history of directed evolution, highlight the most promising recent developments in the field, and discuss the future challenges and opportunities that lie ahead. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1432–1440, 2013
Use of Alternative Plant Resources by Common Marmosets (Callithrix jacchus) in the Semi‐Arid Caatinga Scrub Forests of Northeastern Brazil
Authors: AMORA TACYANA DUARTE , BELTRÃO‐MENDES RAONE , FERRARI STEPHEN F.
Published: December 2012

The common marmoset (Callithrix jacchus) is amply distributed in the Brazilian Northeast, but little is known of its ecology in the semi‐arid Caatinga scrublands. The present study provides the first detailed data on the composition of the diet ofC. jacchusin Caatinga ecosystems, derived from observations at four sites in the state of Sergipe. While exudate sources were gouged at all four sites in a manner typical of the species, fruit was the principal component of the diet at the main study site during most months, and a number of unusual items were eaten, including leaves, and the reproductive parts of cacti and bromeliads. These plants are rarely recorded in marmoset diets, but are common in caatinga habitats. Leaves were ingested during 5 of the 8 months monitored at the main study site, reaching 39.74% of the diet in 1 month, and appeared to be an alternative fallback food to plant exudates during periods when fruit was scarce. Three species of cactus provided both flowers and fruits, while the terrestrial bromeliad,Encholirium spectabile, provided nectar (30.81% of the diet in November). Approximately half of the plant species (and three families) identified in this study had not been recorded previously in the diet ofCallithrix. Overall, the data suggest that, while the marmosets exploit the same types of plant foods in the Caatinga, the resource base is quite distinct from that of the Atlantic Forest. Other differences, such as relatively small groups and large home ranges, may contribute to divergent ecological patterns, which require more systematic investigation. Am. J. Primatol. 75:333‐341, 2013. © 2012 Wiley Periodicals, Inc.
Strong‐field photoemission from silicon field emitter arrays
Authors: Keathley Phillip D. , Sell Alexander , Putnam William P. , Guerrera Stephen , Velásquez‐García Luis , Kärtner Franz X.
Published: December 2012

Strong‐field photoemission from silicon field emitter arrays is investigated experimentally and results are explained using a “simple‐man” optical‐field emission model. Spectra are collected throughout an in‐situ laser annealing process, leading to a red‐shift in emitted electron energy along with an increase in electron yield. After the annealing process, a high energy plateau is formed which is explained through optical‐field emission along with electron re‐scattering with the tip surface.
High order harmonic generation in noble gases using plasmonic field enhancement
Authors: Ciappina Marcelo F. , Shaaran Tahir , Lewenstein Maciej
Published: December 2012

Theoretical studies of high‐order harmonic generation (HHG) in rare gases driven by plasmonic field enhancement are presented. This kind of fields appears when plasmonic nanostructures are illuminated by an intense few‐cycle laser and have a particular spatial dependency, depending on the geometrical shape of the nanostructure. It is demonstrated that the strong nonhomogeneous character of the laser enhanced field plays an important role in the HHG process and significantly extends the harmonic cutoff. The models are based on numerical solution of the time dependent Schrödinger equation (TDSE) and supported by classical and semiclassical calculations.
Probing ultrafast carrier tunneling dynamics in individual quantum dots and molecules
Authors: Müller Kai , Bechtold Alexander , Ruppert Claudia , Kaldewey Timo , Zecherle Markus , Wildmann Johannes S. , Bichler Max , Krenner Hubert J. , Villas‐Bôas José M. , Abstreiter Gerhard , Betz Markus , Finley Jonathan J.
Published: December 2012

Ultrafast pump‐probe spectroscopy is employed to directly monitor the tunneling of charge carriers from single and vertically coupled quantum dots and probe intra‐molecular dynamics. Immediately after resonant optical excitation, several peaks are observed in the pump‐probe spectrum arising from Coulomb interactions between the photogenerated charge carriers. The influence of few‐Fermion interactions in the photoexcited system and the temporal evolution of the optical response is directly probed in the time domain. In addition, the tunneling times for electrons and holes from the QD nanostructure are independently determined. In polarization resolved measurements, near perfect Pauli‐spin blockade is observed in the spin‐selective absorption spectrum as well as stimulated emission. While electron and hole tunneling from single quantum dots is shown to be well explained by the WKB formalism, for coupled quantum dots pronounced resonances in the electron tunneling rate are observed arising from elastic and inelastic electron tunneling between the different dots.
Biopolymere als vielseitige Ressource für die Nanochemie
Authors: Schnepp Zoe
Published: December 2012

Biologisches Material ist eine ergiebige Quelle für chemisch vielfältige Makromoleküle wie Polysaccharide, Polypeptide und polyaromatische Verbindungen. Viele dieser biologischen Polymere (Biopolymere) sind auf spezifische Funktionen hin evolutionär optimiert, z. B. über die Molekülkettenlänge, die Funktionalisierung und die Monomersequenz. Gegenwärtig werden zahlreiche Anstrengungen unternommen, die sich auf den chemischen Aufschluss von Biopolymeren für die Verwendung als Treibstoff oder als Ausgangsverbindungen für die Synthese richten. Darüber hinaus gibt es ein steigendes Interesse an der unmittelbaren Verwendung von Biopolymeren für die Herstellung funktioneller Materialien. Dieser Kurzaufsatz zieht Beispiele aus der jüngeren Vergangenheit heran, um aufzuzeigen, wie Biopolymere neue Wege für die Synthese nanostrukturierter Materialien eröffnen können.
Biopolymers as a Flexible Resource for Nanochemistry
Authors: Schnepp Zoe
Published: December 2012

