bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flipping a G‐Tetrad in a Unimolecular Quadruplex Without Affecting Its Global Fold
Authors: Dickerhoff Jonathan , Weisz Klaus 
Published: March 2015

AbstractA unimolecular G‐quadruplex with a hybrid‐type topology and propeller, diagonal, and lateral loops was examined for its ability to undergo structural changes upon specific modifications. Substituting 2′‐deoxy‐2′‐fluoro analogues with a propensity to adopt an anti glycosidic conformation for two or three guanine deoxyribonucleosides in syn positions of the 5′‐terminal G‐tetrad significantly alters the CD spectral signature of the quadruplex. An NMR analysis reveals a polarity switch of the whole tetrad with glycosidic conformational changes detected for all four guanine nucleosides in the modified sequence. As no additional rearrangement of the overall fold occurs, a novel type of G‐quadruplex is formed with guanosines in the four columnar G‐tracts lined up in either an all‐syn or an all‐anti glycosidic conformation.
Enantioselektive intramolekulare Hydroacylierung von nichtaktivierten Alkenen: robuste und vielseitige NHC‐katalysierte Bildung von cyclischen chiralen Ketonen
Authors: Janssen‐Müller Daniel , Schedler Michael , Fleige Mirco , Daniliuc Constantin G. , Glorius Frank 
Published: March 2015

AbstractEine enantioselektive intramolekulare Hydroacylierung mit einem N‐heterocyclischen Carben (NHC) als Katalysator ermöglicht die Bildung von cyclischen Ketonen aus nichtaktivierten Olefin‐substituierten Aldehyden (bis zu 99 % ee). Darüber hinaus wurden zum ersten Mal aliphatische Aldehyde in einer effizienten NHC‐katalysierten Hydroacylierung eingesetzt.
Tandem Catalytic C(sp3)H Amination/Sila‐Sonogashira–Hagihara Coupling Reactions with Iodine Reagents
Authors: Buendia Julien , Darses Benjamin , Dauban Philippe 
Published: March 2015

AbstractA new tandem CN and CC bond‐forming reaction has been achieved through RhII/Pd0 catalysis. The sequence first involves an iodine(III) oxidant, then the in situ generated iodine(I) by‐product is used as a coupling partner. The overall process demonstrates the synthetic value of iodoarenes produced in trivalent iodine reagent mediated oxidations.
Mixing Biomimetic Heterodimers of Nucleopeptides to Generate Biocompatible and Biostable Supramolecular Hydrogels
Authors: Yuan Dan , Du Xuewen , Shi Junfeng , Zhou Ning , Zhou Jie , Xu Bing 
Published: March 2015

AbstractAs a new class of biomaterials, most supramolecular hydrogels formed by small peptides require the attachment of long alkyl chains, multiple aromatic groups, or strong electrostatic interactions. Based on the fact that the most abundant protein assemblies in nature are dimeric, we select short peptide sequences from the interface of a heterodimer of proteins with known crystal structure to conjugate with nucleobases to form nucleopeptides. Being driven mainly by hydrogen bonds, the nucleopeptides self‐assemble to form nanofibers, which results in supramolecular hydrogels upon simple mixing of two distinct nucleopeptides in water. Moreover, besides being biocompatible to mammalian cells, the heterodimer of the nucleopeptides exhibit excellent proteolytic resistance against proteinase K. This work illustrates a new and rational approach to create soft biomaterials by a supramolecular hydrogelation triggered by mixing heterodimeric nucleopeptides.
A Promiscuous De Novo Retro‐Aldolase Catalyzes Asymmetric Michael Additions via Schiff Base Intermediates
Authors: Garrabou Xavier , Beck Tobias , Hilvert Donald 
Published: March 2015

AbstractRecent advances in computational design have enabled the development of primitive enzymes for a range of mechanistically distinct reactions. Here we show that the rudimentary active sites of these catalysts can give rise to useful chemical promiscuity. Specifically, RA95.5‐8, designed and evolved as a retro‐aldolase, also promotes asymmetric Michael additions of carbanions to unsaturated ketones with high rates and selectivities. The reactions proceed by amine catalysis, as indicated by mutagenesis and X‐ray data. The inherent flexibility and tunability of this catalyst should make it a versatile platform for further optimization and/or mechanistic diversification by directed evolution.
Controlling Radical Formation in the Photoactive Yellow Protein Chromophore
Authors: Mooney Ciarán R. S. , Parkes Michael A. , Iskra Andreas , Fielding Helen H. 
Published: March 2015

