Pengfei Zhang, Shuhui Liu, Duyang Gao, Dehong Hu, Ping Gong, Zonghai Sheng, Jizhe Deng, Yifan Ma, and Lintao Cai
Publication Date (Web): May 8, 2012 (Communication)
DOI: 10.1021/ja302367s
Single-Molecular Artificial Transmembrane Water Channels
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, China
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/ja302292c
Publication Date (Web): May 10, 2012
Copyright © 2012 American Chemical Society
Hydrazide-appended pillar[5]arene derivatives have been synthesized. X-ray crystal structure analysis and 1H NMR studies revealed that the molecules adopt unique tubular conformations. Inserting the molecules into the lipid membranes of vesicles leads to the transport of water through the channels produced by single molecules, as supported by dynamic light scattering and cryo-SEM experiments. The channels exhibit the transport activity at a very low channel to lipid ratio (0.027 mol %), and a water permeability of 8.6 × 10–10 cm s–1 is realized. In addition, like natural water channel proteins, the artificial systems also block the transport of protons.
Two-Strain, Cell-Selective Protein Labeling in Mixed Bacterial Cultures
Frank Truong†, Tae Hyeon Yoo‡, Thomas J. Lampo†, and David A. Tirrell*†
† Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
‡ Department of Molecular Science and Technology, Division of Applied Chemistry and Biological Engineering, Ajou University, Suwon, South Korea
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/ja3004667
Publication Date (Web): May 10, 2012
Copyright © 2012 American Chemical Society
ell-selective metabolic labeling of proteins with noncanonical amino acids enables the study of proteomic changes in specified subpopulations of complex multicellular systems. For example, azidonorleucine (Anl) and 2-aminooctynoic acid, both of which are activated by an engineered methionyl-tRNA synthetase (designated NLL-MetRS), are excluded from proteins made in wild-type cells but incorporated readily into proteins made in cells that carry NLL-MetRS. To expand the set of tools available for cell-selective metabolic labeling, we sought a MetRS variant capable of activating propargylglycine (Pra). Pra was chosen as the target amino acid because its alkynyl side chain can be selectively and efficiently conjugated to azide-functionalized fluorescence probes and affinity tags. Directed evolution, using active-site randomization and error-prone PCR, yielded a MetRS variant (designated PraRS) capable of incorporating Pra at near-quantitative levels into proteins made in a Met-auxotrophic strain of Escherichia coli cultured in Met-depleted media. Proteins made in E. coli strains expressing PraRS were labeled with Pra in Met-supplemented media as shown by in-gel fluorescence after conjugation to Cy5-azide. The combined use of NLL-MetRS and PraRS enabled differential, cell-selective labeling of marker proteins derived from two bacterial strains cocultured in media supplemented with Met, Anl, and Pra. Treatment of the mixed marker proteins by sequential strain-promoted and copper(I)-catalyzed cycloadditions allowed straightforward identification of the cellular origin of each protein
Paper-Based, Capacitive Touch Pads
Article first published online: 27 APR 2012
DOI: 10.1002/adma.201200137
This paper describes low-cost, thin, and pliable touch pads constructed from a commercially available, metallized paper commonly used as packaging material for beverages and book covers. The associated electronics with the individual keys in the touch pads detect changes in capacitance or contact with fingers by using the effective capacitance of the human body and the electrical impedance across the tip of a finger. To create the individual keys, a laser cutter ablates lines through the film of evaporated aluminum on the metallized paper to pattern distinct, conductive regions. This work includes the experimental characterization of two types of capacitive buttons and illustrates their use with applications in a keypad with 10 individually addressable keys, a keypad that conforms to a cube, and a keypad on an alarmed cardboard box. With their easily arrayed keys, environmentally benign material, and low cost, the touch pads have the potential to contribute to future developments in disposable, flexible electronics, active, “smart” packaging, user interfaces for biomedical instrumentation, biomedical devices for the developing world, applications for monitoring animal and plant health, food and water quality, and disposable games (e.g., providers of content for consumer products).