Biomass is an abundant source of chemically diverse macromolecules, including polysaccharides, polypeptides, and polyaromatics. Many of these biological polymers (biopolymers) are highly evolved for specific functions through optimized chain length, functionalization, and monomer sequence. As biopolymers are a chemical resource, much current effort is focused on the breakdown of these molecules into fuels or platform chemicals. However there is growing interest in using biopolymers directly to create functional materials. This Minireview uses recent examples to show how biopolymers are providing new directions in the synthesis of nanostructured materials.
CFD analysis to study the effect of design variables on the particle cut size in hydrocyclones
Authors: Delgadillo J. A. , Rosales‐Marin G. , Perez‐Alonso C. , Ojeda C.
Published: December 2012

The modification of hydrocyclone geometry changes the dynamics of the flow, so the particle cut size is affected. Computational fluid dynamics was applied to predict particle classification according to size. Fluent code was used to perform computer simulations for five different hydrocyclone geometries using large eddy simulation and volume of fluid models. The sensitivity to computed modifications in particle classification was evaluated by changing basic design variables, such as spigot diameter, vortex finder diameter, and cone angle. The results show that the particle cut size can be predicted for changes in geometric configuration for a wide range of slurry concentration with a small degree of error using computational fluid dynamics. The error can be attributed to the absence of particle–particle and fluid–particle interaction modeling. However, this assumption is known to be valid only for diluted slurries and some regions within the hydrocyclone. As soon as the particles enter the system, most of them are located within the walls, creating diluted slurry conditions in the main core of the hydrocyclone. The computed results for more concentrated slurries were therefore close to the experimental cut‐size values. In all cases, the particle cut size was predicted successfully. Therefore, the evaluation of changes in the standard geometry to manipulate the dynamics and achieve the desired particle cut size becomes possible. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.
Multicolor electrochromism of low‐bandgap copolymers based on pyrrole and 3,4‐ethylenedioxythiophene: Fine‐tuning colors through feed ratio
Authors: Zhao‐yang Zhang , Yi‐jie Tao , Xiao‐qian Xu , Yong‐jiang Zhou , Hai‐feng Cheng , Wen‐wei Zheng
Published: December 2012

The copolymerization of pyrrole with 3,4‐ethylenedioxythiophene (EDOT) is successfully achieved in boron trifluoride diethyl etherate via direct anodic oxidation of the monomer mixtures on indium‐tin oxide working electrodes. The resultant copolymers are characterized by electrochemical methods, FT‐IR, XPS, SEM, and spectroelectrochemical analysis. The copolymer films present excellent electrochromic properties especially the multicolor electrochromism which can be tuned through the feed ratio of pyrrole and EDOT. The neutral copolymer films exhibit blue‐shift with the increasing feed ratio of pyrrole and EDOT, and the calculated band gaps of the copolymers are as low as that of PEDOT film. Furthermore, the electrochemical and optical stability has been improved by the incorporation of EDOT units into the polymer chains. The copolymer prepared with the changing feed ratio of pyrrole and EDOT at 1/4 retains 71% of its original electroactivity after 500 cycles and 72% of its optical contrast after 500 steps. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Film‐forming behavior and mechanical properties of colloidal silica/polymer latex blends with high silica load
Authors: Yang Ling , Zhou Shuxue , Gu Guangxin , Wu Limin
Published: December 2012

In this article, silica sol (diameter: 8–100 nm) and polymer latex (Tg < 25°C) were mixed and dried at room temperature to prepare nanocomposite films with high silica load (≥50 wt %). Effects of silica size, silica load, and the Tg of the polymer on the film‐forming behavior of the silica/polymer latex blend were investigated. The transparency, morphology, and mechanical properties of the nanocomposite films were examined by UV–Vis spectroscopy, SEM, and nanoindentation tests, respectively. Transparent and crack‐free films were produced with silica loads as high as 70 wt %. Thirty nanometers was found to be the critical silica size for the evolution of film‐forming behavior, surface morphology, and mechanical properties. Colloidal silica particles smaller than this critical size act as binders to form strong silica skeleton. This gives the final silica/polymer nanocomposite film its porous surface and high mechanical strength. However, silica particles with sizes of 30 nm or larger tend to work as nanofillers rather than binders, causing poor mechanical strength. We also determined the critical silica load appeared for the mechanical strength of silica/polymer film at high silica load. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Development of olive oil based organogels using sorbitan monopalmitate and sorbitan monostearate: A comparative study
Authors: Shah Dipak K. , Sagiri Sai S. , Behera B. , Pal Kunal , Pramanik Krishna
Published: December 2012

