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Electric arc furnaces (EAFs) are used for steel production, particularly when recycling scrap material. In EAFs, carbonaceous material is charged with other raw materials or injected into molten slag to generate foam on top of liquid metal to increase energy efficiency. However, the consumption of fossil carbon leads to greenhouse gas emissions (GHGs). To reduce net GHG emissions from EAF steelmaking, the substitution of fossil carbon with sustainable biogenic carbon can be applied. This study explores the possibility of the substitution of fossil material with biogenic material produced by different pyrolysis methods and from various raw materials in EAF steelmaking processes. Experimental work was performed to study the effect of biogenic material utilization on steel and slag composition using an induction melting furnace with 50 kg of steel capacity. The interaction of biogenic material derived from different raw materials and pyrolysis processes with molten synthetic slag was also investigated using a tensiometer. Relative to other biogenic materials tested, a composite produced with densified softwood had higher intensity interfacial reactions with slag, which may be attributed to the rougher surface morphology of the densified biogenic material.

The effect of organic liquids (white spirit, perchloroethylene and methylene bromide) typically used in float/sink gravity separations (specific gravity 1.4–1.8) on the fundamental properties of a higher-inert Western Canadian metallurgical coal of mvb rank (Romax 1.22) and its resultant coking ability were examined. Over a 6-month period, untreated (control) and treated coal were characterized using a wide range of analyses including elemental chemistry, FTIR spectroscopy, alkali extraction via light transmittance test and thermal rheology, specifically fluidity, Dilatation, FSI and Caking Index G. Exposure to organic liquids was found to have a minor effect on coal chemistry (Ultimate) and oxidation level (Alkali Extraction via Light Transmission Test and FTIR-Spectroscopy). Trends of H/C, O/C, Light Transmittance and FTIR absorbance spectra versus storage time, following initial 1 h exposure to the organic liquids of varying specific gravities, revealed only minor changes, within the scatter/accuracy of the measurements. However, several coal plastic properties were decreased significantly including Gieseler Maximum Fluidity, Dilatation and G Caking Index. Of these, most affected was Maximum Fluidity which underwent an immediate and dramatic decrease of over 80% following organic liquids treatment. Other rheology indicators including FSI and Sapozhnikov were significantly less sensitive in detecting initial stages of degradation in plastic properties. The coking ability of both the untreated and treated coal in perchloroethylene (PCE) organic liquid, s.g. 1.6, after storage for 1 and 6 months was assessed through carbonization trials in both a small-scale sole-heated oven (12.5 kg capacity) and in a pilot-scale movable wall oven (350 kg capacity) at CanmetENERGY Carbonization facility, Ottawa, Canada. The treated samples had appreciably poorer quality ambient (ASTM, IRSID, JIS tumbler tests) and hot (CSR, CRI) coke strength and modified coke structure. Coke ASTM strength for untreated and treated coal at time 1 month was respectively decreased from 62 down to 57 for Stability and from 72 to 67 for Hardness. Similarly, Coke CSR and CRI for untreated and treated coal at time 1 month was respectively decreased from 74 down to 58 and increased from 21 to 29. The treated sample resulted in a lower coke yield, 71%, in comparison with 78% for the untreated sample, produced coke of smaller mean size, 46 mm, than the untreated sample, 53 mm, and generated an appreciably higher fraction of fines (− 12.5 mm), 21%, than untreated sample, 4%. The coke textures from the untreated coal consist of higher carbon forms, mosaic and flow in medium size, compared to those from s.g. 1.6 treated coal of lower carbon forms, very fine and fine mosaic, which renders the coke more reactive to CO2 gasification during CSR test. The higher effective coking rank, 1.2, and Coke Mosaic Size Index, 2.4, of untreated sample relative to that of treated one, 1.1 and 2.2, respectively, supports the better coke quality of the untreated sample. Extension of storage time to 6 months resulted in negligible changes in coke quality showing that the greatest changes occurred within the first month following exposure to organic liquids. Comparison of 1 month untreated and PCE treated mid coking rank Western Canadian (Romax 1.22) and Australian (Romax 1.17) coals show both to undergo comparable decrease in fluidity (50–60%) post treatment with PCE although only the Western Canadian coal leads to lower dilatation. Coke yield is also decreased for the Western Canadian coal and essentially maintained for the Australian coal. Both CSR and CRI are affected negatively and more so for the Western Canadian coal, 16 point drop in CSR and 8 point increase in CRI, relative to the Australian coal, 3 point drop in CSR and 4 point increase in CRI.

