The Experts below are selected from a list of 80781 Experts worldwide ranked by ideXlab platform
Stewart Shuman - One of the best experts on this subject based on the ideXlab platform.
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structural basis for nick recognition by a minimal pluripotent dna ligase
Nature Structural & Molecular Biology, 2007Co-Authors: Pravin A Nair, Mark Odell, Jayakrishnan Nandakumar, Paul Smith, Christopher D Lima, Stewart ShumanAbstract:Chlorella virus DNA ligase, the smallest eukaryotic ligase known, has pluripotent biological activity and an intrinsic nick-Sensing Function, despite having none of the accessory domains found in cellular ligases. A 2.3-A crystal structure of the Chlorella virus ligase-AMP intermediate bound to duplex DNA containing a 3'-OH-5'-PO4 nick reveals a new mode of DNA envelopment, in which a short surface loop emanating from the OB domain forms a beta-hairpin 'latch' that inserts into the DNA major groove flanking the nick. A network of interactions with the 3'-OH and 5'-PO4 termini in the active site illuminates the DNA adenylylation mechanism and the crucial roles of AMP in nick Sensing and catalysis. Addition of a divalent cation triggered nick sealing in crystallo, establishing that the nick complex is a bona fide intermediate in the DNA repair pathway.
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crystal structure of eukaryotic dna ligase adenylate illuminates the mechanism of nick Sensing and strand joining
Molecular Cell, 2000Co-Authors: Mark Odell, Stewart Shuman, Verl Sriskanda, Dimitar B NikolovAbstract:Abstract Chlorella virus DNA ligase is the smallest eukaryotic ATP-dependent ligase known; it has an intrinsic nick-Sensing Function and suffices for yeast cell growth. Here, we report the 2.0 A crystal structure of the covalent ligase–AMP reaction intermediate. The conformation of the adenosine nucleoside and contacts between the enzyme and the ribose sugar have undergone a significant change compared to complexes of T7 ligase with ATP or mRNA capping enzyme with GTP. The conformational switch allows the 3′ OH of AMP to coordinate directly the 5′ PO 4 of the nick. The structure explains why nick Sensing is restricted to adenylated ligase and why the 5′ phosphate is required for DNA binding. We identify a metal binding site on ligase–adenylate and propose a mechanism of nick recognition and catalysis supported by mutational data.
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nick Sensing by vaccinia virus dna ligase requires a 5 phosphate at the nick and occupancy of the adenylate binding site on the enzyme
Journal of Virology, 1997Co-Authors: Joann Sekiguchi, Stewart ShumanAbstract:Vaccinia virus DNA ligase has an intrinsic nick-Sensing Function. The enzyme discriminates at the substrate binding step between a DNA containing a 5' phosphate and a DNA containing a 5' hydroxyl at the nick. Further insights into nick recognition and catalysis emerge from studies of the active-site mutant K231A, which is unable to form the covalent ligase-adenylate intermediate and hence cannot activate a nicked DNA substrate via formation of the DNA-adenylate intermediate. Nonetheless, K231A does catalyze phosphodiester bond formation at a preadenylated nick. Hence, the active-site lysine of DNA ligase is not required for the strand closure step of the ligation reaction. The K231A mutant binds tightly to nicked DNA-adenylate but has low affinity for a standard DNA nick. The wild-type vaccinia virus ligase, which is predominantly ligase-adenylate, binds tightly to a DNA nick. This result suggests that occupancy of the AMP binding pocket of DNA ligase is essential for stable binding to DNA. Sequestration of an extrahelical nucleotide by DNA-bound ligase is reminiscent of the base-flipping mechanism of target-site recognition and catalysis used by other DNA modification and repair enzymes.
Jianjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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electrical resistivity based study of self Sensing properties for shape memory alloy actuated artificial muscle
Sensors, 2013Co-Authors: Jianjun ZhangAbstract:Shape memory alloy (SMA) has great potential to develop light and compact artificial muscle (AM) due to its muscle-like high power-to-weight ratio, flexibility and silent operation properties. In this paper, SMA self-Sensing properties are explored and modeled in depth to imitate the integrated muscle-like Functions of actuating and self-Sensing for SMA-AM based on the investigation of SMA electrical resistivity (ER). Firstly, an ER transformation kinetics model is proposed based on the simulation of SMA differential scanning calorimetry (DSC) curves. Then a series of thermal-electrical-mechanical experiments are carried out to verify the validity of the ER model, whereby the SMA-AM self-Sensing Function is well established under different stress conditions. Finally the self-Sensing capability is further demonstrated by its application to a novel SMA-AM-actuated active ankle-foot orthosis (AAFO).
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sma based bionic integration design of self sensor actuator structure for artificial skeletal muscle
Sensors and Actuators A-physical, 2012Co-Authors: Jianjun Zhang, Yuehong YinAbstract:Abstract This paper presents a novel shape memory alloy (SMA)-based artificial skeletal muscle (AM) with Functions of actuating, energy-storing and self-Sensing. The design is based on the comparison of skeletal muscle and SMA wire mechanical properties that are described by force–velocity and force–length relationships. Experimental results have shown that SMA wires can initially imitate force–velocity properties of skeletal muscles, but cannot imitate their force–length properties, which is improved by adding an anti-overstretching flexible body. Besides, a simple but effective artificial tendon is utilized to achieve energy storage like human tendon. In order to realize the self-Sensing Function of the AM, self-Sensing properties of SMA wires are explored and modeled based on the experimental study of resistivity variations. The AM self-Sensing capability is further demonstrated by its application to a 1 degree of freedom (DOF) robotic ankle-foot.