The present work deals with preparation of the olive oil (OO) based organogels using sorbitan monostearate (SMS) and sorbitan monopalmitate (SMP) as organogelators for controlled drug delivery applications. Metronidazole (MZ) was used as the model drug. Gels were prepared by solubilizing the organogelators in OO at 60°C under stirring. As the solution was cooled down, the gelator molecules precipitate as an isotropic phase having networked structures, which immobilized OO. Formation of 3D networked structure was confirmed by light, phase contrast, and scanning electron microscopy. Accelerated thermal stability studies demonstrated the thermal stability and thermoreversibility of the organogels. DSC and gel disintegration studies suggested that the SMS based organogels were having higher thermal and physical strength as compared to the SMP based organogels. Viscometric analysis suggested the pseudoplastic flow behavior of the gels. The SMS organogels were more amorphous as compared to the SMP organogels of same composition. Drug release from the organogels followed Fickian diffusion kinetics. The drug loaded gels have shown good antimicrobial property against Escherichia coli and Bacillus subtilis and were found to be highly hemocompatible in nature. On the basis of the preliminary results, the developed organogels can be used as matrices for the topical drug delivery. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
A process for preparing polyethylene wax microspheres and optimization of their dissolution precipitation by response surface methodology
Authors: Jia Yin‐yin , Zhang Long
Published: December 2012

Polyethylene wax (PEW) microspheres were prepared by the dissolution precipitation method using a PEW byproduct as the starting material. The influence of surfactant type on the morphology and melting point of the product was investigated. The effects of each factor, including the concentration of anionic surfactants, cooling rate, and stirring rate, on the particle sizes were studied using a three‐level, three‐factor Box–Behnken design. The experimental parameters were optimized using response surface methodology. The melting point was found to increase when the blend surfactant was employed. The optimal conditions were an anionic surfactant concentration, cooling rate, and stirring rate of 1.0–3.5%, 1.00 °C/s and 1000 rpm, respectively. Under these conditions, the mean particle size was 15 μm, and the highest yield was 94.25%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Novel preparation method for enhancing nanoparticle dispersion and barrier properties of poly(ethylene terephthalate) and poly(m‐xylylene adipamide)
Authors: Wang Yin , Jabarin Saleh A.
Published: December 2012

A modified melt blending method has been developed for preparing exfoliated nanocomposites of poly(ethylene terephthalate) with sodium‐montmorillonite (Na‐MMT) and poly(m‐xylylene adipamide) with Na‐MMT. In this novel compounding process, a Na‐MMT water solution was blended with the polymer in a twin screw extruder. This mixing process ensured that the silica nanoparticles were exfoliated in the polymer matrix through fixing the nanoparticles within the polymer matrix almost as they were in water. Transmission electron microscopy (TEM) and X‐ray diffraction were used to determine nanoparticle dispersion level. The absence of the X‐ray basal reflections in conjunction with the TEM images revealed the exfoliation of clay platelets. Differential scanning calorimetry illustrated that the nucleating abilities of montmorillonite were related to clay content and dispersion morphology. Oxygen permeation results indicated that the improved morphologies had enhanced the barrier properties of the nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Loss of methylation in CpG sites in the NF‐κB enhancer elements of inducible nitric oxide synthase is responsible for gene induction in human articular chondrocytes
Authors: de Andrés María C. , Imagawa Kei , Hashimoto Ko , Gonzalez Antonio , Roach Helmtrud I. , Goldring Mary B. , Oreffo Richard O. C.
Published: December 2012

Objective

To investigate whether the abnormal expression of inducible nitric oxide synthase (iNOS) by osteoarthritic (OA) human chondrocytes is associated with changes in the DNA methylation status in the promoter and/or enhancer elements of iNOS.

Methods

Expression of iNOS was quantified by quantitative reverse transcriptase–polymerase chain reaction. The DNA methylation status of the iNOS promoter and enhancer regions was determined by bisulfite sequencing or pyrosequencing. The effect of CpG methylation on iNOS promoter and enhancer activities was determined using a CpG‐free luciferase vector and a CpG methyltransferase. Cotransfections with expression vectors encoding NF‐κB subunits were carried out to analyze iNOS promoter and enhancer activities in response to changes in methylation status.

Results

The 1,000‐bp iNOS promoter has only 7 CpG sites, 6 of which were highly methylated in both control and OA samples. The CpG site at −289 and the sites in the starting coding region were largely unmethylated in both groups. The NF‐κB enhancer region at −5.8 kb was significantly demethylated in OA samples compared with control samples. This enhancer element was transactivated by cotransfection with the NF‐κB subunit p65, alone or together with p50. Critically, methylation treatment of the iNOS enhancer element significantly decreased its activity in a reporter assay.

Conclusion

These findings demonstrate the association between demethylation of specific NF‐κB–responsive enhancer elements and the activation of iNOS transactivation in human OA chondrocytes, consistent with the differences in methylation status observed in vivo in normal and human OA cartilage and, importantly, show association with the OA process.
Hearing loss in Muckle‐Wells syndrome
Authors: Kuemmerle‐Deschner Jasmin B. , Koitschev Assen , Ummenhofer Katharina , Hansmann Sandra , Plontke Stefan K. , Koitschev Christiane , Koetter Ina , Angermair Eva , Benseler Susanne M.
Published: December 2012

Objective

Muckle‐Wells syndrome (MWS) is an inherited autoinflammatory disease characterized by fevers, rashes, arthralgia, conjunctivitis, and sensorineural hearing loss. In MWS, NLRP3 gene mutations are associated with excessive interleukin‐1 release. The aims of this study were to determine the otologic characteristics of MWS, define trajectories of hearing loss, and explore the association with distinct NLRP3 genotypes.

