Press release from Nature and the Nature Research Journals

[1] NANOSCALE ARMS CONTROL
DOI: 10.1038/nmat902 (http://dx.doi.org/10.1038/nmat902)

Some of the tiniest structures over which scientists exert control, such as nanowires and nanocrystals, are key building blocks for the future development of nanotechnology. Semiconductor nanocrystals now come in many forms: from spheres to discs and rods, with interesting mechanical, optical and electrical properties. In the June issue of Nature Materials, Paul Alivisatos and colleagues add nanocrystal tetrapods to this list and demonstrate impressive control over their specific size and shape.

Tetrapods have four arms, and Alivisatos and co-workers are able to independently control the length and width of the arms by varying the growth conditions of the semiconductor colloid used to make the nanocrystal. They achieve this level of control by exploiting the relative stability of two different crystal phases, which allows them to grow one phase at a time.

The authors suggest that their tetrapods could make useful additives for plastic composites or to improve the efficiency of polymer-based solar cells. As Charles Lieber and Deli Wang of Harvard University describe in an accompanying News and Views article: "it is interesting to see that the branched structures of both nanocrystals and nanowires are converging to a very similar point". And before long, multi-branched structures may be developed with novel electronic and optical properties.

Author contact:
Paul Alivisatos
Department of Chemistry, University of California, Berkeley, CA, USA
Tel: +1 510 643 7371; E-mail: alivis@uclink4.berkeley.edu

Additional contact for comment on paper:
Charles Lieber
Department of Chemistry, Harvard University, Boston, MA, USA
Tel: +1 617 496 3169; Email: cml@cmliris.harvard.edu

[2] STEPMOTHER OF PEARL
DOI: 10.1038/nmat906 (http://dx.doi.org/10.1038/nmat906)

Creating artificial analogs of natural materials, such as bone, is an attractive way to make composites that are lightweight, yet hard and resilient. But previous attempts have failed to produce samples large enough to measure their mechanical properties, such as strength and elasticity. By using an alternative approach, described in the June issue of Nature Materials, Nicholas Kotov and colleagues show how to produce large-scale samples that mimic the properties of natural composite materials, including seashell nacre (mother-of-pearl).

Kotov and colleagues created their composites through controlled layer-by-layer deposition of polyelectrolytes and clays. This approach is usually used to create versatile organic coatings known as polyelectrolyte multilayers. By adding an inorganic material (clay) to the mix, Kotov and co-workers have created a composite material that exhibits striking similarities to bone and nacre in standard mechanical tests.

In principle, the layered structure that characterizes these new composites could be reproduced using various combinations of different organic/inorganic building blocks, leading to a whole new family of artificial nacre-like materials.

Author contact:
Nicholas Alexander Kotov
Department of Chemistry, Oklahoma State University, Stillwater, OK, USA
Tel: 405-744-3991; E-mail kotov@okstate.edu

Other papers from Nature Materials to be published online at the same time and with the same embargo:

[3] Dextran templating for the synthesis of metallic and metal oxide sponges (DOI: 10.1038/nmat903) (http://dx.doi.org/10.1038/nmat903)

NATURE MEDICINE
(http://www.nature.com/naturemedicine)

[4] COMBINATION VACCINE DELIVERS DOUBLE BLOW
DOI:10.1038/nm881 (http://dx.doi.org/10.1038/nm881)

A new vaccine approach that delivers a one-two punch could give the immune system an edge against malaria, AIDS and other exigent diseases in people, Adrian Hill and colleagues report in the June issue of Nature Medicine.

The researchers tested their method using a malaria vaccine in human volunteers. They first treated the volunteers with the parasite's DNA, followed by a boost with a modified poxvirus that expresses parasite proteins. The 'prime' and 'boost' contained distinctly different proteins from the parasite.

Neither DNA nor poxvirus in isolation induced a potent response, the team found. But the combination ramped up the activation of T cells--a subset of immune cells--and provided partial protection against malaria infection. The approach has the potential to outshine more conventional experimental vaccines against malaria. Similar vaccine approaches have already shown promise in AIDS vaccine trials.

Author contact:
Adrian Hill
Nuffield Department of Medicine, University of Oxford, UK
Tel: +44 1865 222301; E-mail: adrian.hill@imm.ox.ac.uk

NATURE IMMUNOLOGY(http://www.nature.com/natureimmunology)

[5] STEM CELL ENGRAFTMENT SUCCESS DOES NOT ENSURE LONG-TERM SURVIVAL
DOI: 10.1038/ni940 (http://dx.doi.org/10.1038/ni940)

Hematopoietic stem cells engraft much more efficiently than previously thought. In the July issue of Nature Immunology, Canadian researchers report that every stem cell introduced by transplantation successfully engrafts in the bone marrow. However, only a minority of these established stem cells contribute to long-term hematopoiesis.

Iscove and colleagues show nearly every irradiated mouse that received only one stem cell, on average, can generate blood cells of donor origin within the first 4-8 weeks, signaling successful engraftment. But when these mice were analyzed 32 weeks later, only 25% generated donor blood cells, suggesting that a loss of stem cell self-renewal occurred. Thus, long-term hematopoietic stem cell potential does not appear to be limited by their engraftment success, rather it reflects the variable ability to self-renew once established in the bone marrow.

Author contact:
Norman N. Iscove
The Ontario Cancer Institute, University of Toronto, Ontario, Canada
Tel: +1 416 946 4501 ext 4987; E-mail: iscove@uhnres.utoronto.ca

Other papers from Nature Immunology to be published online at the same time and with the same embargo:

[6] CpG directly induces T-bet expression and inhibits Igg1 and Ige switching in B cells (DOI: 10.1038/ni941) (http://dx.doi.org/10.1038/ni941)

[7] The inhibitory function of B7 costimulators in T cell responses to foreign and self-antigens (DOI: 10.1038/ni939) (http://dx.doi.org/10.1038/ni939)

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Items from other Nature journals to be published online at the same time and with the same embargo:

NATURE (http://www.nature.com/nature)

[8] Functional proteomic identification of DNA replication proteins by induced proteolysis in vivo (DOI: 10.1038/nature01692) (http://dx.doi.org/10.1038/nature01692)

[9] POT1 as a terminal transducer of TRF1 telomere length control (DOI: 10.1038/nature01688) (http://dx.doi.org/10.1038/nature01688)

NATURE GENETICS (http://www.nature.com/naturegenetics)

[10] Fraser syndrome and mouse blebbed phenotype caused by mutations in FRAS1/Fras1 encoding a putative extracellular matrix protein (DOI: 10.1038/ng1142) (http://dx.doi.org/10.1038/ng1142)

[11] Fras1 deficiency results in cryptophthalmos, renal agenesis and blebbed phenotype in mice (DOI: 10.1038/ng1168) (http://dx.doi.org/10.1038/ng1168)

NATURE NEUROSCIENCE (http://www.nature.com/natureneuroscience)

[12] Specification of dorsal telencephalic character by sequential Wnt and FGF signaling (DOI: 10.1038/nn1068) (http://dx.doi.org/10.1038/nn1068)

NATURE STRUCTURAL BIOLOGY (http://www.nature.com/naturestructuralbiology)

[13] A conformational switch between transcriptional repression and replication initiation in RepA dimerization domain (DOI: 10.1038/nsb937) (http://dx.doi.org/10.1038/nsb937)

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