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Single molecule

Ahmad A Almasalma, Esteban Mejía
C-H bond functionalization is a well-developed concept that has been thoroughly studied and gives entry to rather complex molecules without the need of previous derivatization of the substrates, although the use of copper complexes for allylic C-H bond functionalization under oxidative conditions as an alternative to the well-established palladium-based methodologies remains largely underdeveloped. Here we show for the first time a selective cross-dehydrogenative coupling reaction between underivatized allylic substrates and terminal alkynes to produce 1,4-enynes in high yields in a single step, using an in situ synthesized copper catalyst and an oxidant...
May 22, 2018: Chemistry: a European Journal
Tania Patiño, Natalia Feiner-Gracia, Xavier Arque, Albert Miguel-López, Anita Jannasch, Tom Stumpp, Erik Schäffer, Lorenzo Albertazzi, Samuel Sanchez
The use of enzyme catalysis to power micro and nanomachines offers unique features such as biocompatibility, versatili-ty and fuel bioavailability. Yet, the key parameters underlying the motion behavior of enzyme-powered motors are not completely understood. Here, we investigate the role of enzyme distribution and quantity on the generation of active mo-tion. Two different micromotor architectures based on either polystyrene (PS) or polystyrene coated with a rough silicon dioxide shell (PS@SiO2) were explored...
May 22, 2018: Journal of the American Chemical Society
Jing L Wang, Camille Duboc, Qian Wu, Takashi Ochi, Shikang Liang, Susan E Tsutakawa, Susan P Lees-Miller, Marc Nadal, John A Tainer, Tom L Blundell, Terence R Strick
Repairing DNA double-strand breaks (DSBs) by nonhomologous end joining (NHEJ) requires multiple proteins to recognize and bind DNA ends, process them for compatibility, and ligate them together. We constructed novel DNA substrates for single-molecule nanomanipulation, allowing us to mechanically detect, probe, and rupture in real-time DSB synapsis by specific human NHEJ components. DNA-PKcs and Ku allow DNA end synapsis on the 100 ms timescale, and the addition of PAXX extends this lifetime to ~2 s. Further addition of XRCC4, XLF and ligase IV results in minute-scale synapsis and leads to robust repair of both strands of the nanomanipulated DNA...
May 21, 2018: Nature Structural & Molecular Biology
Diamantoula Maniaki, Ioannis Mylonas-Margaritis, Julia Mayans, Aikaterini Savvidou, Catherine P Raptopoulou, Vlasoula Bekiari, Vassilis Psycharis, Albert Escuer, Spyros P Perlepes
The initial use of anils, i.e. bidentate Schiff bases derived from the condensation of anilines with salicylaldehyde or its derivatives, in 4f-metal chemistry is described. The 1 : 1 reactions between Ln(NO3)3·xH2O (Ln = lanthanide) or Y(NO3)3·6H2O and N-(5-bromosalicylidene)aniline (5BrsalanH) in MeCN has provided access to complexes [Ln(NO3)3(5BrsalanH)2(H2O)]·MeCN (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) and [Y(NO3)3(5BrsalanH)2(H2O)]·MeCN, respectively, in good yields. The structures of the isomorphous complexes with Ln = Pr(1·MeCN), Sm(3·MeCN), Gd(5·MeCN), Dy(7·MeCN) and Er(9·MeCN) have been determined by single-crystal X-ray crystallography...
May 22, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Sihuai Chen, Valeriu Mereacre, Zhiying Zhao, Wanwan Zhang, Mengsi Zhang, Zhangzhen He
Three dodecanuclear 3d-4f coordination clusters, [CrIII6LnIII6(μ3-OH)8(tbdea)6(C6H5COO)16]·2H2O (Ln = Dy (1), Y (2)) and [CoIII6DyIII6(μ3-OH)8(nbdea)6(m-CH3C6H4COO)16]·2H2O·2CH3CN (3), have been synthesized under solvothermal conditions and characterized. Single-crystal X-ray diffraction analysis revealed that all three compounds possess an analogous {MIII6LnIII6} core (M = Cr, Co; Ln = Dy, Y) and dc magnetic susceptibility studies indicated that the magnetic exchange couplings between DyIII ions are dominant antiferromagnetic, while the CrIII-DyIII interactions are weakly ferromagnetic...