Methods

A prospective observational cohort study of children and adults diagnosed as having MWS was conducted at a single center. NLRP3 gene mutations were determined. Patients underwent standardized clinical, laboratory, and otologic assessments, including pure tone audiometry, vestibular organ testing, and tinnitus evaluation. Trajectories of hearing loss were defined for each genotype. The genotype‐specific risk of progression of hearing loss was determined.

Results

A total of 33 patients ages 3–75 years who were members of 5 families with 4 different NLRP3 gene mutations were included. The majority of patients (67%) experienced bilateral sensorineural hearing loss. Even in cases of profound hearing loss vestibular reactivity remained normal. Fourteen adult patients reported nondebilitating tinnitus. Overall, hearing impairment progressed with age. Patients with the T348M mutation were at highest risk of rapid progression of sensorineural hearing loss.

Conclusion

Patients with MWS are at risk of developing progressive sensorineural hearing loss without vestibular involvement. Hearing impairment starts at high frequencies and can subsequently progress to profound hearing loss. Progression is age dependent. Patients with different NLRP3 mutations had distinctly different trajectories of hearing loss, suggesting a mutation‐specific risk that should be considered when making treatment decisions.
Modeling geographic, temporal, and proximity contexts for improving geotemporal search
Authors: Daoud Mariam , Huang Jimmy Xiangji
Published: December 2012

Traditional information retrieval (IR) systems show significant limitations on returning relevant documents that satisfy the user's information needs. In particular, to answer geographic and temporal user queries, the IR task becomes a nonstraightforward process where the available geographic and temporal information is often unstructured. In this article, we propose a geotemporal search approach that consists of modeling and exploiting geographic and temporal query context evidence that refers to implicit multivarying geographic and temporal intents behind the query. Modeling geographic and temporal query contexts is based on extracting and ranking geographic and temporal keywords found in pseudo‐relevant feedback (PRF) documents for a given query. Our geotemporal search approach is based on exploiting the geographic and temporal query contexts separately into a probabilistic ranking model and jointly into a proximity ranking model. Our hypothesis is based on the concept that geographic and temporal expressions tend to co‐occur within the document where the closer they are in the document, the more relevant the document is. Finally, geographic, temporal, and proximity scores are combined according to a linear combination formula. An extensive experimental evaluation conducted on a portion of the New York Times news collection and the TREC 2004 robust retrieval track collection shows that our geotemporal approach outperforms significantly a well‐known baseline search and the best known geotemporal search approaches in the domain. Finally, an in‐depth analysis shows a positive correlation between the geographic and temporal query sensitivity and the retrieval performance. Also, we find that geotemporal distance has a positive impact on retrieval performance generally.
Topic familiarity and information skills in online credibility evaluation
Authors: Lucassen Teun , Muilwijk Rienco , Noordzij Matthijs L. , Schraagen Jan Maarten
Published: December 2012

With the rise of user‐generated content, evaluating the credibility of information has become increasingly important. It is already known that various user characteristics influence the way credibility evaluation is performed. Domain experts on the topic at hand primarily focus on semantic features of information (e.g., factual accuracy), whereas novices focus more on surface features (e.g., length of a text). In this study, we further explore two key influences on credibility evaluation: topic familiarity and information skills. Participants with varying expected levels of information skills (i.e., high school students, undergraduates, and postgraduates) evaluated Wikipedia articles of varying quality on familiar and unfamiliar topics while thinking aloud. When familiar with the topic, participants indeed focused primarily on semantic features of the information, whereas participants unfamiliar with the topic paid more attention to surface features. The utilization of surface features increased with information skills. Moreover, participants with better information skills calibrated their trust against the quality of the information, whereas trust of participants with poorer information skills did not. This study confirms the enabling character of domain expertise and information skills in credibility evaluation as predicted by the updated 3S‐model of credibility evaluation.
Contributing high quantity and quality knowledge to online Q&A communities
Authors: Lou Jie , Fang Yulin , Lim Kai H. , Peng Jerry Zeyu
Published: December 2012

This study investigates the motivational factors affecting the quantity and quality of voluntary knowledge contribution in online Q&A communities. Although previous studies focus on knowledge contribution quantity, this study regards quantity and quality as two important, yet distinct, aspects of knowledge contribution. Drawing on self‐determination theory, this study proposes that five motivational factors, categorized along the extrinsic‐intrinsic spectrum of motivation, have differential effects on knowledge contribution quantity versus quality in the context of online Q&A communities. An online survey with 367 participants was conducted in a leading online Q&A community to test the research model. Results show that rewards in the reputation system, learning, knowledge self‐efficacy, and enjoy helping stand out as important motivations. Furthermore, rewards in the reputation system, as a manifestation of the external regulation, is more effective in facilitating the knowledge contribution quantity than quality. Knowledge self‐efficacy, as a manifestation of intrinsic motivation, is more strongly related to knowledge contribution quality, whereas the other intrinsic motivation, enjoy helping, is more strongly associated with knowledge contribution quantity. Both theoretical and practical implications are discussed.
3,14‐Bis(p‐nitrophenyl)‐17,17‐dipentyltetrabenzo[a,c,g,i]‐fluorene: A New Fluorophore Displaying Both Remarkable Solvatochromism and Crystalline‐Induced Emission
Authors: Ueda Yoshiaki , Tanigawa Yusuke , Kitamura Chitoshi , Ikeda Hiroshi , Yoshimoto Yuichi , Tanaka Mirai , Mizuno Kazuhiko , Kurata Hiroyuki , Kawase Takeshi
Published: December 2012