AbstractTo understand how photoactive proteins function, it is necessary to understand the photoresponse of the chromophore. Photoactive yellow protein (PYP) is a prototypical signaling protein. Blue light triggers trans–cis isomerization of the chromophore covalently bound within PYP as the first step in a photocycle that results in the host bacterium moving away from potentially harmful light. At higher energies, photoabsorption has the potential to create radicals and free electrons; however, this process is largely unexplored. Here, we use photoelectron spectroscopy and quantum chemistry calculations to show that the molecular structure and conformation of the isolated PYP chromophore can be exploited to control the competition between trans–cis isomerization and radical formation. We also find evidence to suggest that one of the roles of the protein is to impede radical formation in PYP by preventing torsional motion in the electronic ground state of the chromophore.
Regioselective Chromatic Orthogonality with Light‐Activated Metathesis Catalysts
Authors: Levin Efrat , Mavila Sudheendran , Eivgi Or , Tzur Eyal , Lemcoff N. Gabriel 
Published: March 2015

AbstractThe ability to selectively guide consecutive chemical processes towards a preferred pathway by using light of different frequencies is an appealing concept. Herein we describe the coupling of two photochemical reactions, one the photoisomerization and consequent activation of a sulfur‐chelated latent olefin‐metathesis catalyst at 350 nm, and the other the photocleavage of a silyl protecting group at 254 nm. Depending on the steric stress exerted by a photoremovable neighboring chemical substituent, we demonstrate the selective formation of either five‐ or six‐membered‐ring frameworks by light‐triggered ring‐closing metathesis. The orthogonality of these light‐induced reactions allows the initiation of these processes independently and in interchangeable order, according to the wavelength of light used to promote them.
Ortho‐Quinone Methides as Reactive Intermediates in Asymmetric Brønsted Acid Catalyzed Cycloadditions with Unactivated Alkenes by Exclusive Activation of the Electrophile
Authors: Hsiao Chien‐Chi , Raja Sadiya , Liao Hsuan‐Hung , Atodiresei Iuliana , Rueping Magnus 
Published: March 2015

AbstractAn efficient method for the highly enantioselective synthesis of chiral chromanes bearing multiple stereogenic centers was developed. A chiral BINOL‐based N‐triflylphosphoramide proved to be an effective catalyst for the in situ generation of ortho‐quinone methides (o‐QMs) and their subsequent cycloaddition reaction with unactivated alkenes provided chromanes with excellent diastereo‐ and enantioselectivity.
Direct C(sp2)C(sp3) Cross‐Coupling of Diaryl Zinc Reagents with Benzylic, Primary, Secondary, and Tertiary Alkyl Halides
Authors: Dunsford Jay J. , Clark Ewan R. , Ingleson Michael J. 
Published: March 2015

AbstractThe direct C(sp2)C(sp3) cross‐coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides proceeded in the absence of coordinating ethereal solvents at ambient temperature without the addition of a catalyst. The C(sp2)C(sp3) cross‐coupling showed excellent functional‐group tolerance, and products were isolated in high yields, generally without the requirement for purification by chromatography. This process represents an expedient, operationally simple method for the construction of new C(sp2)C(sp3) bonds.
Intracellular Delivery of Peptidyl Ligands by Reversible Cyclization: Discovery of a PDZ Domain Inhibitor that Rescues CFTR Activity
Authors: Qian Ziqing , Xu Xiaohua , Amacher Jeanine F. , Madden Dean R. , Cormet‐Boyaka Estelle , Pei Dehua 
Published: March 2015

AbstractA general strategy was developed for the intracellular delivery of linear peptidyl ligands through fusion to a cell‐penetrating peptide and cyclization of the fusion peptides via a disulfide bond. The resulting cyclic peptides are cell permeable and have improved proteolytic stability. Once inside the cell, the disulfide bond is reduced to produce linear biologically active peptides. This strategy was applied to generate a cell‐permeable peptide substrate for real‐time detection of intracellular caspase activities during apoptosis and an inhibitor for the CFTR‐associated ligand (CAL) PDZ domain as a potential treatment for cystic fibrosis.
Heterogeneously Catalyzed Direct CH Thiolation of Heteroarenes
Authors: Vásquez‐Céspedes Suhelen , Ferry Angélique , Candish Lisa , Glorius Frank 
Published: March 2015

