Popular science articles: December 2012

Optical Motion Control of Maglev Graphite

^† Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan

^‡ CREST, Japan Science and Technology Agency, K’s Gobancho, 7 Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja310365k

Publication Date (Web): December 12, 2012

Graphite has been known as a typical diamagnetic material and can be levitated in the strong magnetic field. Here we show that the magnetically levitating pyrolytic graphite can be moved in the arbitrary place by simple photoirradiation. It is notable that the optical motion control system described in this paper requires only NdFeB permanent magnets and light source. The optical movement is driven by photothermally induced changes in the magnetic susceptibility of the graphite. Moreover, we demonstrate that light energy can be converted into rotational kinetic energy by means of the photothermal property. We find that the levitating graphite disk rotates at over 200 rpm under the sunlight, making it possible to develop a new class of light energy conversion system.

Conformational Control of Energy Transfer: A Mechanism for Biocompatible Nanocrystal-Based Sensors†

Dr. Euan R. Kay^1,2,‡,
Jungmin Lee^1,‡,
Prof. Daniel G. Nocera¹,
Prof. Moungi G. Bawendi^1,*

DOI: 10.1002/anie.201207181

Know when to fold ’em: Combination of a pH-triggered oligonucleotide conformational switch with fluorescent nanocrystals gives a sensitive pH nanosensor (see scheme). Analyte-dependent conformational changes control the distance between the nanocrystal energy donor (green) and a FRET acceptor (red), which results in a reporter for pH values in individual endosomes of living cells.

Cytoplasmic ATP Hydrolysis Powers Transport of Lipopolysaccharide Across the Periplasm in E. coli

Suguru Okuda¹,

Elizaveta Freinkman¹,

Daniel Kahne¹,²,*

ABSTRACT

Millions of molecules of lipopolysaccharide (LPS) must be assembled on the Escherichia coli cell surface each time the cell divides. The biogenesis of LPS requires seven essential lipopolysaccharide transport (Lpt) proteins to move LPS from the inner membrane through the periplasm to the cell surface. However, no intermediate transport states have been observed. We developed methods to observe intermediate LPS molecules bound to Lpt proteins in the process of being transported in vivo. Movement of individual LPS molecules along these binding sites required multiple rounds of adenosine triphosphate (ATP) hydrolysis in vitro, which suggests that ATP is used to push a continuous stream of LPS through a transenvelope bridge in discrete steps against a concentration gradient.

Published Online November 8 2012

Science 30 November 2012:
Vol. 338 no. 6111 pp. 1214-1217
DOI: 10.1126/science.1228984

Touring the Tomato: A Suite of Chemistry Laboratory Experiments

J. Chem. Educ.

DOI: 10.1021/ed3004148

Publication Date (Web): December 14, 2012

An eight-session interdisciplinary laboratory curriculum has been designed using a suite of analytical chemistry techniques to study biomaterials derived from an inexpensive source such as the tomato fruit. A logical progression of research-inspired laboratory modules serves to "tour" the macroscopic characteristics of the fruit and the submicroscopic properties of its constituent cuticular biopolymers by atomic force microscopy (AFM), UV–visible, and nuclear magnetic resonance (NMR) methods at increasingly detailed molecular levels. The modular curriculum can be tailored for specialty undergraduate courses or summer high school workshops. By applying analytical tools to investigate biopolymers, making connections between molecular and microscale structure, and linking both structural regimes to the functional properties of natural polymers, groundwork is established for further student investigations at the interface of chemistry with biology or chemical engineering.

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