A series of 17,17‐dialkyl‐3,14‐diaryltetrabenzofluorenes were efficiently prepared by using Suzuki–Miyaura cross‐coupling reactions of the corresponding 3,14‐dibromo derivatives. Studies of the unique fluorescence properties of these compounds showed that they display intense blue to yellow fluorescence with high quantum yields in the solution state and blue to orange fluorescence with moderate quantum yields in the solid state. In addition, the fluorescence wavelength of the bis(p‐nitrophenyl) derivative is remarkably solvent‐dependent in a manner that correlates with the solvent polarity parameter ET(30). The results of density function theory calculations suggest that the intramolecular charge‐transfer character of the HOMO–LUMO transition is responsible for the large solvent effect. Moreover, addition of water to a tetrahydrofuran (THF) solution of this compound leads to quenching of the yellow fluorescence owing to an increase in the solvent polarity. However, when the amount of water fraction exceeds 70 %, a new fluorescence band appears at the same orange‐red emission wavelength as that of the solid‐state fluorescence. This observation suggests the occurrence of a crystallization‐induced emission (CIE) phenomenon in highly aqueous THF.
Stereocontrolled Organocatalytic Strategy for the Synthesis of Optically Active 2,3‐Disubstituted cis‐2,3‐Dihydrobenzofurans
Authors: Christensen Jannie , Albrecht Łukasz , Jørgensen Karl Anker
Published: December 2012

An intramolecular, organocatalyzed Michael addition has been developed to obtain biologically important 2,3‐disubstituted cis‐2,3‐dihydrobenzofurans. By using mandelic acid salts of primary aminocatalysts, derived from cinchona alkaloids, the intramolecular cyclization reaction has been developed to proceed in high yield, with moderate to good diastereoselectivity, and up to 99 % ee. Based on the absolute configuration of the formed 2,3‐disubstituted‐cis‐2,3‐dihydrobenzofurans and by considering the observed substrate scope restrictions, a mechanistic rationalization has been presented.
Dividends in finite time horizon
Authors: Cardoso Rui M.R.
Published: December 2012

In this paper, we consider the classical risk model modified in two different ways by the inclusion of a dividend barrier. For Model I, we present numerical algorithms, which can be used to approximate or bound the expected discounted value of dividends up to a finite time horizon, t, or ruin if this occurs earlier. We extend this by requiring the shareholders to provide the initial capital and to pay the deficit at ruin each time it occurs so that the process then continues after ruin up to time t. For Model I, we assume the full premium income is paid as dividends whenever the surplus exceeds a set level.

In our Model II, we assume dividends are paid at a rate less than the rate of premium income. Copyright © 2012 John Wiley & Sons, Ltd.
Functional motor recovery is improved due to local placement of GDNF microspheres after delayed nerve repair
Authors: Wood Matthew D. , Gordon Tessa , Kemp Stephen W.P. , Liu Edward H. , Kim Howard , Shoichet Molly S. , Borschel Gregory H.
Published: December 2012

The majority of bioengineering strategies to promote peripheral nerve regeneration after injury have focused on therapies to bridge large nerve defects while fewer therapies are being developed to treat other nerve injuries, such as nerve transection. We constructed delivery systems using fibrin gels containing either free GDNF or polylactide–glycolic acid (PLGA) microspheres with GDNF to treat delayed nerve repair, where ELISA verified GDNF release. We determined the formulation of microspheres containing GDNF that optimized nerve regeneration and functional recovery in a rat model of delayed nerve repair. Experimental groups underwent delayed nerve repair and treatment with GDNF microspheres in fibrin glue at the repair site or control treatments (empty microspheres or free GDNF without microspheres). Contractile muscle force, muscle mass, and MUNE were measured 12 weeks following treatment, where GDNF microspheres (2 weeks formulation) were superior compared to either no GDNF or short‐term release of free GDNF to nerve. Nerve histology distal to the repair site demonstrated increased axon counts and fiber diameters due to GDNF microspheres (2 weeks formulation). GDNF microspheres partially reversed the deleterious effects of chronic nerve injury, and recovery was slightly favored with the 2 weeks formulation compared to the 4 weeks formulation. Biotechnol. Bioeng. 2013; 110: 1272–1281. © 2012 Wiley Periodicals, Inc.
Whole‐cell‐based CYP153A6‐catalyzed (S)‐limonene hydroxylation efficiency depends on host background and profits from monoterpene uptake via AlkL
Authors: Cornelissen Sjef , Julsing Mattijs K. , Volmer Jan , Riechert Ole , Schmid Andreas , Bühler Bruno
Published: December 2012

