Structure properties of pyrolytic lignin extracted from aged bio-oil

Fast pyrolysis is a promising technology that can convert biomass into liquid.Bio-oil is one such product,known not only as a greenhouse gas-neutral energy source,but also an opportunity to reduce reliance on fossil fuels.Pyrolytic lignin,a fine homogeneous powder,is the water-insoluble fraction of bio-oil and it contributes to the instability of bio-oil.Additionally,pyrolytic lignin can be used in commercial materials such as adhesives in the wood-based panel industry.This paper presents the structural characterization of pyrolytic lignin extracted from aged bio-oil and the relationship between its properties and the treatment temperature of the aged bio-oil.Pyrolytic lignin samples were characterized by Fourier transform infrared spectroscopy,gel permeation chromatography,differential scanning calorimetry,thermogravimetric analysis and proton nuclear magnetic resonance spectroscopy.The average molecular weight of pyrolytic lignin increased from 700 to 1000 g/mol with increasing aging temperature (6-50°C).Differential scanning calorimetry showed that the glass transition temperature of pyrolytic lignin increases with lower heating rate and higher treatment temperature of bio-oil.An increase in the initial decomposition temperature and the temperature at 95 wt% weight loss of the aged pyrolytic lignin in thermogravimetry were observed for the bio-oil aged at higher temperature.An increase in residue weight of aged pyrolytic lignin was found in bio-oil aged at higher temperatures.     

N2O binding at a [4Cu:2S] copper-sulphur cluster in nitrous oxide reductase

Nitrous oxide (N(2)O) is generated by natural and anthropogenic processes and has a critical role in environmental chemistry. It has an ozone-depleting potential similar to that of hydrochlorofluorocarbons as well as a global warming potential exceeding that of CO(2) 300-fold. In bacterial denitrification, N(2)O is reduced to N(2) by the copper-dependent nitrous oxide reductase (N(2)OR). This enzyme carries the mixed-valent Cu(A) centre and the unique, tetranuclear Cu(Z) site. Previous structural data were obtained with enzyme isolated in the presence of air that is catalytically inactive without prior reduction. Its Cu(Z) site was described as a [4Cu:S] centre, and the substrate-binding mode and reduction mechanism remained elusive. Here we report the structure of purple N(2)OR from Pseudomonas stutzeri, handled under the exclusion of dioxygen, and locate the substrate in N(2)O-pressurized crystals. The active Cu(Z) cluster contains two sulphur atoms, yielding a [4Cu:2S] stoichiometry; and N(2)O bound side-on at Cu(Z), in close proximity to Cu(A). With the substrate located between the two clusters, electrons are transferred directly from Cu(A) to N(2)O, which is activated by side-on binding in a specific binding pocket on the face of the [4Cu:2S] centre. These results reconcile a multitude of available biochemical data on N(2)OR that could not be explained by earlier structures, and outline a mechanistic pathway in which both metal centres and the intervening protein act in concert to achieve catalysis. This structure represents the first direct observation, to our knowledge, of N(2)O bound to its reductase, and sheds light on the functionality of metalloenzymes that activate inert small-molecule substrates. The principle of using distinct clusters for substrate activation and for reduction may be relevant for similar systems, in particular nitrogen-fixing nitrogenase.     

Molecular mechanisms and clinical applications of angiogenesis

Blood vessels deliver oxygen and nutrients to every part of the body, but also nourish diseases such as cancer. Over the past decade, our understanding of the molecular mechanisms of angiogenesis (blood vessel growth) has increased at an explosive rate and has led to the approval of anti-angiogenic drugs for cancer and eye diseases. So far, hundreds of thousands of patients have benefited from blockers of the angiogenic protein vascular endothelial growth factor, but limited efficacy and resistance remain outstanding problems. Recent preclinical and clinical studies have shown new molecular targets and principles, which may provide avenues for improving the therapeutic benefit from anti-angiogenic strategies.     