Pendant Polymer:Amino-β-Cyclodextrin:siRNA Guest:Host Nanoparticles as Efficient Vectors for Gene Silencing
Aditya Kulkarni, Kyle DeFrees, Seok-Hee Hyun, and David H. Thompson
Publication Date (Web): April 30, 2012 (Communication)
DOI: 10.1021/ja300690j
Silicene: Compelling Experimental Evidence for Graphenelike Two-Dimensional Silicon
Patrick Vogt,* Paola De Padova, Claudio Quaresima, Jose Avila, Emmanouil Frantzeskakis,Maria Carmen Asensio, Andrea Resta, Be´ne´dicte Ealet, and Guy Le Lay
Because of its unique physical properties, graphene, a 2D honeycomb arrangement of carbon atoms, has
attracted tremendous attention. Silicene, the graphene equivalent for silicon, could follow this trend,
opening new perspectives for applications, especially due to its compatibility with Si-based electronics.
Silicene has been theoretically predicted as a buckled honeycomb arrangement of Si atoms and having an
electronic dispersion resembling that of relativistic Dirac fermions. Here we provide compelling evidence,
from both structural and electronic properties, for the synthesis of epitaxial silicene sheets on a
silver (111) substrate, through the combination of scanning tunneling microscopy and angular-resolved
photoemission spectroscopy in conjunction with calculations based on density functional theory.
Flexible, Angle-Independent, Structural Color Reflectors Inspired by Morpho Butterfly Wings
Advanced Materials
Thin-film color reflectors inspired by Morpho butterflies are fabricated. Using a combination of directional deposition, silica microspheres with a wide size distribution, and a PDMS (polydimethylsiloxane) encasing, a large, flexible reflector is created that actually provides better angle-independent color characteristics than Morpho butterflies and which can even be bent and folded freely without losing its Morpho-mimetic photonic properties.
Selective Detection of Ethylene Gas Using Carbon Nanotube-based Devices: Utility in Determination of Fruit Ripeness
Birgit Esser, Jan M. Schnorr, and Timothy M. Swager
Ethylene, the smallest plant hormone, plays a role in many developmental processes in plants. For example, it initiates the ripening of fruit, promotes seed germination and flowering, and is responsible for the senescence of leaves and flowers.[1] The rate-limiting step in the biosynthetic pathway to ethylene, elucidated by Yang et al., is catalyzed by 1- aminocyclopropane-1-carboxylic acid (ACC) synthase. [2] Ethylene production in plants is induced during several developmental stages as well as by external factors. The ripening process is the result of ethylene binding to the receptor ETR1,which leads to the translation of ripening genes and eventually the production of enzymes that induce the visible effects of ripening. The monitoring of the ethylene concentration is of utmost importance in the horticultural industries. The internal ethylene concentration in fruit can serve as an
indicator for determining the time of harvest, while the monitoring of the atmospheric ethylene level in storage
facilities and during transportation is crucial for avoiding
overripening of fruit
Ethylene, the smallest plant hormone, plays a role in many developmental processes in plants. For example, it initiates the ripening of fruit, promotes seed germination and flowering, and is responsible for the senescence of leaves and flowers.[1] The rate-limiting step in the biosynthetic pathway to ethylene, elucidated by Yang et al., is catalyzed by 1- aminocyclopropane-1-carboxylic acid (ACC) synthase. [2] Ethylene production in plants is induced during several developmental stages as well as by external factors. The ripening process is the result of ethylene binding to the receptor ETR1,which leads to the translation of ripening genes and eventually the production of enzymes that induce the visible effects of ripening. The monitoring of the ethylene concentration is of utmost importance in the horticultural industries. The internal ethylene concentration in fruit can serve as an
indicator for determining the time of harvest, while the monitoring of the atmospheric ethylene level in storage
facilities and during transportation is crucial for avoiding
overripening of fruit
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