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tions on the fields of drug design and nanomaterials. Across the biological kingdoms, ferritin regulates the distribution of iron, which is necessary for a number of cellular functions but also forms reactive ions that can be lethal to cells. Shaped like a sphe-

rical nanocage, ferritin is made up of 24 proteins,

and it sequesters the reactive iron ions in its hollow interior. In humans, ferritin prevents iron deficiency and overload.

“The rules that govern self-assembling nanosystems, like the ferritin model, are poorly understood,” Brendan P. Orner, the assistant professor who over- saw the team‘s work, explained. “We systematically analyzed the interactions between the 24 ferritin units that make up the nanocage and identified the hot spots that are crucial to the cage‘s formation.”

Yu Zhang, Siti Raudah, Huihian Teo, Gwenda W. S. Teo, Rongli Fan, Xiaoming Sun, and Brendan P. Orner: Alanine-shaving Mutagenesis to Determine Key Interfacial Residues Governing the Assembly of a Nano-cage Maxi- ferritin, In: Journal Biological Chemistry, Vol. 285, Num. 16, April 16, 2010, Pages 12078-12086, DOI:10.1074/ jbc.M109.092445:

http://dx.doi.org/10.1074/jbc.M109.092445

A closer look at a promising nanotube coating that might one day improve solar cells has turned up a few unexpected wrinkles, according to new research conducted at the National Institute of

Standards and Technology (NIST) and North Da- kota State University (NDSU) – research that also

may help scientists iron out a solution. The scientists

have found that coatings made of single-walled carbon nanotubes (SWCNTs) are not quite as de-

formable as hoped, implying that they are not an

10-04 :: April 2010

easy answer to problems that other materials pre- sent. Though films made of nanotubes possess many desirable properties, the team‘s findings reveal some issues that might need to be addressed before the full potential of these coatings is realized.

“The irony of these nanotube coatings is that they can change when they bend,” says Erik Hobbie, now the director of the Materials and Nanotech- nology program at NDSU. “Under modest strains, these films can develop irreversible changes in nanotube arrangement that reduce their conductivi- ty. Our work is the first to suggest this, and it opens up new approaches to engineering the films in ways that minimize these effects.”

IMAGE: This atomic- force mi- croscopy image shows wrinkling in a single-wall carbon nano- tube membra- ne; the inset shows an op- tical reflection micrograph of the membrane without any strain. The random arrange- ment of the nanotubes shown in the inset creates con- ductivity, but wrinkling can disrupt that. Each image is 40 micrometers in width. © NIST

E. K. Hobbie, D. O. Simien, J. A. Fagan, J. Y. Huh, J. Y.Chung, S. D. Hudson, J. Obrzut, J. F. Douglas, and C. M. Stafford: Wrinkling and Strain Softening in Single-Wall Carbon Nanotube Membranes, In: Physical Review Letters, Vol. 104(2010), Issue 12, March 26, 2010, Article 125505