Using archival data from the Chandra X-ray telescope, we have measured the spatial extent of the hot interstellar gas in a sample of 49 nearby interacting galaxy pairs, mergers, and merger remnants. For systems with SFR > 1 M(sun)/yr, the volume and mass of hot gas are strongly and linearly correlated with the star formation rate (SFR). This supports the idea that stellar/supernovae feedback dominates the production of hot gas in these galaxies. We compared the mass of X-ray-emitting hot gas Mx(gas) with the molecular and atomic hydrogen interstellar gas masses in these galaxies (M(H2) and M(HI), respectively), using published carbon monoxide and 21 cm HI measurements. Systems with higher SFRs have larger Mx(gas)/(M(H2) + M(HI)) ratios on average, in agreement with recent numerical simulations of star formation and feedback in merging galaxies. The Mx(gas)/(M(H2) + M(HI)) ratio also increases with dust temperature on average. The ratio Mx(gas)/SFR is anti-correlated with the IRAS 60 micron to 100 micron flux ratio and with the Spitzer 3.6 micron to 24 micron. These trends may be due to variations in the spatial density of young stars, the stellar age, the ratio of young to old stars, the initial mass function, and/or the efficiency of stellar feedback. Galaxies with low SFR (, Astronomical Journal, in press

With the emergence of wide-spread application of new optical techniques to monitor δ13C in atmospheric CO2 there is a growing need to ensure well-calibrated measurements. We characterized one commonly available instrument, a cavity ring-down spectrometer (CRDS) system used for continuous in situ monitoring of atmospheric 13CO2. We found no dependency of δ13C on the CO2 concentration in the range of 303–437 ppm. We designed a calibration scheme according to the diagnosed instrumental drifts and established a quality assurance protocol. We find that the repeatability (1-σ) of measurements is 0.25‰ for 10 min and 0.15‰ for 20 min integrated averages, respectively. Due to a spectral overlap, our instrument displays a cross-sensitivity to CH4 of 0.42 ± 0.024‰ ppm−1. Our ongoing target measurements yield standard deviations of δ13C from 0.22‰ to 0.28‰ for 10 min averages. We furthermore estimate the reproducibility of our system for ambient air samples from weekly measurements of a long-term target gas to be 0.18‰. We find only a minuscule offset of 0.002 ± 0.025‰ between the CRDS and Environment Canada's isotope ratio mass spectrometer (IRMS) results for four target gases used over the course of one year.

Incorporation of biomass-derived materials in coal blends for cokemaking is one of the strategies that could reduce the levels of greenhouse gas emissions produced by the steelmaking process. Bio-coke refers to the resultant coke prepared with the addition of charcoal to a coal blend. In this work, characteristics of bio-coke gasification by reacting with CO 2 were examined using Thermal Gravimetric Analysis. Bio-coke samples with different levels of charcoal addition to a coal blend were prepared in the CanmetENERGY pilot-scale coke oven. These samples were heated in CO 2 for identification of the minimum gasification temperature. Sample gasification rates at 1000 °C were also measured. It was observed that mineral content plays an important role in the gasification characteristics of the bio-cokes. Those with low mineral content behave very similarly to the reference coke. Higher mineral content bio-coke reacts with CO 2 at a lower temperature. It was found that the gasification characteristics of the bio-cokes are well described by the alkalinity index.

Processes involving biomass oxidation are considered to be CO 2 neutral since the replenishing of the biomass by normal growth will remove CO 2 from the atmosphere. Thus the use of charcoal in the production of metallurgical coke, to be used as a reducing agent in the formation of iron, would be a strategy for the reduction of CO 2 in the overall ironmaking process. This paper describes experimental attempts to produce industrial grade coke from coking coal blends to which are added amounts of charcoal up to 10%. Coking experiments were carried out partly in a 30 lb coke oven and partly in a sole heated oven. The influence of blend composition, heating rates and charcoal particle size was investigated. Cokes made using fine charcoal addition (− 60 mesh) were considerably weaker than cokes made from the base blend. This is interpreted to be the effect of the ash constituents in the charcoal which, among other things, contains much higher calcium than the coals used. However, carefully sized fractions of coarse charcoal (− 3/8 + 1/4 in) produced much higher quality coke, possibly the result of a different dispersion of the charcoal mineral components.