Living microbial cells are considered to be the catalyst of choice for selective terpene functionalization. However, such processes often suffer from side product formation and poor substrate mass transfer into cells. For the hydroxylation of (S)‐limonene to (S)‐perillyl alcohol by Pseudomonas putida KT2440 (pGEc47ΔB)(pCom8‐PFR1500), containing the cytochrome P450 monooxygenase CYP153A6, the side products perillyl aldehyde and perillic acid constituted up to 26% of the total amount of oxidized terpenes. In this study, it is shown that the reaction rate is substrate‐limited in the two‐liquid phase system used and that host intrinsic dehydrogenases and not CYP153A6 are responsible for the formation of the undesired side products. In contrast to P. putida KT2440, E. coli W3110 was found to catalyze perillyl aldehyde reduction to the alcohol and no oxidation to the acid. Furthermore, E. coli W3110 harboring CYP153A6 showed high limonene hydroxylation activities (7.1 U g). The outer membrane protein AlkL was found to enhance hydroxylation activities of E. coli twofold in aqueous single‐phase and fivefold in two‐liquid phase biotransformations. In the latter system, E. coli harboring CYP153A6 and AlkL produced up to 39.2 mmol (S)‐perillyl alcohol L within 26 h, whereas no perillic acid and minor amounts of perillyl aldehyde (8% of the total products) were formed. In conclusion, undesired perillyl alcohol oxidation was reduced by choosing E. coli's enzymatic background as a reaction environment and co‐expression of the alkL gene in E. coli represents a promising strategy to enhance terpene bioconversion rates. Biotechnol. Bioeng. 2013; 110: 1282–1292. © 2012 Wiley Periodicals, Inc.
Real‐time detection of cellular death receptor‐4 activation by fluorescence resonance energy transfer
Authors: Dereli‐Korkut Zeynep , Gandhok Harmeet , Zeng Ling Ge , Waqas Sidra , Jiang Xuejun , Wang Sihong
Published: December 2012

Targeted therapy involving the activation of death receptors DR4 and/or DR5 by its ligand, TRAIL, can selectively induce apoptosis in certain tumor cells. In order to profile the dynamic activation or trimerization of TRAIL–DR4 in live cells in real‐time, the development of an apoptosis reporter cell line is essential. Fluorescence resonance energy transfer (FRET) technology via a FRET pair, cyan fluorescence protein (CFP) and yellow fluorescence protein (YFP), was used in this study. DR4‐CFP and DR4‐YFP were stably expressed in human lung cancer PC9 cells. Flow cytometer sorting and limited dilution coupled with fluorescence microscopy were used to select a monoclonal reporter cell line with high and compatible expression levels of DR4‐CFP and DR4‐YFP. FRET experiments were conducted and FRET efficiencies were monitored according to the Siegel's YFP photobleaching FRET protocol. Upon TRAIL induction a significant increase in FRET efficiencies from 5% to 9% demonstrated the ability of the DR4‐CFP/YFP reporter cell line in monitoring the dynamic activation of TRAIL pathways. 3D reconstructed confocal images of DR4‐CFP/YFP reporter cells exhibited a colocalized expression of DR4‐CFP and DR4‐YFP mainly on cell membranes. FRET results obtained during this study complements the use of epi‐fluorescence microscopy for FRET analysis. The real‐time FRET analysis allows the dynamic profiling of the activation of TRAIL pathways by using the time‐lapse fluorescence microscopy. Therefore, DR4‐CFP/YFP PC9 reporter cells along with FRET technology can be used as a tool for anti‐cancer drug screening to identify compounds that are capable of activating TRAIL pathways. Biotechnol. Bioeng. 2013; 110: 1396–1404. © 2012 Wiley Periodicals, Inc.
Resection margin involvement and tumour origin in pancreatic head cancer (Br J Surg 2012 99 1036–1049)
Authors: Erdmann J , van Eijck C H J
Published: December 2012

The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved, appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length.
A century at the cutting edge
Authors: Alderson D , Earnshaw J J
Published: December 2012

Where next
Characterization of in vivo antioxidant constituents and dual‐standard quality assessment of Danhong injection
Authors: Liu Hai‐Tao , Wang Yue‐Fei , Olaleye Olajide , Zhu Yan , Gao Xiu‐Mei , Kang Li‐Yuan , Zhao Tao
Published: December 2012

Antioxidants and oxidative stress play a critical role in cardiovascular diseases. Danhong injection (DHI) is a well prescribed cardiovascular medication in China, but its detailed chemical basis and mechanisms of action remain unknown. To prove the antioxidant activity of DHI, its free radical scavenging capacity (RSC) was assessed by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) spectrophotometric assay. The 50% radical scavenging activity value was 1:129.2 mL/mL, against 0.95 mm DPPH. To further identify the antioxidant compounds, modified thin‐layer chromatography combined with DPPH bioautography assay was used. Compared with vitamin C, 11 of 16 available compounds displayed strong antioxidant activity, which were also detected in rat serum after intravenous administration of DHI by ultra‐performance liquid chromatography–tandem mass spectrometry, except for hydroxysafflor yellow A. Therefore, 10 antioxidants remaining in the blood as key markers, and six other compounds as general markers, were employed to perform the quality control of DHI by ultra‐performance liquid chromatography–ultraviolet detection after systematic methodological validation. The analytical results indicate a high correlation (r = 0.9) between the total content of those antioxidants remaining in blood and RSC of DHI among 10 batches. Further, the antioxidant profiling and chemical marker quantification as dual‐standard quality assessment was successfully applied to evaluate Danshen and safflower injections. Copyright © 2012 John Wiley & Sons, Ltd.
Pt/Al2O3 Catalyzed 1,3‐Propanediol Formation from Glycerol using Tungsten Additives
Authors: ten Dam Jeroen , Djanashvili Kristina , Kapteijn Freek , Hanefeld Ulf
Published: December 2012

