Carbon Monoxide Dehydrogenase Reduces Cyanate to Cyanide

The biocatalytic function of carbon monoxide dehydrogenase (CODH) has a high environmental relevance owing to its ability to reduce CO₂. Despite numerous studies on CODH over the past decades, its catalytic mechanism is not yet fully understood. In the present combined spectroscopic and theoretical study, we report first evidences for a cyanate (NCO⁻) to cyanide (CN⁻) reduction at the C-cluster. The adduct remains bound to the catalytic center to form the so-called CN⁻-inhibited state. Notably, this conversion does not occur in crystals of the Carboxydothermus hydrogenoformans CODH enzyme (CODHII_Ch), as indicated by the lack of the corresponding CN⁻ stretching mode. The transformation of NCO⁻, which also acts as an inhibitor of the two-electron-reduced C_red2 state of CODH, could thus mimic CO₂ turnover and open new perspectives for elucidation of the detailed catalytic mechanism of CODH.     

Effect of Gd-EOB-DTPA on hepatic fat quantification using high-speed T2-corrected multi-echo acquisition in H MR spectroscopy

Purpose

To determine whether gadolinium ethoxybenzyldiethylenetriaminepentaacetic acid (Gd-EOB-DTPA) administration affects hepatic fat quantification by magnetic resonance spectroscopy (MRS) using the fast breath-hold high-speed T2-corrected multiecho (HISTO) technique.

Materials and Methods

Seventy-six patients underwent Gd-EOB-DTPA-enhanced liver MR and 15 sec breath-hold HISTO MRS (4 times), twice before and twice after Gd-EOB-DTPA administration. Two consecutive MRSs were performed immediately before the dynamic study. Post-contrast MRS was performed twice continuously, approximately 15 min after contrast injection, prior to obtaining 20-min hepatobiliary phase images. We used paired t-test and intraclass correlation coefficient (ICC) to evaluate the variability of the mean fat fraction (FF) on pre-contrast MRS and post-contrast MRS and the effect of the contrast agent on the mean FF.

Results

The mean FFs were not significantly different between pre-contrast MRS and post-contrast MRS (6.50% ± 6.54 versus 6.70% ± 6.61, P = 0.15). The ICC of FF calculation between pre- and post-contrast MRS was 0.984. The ICCs for the FF magnitude between pre- and post-contrast MRS were 0.452, 0.771, and 0.995 for FF < 5%, FF 5–10%, and FF ≥ 10%, respectively.

Conclusion

Gd-EOB-DTPA does not appear to influence hepatic fat quantification, especially for patients with hepatic steatosis.     

Silicon substrate temperature effects on surface roughness induced by ultrafast laser processing

We report the effect of substrate temperature (T_sub) in the range 300-900 K on the surface roughness of silicon wafer resulted from femtosecond laser ablation. The surface roughness observed at the laser fluences less then 0.3 J/cm² increases with increasing T_sub. However, the surface roughness decreases with increasing T_sub for the laser fluences between 0.5 and 1.0 J/cm². If the laser fluence is higher than 2.0 J/cm², the surface roughness is independent of T_sub. The effect of T_sub on the surface roughness can be understood in terms of the temperature dependence of optical absorption coefficient of silicon substrate, which eventually alters a mechanism underlying the fs-laser-material ablation process between optical penetration and thermal diffusion processes.     

The influence of substrate temperature on femtosecond laser micro-processing of silicon,stainless steel and glass

We report the influence of substrate temperature on femtosecond laser ablation of silicon, stainless steel, and glass. Remarkable decrease in surface roughness was observed under high substrate temperature for silicon and stainless steel. While the ablation efficiency of glass as a typical wide band-gap material is scarcely altered at 900 K, the efficiency for stainless steel as a conductor apparently increased about 20% accompanied to the elevation of substrate temperature from 300 to 900 K. Silicon wafer results in slight increase of the ablation efficiency with decreasing the ablation threshold. Considering that the melting temperature of glass is much lower than those of silicon and steel, the observations from this work suggests that the material ablation caused by the ultrafast laser irradiation could not be explained in term of only laser-induced thermal excitation.     