AbstractThe first general methodology for the direct thiolation of electron‐rich heteroarenes was developed by employing Pd/Al2O3, a recoverable and commercially available heterogeneous catalyst, and CuCl2. This method represents an operationally simple approach for the synthesis of these valuable compounds. Preliminary mechanistic studies indicate a heterogeneous catalytic system, in which both metals play a complementary role in the formation of the thiolated products.
Characterization of a Palladium Dihydrogen Complex
Authors: Connelly Samantha J. , Chanez Andrew G. , Kaminsky Werner , Heinekey D. Michael 
Published: March 2015

AbstractThe preparation and isolation of the first palladium dihydrogen complex is described. NMR spectroscopy reveals a very short HH bond length, but the hydrogen molecule is activated toward heterolytic cleavage. An X‐ray crystal structure suggests that proton transfer to the tBuPCP (κ3‐2,6‐(tBu2PCH2)2C6H3) pincer ligand is possible. The basicity of the ipso‐carbon atom of the pincer ligand was investigated in a related complex.
Coassembly of Nanorods and Nanospheres in Suspensions and in Stratified Films
Authors: Thérien‐Aubin Héloïse , Lukach Ariella , Pitch Natalie , Kumacheva Eugenia 
Published: March 2015

AbstractThe entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and nanospheres (dye‐labeled spherical latex nanoparticles, NPs) was studied in aqueous suspensions and in solid films. In mixed CNC‐latex suspensions, phase separation into an isotropic latex‐NP‐rich and a chiral nematic CNC‐rich phase took place; the latter contained a significant amount of latex NPs. Drying the mixed suspension resulted in CNC‐latex films with planar disordered layers of latex NPs, which alternated with chiral nematic CNC‐rich regions. In addition, fluorescent latex NPs were embedded in the chiral nematic domains. The stratified morphology of the films, together with a random distribution of latex NPs in the anisotropic phase, led to the films having close‐to‐uniform fluorescence, birefringence, and circular dichroism properties.
Highly Regio‐ and Stereoselective Hydrosilylation of Internal Thioalkynes under Mild Conditions
Authors: Ding Shengtao , Song Li‐Juan , Wang Yong , Zhang Xinhao , Chung Lung Wa , Wu Yun‐Dong , Sun Jianwei 
Published: March 2015

AbstractA general and mild hydrosilylation of thioalkynes is described. With the cationic catalyst [Cp*Ru(MeCN)3]+ and the bulky silane (TMSO)3SiH, a range of thioalkynes underwent smooth hydrosilylation at room temperature with excellent α regioselectivity and syn stereoselectivity. DFT calculations provided important insight into the mechanism, particularly the unusual syn selectivity with the [Cp*Ru(MeCN)3]+ catalyst. The sulfenyl group in the substrates was found to provide important chelation stabilization to direct the reaction through a new mechanistic pathway.
The research for high‐elastic modified asphalt
Authors: Zhang Feng , Hu Changbin 
Published: March 2015

ABSTRACTHigh‐elastic modified (HEM) asphalt was prepared by the addition of styrene‐butadiene‐styrene (SBS), plasticizer, and crosslinker to base asphalt. The effect and proportion of each modifier in asphalt were studied using physical and rheological tests. It was found that SBS determined the high‐temperature performance of HEM asphalt mainly. Plasticizer (dioctyl phthalate) is very helpful in improving the low‐temperature flexibility and elastic recovery. Crosslinker (sulfur) is necessary in maintaining high‐temperature stability. In this study, Fourier transform infrared, hydrogen nuclear magnetic resonance analysis, and microscopy observation were used to investigate the structural characteristics of modified asphalts further before and after ageing. The research showed the structural characteristics of modified asphalt were influenced evidently by ageing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42132.
Synthesis and Photophysics of BF2‐Rigidified Partially Closed Chain Bromotetrapyrroles: Near Infrared Emitters and Photosensitizers
Authors: Dai En , Pang Weidong , Zhang Xian‐Fu , Yang Xudong , Jiang Ting , Zhang Ping , Yu Changjiang , Hao Erhong , Wei Yun , Mu Xiaolong , Jiao Lijuan 
Published: March 2015