A Victorian lignite, designated Loy Yang low ash, run of mine (LYLA (R)) has been dewatered using mechanical thermal expression (MTE) at 150–200 °C and 6–25 MPa and by hydrothermal dewatering (HTD) at 200–300 °C and the products compared. Total acidity values for all samples as measured by a pyrolysis thermogravimetric Fourier transform infrared (TG–FTIR) method were similar to those measured by barium ion exchange. Stronger (carboxylic) acid values determined by pyrolysis TG–FTIR tended to be lower than ion exchange values, except for the 300 °C HTD sample, for which both methods gave similar values although these were much lower than at all of the other treatment temperatures. Equilibrium moisture contents (EMC) for the MTE products and the 200 °C HTD product were similar to those of the original lignite at relative vapour pressure (RVP) ⩽ 52%, but lower at RVP 92%. EMC values for 300 °C HTD products were all lower than for the original lignite, indicating that processing temperature was the most important factor in determining these properties. CO 2 adsorption surface area was also mainly a function of processing temperature, decreasing with increasing temperature. However, the pore volume as determined by mercury porosimetry was influenced by whether dewatering was effected by MTE or HTD, the mechanical pressure applied in the MTE process resulting in a lower porosity.

This paper attempts to relate oxygen-containing gases H2O, CO2, and CO evolved during pyrolysis of the Argonne premium coals to oxygen-containing functional groups as a function of rank. Our approach to functional group analysis of oxygen-containing species in coal has been to use a pyrolysis technique, thermogravimetric Fourier transform infrared spectroscopy (TG−FTIR), involving thermogravimetric analysis with the measurement of the gaseous decomposition products via IR detection. Under suitable heating conditions, TG−FTIR pyrolysis of a coal sample in a stream of inert gas has been shown to expel quantitatively all of the organic oxygen in the form of H2O, CO2, and CO, and consequently, this technique can be effectively applied for determining the total oxygen content. Focusing on the Argonne premium coals, which cover a wide range in rank between lignite (Ro = 0.25) and low-volatile bituminous (Ro = 1.68), TG−FTIR provided complex pyrolysis profiles of oxygen-containing gases, which yield information ...

A study was undertaken with the aim of finding the best practical way of storing small coal samples in a laboratory setting to limit their extent of oxidation for maintaining good thermal rheological properties. Samples of a Canadian medium-volatile bituminous coal of Cretaceous age (‘as received’ and Chemical changes including O content, O / C, H / O, H / C, Volatile Matter, and Calorific Value; Thermal Rheological changes in Fluidity, Plastic range, Dilatation, Free-Swelling Index and Alkali Light Transmittance. Coke Quality changes in Coke Cake Contraction, Coke Reactivity and Coke Strength indices as well as Coke Optical Textures were also examined. For chemistry related changes, the most obvious ones due to oxidation are in atomic oxygen, which increases, and calorific value, which decreases. Concerning thermal rheology changes, fluidity and dilatation were found to decrease the most whereas Free-Swelling Index and Alkali Light Transmittance do not appear to be sensitive indicators of early stages of oxidation for the examined coal. Pertaining to coke quality, coke cake contraction remains essentially unchanged, Coke Strength after Reaction decreases and Coke Reactivity Index increases, and textures reveal a significant increase in coke inerts. This work has found coal oxidation to be mainly influenced by the storage temperature, with rate of oxidation increasing with temperature, and to a lesser extent by particle size, with oxidation being more likely the smaller the particle size. Of the different storage conditions tested in this investigation, keeping coal at cold temperatures (

Thermogravimetric-Fourier transform infrared (TG-FTIR) studies, using a ramp rate of 30 °C/min, have been used to determine the total acidity and carboxylic acid contents for a range of lignites from the Latrobe Valley coal fields, Vic., Australia, some of which were also studied in water- and acid-washed form. The results are compared with values determined by barium ion-exchange. Total acidities from barium ion-exchange showed good agreement with those determined from the total amount of CO+CO 2 evolved. The carboxylic acid content determined from the amount of CO 2 evolved in pyrolysis showed a good correlation with the concentration of stronger acid functional groups determined by barium ion-exchange, but was lower. The effect of ion-exchange with Na, Mg, Ca and Al on CO, CO 2 , pyrolysis H 2 O and hydrocarbon gas production, as well as on the relative yields of these different gases, was similar to that observed by earlier workers for pyrolysis over much longer run times.

