Patterning matter on the nanometre scale is an important objective of current materials chemistry and physics. It is driven by both the need to further miniaturize electronic components and the fact that at the nanometre scale, materials properties are strongly size-dependent and thus can be tuned sensitively. In nanoscale crystals, quantum size effects and the large number of surface atoms influence the, chemical, electronic, magnetic and optical behaviour. 'Top-down' (for example, lithographic) methods for nanoscale manipulation reach only to the upper end of the nanometre regime; but whereas 'bottom-up' wet chemical techniques allow for the preparation of mono-disperse, defect-free crystallites just 1-10 nm in size, ways to control the structure of nanocrystal assemblies are scarce. Here we describe a strategy for the synthesis of 'nanocrystal molecules', in which discrete numbers of gold nanocrystals are organized into spatially defined structures based on Watson-Crick base-pairing interactions. We attach single-stranded DNA oligonucleotides of defined length and sequence to individual nanocrystals, and these assemble into dimers and trimers on addition of a complementary single-stranded DNA template. We anticipate that this approach should allow the construction of more complex two- and three-dimensional assemblies.

No abstract

Specific, designed, nonperiodic arrangements of gold nanocrystals that are 5 and 10 nm in diameter can be prepared with double-stranded DNA serving as a template (see drawing; A' and B' denote oligonucleotide sequences complementary to sequences A and B). The methods described should be applicable to nanocrystals composed of various materials.

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) is a significant source of disability in the HIVHere we demonstrate the anti-inflammatory and neuroprotective effects of URMC-099 in multiple murine and rodent models of HAND. In vitro, URMC-099 treatment reduced inflammatory cytokine production by HIV-1 Tat-exposed microglia and prevented destruction and phagocytosis of cultured neuronal axons by these cells. In vivo, URMC-099 treatment reduced inflammatory cytokine production, protected neuronal architecture, and altered the morphologic and ultrastructural response of microglia to HIV-1 Tat exposure. In conclusion, these data provide compelling in vitro and in vivo evidence to investigate the utility of URMC-099 in other models of HAND with the goal of advancement to an adjunctive therapeutic agent.

COMMUNICATIONS \pectroscop\ (AAS) after di\mlution of known quantities of the zeolites materials i n HF'H,SO, AAS mcasureinents &'ere performed with an Instrumentation Labo-Inc. apparatus uith B nitrous oxide,acetylene flame Scanning electron miiphs (SEM) were obtained by using a Jeol Superprobe 733 instrument. while diffuse reflecrmcc spectroscopy (DRS) was performed on a Varian Cary 5 UVWIS! NIR spectrophotometer at room teniperitture. The diffuse reflectance spectra were recorded against A h;ilon white rellectmce standard in the range 2200 -~200 nm. The computer processing of the spectra consisted of the following steps: 1 ) subtraction of the baseline. 2 ) conversion to wavenumber. and 3) calculation of the Kubelka-Munk ( K M ) function. For ESR spectroscopy. a Bruker ESP300E spectrometer at X-band (ca. 9.5 GHz) was used. Quantitative ESR results were obtained by comparison with Cu(acetylacetonate)..KCI reference samples (spin density : l o i h -10" CU" g-'). The molecular models were generated by the commercial software package HyperchemTM of Autodesk.