AbstractWe report the synthesis, crystallographic, optical, and triplet and singlet oxygen generation properties of a series of BF2‐rigidified partially closed chain bromotetrapyrroles as near infrared emitters and photosensitizers. These novel dyes were efficiently synthesized from a nucleophilic substitution reaction between pyrroles and the 3,5‐bromo‐substituents on the tetra‐ and hexabromoBODIPYs and absorb in the near‐infrared region (681–754 nm) with high molar extinction coefficients. Their fluorescent emission (708–818 nm) and singlet oxygen generation properties are significantly affected by alkyl substitutions on the two uncoordinated pyrrole units of these dyes and the polarity of solvents. Among them, dyes 4 ca and 4 da show good singlet oxygen generation efficiency and good NIR fluorescence emission (fluorescence quantum yields of 0.14–0.43 in different solvents studied).
Dual Functioning Thieno‐Pyrrole Fused BODIPY Dyes for NIR Optical Imaging and Photodynamic Therapy: Singlet Oxygen Generation without Heavy Halogen Atom Assistance
Authors: Watley Ryan L. , Awuah Samuel G. , Bio Moses , Cantu Robert , Gobeze Habtom B. , Nesterov Vladimir N. , Das Sushanta K. , D'Souza Francis , You Youngjae 
Published: March 2015

AbstractWe discovered a rare phenomenon wherein a thieno‐pyrrole fused BODIPY dye (SBDPiR690) generates singlet oxygen without heavy halogen atom substituents. SBDPiR690 generates both singlet oxygen and fluorescence. To our knowledge, this is the first example of such a finding. To establish a structure–photophysical property relationship, we prepared SBDPiR analogs with electron‐withdrawing groups at the para‐position of the phenyl groups. The electron‐withdrawing groups increased the HOMO–LUMO energy gap and singlet oxygen generation. Among the analogs, SBDPiR688, a CF3 analog, had an excellent dual functionality of brightness (82290 m−1 cm−1) and phototoxic power (99170 m−1 cm−1) comparable to those of Pc 4, due to a high extinction coefficient (211 000 m−1 cm−1) and balanced decay (Φflu=0.39 and ΦΔ=0.47). The dual functionality of the lead compound SBDPiR690 was successfully applied to preclinical optical imaging and for PDT to effectively control a subcutaneous tumor.
Distributed Containment Control for Nonlinear Multi‐Agent Systems with Time‐Delayed Protocol
Authors: Hu Jianqiang , Yu Jie , Cao Jinde 
Published: March 2015

AbstractIn this paper, the containment control problem is considered for nonlinear multi‐agent systems with directed communication topology. Under the guidance of designed distributed communication protocols with/without previous state information, the followers are expected to converge to a dynamic convex hull spanned by multiple leaders. Two multi‐step algorithms are proposed to construct the corresponding protocols, the state feedback protocol and the delay‐coupled protocol, under which the containment control can be achieved asymptotically. Furthermore, it is found that the delay‐coupled protocol is rather sensitive to time delays. That is, real‐time tracking will become impossible by only using long‐dated previous state information. Finally, a numerical example is given to demonstrate the applicability and efficiency of the proposed schemes.
Immersion and Invariance Based Robust Adaptive Control of High‐Speed Train with Guaranteed Prescribed Performance Bounds
Authors: Luo Hengyu , Xu Hongze , Liu Xiangbin 
Published: March 2015

AbstractThis paper proposes a novel robust adaptive algorithm for train tracking control with guaranteed prescribed transient and steady‐state performance. As speed increases, the inherent time‐varying uncertainties and unmodeled dynamics in the longitudinal dynamics of a high‐speed train seriously impacts the tracking performance of automatic train operation. To improve train operation performance, an estimator based on immersion and invariance technology is developed to recover the unknown and time‐varying plant parameters, and it renders the estimation error converging to a bounded residual set exponentially while providing more freedom for the controller. After certain error transformation, the prescribed tracking performance is introduced into the controller design. Then, an input‐to‐stable stable controller is developed through the backstepping technique, and it is proven that stabilization of the transformed system is sufficient to guarantee the prescribed performance. Rigorous theoretical analysis for the presented algorithm is provided, and a series of simulation studies also are given to verify the effectiveness of it.
Continuous microwave drying of the seeds of the invasive Chinese tallow tree
Authors: Fennell Laura Picou , Bourgeois Brianna Leilani , Boldor Dorin 
Published: March 2015