Screening of four commercial catalysts (Pt/Al2O3, Pt/SiO2, Pd/Al2O3, and Pd/SiO2) and four acidic additives (hydrochloric, tungstic, phosphotungstic, and silicotungstic acids) shows that the combination of a platinum hydrogenation catalyst with tungsten containing acidic additives yields 1,3‐propanediol from aqueous glycerol. The performance of the best catalytic system Pt/Al2O3 with silicotungstic acid as an additive was optimized by experimental design, capturing the influence of reaction time, glycerol concentration, acid concentration, pressure, and temperature on the formation of 1,3‐propanediol from glycerol. High 1,3‐propanediol yield in an aqueous batch system can be achieved (49 % conversion, 28 % selectivity) with excellent 1,3‐propanediol to 1,2‐propanediol ratios. A mechanistic interpretation is given for this bifunctional system, supported by the relative stability of 1,3‐propanediol in comparison with 1,2‐propanediol under the chosen reaction conditions.
Removal of Cr(VI) from Model Solutions by a Combined Electrocoagulation Sorption Process
Authors: Ait Ouaissa Y. , Chabani M. , Amrane A. , Bensmaili A.
Published: December 2012

The elimination of hexavalent chromium from synthetic effluents in a batch stirred electrocoagulation cell with aluminum electrodes coupled with a sorption process using red onion skin adsorbent is addressed. The effect of process variables such as medium pH and adsorbent concentration was investigated in an attempt to optimize the removal capacity. Adsorption and electrocoagulation were first considered separately, with maximum Cr(VI) removal yields of 47 % and 78 %, respectively, at pH 2. When combining the two processes, a removal of 97 % of the total Cr(VI) in a pH range of 3–6 was achieved. The almost total elimination observed for the considered pollutant demonstrated the feasibility and the synergistic effect of the coupled process.
Multimerization of an Apoptogenic TRAIL‐Mimicking Peptide by Using Adamantane‐Based Dendrons
Authors: Lamanna Giuseppe , Smulski Cristian R. , Chekkat Neila , Estieu‐Gionnet Karine , Guichard Gilles , Fournel Sylvie , Bianco Alberto
Published: December 2012

We have developed a straightforward strategy to multimerize an apoptogenic peptide that mimics the natural tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) by using adamantane‐based dendrons as multivalent scaffolds. The selective binding affinity of the ligands to TRAIL receptor 2 (TR2) was studied by surface plasmon resonance, thus demonstrating that the trimeric and hexameric forms of the peptide exert an increased affinity of about 1500‐ and 20 000‐fold, respectively, relative to the monomer. Moreover, only the trimeric and hexameric ligands were able to induce cell death in TR2 expressing cells (BJAB), thus confirming that a multivalent form of the peptide is necessary to trigger a substantial TR2‐dependent apoptotic response in vitro. These results provide interesting insight into the multivalency effect on biological ligand/receptor interactions for future therapeutic applications.
Tailored Host–Guest Lipidic Cubic Phases: A Protocell Model Exhibiting Nucleic Acid Recognition
Authors: Komisarski Marek , Osornio Yazmin M. , Siegel Jay S. , Landau Ehud M.
Published: December 2012

A classical conundrum in origin‐of‐life studies relates to the nature of the first chemical system: was it a carrier of genetic information or a facilitator of cellular compartmentalization? Here we present a system composed of tailor‐made nucleolipids and hydrated monoolein, which assemble at ambient temperatures to form host–guest lipidic cubic phase (LCP) materials that are stable in bulk water and can perform both functions. As such, they may represent a molecular model for a protocell in origin‐of‐life studies. Nucleolipids within the lipidic material sequester and bind selectively complementary oligonucleotide sequences from solution by virtue of base‐pairing; noncomplementary sequences diffuse freely between the LCP material and the bulk aqueous environment. Sequence specific enrichment of nucleic acids within the LCP material demonstrates an effective mechanism for selection of genetic material in these cell‐mimetic systems.
Metal–Organic Frameworks (MOFs) as Safer, Structurally Reinforced Energetics
Authors: Bushuyev Oleksandr S. , Peterson Geneva R. , Brown Preston , Maiti Amitesh , Gee Richard H. , Weeks Brandon L. , Hope‐Weeks Louisa J.
Published: December 2012

Second‐generation cobalt and zinc coordination architectures were obtained through efforts to stabilize extremely sensitive and energetic transition‐metal hydrazine perchlorate ionic polymers. Partial ligand substitution by the tridentate hydrazinecarboxylate anion afforded polymeric 2D‐sheet structures never before observed for energetic materials. Carefully balanced reaction conditions allowed the retention of the noncoordinating perchlorate anion in the presence of a strongly chelating hydrazinecarboxylate ligand. High‐quality X‐ray single‐crystal structure determination revealed that the metal coordination preferences lead to different structural motifs and energetic properties, despite the nearly isoformulaic nature of the two compounds. Energetic tests indicate highly decreased sensitivity and DFT calculations suggest a high explosive performance for these remarkable structures.
Heterogeneously Catalyzed Hydrogenation of Carbon Dioxide to Methane at Increased Reaction Pressures
Authors: Schoder Melanie , Armbruster Udo , Martin Andreas
Published: December 2012