Crystal structure of metarhodopsin II

G-protein-coupled receptors (GPCRs) are seven transmembrane helix (TM) proteins that transduce signals into living cells by binding extracellular ligands and coupling to intracellular heterotrimeric G proteins (Gαβγ). The photoreceptor rhodopsin couples to transducin and bears its ligand 11-cis-retinal covalently bound via a protonated Schiff base to the opsin apoprotein. Absorption of a photon causes retinal cis/trans isomerization and generates the agonist all-trans-retinal in situ. After early photoproducts, the active G-protein-binding intermediate metarhodopsin II (Meta?II) is formed, in which the retinal Schiff base is still intact but deprotonated. Dissociation of the proton from the Schiff base breaks a major constraint in the protein and enables further activating steps, including an outward tilt of TM6 and formation of a large cytoplasmic crevice for uptake of the interacting C terminus of the Gα subunit. Owing to Schiff base hydrolysis, Meta?II is short-lived and notoriously difficult to crystallize. We therefore soaked opsin crystals with all-trans-retinal to form Meta?II, presuming that the crystal's high concentration of opsin in an active conformation (Ops*) may facilitate all-trans-retinal uptake and Schiff base formation. Here we present the 3.0?? and 2.85?? crystal structures, respectively, of Meta?II alone or in complex with an 11-amino-acid C-terminal fragment derived from Gα (GαCT2). GαCT2 binds in a large crevice at the cytoplasmic side, akin to the binding of a similar Gα-derived peptide to Ops* (ref. 7). In the Meta?II structures, the electron density from the retinal ligand seamlessly continues into the Lys?296 side chain, reflecting proper formation of the Schiff base linkage. The retinal is in a relaxed conformation and almost undistorted compared with pure crystalline all-trans-retinal. By comparison with early photoproducts we propose how retinal translocation and rotation induce the gross conformational changes characteristic for Meta?II. The structures can now serve as models for the large GPCR family.     

Ascaris suum draft genome

Parasitic diseases have a devastating, long-term impact on human health, welfare and food production worldwide. More than two billion people are infected with geohelminths, including the roundworms Ascaris (common roundworm), Necator and Ancylostoma (hookworms), and Trichuris (whipworm), mainly in developing or impoverished nations of Asia, Africa and Latin America. In humans, the diseases caused by these parasites result in about 135,000 deaths annually, with a global burden comparable with that of malaria or tuberculosis in disability-adjusted life years. Ascaris alone infects around 1.2 billion people and, in children, causes nutritional deficiency, impaired physical and cognitive development and, in severe cases, death. Ascaris also causes major production losses in pigs owing to reduced growth, failure to thrive and mortality. The Ascaris-swine model makes it possible to study the parasite, its relationship with the host, and ascariasis at the molecular level. To enable such molecular studies, we report the 273 megabase draft genome of Ascaris suum and compare it with other nematode genomes. This genome has low repeat content (4.4%) and encodes about 18,500 protein-coding genes. Notably, the A. suum secretome (about 750 molecules) is rich in peptidases linked to the penetration and degradation of host tissues, and an assemblage of molecules likely to modulate or evade host immune responses. This genome provides a comprehensive resource to the scientific community and underpins the development of new and urgently needed interventions (drugs, vaccines and diagnostic tests) against ascariasis and other nematodiases.     

Color change characteristics of two shear-sensitive liquid crystal mixtures （BCN/192, BN/R50C） and their application in surface shear stress measurements

A previously determined surface shear stress measurement technique using shear-sensitive liquid crystal (SSLC) coating is extended for use in wind tunnel-like conditions. Simple and common everyday equipment is used in the measurement; in particular a tungsten halogen light bulb provides illumination. The color change characteristics of two SSLC mixtures, BCN192 and BN/ R50C, are investigated. BCN/192 is found sensitive to both magnitude and direction of the shear stress at different shear stress levels with little noise, and is suitable for surface shear stress distribution measurements. The spatial shear stress vector distribution beneath a tangential jet is obtained using BCN/192, although the magnitude is not fully calibrated. BN/R50C is found to be sensitive to shear stress magnitude, but only slightly sensitive to shear stress direction at both low and high levels. Moreover, jumps in the reflected hue are found when the viewing orientation is perpendicular to the shear stress direction. These characteristics render the use of BN/R50C for surface shear stress measurement difficult.