AbstractThe Chinese tallow tree (CTT) (Triadica sebifera) is an invasive species in the Southeastern portion of the USA. With lipid content between 40% and 55%, the tree's non‐edible seeds are a valuable source for biofuel production. In situ transesterification is a proposed method for optimizing the transesterification process since it does not require prior oil extraction; however, for yields greater than 98%, the moisture content of the seeds should be less than 2%. In this paper we highlight an innovative microwave assisted drying method, used for the first time for these seeds, as a solution which drastically reduces the drying time and energy consumption compared to other drying methods. To optimize the microwave‐assisted drying of CTT seeds, temperatures of 25 and 55 °C were tested with microwave powers of 0, 200, and 600 W using a continuous microwave drying system. The decrease in moisture content is greatest at 600 W of microwave power, with ambient temperature having little effect on the heat generation. The drying rate to power consumption ratio is greatest with a combination of 600 W at 25 °C ambient temperature. The microwave assisted drying reduced the drying time to about 300 seconds compared to the 4 h required for conventional oven drying. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd
Association of facilitated glucose transporter 2 gene variants with the myelomeningocele phenotype
Authors: Ruggiero Jaclyn E. , Northrup Hope , Au Kit Sing 
Published: March 2015

BACKGROUNDNeural tube defects (NTDs) remain the second most common cause of congenital malformations. Myelomeningocele (MM), the most common NTD compatible with survival, results from genetic and environmental factors. Epidemiologic studies and murine models support the hypotheses that obesity, diabetes and hyperglycemia confer increased risk of NTDs. Presence of wild‐type facilitated glucose transporter, Glut2, in mouse embryos has been shown to increase risk for NTDs in hyperglycemic pregnancy.METHODSThe GLUT2 gene of 96 MM patients was amplified, sequenced and compared with the reference sequence (NM_000340). Variants previously unreported in the single nucleotide polymorphisms (SNP) database were considered novel. Allele frequencies of reported SNPs were compared with reference populations using Fisher's exact test.RESULTSAnalysis revealed three novel variants: a substitution in the core promoter region (c.−331c>t), a substitution (c.−182g>a) in the 5′‐untranslated region, and a single base pair deletion (c.1441delT) in the coding sequences. Polymorphic alleles for 10 SNPs were also identified. Seven SNPs are significantly associated with MM in the Mexican American patients tested (p < 0.05) and two of the seven remained significant after Bonferroni correction.CONCLUSIONWe identified three novel variants and seven SNPs associated with MM. The novel variants in the core promoter and in the 5′‐untranslated region could affect GLUT2 mRNA transcription and stability and translation efficiency. The c.1441delT variant is predicted to alter the reading frame and prematurely terminate translation of the GLUT2 protein at the C‐terminus, affecting GLUT2 protein function. Presence of GLUT2 variants may disrupt GLUT2 activity and influence MM susceptibility. Birth Defects Research (Part A) 103:479–487, 2015. © 2015 Wiley Periodicals, Inc.
Effect of maternal diabetes on the embryo, fetus, and children: Congenital anomalies, genetic and epigenetic changes and developmental outcomes
Authors: Ornoy Asher , Reece E. Albert , Pavlinkova Gabriela , Kappen Claudia , Miller Richard Kermit 
Published: March 2015

IntroductionPregestational and gestational diabetes mellitus (PGDM; GDM) are significant health concerns because they are associated with an increased rate of malformations and maternal health complications.MethodsWe reviewed the data that help us to understand the effects of diabetes in pregnancy.ResultsDiabetic embryopathy can affect any developing organ system, but cardiovascular and neural tube defects are among the most frequent anomalies. Other complications include preeclampsia, preterm delivery, fetal growth abnormalities, and perinatal mortality. Neurodevelopmental studies on offspring of mothers with diabetes demonstrated increased rate of Gross and Fine motor abnormalities, of Attention Deficit Hyperactivity Disorder, learning difficulties, and possibly also Autism Spectrum Disorder. The mechanisms underlying the effects of maternal hyperglycemia on the developing fetus may involve increased oxidative stress, hypoxia, apoptosis, and epigenetic changes. Evidence for epigenetic changes are the following: not all progeny are affected and not to the same extent; maternal diet may influence pregnancy outcomes; and maternal diabetes alters embryonic transcriptional profiles and increases the variation between transcriptomic profiles as a result of altered gene regulation. Research in animal models has revealed that maternal hyperglycemia is a teratogen, and has helped uncover potential therapeutic targets which, when blocked, can mitigate or ameliorate the negative effects of diabetes on the developing fetus.ConclusionsTight metabolic control, surveillance, and labor management remain the cornerstone of care for pregnant women with diabetes, but advances in the field indicate that new treatments to protect the mother and baby are not far from becoming clinical realities. Birth Defects Research (Part C) 105:53–72, 2015. © 2015 Wiley Periodicals, Inc.