Influenza A virus is a major human and animal pathogen with the potential to cause catastrophic loss of life. Influenza virus reproduces rapidly, mutates frequently, and occasionally crosses species barriers. The recent emergence of swine-origin influenza H1N1 and avian influenza related to highly pathogenic forms of the human virus has highlighted the urgent need for new effective treatments. Here, we describe two crystal structures of complexes made by fragments of PA and PB1, and PB1 and PB2. These novel interfaces are surprisingly small, yet they play a crucial role in regulating the 250 kDa polymerase complex, and are completely conserved among swine, avian and human influenza viruses. Given their importance to viral replication and strict conservation, the PA/PB1 and PB1/PB2 interfaces appear to be promising targets for novel anti-influenza drugs of use against all strains of influenza A virus. It is hoped that the structures presented here will assist the search for such compounds.
In 1919, Perucca reported anomalous optical rotator dispersion from chiral NaClO3 crystals that were colored by an equilibrium racemic mixture of a triarylmethane dye, and this chiroptical observation was consistent with a resolution of the propeller-shaped dye molecules by NaClO3 crystals. Which was regarded as the first report on enantioselevtie adsorption of a racemic mixture on surface of a chiral crystal. In those days, P- or M-configuration of the propeller-shaped triarylmethane dyes were not known, chiroptical observation of oriented chiral molecules on chiralinorganic crystals were investigated. Recently (in 2010), Kahr et al. reinvestigated the similar system by means of differential polarization imaging techniques and concluded that Perucca's observation was a convolution of linear and circular optical properties. In this essay, we appreciate the deepening understanding about this issue in view of historical as well as technical development.
Thermostable direct hemolysin (TDH) is a major virulence factor of Vibrio parahaemolyticus that causes pandemic food-borne enterocolitis mediated by seafood. TDH exists as a tetramer in solution, and it possesses extreme hemolytic activity. Here, we present the crystal structure of the TDH tetramer at 1.5 Å resolution. The TDH tetramer forms a central pore with dimensions of 23 Å in diameter and ∼50 Å in depth. π-cation interactions between protomers comprising the tetramer were indispensable for hemolytic activity of TDH. The N-terminal region was intrinsically disordered outside the pore. Molecular dynamics (MD) simulations suggested that water molecules permeate freely through the central and side channel pores. These findings imply a novel membrane attachment mechanism by a soluble tetrameric pore-forming toxin.
Nanometer-size columnar superstructures with a chessboard pattern in Mn-based spinels have been fabricated by harnessing the Jahn-Teller structural distortion. Transmission electron microscope images reveal that the fundamental building blocks are two types of long nanorods with the ∼4×∼4×∼70 nm3 in size, which are alternatively stacked in a way that the cross sectional and side views show chessboard and herringbone patterns, respectively. The strain induced by the Jahn-Teller distortion is discussed to result in this peculiar self-assembled nanostructure.
The rational assembly of ultrathin films of metal-organic frameworks (MOFs) —highly ordered microporous materials— with well-controlled growth direction and film thickness is a critical and as yet unrealised issue for enabling the use of MOFs in nanotechnological devices, such as sensors, catalysts, and electrodes for fuel cells. Here we explain our recent success of the facile bottom-up fabrication of such a perfect preferentially-oriented MOF nanofilm on a solid surface (NAFS-1), consisting of metalloporphyrin building units. The assembly of NAFS-1 was achieved by the unconventional integration in a modular fashion of a layer-by-layer (LbL) growth technique coupled with the Langmuir-Blodgett (LB) method. NAFS-1 is endowed with highly crystalline order both in the out-of-plane and in-plane orientations to the substrate, as determined by synchrotron X-ray surface crystallography. We expect that the versatility of the solution-based growth strategy presented here will allow the fabrication of various well-ordered MOF nanofilms, opening the way for their use in a range of important applications.