Direct spectrophotometric assay of laccase using diazo derivatives of guaiacol

Laccase (EC 1.10.3.2) is a widespread cuproenzyme able to oxidize various types of phenols and similar aromatic compounds through a one-electron transfer mechanism. The enzyme has already found its way into the market as a biocatalyst. Because of its ability to be paired by electron mediators, the expectation for employing laccases in versatile processes is very high. There are a few spectrophotometric methods for assaying the laccase activity; however, all of them are based on the formation of product(s) resulting from the enzymatic and inevitable succeeding chemical reactions. Use of diazo derivatives of guaiacol (DdG) was developed as a new spectrophotometric method based on substrate depletion allowing direct assessment of enzyme activity has been introduced. This method allows accurate comprehensive kinetic studies of laccases and provides reliable information about the quality of docking of different substrates or one substrate to the active sites of different laccases. Using this method, the kinetic parameters of various DdG carrying different electron donating and withdrawing substituents were used to assay laccase from Neurospora crassa. 2-Methoxy-4-[(4-phenyl)azo]-phenol (K(m) = 93.5 μM and V = 1.98 μM/min) was identified as an appropriate substrate for the accurate and routine spectrophotometric based assay of laccases.     

The Liquidus Temperature of Nuclear Waste Glasses: An International Round-Robin Study

Eight institutions from four countries participated in a round-robin study to determine the precision and bias of a liquidus temperature (T_L) procedure for waste glasses being adopted by ASTM International as ASTM C 1720-11. The participants of the round-robin study were asked to measure three different glasses with one or a combination of the following T_L measurement methods: a gradient temperature (GT) method, a uniform temperature (UT) method, and/or a crystal fraction extrapolation (CF) method. The T_L values reported by different institutions are generally consistent. The precision of T_L measurements with each method was evaluated and is presented herein. The round-robin glasses were all previously studied at Pacific Northwest National Laboratory and included ARG-1 (Glass A), Zr-9 (Glass B), and AmCm2-19 (Glass C), with measured T_L values spanning the temperature range of 960–1240°C. A precision (i.e., standard deviation) for T_L has been obtained from the data, even though the data were not acquired for all three glasses using all three methods from each participating organization. Also, the article provides a brief overview and the importance of the T_L measurement.     

Effect of sucrose on foaming and melting behavior of a low-activity waste melter feed

Reductants, such as sucrose (C₁₂H₂₂O₁₁), are added to nuclear waste melter feeds containing high fractions of nitrates and nitrites to reduce excessive foaming during feed-to-glass conversion, decrease sulfate segregation, and increase technetium retention. The effect of sucrose on foaming and melting reactions during the conversion was examined using the feed volume expansion test, thermogravimetric analysis, evolved gas analysis, x-ray diffraction, and scanning electron microscopy with energy dispersive x-ray spectrometry. Different amounts of sucrose were added to vary the carbon to nitrogen (C/N) ratio in the melter feed. As the C/N ratio increased, the extent of foaming decreased, and the N₂/NO ratio increased in the evolved gas. Significant foam suppression, rapid gas release at approximately 250°C, and reduction in transition metal oxides were observed at C/N > 1.1.     

Investigating the degradation resistance of silicone-acrylate containing automotive clearcoats exposed to bird droppings

This work reports preparation of acrylic/melamine based clearcoats containing various loads of a reactive polysiloxane additive. The additive was incorporated into the clearcoat formulations up to 8 wt% to enhance its resistance against bird droppings. Contact angle measurements, ATR spectroscopy, energy dispersive X-ray analysis, appearance measurements together with different microscopic techniques were utilized to reveal the effects of additive on the properties of the coating prior and after exposure to pancreatin, the synthetic equivalent of natural bird droppings. Appearance measurements, as well as optical microscope images obviously indicated that the additive improved the clearcoats resistance against pancreatin. Results revealed that surface free energy of the films was reduced in the presence of additive. It was also found that at high concentrations of additive, a significant part of it remained in the bulk, forming a second phase. This resulted in a lack of sufficient reactive groups and lead to an under-cure state at the clearcoat surface.     

Controlled Generation of Solid Spheroidal Dielectric Microparticles

Our recent research has been pioneering the generation of single solid particles with adjustable eccentricity. This new technique permits the production of particles in the range of 200 w m to 2 mm and an approximate eccentricity of 1:1.2 to 1:1.8 along an axis. Single droplets consisting of multiacrylate monomers were levitated by an ultrasonic levitator and were cured by UV illumination after adjusted eccentricity. For special applications we can produce particles that are attached to a stem (optical fiber), which allows a controlled orientation of the particle. One possible application for such particles is the investigation of light scattering on nonspherical particles.     

Determination of Temperature‐Dependent Heat Conductivity and Thermal Diffusivity of Waste Glass Melter Feed

The cold cap is a layer of reacting glass batch floating on the surface of melt in an all‐electric continuous glass melter. The heat needed for the conversion of the melter feed to molten glass must be transferred to and through the cold cap. Since the heat flux into the cold cap influences the rate of melting, the heat conductivity is a key property of the reacting feed. We designed an experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples (TC) that monitors the evolution of the temperature field while the crucible is heated at a constant rate. Then we used two methods to calculate the heat conductivity and thermal diffusivity of the reacting feed: the approximation of the temperature field by polynomial functions and the finite‐volume method (FVM) coupled with least‐squares analysis. Up to 680°C, the heat conductivity of the reacting melter feed was represented by a linear function of temperature.     

Estimating surface radiation fluxes in the Arctic from TOVS brightness temperatures

A new method for estimating downwelling shortwave and longwave radiation fluxes in the Arctic from TOVS brightness temperatures has been developed. The method employs a neural network to bypass computationally intensive inverse and forward radiative transfer calculations. Results from two drifting ice camps (CEAREX, LeadEx) and from one coastal station show that downwelling fluxes can be estimated with r.m.s. errors of 20Wm-2 for longwave radiation and 35Wm-2for shortwave radiation. Mean errors are less than 4 Wm-2 and are well within the bounds required for many climate process studies.     

Novel hexarelin analogs stimulate feeding in the rat through a mechanism not involving growth hormone release

Growth hormone-releasing peptides (GHRPs) are a class of small peptides that stimulate growth hormone (GH) release in several animal species, including the human. Moreover, GHRPs injected into the brain ventricles stimulate feeding in the rat. The aim of this study was to evaluate the GH-releasing properties of a series of novel GHRP analogs and the possible existence of functional correlations between the GH-releasing activity and the effects on feeding behavior. Two well-known hexapeptides, GHRP-6 and hexarelin, given s.c., dose dependently stimulated both GH release and feeding behavior in satiated rats. However, in a series of tri-, penta- and hexapeptide analogs of hexarelin, some compounds were active either on GH release or on eating behavior. Interestingly, even minor structural modifications resulted in major changes of the pharmacological profile. We conclude that GHRPs have orexigenic properties after systemic administration which are largely independent from the effects they exert on GH release.