During rapid pyrolysis of coal, TG–FTIR (thermogravimetry – Fourier transform infrared) technique can be effectively used to simultaneously detect and measure the three main O-containing gases, namely H 2 O, CO and CO 2 . Their sum corresponds to the quantitative amount of oxygen in the coal and is, in general, inherently more accurate than the ‘by-difference’ values. In this paper, we first attempt to relate the ‘by-difference’ values for %O reported for the Argonne premium coal samples (lignite to bituminous rank) (Argonne Users Handbook) to those determined from a TG–FTIR examination of the pyrolysis gases evolved. Another objective of the work is to relate the pyrolysis gases (H 2 O, CO and CO 2 ) evolved to oxygen-containing functional groups found in coals as well as the evolution of these functional groups as a function of rank. Correlations are also developed between the TG–FTIR oxygen values and other parameters determined for the Argonne Premium Coals. In particular, comparisons of our results using TG–FTIR with analyses carried out by other workers on functional group analysis of acidic groups are considered.

The natural oxidation/weathering of coal continues to be a subject of interest both scientifically and industrially, in part due to the complexity of the molecular processes at hand as well as to the commercial implications involved. It is widely recognized that coking can be adversely affected by weathering whereas, combustion processes appear to be enhanced as result of oxidation. Combustion techniques are commonly used in the analysis of coal, and organic compounds in general, for the determination of elemental hydrogen, carbon and nitrogen. For oxygen, the method in common practice involves the determination by difference from directly determined values for moisture, ash, sulphur, hydrogen, carbon and nitrogen. This has led us to consider the use of thermogravimetry coupled to gas analysis by infrared spectroscopy (TG-FTIR) to measure organic oxygen in coal directly. Although this technique, developed by Solomon and coworkers, has been extensively used by our group and others, it appears not to have been considered for this particular purpose. Recently, we have shown that TG-FTIR is capable of measuring all the organic oxygen in both fresh and oxidized coal by simultaneous measurement of the three main oxygen-containing gases H2O, CO and CO2 evolved during rapid pyrolysis. This gives us a way of measuring quantitatively the oxygen introduced into the coal matrix during oxidation and at least a partial capability of establishing oxygen speciation. We have found, using TG-FTIR, that the early stages of coal oxidation results in the appearance of O-containing functional groups not present in the original coal. The nature of these functional groups is directly related to the oxidation reaction mechanism. These results will be presented and discussed in detail.

Thermogravimetry with Fourier Transform Infrared Analysis (TG-FTIR) has been used to measure the organic oxygen content in a suite of coals of differing rank and compare these with the values determined by difference according to ASTM D3176-89. Two coking coals, one Cretaceous and one Carboniferous, were oxidized at 50 °C to simulate natural weathering and analyzed for their oxygen content by both techniques. Results indicate that the pyrolysis technique is reliable and rapid and is free of the large possible errors inherent in the determination of organic oxygen content by difference.

Partitioning of volatile organic compounds (VOCs) into surfactant micelles affects the apparent vapor−liquid equilibrium of VOCs in surfactant solutions. This partitioning will complicate removal of VOCs from surfactant solutions by standard separation processes. Headspace experiments were performed to quantify the effect of four anionic surfactants and one nonionic surfactant on the Henry's law constants of 1,1,1-trichloroethane, trichloroethylene, toluene, and tetrachloroethylene at temperatures ranging from 30 to 60 °C. Although the Henry's law constant increased markedly with temperature for all solutions, the amount of VOC in micelles relative to that in the extramicellar region was comparatively insensitive to temperature. The effect of adding sodium chloride and isopropyl alcohol as cosolutes also was evaluated. Significant partitioning of VOCs into micelles was observed, with the micellar partitioning coefficient (tendency to partition from water into micelle) increasing according to the following...

A vibrating membrane module currently marketed for filtration applications was evaluated for the separation of volatile organic compounds (VOCs) from aqueous solutions by pervaporation. Preliminary screening experiments with three VOCs, three silicone membranes, and in the presence and absence of a surfactant were performed to determine if further consideration of the vibrating module for a field demonstration project was warranted. The primary process variables studied were vibrational amplitude and liquid flow rate. The vibrations greatly reduced concentration polarization in the system as inferred from an order of magnitude increase in the overall mass transport coefficient. Mass transfer coefficients for the vibrating module compared favorably with those for traditional spiral wound modules.