May 22, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Maria Cristina Moran-Moguel, Stefania Petarra-Del Rio, Evangelina E Mayorquin-Galvan, Maria G Zavala-Cerna
Rheumatoid arthritis (RA) is a systemic autoimmune disease with severe joint inflammation and destruction associated with an inflammatory environment. The etiology behind RA remains to be elucidated; most updated concepts include the participation of environmental, proteomic, epigenetic, and genetic factors. Epigenetic is considered the missing link to explain genetic diversification among RA patients. Within epigenetic factors participating in RA, miRNAs are defined as small noncoding molecules with a length of approximately 22 nucleotides, capable of gene expression modulation, either negatively through inhibition of translation and degradation of the mRNA or positively through increasing the translation rate...
2018: Journal of Immunology Research
Fang Xie, Kelsey A Timme, Jennifer R Wood
Changes in abundance of mRNAs during oocyte growth and maturation and during pre-implantation embryo development have been documented using quantitative real-time RT-PCR (qPCR), microarray analyses, and whole genome sequencing. However, these techniques require amplification of mRNAs, normalization using housekeeping genes, can be biased for abundant transcripts, and/or require large numbers of oocytes and embryos which can be difficult to acquire from mammalian species. We optimized a single molecule RNA fluorescence in situ hybridization (RNA-FISH) protocol, which amplifies fluorescence signal to detect candidate transcripts, for use with individual oocytes and embryos...
May 21, 2018: Scientific Reports
Patric Eberle, Christian Höller, Philipp Müller, Maarit Suomalainen, Urs F Greber, Hadi Eghlidi, Dimos Poulikakos
Investigating biological and synthetic nanoscopic species in liquids, at the ultimate resolution of single entity, is important in diverse fields1-5 . Progress has been made6-10 , but significant barriers need to be overcome such as the need for intense fields, the lack of versatility in operating conditions and the limited functionality in solutions of high ionic strength for biological applications. Here, we demonstrate switchable electrokinetic nanovalving able to confine and guide single nano-objects, including macromolecules, with sizes down to around 10 nanometres, in a lab-on-chip environment...
May 21, 2018: Nature Nanotechnology
Stephany Y Tzeng, Kevin J McHugh, Adam M Behrens, Sviatlana Rose, James L Sugarman, Shiran Ferber, Robert Langer, Ana Jaklenec
Vaccination in the developing world is hampered by limited patient access, which prevents individuals from receiving the multiple injections necessary for protective immunity. Here, we developed an injectable microparticle formulation of the inactivated polio vaccine (IPV) that releases multiple pulses of stable antigen over time. To accomplish this, we established an IPV stabilization strategy using cationic polymers for pH modulation to enhance traditional small-molecule-based stabilization methods. We investigated the mechanism of this strategy and showed that it was broadly applicable to all three antigens in IPV...
May 21, 2018: Proceedings of the National Academy of Sciences of the United States of America
Zhenning Ren, Jumin Lee, Mahdi Muhammad Moosa, Yin Nian, Liya Hu, Zhichun Xu, Jason G McCoy, Allan Chris M Ferreon, Wonpil Im, Ming Zhou
The phosphoenolpyruvate-dependent phosphotransferase system (PTS) transports sugar into bacteria and phosphorylates the sugar for metabolic consumption. The PTS is important for the survival of bacteria and thus a potential target for antibiotics, but its mechanism of sugar uptake and phosphorylation remains unclear. The PTS is composed of multiple proteins, and the membrane-embedded Enzyme IIC (EIIC) component transports sugars across the membrane. Crystal structures of two members of the glucose superfamily of EIICs, bcChbC and bcMalT, were solved in the inward-facing and outward-facing conformations, and the structures suggest that sugar translocation could be achieved by movement of a structured domain that contains the sugar-binding site...
