UV resonance Raman probe of heme-bound imidazole established by 15N-labeling of hemoglobin

Recent studies of Cu, Zn superoxide dismutase, and of zinc-finger peptides have established that histidine ligands can be detected in ultraviolet resonance Raman (UVRR) spectra, following NH/D exchange of the imidazole. UVRR spectroscopy therefore offers promise for monitoring histidine ligation in heme proteins. In this work, we characterize heme-bound histidine UVRR bands for N-acetyl-microperoxidase-8 (MP-8) and microperoxidase-11 (MP-11), and also for hemoglobin (Hb). The Hb UVRR spectra are dominated by tyrosine and tryptophan contributions, but a band appears at 1340 cm⁻¹ in D₂O solution, which is assigned to a mode of Fe-bound imidazole. This band shifted 24 cm⁻¹ in protein which was labeled with ¹⁵N via expression of the Hb gene in E. coli grown on ¹⁵NH₄⁺. In MP-11, the position of this band is insensitive to ligation or oxidation state changes, but it is 2 cm⁻¹ lower in deoxyHb than in the CO adduct. This shift may reflect mechanical forces on the proximal histidine in the T state, and/or changes in its H-bonding.     

Mass spectrometry in viral proteomics

Mass spectrometry is a valuable tool in structural and functional viral proteomics, where it has been used to identify viral capsid proteins, viral mutants, and posttranslational modifications. Further, mass-based approaches combined with time-resolved proteolysis (mass mapping) have revealed the dynamic nature of viral particles in solution; this method is contributing to an understanding of the dynamic domains of the viral capsid which may have significant value in developing new approaches for viral inactivation. As a result of these experiments, and by comparison with complementary data from X-ray crystallography, a new dimension to viral protein structure and function is emerging.     

Production Of Ozone in an Electrical Discharge Using Inert Gases as Catalysts

The catalytic role of using inert gases to increase the efficiency and lower the power cost of producing ozone (O₃) from high purity oxygen (O₂) in a process incorporating an electrical discharge is demonstrated. Three inert gases (Ar, Ne, He) and N₂ are individually mixed with O₂ and the results presented. The increase in ozone production is partially attributed to the increase in electron density provided by the ionization of the inert gas in the discharge.     

Steady bi‐directional drag flow of non‐newtonian liquids in shallow channels

This paper reexamines the analytical framework for the steady, fully developed two‐dimensional flow in shallow channels, typical of screw extruders, and provides comprehensive solution sets for the Carreau‐Yasuda and the Ostwald‐deWaele model fluids. An application example for polymethylmethacrylate (PMMA) is included to compare the relative merits of the two models under specific extrusion conditions. The Ostwald‐deWaele model, standard in engineering practice, can produce gross misrepresentations of the flow in extruder channels. Particularly, when dealing with highly shear‐sensitive polymers, n < 0.3, or polymers with extended Newtonian plateau, ∧ ～ 1, the Carreau‐Yasuda model becomes preferable. The inclusion of the Carreau model does not necessarily add to the complexity of the analysis.     

Effect of Thermal Treatment on the Photocatalytic Activity in Visible Light of TiO<Subscript>2</Subscript>-W Flame Spray Synthesised Nanopowders

Effect of W doping as well as a thermal treatment on the structural and photocatalytic properties of TiO₂ produced by flame spray synthesis (FSS) were the subject of investigation. Structural properties were studied by means of X-ray diffraction (XRD), BET adsorption isotherm and transmission electron microscopy (TEM). The surface condition was investigated by X-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC) and differential thermal and thermogravimetric analysis (DTA-TGA). The photocatalytic properties were studied by optical measurements and photodecomposition of methylene blue under visible irradiation. It was found that the photoactivity in the visible region was enhanced significantly by the W-doping as well as by additional thermal treatment of those nanopowders. The obtained TiO₂-W nanopowders exhibited higher performance under visible light than P25.     

Defensive secretion of the carabid beetlePasimachus subsulcatus

The defensive secretion of the carabid beetlePasimachus subsulcatus is a concentrated solution (up to 90%) of carboxylic acids, amounting to about 1% of body mass. It contains three major components (methacrylic, tiglic, and angelic acids) and four minor components (isobutyric, 2-methyl-butyric, isovaleric, and senecioic acids). In the single population of this large flightless beetle that was examined, the relative ratio of acidic components was remarkably constant from individual to individual.Report No. 87 of the series Defense Mechanisms of Arthropods; No. 86 is Dussourd, D., et al.,Proc. Natl. Acad. Sci. 85, 5992 (1988).     

Ruffed grouse feeding behavior and its relationship to secondary metabolites of quaking aspen flower buds

Quaking aspen (Populus tremuloides Michx.) staminate flower buds and the extended catkins are primary food resources for ruffed grouse (Bonasa umbellus). Winter feeding observations indicate that ruffed grouse select specific trees or clones of quaking aspen to feed in. Flower buds and catkins of quaking aspen were analyzed for secondary compounds (tannins, alkaloids, and phenolics) that might cause ruffed grouse to avoid trees with high levels of these compounds. Coniferyl benzoate, a compound that has not been previously found in quaking aspen, exists in significantly higher concentrations in buds from trees with no feeding history as compared to ruffed grouse feeding trees. Aspen catkins were also significantly lower in coniferyl benzoate than buds from the same tree. Ruffed grouse feeding preference was not related to the tannin or total phenolic levels found in buds or catkins. Buds from feeding trees had higher protein levels than trees with no feeding history; however, catkins did not differ from buds in protein concentration. The high use of extended catkins in the spring by ruffed grouse is probably due to a lower percentage of bud scale material in the catkin as opposed to the dormant bud. Bud scales contain almost all of the nontannin phenolics in catkins and dormant buds. A feeding strategy where bud scales are avoided may exist for other bird species that feed on quaking aspen. Dormant flower buds are significantly lower in protein-precipitable tannins than catkins and differ in secondary metabolite composition from other aspen foliage.Minnesota Agriculture Experiment Station Journal Series No. 16,953.     

Increased plasma triglyceride secretion in EFA-deficient rats fed diets with or without saturated fat

Metabolic responses to essential fatty acid-deficiency in rats include an increased rate of triglyceride secretion into the plasma, a large reduction in the HDL₁ plasma lipoprotein concentration, and increased concentrations of liver triacylglycerols and cholesteryl esters. Because of differences in the types of EFA-deficient diets used, it is not clear whether these responses were solely due to the absence of EFA from the diet or whether saturated fat, or differences in acyl group chain length in this fat, might be responsible. Therefore, we fed rats diets differing only in amounts and kinds of fat, and measured triacylglycerol secretion rates and liver concentrations of triacylglycerols and cholesteryl esters, for comparison with our earlier measurements of plasma high density lipoprotein subpopulations in rats fed exactly the same diets. The purified diets contained either no fat, 5% by weight hydrogenated coconut oil, 5% hydrogenated cottonseed oil, or each of these three diets supplemented with 1% safflower oil, or 5% corn oil. We also fed some rats a nonpurified stock diet for comparison with literature reports. The present results indicate that the metabolic responses to essential fatty acid deficiency described above are definitely due to essential fatty acid-deficiency and not to the presence or chain length of acyl groups in saturated fat in the diet. Presented in part at the May 1984 meeting of the American Oil Chemists' Society in Dallas, Texas.