BACKGROUND Nisoldipine, a calcium antagonist, has been reported to improve the quality of grafted rat livers. We thus assessed the protective effect of two calcium antagonists, nisoldipine and nickel, during extended cold ischemia-reperfusion. METHODS Rat livers were isolated and perfused before or after 24 hr of cold ischemia in University of Wisconsin solution (4 degrees C) with or without nisoldipine or nickel. Sinusoidal endothelial cell and hepatocyte functions were measured by hyaluronic acid and taurocholate elimination, respectively. RESULTS Similar alterations in hepatocyte and sinusoidal cell functions were found in all groups after cold ischemia with or without calcium antagonists. In a second set of experiments, liver transplantation was performed in two groups of rats with livers stored under identical conditions with or without nisoldipine. Seven of 12 animals (62.5%) in both groups survived for over 10 days after 24-hr preservation in University of Wisconsin solution. Survival rates were similar in both groups. CONCLUSIONS Calcium antagonists do not appear to have a direct protective effect on sinusoidal endothelial cell and hepatocyte functions, nor on the overall liver preservation after extended cold preservation-reperfusion.

Site-specific mutagenesis has been used to replace Glu-98 with Glutamine in pig kidney fructose-1,6-bisphosphatase (Fru-1,6- P 2 ase) in order to evaluate the role of this residue in catalysis. The combination of lower k cat and higher K m resulted in an approximately 12,000-fold reduction in the catalytic efficiency of the Glu-98 → Gln enzyme when compared to the wild-type enzyme. The affinity of the enzyme for Mg 2+ and for the allosteric inhibitor AMP was altered only slightly; however, cooperativity in the binding of both of these effectors was eliminated. In addition, AMP could not fully inhibit the Glu-98 → Gln enzyme. These data suggest a critical role for the carboxylate of Glu-98 both as a general base in the reaction, and in the mechanism of allosteric inhibition of the enzyme by AMP.

A comparison of the X-ray crystallographic structures of the R and T allosteric states [Ke, H. M., Liang, J.-Y., Zhang, Y., & Lipscomb, W. N. (1991) Biochemistry 30, 4412-4420] of the pig kidney fructose-1,6-bisphosphatase (EC 3.1.3.11) reveals major changes in the quaternary structure of the enzyme upon the binding of the allosteric inhibitor AMP. This change in quaternary structure involves the breaking of one set of interactions that stabilize the R state and the formation of another set of interactions that stabilize the T state of the enzyme. In particular, the interactions of Arg-22 with nearby amino acid residues are quite different in the R and T states of the enzyme. Although the crystallographic data suggest that intersubunit interactions such as those involving Arg-22 are important for stabilization of the R and/or T states, the X-ray structures do not provide direct evidence concerning the functional role of specific amino acid residues. Therefore, site-specific mutagenesis has been used to probe the function of Arg-22 in pig kidney fructose-1,6-bisphosphatase. The replacement of Arg-22 by Ala results in a mutant enzyme with enhanced catalytic efficiency compared to the wild-type, as indicated by a kinetic analysis showing a slightly lower Km and increased Vmax compared to the wild-type enzyme. In addition, the substitution enhances both substrate inhibition and the affinity of the inhibitor fructose 2,6-bisphosphate. Moreover, the replacement of Arg-22 by Ala results in a more than 10-fold loss of the ability of AMP to inhibit the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

The active site of pig kidney fructose-1,6-bisphosphatase (EC 3.1.3.11) is shared between subunits, Arg-243 of one chain interacting with fructose-1,6-bisphosphate or fructose-2,6-bisphosphate in the active site of an adjacent chain. In this study, Arg-243 was replaced by alanine using techniques of site-specific mutagenesis and the cloned pig kidney enzyme expressed in Escherichia coli. Compared with wild-type enzyme, kinetic parameters of the altered enzyme characterizing catalytic efficiency, magnesium binding, and inhibition by AMP differed but by less than an order of magnitude; affinity for substrate fructose 1,6-bisphosphate was 10-fold poorer, and affinity for inhibitor fructose 2,6-bisphosphate was 1000-fold poorer. Molecular dynamics simulations were undertaken to determine possible alterations in active sites of the enzyme due to replacement of Arg-243 by Ala and suggested that in the mutant enzyme loss of one cationic group leads to reorganization of the active site especially involving lysine residues 269 and 274. The differences in properties of the mutant enzyme indicate the key importance of Arg-243 in the function of fructose-1,6-bisphosphatase and confirm on a functional basis the shared active site in this important metabolic enzyme.

