The Discovery of Fullerenes in the 1.85 Billion-Year-Old Sudbury Meteorite Crater

Fullerenes (C{sub 60}, C{sub 70}) have been identified by laser time-of-flight and electron-ionization mass spectroscopy in rock samples (black tuff in the Onaping formation) from the crater. They were likely synthesized within the impact plume from carbon contained in the meteorite. The isotopic ratios suggest {sup 13}C enrichment. They are associated with sulfur which may have protected them. This is the largest known deposit of naturally occurring fullerenes

Adsorbate-induced structural changes in 1-3 nm platinum nanoparticles

We investigated changes in the Pt–Pt bond distance, particle size, crystallinity, and coordination of Pt nanoparticles as a function of particle size (1–3 nm) and adsorbate (H2, CO) using synchrotron radiation pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) measurements. The ∼1 nm Pt nanoparticles showed a Pt–Pt bond distance contraction of ∼1.4%. The adsorption of H2 and CO at room temperature relaxed the Pt–Pt bond distance contraction to a value close to that of bulk fcc Pt. The adsorption of H2 improved the crystallinity of the small Pt nanoparticles. However, CO adsorption generated a more disordered fcc structure for the 1–3 nm Pt nanoparticles compared to the H2 adsorption Pt nanoparticles. In situ XANES measurements revealed that this disorder results from the electron back-donation of the Pt nanoparticles to CO, leading to a higher degree of rehybridization of the metal orbitals in the Pt-adsorbate system

An Unusual Topological Structure of the HIV-1 Rev Response Element

SummaryNuclear export of unspliced and singly spliced viral mRNA is a critical step in the HIV life cycle. The structural basis by which the virus selects its own mRNA among more abundant host cellular RNAs for export has been a mystery for more than 25 years. Here, we describe an unusual topological structure that the virus uses to recognize its own mRNA. The viral Rev response element (RRE) adopts an “A”-like structure in which the two legs constitute two tracks of binding sites for the viral Rev protein and position the two primary known Rev-binding sites ∼55 Å apart, matching the distance between the two RNA-binding motifs in the Rev dimer. Both the legs of the “A” and the separation between them are required for optimal RRE function. This structure accounts for the specificity of Rev for the RRE and thus the specific recognition of the viral RNA

Small Angle X-Ray Scattering Measurements Probe Water Nanodroplet Evolution under Highly Non-Equilibrium Conditions

Our in situ small angle X-ray scattering (SAXS) measurements yield an unprecedented and detailed view of rapidly evolving H2O nanodroplets formed in supersonic nozzles. The SAXS experiments produce spectra in a few seconds that are comparable to small angle neutron scattering (SANS) spectra requiring several hours of integration time and the use of deuterated compounds. These measurements now make it possible to quantitatively determine the maximum nucleation and growth rates of small droplets formed under conditions that are far from equilibrium. Particle growth is directly followed from about 10 µs to 100 µs after particle formation with growth rates of 0.2 to 0.02 nm µs-1. The peak H2O nucleation rates lie between 1017 and 1018 cm-3 s-1