X-ray and neutron scattering

Abstract:

HIV-1 protease is an important target for the development of antiviral inhibitors to treat AIDS. A room-temperature joint X-ray/neutron structure of the protease in complex with clinical drug amprenavir has been determined at 2.0 Å resolution. The structure provides direct determination of hydrogen atom positions in the enzyme active site. Analysis of the enzyme-drug interactions suggests that some hydrogen bonds may be weaker than deduced from the non-hydrogen interatomic distances. This information may be valuable for the design of improved protease inhibitors.

Abstract:

Magnetic fluctuations in the molecular-intercalated FeSe superconductor Lix(ND2)y(ND3)1-yFe2Se2 (Tc=43K) have been measured by inelastic neutron scattering from a powder sample. The strongest magnetic scattering is observed at a wave vector Q≈1.4 Å-1, which is not consistent with the (π,0) nesting wave vector that characterizes magnetic fluctuations in several other iron-based superconductors but is close to the (π,π/2) position found for AxFe2-ySe2 systems. At the energies probed (∼5kBTc), the magnetic scattering increases in intensity with decreasing temperature below Tc, consistent with the superconductivity-induced magnetic resonance found in other iron-based superconductors. © 2013 American Physical Society.

Abstract:

The I2-sorption and -retention properties of several existing zeolitic imidazolate frameworks (ZIF-4, -8, -69) and a novel framework, ZIF-mnIm ([Zn(mnIm)2 ]; mnIm=4-methyl-5-nitroimidazolate), have been characterised using microanalysis, thermogravimetric analysis and X-ray diffraction. The topologically identical ZIF-8 ([Zn(mIm)2]; mIm=2-methylimidazolate) and ZIF-mnIm display similar sorption abilities, though strikingly different guest-retention behaviour upon heating. We discover that this guest retention is greatly enhanced upon facile amorphisation by ball milling, particularly in the case of ZIF-mnIm, for which I2 loss is retarded by as much as 200 °C. It is anticipated that this general approach should be applicable to the wide range of available metal-organic framework-type materials for the permanent storage of harmful guest species.