May 21, 2018: Proceedings of the National Academy of Sciences of the United States of America
Sumeng Zou, Lingwei Ma, Jianghao Li, Zheng Xie, Dongliang Zhao, Yunhan Ling, Zhengjun Zhang
The chemical quantitative analysis at trace level has been widely explored by means of various techniques. While it still remains challenging to achieve ultrasensitive but facile, rapid, and inexpensive detection methods. In this paper, the possibility of employing surface-enhanced Raman scattering technique on a portable Raman system for rapid and accurate quantitative analysis of target chemicals in unknown systems was investigated. This detection approach contains 3 steps: (1) adding target chemicals with different amount to the initial unknown solution, leading to new solutions with target molecules of various concentrations; (2) Obtaining different samples' SERS spectra and capturing featured SERS peaks whose intensity grew up with the addition of target chemicals; (3) examining the relationship between featured peak intensity increment after adding target chemicals and its corresponding addition amount, and thus we could perform quantitative analysis of the chemical in an unknown solution and obtain its initial concentration...
August 15, 2018: Talanta
Münteha Nur Sonuç Karaboğa, Mustafa Kemal Sezgintürk
This paper demonstrates a new and sensitive electrochemical immunosensor for the analysis of C-reactive protein, an important marker of inflammation. Indium Tin Oxide (ITO) disposable sheets were modified by using 11-cyanoundecyltrimethoxysilane (CUTMS) and PAMAM dendrimers (G:1 amino surfaces) for the first time to immobilize the anti-CRP antibody via covalent interactions. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), as well as square wave voltammetry (SWV) methods, were applied to characterize the immobilization stages of anti-CRP and to determine the CRP concentrations...
August 15, 2018: Talanta
David C Hornigold, Emma Roth, Victor Howard, Sarah Will, Stephanie Oldham, Matthew P Coghlan, Clemence Blouet, James L Trevaskis
Combination approaches for the treatment of metabolic diseases such as obesity and diabetes are becoming increasingly relevant. Co-administration of a glucagon-like peptide-1 receptor (GLP-1R) agonist with a cholecystokinin receptor-1 (CCKR1) agonist exert synergistic effects on weight loss in obese rodents. Here, we report on the effects of a novel fusion peptide (C2816) comprised of a stabilized GLP-1R agonist, AC3174, and a CCKR1-selective agonist, AC170222. C2816 was constructed such that AC3174 was linked to the N-terminus of AC170222, thus preserving the C-terminal amide of the CCK moiety...
May 18, 2018: Appetite
Yuhan Peng, Zhigang Geng, Songtao Zhao, Liangbing Wang, Hongliang Li, Xu Wang, XuSheng Zheng, Junfa Zhu, Zhenyu Li, Rui Si, Jie Zeng
Single-atom catalysts exhibit high selectivity in hydrogenation due to their isolated active sites which ensure uniform adsorption configurations of substrate molecules. Compared with the achievement in catalytic selectivity, there is still a long way to go in exploiting the catalytic activity of single-atom catalysts. Herein, we developed highly active and selective catalysts in selective hydrogenation by embedding Pt single atoms in the surface of Ni nanocrystals (denoted as Pt1/Ni nanocrystals). During the hydrogenation of 3-nitrostyrene, the TOF numbers based on surface Pt atoms of Pt1/Ni nanocrystals reached ~1800 h-1 under 3 atm of H2 at 40 oC, much higher than that of Pt single atoms supported on active carbon, TiO2, SiO2, and ZSM-5...