Monica Mars - One of the best experts on this subject based on the ideXlab platform.
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training of a dutch and malaysian sensory panel to assess intensities of basic tastes and fat sensation of commonly consumed foods
Food Quality and Preference, 2017Co-Authors: Astrid W B Van Langeveld, Els Siebelink, Christophe L Martin, Cees De Graaf, Sylvie Issanchou, Monica MarsAbstract:Abstract Taste has a nutrient Sensing Function and guides food choices. Therefore, investigating taste profiles of dietary patterns – within and across cultures – is highly relevant for nutritional research. However, this demands for accurately described food-taste databases, which are supported with data on the reliability and performance of the sensory panel that determined the taste values. This study aimed to assess the performance of a trained Dutch and Malaysian sensory panel. More importantly, we assessed whether the standardized training procedure in the two countries yielded similar taste profiles with respect to 15 basic taste solutions, and 19 foods differing in tastes. A Dutch (n = 15) and Malaysian panel (n = 20) were trained for 56–63 h, using basic taste solutions and reference foods on 6 scales, i.e. sweetness, sourness, bitterness, umami, saltiness and fat sensation. Performance of both panels was described by discrimination, repeatability (RMSE), and agreement. Nineteen products with different sensory characteristics were profiled in the Netherlands and Malaysia; subsequently the obtained taste profiles were compared. Both panels were able to discriminate between solutions and products (all p Our descriptive training procedure yielded two panels from different cultures that were similar in panel performance. More importantly, they obtained similar taste profiles for 19 different foods. This implies that food-taste databases obtained with valid and standardized training procedures may be used to quantify the sensory profiles of dietary patterns of populations.
Mark Odell - One of the best experts on this subject based on the ideXlab platform.
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structural basis for nick recognition by a minimal pluripotent dna ligase
Nature Structural & Molecular Biology, 2007Co-Authors: Pravin A Nair, Mark Odell, Jayakrishnan Nandakumar, Paul Smith, Christopher D Lima, Stewart ShumanAbstract:Chlorella virus DNA ligase, the smallest eukaryotic ligase known, has pluripotent biological activity and an intrinsic nick-Sensing Function, despite having none of the accessory domains found in cellular ligases. A 2.3-A crystal structure of the Chlorella virus ligase-AMP intermediate bound to duplex DNA containing a 3'-OH-5'-PO4 nick reveals a new mode of DNA envelopment, in which a short surface loop emanating from the OB domain forms a beta-hairpin 'latch' that inserts into the DNA major groove flanking the nick. A network of interactions with the 3'-OH and 5'-PO4 termini in the active site illuminates the DNA adenylylation mechanism and the crucial roles of AMP in nick Sensing and catalysis. Addition of a divalent cation triggered nick sealing in crystallo, establishing that the nick complex is a bona fide intermediate in the DNA repair pathway.
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crystal structure of eukaryotic dna ligase adenylate illuminates the mechanism of nick Sensing and strand joining
Molecular Cell, 2000Co-Authors: Mark Odell, Stewart Shuman, Verl Sriskanda, Dimitar B NikolovAbstract:Abstract Chlorella virus DNA ligase is the smallest eukaryotic ATP-dependent ligase known; it has an intrinsic nick-Sensing Function and suffices for yeast cell growth. Here, we report the 2.0 A crystal structure of the covalent ligase–AMP reaction intermediate. The conformation of the adenosine nucleoside and contacts between the enzyme and the ribose sugar have undergone a significant change compared to complexes of T7 ligase with ATP or mRNA capping enzyme with GTP. The conformational switch allows the 3′ OH of AMP to coordinate directly the 5′ PO 4 of the nick. The structure explains why nick Sensing is restricted to adenylated ligase and why the 5′ phosphate is required for DNA binding. We identify a metal binding site on ligase–adenylate and propose a mechanism of nick recognition and catalysis supported by mutational data.
Liwei Lin - One of the best experts on this subject based on the ideXlab platform.
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a flexible piezoelectret actuator sensor patch for mechanical human machine interfaces
ACS Nano, 2019Co-Authors: Junwen Zhong, Yu Song, Qize Zhong, Yao Chu, Ilbey Karakurt, D B Bogy, Liwei LinAbstract:Flexible and wearable devices with the capabilities of both detecting and generating mechanical stimulations are critical for applications in human-machine interfaces, such as augmented reality (AR) and virtual reality (VR). Herein, a flexible patch based on a sandwiched piezoelectret structure is demonstrated to have a high equivalent piezoelectric coefficient of d33 at 4050 pC/N to selectively perform either the actuating or Sensing Function. As an actuator, mechanical vibrations with a peak output force of more than 20 mN have been produced, similar to those from the vibration mode of a modern cell phone, and can be easily sensed by human skin. As a sensor, both the pressure detection limit of 1.84 Pa for Sensing resolution and excellent stability of less than 1% variations in 6000 cycles have been achieved. The design principle together with the Sensing and driving characteristics can be further developed and extended to other soft matters and flexible devices.
