Amphiphilic block copolymers of suitable proportions can self-assemble into surprisingly long and stable worm-like micelles, but the intrinsic polydispersity of polymers as well as polymer blending efforts and the increasing use of degradable chains all raise basic questions of curvature-composition coupling and morphological stability of these high curvature assemblies. Molecular simulations here of polyethylene glycol (PEG) based systems show that a systematic increase in the hydrated PEG fraction, in both monodisperse and binary blends, induces budding and breakup into spherical and novel "dumbbell" micelles-as seen in electron microscopy images of degradable worm-like micelles.

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Chemistry creates its own object. This creative ability, similar to an art, is the main feature that distinguishes chemistry from the natural and humanitarian sciences.

Marcellin Berthelot (1827-1907)

This quote from the French chemist Berthelot is illustrated by our cover, which depicts a single-stranded DNA-carbon nanotube (CNT) hybrid. This material was modeled and synthesized by Robert R. Johnson, A. T. Charlie Johnson, and Michael L. Klein at the University of Pennsylvania. The combination of an inorganic nanomaterial such as a carbon nanotube with a biomolecule, while unheard of in nature, opens the possibility of creating new materials with novel properties for applications in biology and chemistry. DNA-CNT hybrids have remarkable properties that are useful in CNT sorting, chemical sensing, and the detection of DNA hybridization.

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The interactions between DNA bases and carbon nanotubes (CNTs) govern the self-assembly of DNA-CNT hybrids (see image), a novel class of nanomaterials with many applications in nanotechnology. The free-energy calculations presented here reveal the importance of van der Waals and electrostatic interactions, solvent-mediated effects, and entropy in base-CNT binding and provide a better understanding of these hybrid nanomaterials.

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Snapshot of a self-assembled elongated micelle of non-ionic surfactant molecules (penta-(ethyleneglycol)-dodecylether, C12E5) in water simulated with coarse grain molecular dynamics. Surfactants are used in a large variety of applications. Structures like micelles and vesicles form and can trap or protect other materials. Researchers at Temple University model these structures on NCSA’s Abe and Lincoln supercomputers.

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A nanobiosensor consisting of a single-walled carbon nanotube (gray cylinder) covalently attached to the coxsackie-adenovirus receptor (green). This complex can detect the presence of the adenovirus by specifically binding the Knob protein domain (orange) located on the virus capsid. Computer simulations have shed light on the physics of this nanoscale device and provide a means to rationalize the design of similar biosensors.

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A team of researchers at the University of Pennsylvania’s Center for Molecular Modeling is changing the way scientists view cholesterol in the nicotinic acetylcholine receptor (nAChR). For years, cholesterol was thought only to be in the outer membrane. Simulations conducted on NCSA’s Abe demonstrated the possibility that the cholesterol, colored yellow, orange, and red, may actually bind to sites within the protein’s transmembrane domain.

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Simulation of a vesicle interacting with a lipid bilayer (lipid head groups in green and blue, tails in cyan; water is not shown). The computation uses a coarse-grained model with over 1 million interaction sites, equivalent to more than 10 million atoms.

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