May 21, 2018: Nano Letters
Darach Miller, Nathan Brandt, David Gresham
Cellular responses to changing environments frequently involve rapid reprogramming of the transcriptome. Regulated changes in mRNA degradation rates can accelerate reprogramming by clearing or stabilizing extant transcripts. Here, we measured mRNA stability using 4-thiouracil labeling in the budding yeast Saccharomyces cerevisiae during a nitrogen upshift and found that 78 mRNAs are subject to destabilization. These transcripts include Nitrogen Catabolite Repression (NCR) and carbon metabolism mRNAs, suggesting that mRNA destabilization is a mechanism for targeted reprogramming of the transcriptome...
May 21, 2018: PLoS Genetics
Zixuan Chen, Yujiao Peng, Yue Cao, Hui Wang, Jian-Rong Zhang, Hong-Yuan Chen, Jun-Jie Zhu
Here, we present a mapping tool based on individual light-driven nano-oscillators for label-free single-molecule monitoring of microRNA. This design uses microRNA as a single-molecule damper for nano-oscillators by forming a rigid dual-strand structure in the gap between nano-oscillators and the immobilized surface. The ultrasensitive detection is attributed to comparable dimensions of the gap and microRNA. A developed surface plasmon-coupled scattering imaging technology enables us to directly measure the real-time gap distance vibration of multiple nano-oscillators with high accuracy and fast dynamics...
May 22, 2018: Nano Letters
Daniel Martín-Yerga, Alejandro Pérez-Junquera, María Begoña González-García, David Hernández-Santos, Pablo Fanjul-Bolado
Dynamic time-resolved Raman spectroelectrochemistry demonstrates the strong influence of nanostructuring and surface charge of in situ activated disposable substrates for SERS detection. Under specific conditions, a large enhancement factor and estimated calculations agree with the feasible detection of only a few molecules, approaching the limit of single-entity detection.
May 21, 2018: Chemical Communications: Chem Comm
Junghyun Kim, Sewoon Han, Andy Lei, Masaru Miyano, Jessica Bloom, Vasudha Srivastava, Martha M Stampfer, Zev J Gartner, Mark A LaBarge, Lydia L Sohn
The mechanical properties of cells change with their differentiation, chronological age, and malignant progression. Consequently, these properties may be useful label-free biomarkers of various functional or clinically relevant cell states. Here, we demonstrate mechano-node-pore sensing (mechano-NPS), a multi-parametric single-cell-analysis method that utilizes a four-terminal measurement of the current across a microfluidic channel to quantify simultaneously cell diameter, resistance to compressive deformation, transverse deformation under constant strain, and recovery time after deformation...
2018: Microsystems & Nanoengineering
Wen-Cheng Chen, Yi Yuan, Ze-Lin Zhu, Zuo-Quan Jiang, Shi-Jian Su, Liang-Sheng Liao, Chun-Sing Lee
Two novel D-σ-A host materials 11,11-bis(9-phenyl-9 H -carbazol-3-yl)-11 H -benzo[4,5]imidazo[1,2- a ]indole (BII-BCz) and 4,4'-(11 H -benzo[4,5]imidazo[1,2- a ]indole-11,11-diyl)bis( N , N -diphenylaniline) (BII-TPA) are synthesized by using the sp3 carbon attached to a newly designed 11 H -benzo[4,5]imidazo[1,2- a ]indole building block to link two electron-donating groups. The resulting materials feature high triplet energy levels, good thermal properties and suitable photophysical properties as universal hosts for full-color phosphorescent organic light-emitting diodes (OLEDs)...
May 7, 2018: Chemical Science
Matthew J DiTucci, Christiane N Stachl, Evan R Williams
The effect of temperature on the patterning of water molecules located remotely from a single SO4 2- ion in aqueous nanodrops was investigated for nanodrops containing between 30 and 55 water molecules using instrument temperatures between 135 and 360 K. Magic number clusters with 24, 36 and 39 water molecules persist at all temperatures. Infrared photodissociation spectroscopy between 3000 and 3800 cm-1 was used to measure the appearance of water molecules that have a free O-H stretch at the nanodroplet surface and to infer information about the hydrogen bonding network of water in the nanodroplet...
April 28, 2018: Chemical Science
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