Popular science articles

Incorporation of Amphiphilic Cyclodextrins into Liposomes as Artificial Receptor Units

Langmuir, Article ASAP

DOI: 10.1021/la3045434

Publication Date (Web): January 24, 2013

In this article, we describe the introduction of amphiphilic β-cyclodextrins into liposomes to act as artificial receptor units. Using dynamic light scattering, dye encapsulation, and cryogenic transmission electron microscopy, we show that amphiphilic β-cyclodextrins can be mixed in any proportion with a typical mixture of phospholipids and cholesterol to provide stable, spherical, and unilamellar mixed vesicles. It is also possible to form giant unilamellar vesicles with mixtures of lipids and cyclodextrin. The permeability of the mixed vesicles increases with the percentage of cyclodextrin. The cyclodextrins can act as host molecules for hydrophobic guest molecules, even when they are dispersed at a low percentage in the vesicle membrane. It is shown that mixed vesicles can be decorated with carbohydrate-functionalized guest molecules, with photoresponsive guest molecules, and with dye-functionalized guest molecules. Taken together, it is demonstrated that the host–guest chemistry of amphiphilic cyclodextrins is fully compatible with a liposomal bilayer membrane and the advantages of each can be combined to give superior nanocontainers.

Statistical Thermodynamics of Natural Images

Phys. Rev. Lett. 110, 018701 (2013)

Greg J. Stephens^*, Thierry Mora^†, Gašper Tkačik^‡, and William Bialek
Joseph Henry Laboratories of Physics and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA

The scale invariance of natural images suggests an analogy to the statistical mechanics of physical systems at a critical point. Here we examine the distribution of pixels in small image patches and show how to construct the corresponding thermodynamics. We find evidence for criticality in a diverging specific heat, which corresponds to large fluctuations in how “surprising” we find individual images, and in the quantitative form of the entropy vs energy. We identify special image configurations as local energy minima and show that average patches within each basin are interpretable as lines and edges in all orientations.

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

Shivendra Pandey¹, Evin Gultepe¹, David H. Gracias^1,2

¹Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, ²Department of Chemistry, The Johns Hopkins University

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods^1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.

Microfluidic Mixing Triggered by an External LED Illumination

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja311837r

Publication Date (Web): January 25, 2013

Anna Venancio-Marques †‡§, Fanny Barbaud †‡§, and Damien Baigl *†‡§

The mixing of confined liquids is a central yet challenging operation in miniaturized devices. Microfluidic mixing is usually achieved with passive mixers that are robust but poorly flexible, or active mixers that offer dynamic control but mainly rely on electrical or mechanical transducers, which increase the fragility, cost, and complexity of the device. Here, we describe the first remote and reversible control of microfluidic mixing triggered by a light illumination simply provided by an external LED illumination device. The approach is based on the light-induced generation of water microdroplets acting as reversible stirrers of two continuous oil phase flows containing samples to be mixed. We demonstrate many cycles of reversible photoinduced transitions between a nonmixing behavior and full homogenization of the two oil phases. The method is cheap, portable, and adaptable to many device configurations, thus constituting an essential brick for the generation of future all-optofluidic chip.

Formation of Diverse Supercrystals from Self-Assembly of a Variety ofPolyhedral Gold Nanocrystals

Ching-Wen Liao †, Yeh-Sheng Lin †, Kaushik Chanda †, Yen-Fang Song ‡, and Michael H. Huang *†
† Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
‡ National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan

Adaptive aerial righting during the escape dropping of wingless pea aphids

Gal Ribak¹^,^#^,^, , Moshe Gish²^,^#, Daniel Weihs¹ and Moshe Inbar²

http://www.cell.com/current-biology/abstract/S0960-9822(12)01450-9

Summary
Pea aphids (Acyrthosiphon pisum) are small sap-sucking insects that live on plants in colonies containing mostly wingless individuals. They often escape predators, parasitoids and grazing mammalian herbivores by dropping off the plant [1,2], avoiding immediate danger but exposing themselves to ground predators, starvation and desiccation [3]. We show here that dropping pea aphids land on their legs, regardless of their initial orientation on the plant (like a defenestrated cat), by rotating their body during the fall. This righting ability is intriguing, as wingless aphids have no specialized structures for maneuvering in mid-air. Instead, they assume a stereotypic posture which is aerodynamically stable only when the aphids fall right-side up. Consequently, the body passively rotates to the stable upright orientation, improving the chance of clinging to leaves encountered on the way down and lowering the danger of reaching the ground.