In der vorliegenden Arbeit wurden vor allem Ni‐ und Ru‐haltige Trägerkatalysatoren synthetisiert und für die Hydrierung von Kohlendioxid zu Methan (Sabatier‐Reaktion) geprüft. Im Mittelpunkt der Untersuchungen standen Versuche zum Einfluss von Reaktionstemperatur und ‐druck. Als sehr geeignete Trägermaterialien erwiesen sich ZrO2 und γ‐Al2O3, die im Temperaturbereich von 300 – 400 °C hohe CO2‐ und H2‐Umsätze (70 – 80 %) und Methan‐Selektivitäten über 99 % erlauben. Im Gegensatz dazu führten TiO2‐ und SiO2‐basierte Katalysatoren fast ausschließlich zu CO und scheinen für die Reaktion nicht geeignet. Die Untersuchungen zur Druckabhängigkeit zeigten eindrucksvoll den Einfluss auf die Lage des chemischen Gleichgewichts. Die CO2‐ und H2‐Umsätze lagen an einem Ru/ZrO2‐Katalysator oberhalb 95 % und Methan wurde mit einer Selektivität von > 99,9 % gebildet.
Assessment of Climate Change Impact on the Gharesou River Basin Using SWAT Hydrological Model
Authors: Zahabiyoun B. , Goodarzi M. R. , Bavani A. R. Massah , Azamathulla H. M.
Published: December 2012

The evaluation of climate change and its side effects on the hydrological processes of the basin can increasingly help in dealing with the challenges that water resource managers and planners face in future courses. These side effects are investigated using the simulation of hydrological processes with the help of physical rainfall‐runoff model. Hydrological models provide a framework for examining the relationship between climate and water resources. This research aims at the investigation of the effect of climate change on the runoff of Gharesou, which is one of the main branches of the “Karkheh” River in Iran during the periods 2040–2069. To achieve this, the distributed hydrological model Soil and Water Assessment Tool (SWAT) – a model that is sensitive to the changes in land, water, and climate – has been used with the aim of evaluating the impact of climate change on the hydrology of the Gharesou Basin. For this reason, first, the continuous distributed model of rainfall‐runoff SWAT for the period 1971–2000 has been calibrated and validated. Next, with the aim of evaluating the impact of climate change and global warming on the basin hydrology for the period 2040–2069, HadCM3‐AR4 global climate model data under the A2 scenario – from the SRES scenario set‐haves been downscaled. Eventually, the downscaled climate data haves been introduced in the SWAT model, and the future runoff changes have been studied. The results showed that the temperature increases in most of the months, and the precipitation rate exhibits a change in the range of ±30%. Moreover, the produced runoff in this period changes from −90 to 120% during different months.
Another Important Factor of Rising Sea Level: Soil Erosion
Authors: Zhang Ruibin , He Jun , Zhao Yanwen , Peng Yao , Fu Li
Published: December 2012

Global mean sea level is a sensitive factor of climate change. Global warming will contribute to worldwide sea‐level rise from thermal expansion of ocean water, melting of glaciers and polar ice. Consideration of global soil erosion, water vapor cycle, and hydraulic actions suggests that soil erosion is another important factor contributing to sea‐level rise in addition to global warming. Much terrestrial sediment flows into the rivers each year but cannot be replenished, resulting in land surface declines. Moreover, sediment flow into rivers and oceans contributes to rising sea level. Ecological protection measure was proposed to prevent rising sea levels caused by soil erosion. This commentary should be useful to attract attention on rising sea levels caused by soil erosion.
The Generalized Energy‐Based Fragmentation Approach with an Improved Fragmentation Scheme: Benchmark Results and Illustrative Applications
Authors: Hua Shugui , Li Wei , Li Shuhua
Published: December 2012

We propose an improved fragmentation scheme for the generalized energy‐based fragmentation (GEBF) approach, which improves the accuracy of the GEBF approach in total energy calculations and intermolecular interactions. The main modification is to introduce some two‐fragment‐centered primitive subsystems, which are neglected in the previous GEBF implementation. Numerical calculations demonstrate that the present GEBF approach can provide more accurate ground‐state energies and intermolecular interactions. The present GEBF approach with the M06‐2X functional and the cc‐pVTZ basis set are employed to investigate the structures and binding energies in two dimeric species, which are related to pseudopolymorphism of a phenyleneethynylene‐based π‐conjugated molecule. A comparison of the binding free energies in a dimeric species and its corresponding model without CH⋅⋅⋅F contacts reveal that the substitution of fluorine atoms weakens the binding of monomers in the dimeric species formed by intermolecular OH⋅⋅⋅O hydrogen bonds, but strengthens the binding in the dimer formed by the π–π stacking interaction. Therefore, the CH⋅⋅⋅F contacts in these two dimeric species are demonstrated to play a less significant role.