Effects of plasma treatments on correlation between chemical structures of DLC films and liquid crystal alignment

In an effort to obtain an improved liquid crystal (LC) alignment layer for liquid crystal display device applications, amorphous diamond‐like carbon thin films were deposited on ITO‐coated glass substrates by an rf magnetron sputtering technique at room temperature and then treated with plasma in various atmospheres. The polarized images and pretilt angles of the LC cells showed that LC alignment was enhanced by post‐plasma treatments of the films. In Raman and X‐ray photoelectron spectroscopy spectra of the films, an increase in the fraction of sp²‐bonding was observed after post‐plasma treatments of the films. In particular, H₂ plasma‐treated film had the largest fraction of sp²‐bonding at the film surface and showed much improved alignment capabilities. These results suggest that π‐bondings of the sp²‐structure at the surface rather than the bulk play an important role in LC alignment.     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

A Hydrogen‐Bonded Organic Framework (HOF) with Type IV NH3 Adsorption Behavior

An S‐shaped gas isotherm pattern displays high working capacity in pressure‐swing adsorption cycle, as established for CO₂, CH₄, acetylene, and CO. However, to our knowledge, this type of adsorption behavior has not been revealed for NH₃ gas. Herein, we design and characterize a hydrogen‐bonded organic framework (HOF) that can adsorb NH₃ uniquely in an S‐shape (type IV) fashion. While conventional porous materials, mostly with type I NH₃ adsorption behavior, require relatively high regeneration temperature, this platform which has significant working capacity is easily regenerated and recyclable at room temperature.     

Stimuli responsive surfaces through recognition-mediated polymer modification

Specific three-point hydrogen bonding between diamidopyridine (DAP) and thymine (Thy) was employed to reversibly anchor "brush-like" Tri-DAP end-functionalized polystyrene onto Thy-modified silica surfaces.     

Effects of high taurocholate load on activities of hepatic alcohol metabolizing enzymes

Membrane-associated cytotoxicity induced by hydrophobic bile salts is a major contributing factor leading to liver diseases. Administration of ursodeoxycholate reduces serum liver enzymes in chronic liver diseases but the nature of this effect is still unclear. Using alcohol metabolising enzymes as cellular markers, the hepatotoxic properties of hydrophobic bile salts and the putative hepatoprotective effect of ursodeoxycholate was examined. Two animal models of biliary retention, bile duct obstruction and choledochocaval fistula was used to investigate the effect of taurocholate on the hepatic alcohol metabolizing enzymes: cytosolic alcohol dehydrogenase, microsomal ethanol oxidizing system, catalase and aldehyde dehydrogenase before and after the infusion of taurocholic acid or tauroursodeoxycholic acid for two days period. Bile duct obstruction was found to be similar to or slightly exceeds choledochocaval fistula in the degree of retention. Following the taurocholic acid infusion, the serum alcohol dehydrogenase activity as well as microsomal ethanol oxidizing system and aldehyde dehydrogenase were greatly increased but the level of cytosolic alcohol dehydrogenase and catalase activities was found to be lower in either or both models in comparison with the control animals. However, the tauroursodeoxycholic acid infusion did not induce any significant changes in the levels of all the alcohol metabolizing enzyme activities in either or both models. These findings suggest that hydrophobic taurocholic acid (7alpha) affects the plasmalemma to allow leakage of cytosolic alcohol dehydrogenase into the blood circulation, stimulates the biosynthesis of microsomal ethanol oxidizing system and aldehyde dehydrogenase, and suppresses the biosynthesis of alcohol dehydrogenase and catalase. But in contrast, the hydrophilic tauroursodeoxycholic acid (7beta) provided hepatoprotective effect.