Peroxidation of rat liver microsomes and of phospholipid isolated from them was studied using iron(III) and ascorbate initiation. One-half equivalent of citrate per iron equivalent maintained solubility of the metal ion at neutral pH. Several metal chelators, including additional citrate, blocked peroxidation, but catalase did not. These characteristics are consistent with those reported by others ( D. M. Miller and S. D. Aust (1989) Arch. Biochem. Biophys. 271, 113–119 ). Several antioxidants, principally tocopherol analogues and nitroxides, and, as well, a nonenzymatic component of “thymol-free” catalase, potently blocked lipid peroxidation, or, equivalently, dioxygen depletion from suspensions of peroxidizing microsomes. Chromanols were the most active antioxidants. No thiol studied had significant antioxidant activity in the test system.

O-Allylation using allyl trichloroimidate 5 was found to be an effective method for the introduction of an acetaldehyde equivalent onto the hydroxyl group of β-hydroxy-α-amino acid derivatives. Rigid oxygen containing tricyclic anti-phenylalanylleucine mimic 1 was efficiently synthesized using this method. This mimetic was further elaborated to provide 7c, a potent inhibitor of angiotensin-1 converting enzyme (ACE).

beta-Carboline agonists produced a left shift of the GABA concentration-chloride uptake curve or a reduction in the maximal increase in GABA-stimulated 36Cl- uptake depending on their concentration. The enhancement of the GABA effect occurs only at lower beta-carboline and GABA concentrations and is smaller for the partial agonist ZK 9126 compared to the full agonist ZK 93423. The opposite effect, inhibition of GABA-stimulated chloride conductance, is observed only at higher concentrations of beta-carboline agonists and GABA. The reduction of the GABA maximal response by the partial agonist ZK 91296 is greater than by the full agonist ZK 93423. The transformation of GABA-stimulated 36Cl- uptake data to specific chloride influx (36Cl- uptake per nM of GABA) reveals that the GABA concentration-response curve consists of three parts characterized by differences in the molar effectiveness of GABA relative to the GABA concentration. The molar effectiveness of GABA is a measure of the sensitivity of the GABAA receptor chloride ionophore complex and shows adaptive changes by this complex to increasing concentrations of GABA and/or beta-carboline. We conclude from our data that the change from GABA-sensitive to GABA-insensitive conformation of the GABAA receptor occurs with increasing concentrations of GABA and/or beta-carboline. Both conformations maintain positive heterotropic cooperativity with beta-carboline binding sites, one responsible for positive and the other responsible for negative effects of beta-carboline agonists on chloride uptake.

The decomposition of ethylene by pulsed, unfocussed CO2-laser radiation has been studied at pressures from 500 to 3000 Torr, using the P(14) line of the 10.6μm band (v=949.48cm−1) at incident fluences from about 0.1 to 1.0J/cm2. Major products in order of decreasing importance were 1,3-butadiene, acetylene, ethane, propane, 1-butene and methane. These are known products of the thermal free-radical chain decomposition, and it is concluded that the laser-induced decomposition under our conditions is a transient bulk thermal reaction occurring in a thin disc of heated gas close to the entrance window of the reaction vessel at temperatures ranging from about 1000 to 1500K. As in the thermal decomposition, cyclobutane was observed to be a minor product, which in a sequence of laser pulses approached a final constant concentration. The possibility that this corresponded to an equilibrium concentration at some “effective” reaction temperature was explored. Computer simulation was used to model the accumulation of cyclobutane in the system, both in a single pulse and in a sequence of pulses, and predictions of this model were compared with experiment. It was concluded that cyclobutane could be used in this way as an approximate internal thermometer, within certain limits. Mechanisms of formation of the free-radical chain products are discussed. It is concluded that the chains are initiated by the bimolecular disproportionation reaction, 2C2H4 → C2H3+C2H5, and that secondary initiation by dissociation of the product, 1-butene, becomes increasingly important as the reaction proceeds, leading to autocatalysis. It is further concluded that the radical chain decomposition in this system is a transient process occurring in a brief time interval following the short laser pulse (FWHM=110ns), and is far from steady-state conditions.

Practical aspects of fitting progress curves deriving from assays of slow-binding enzyme inhibitors in order to extract characteristic parameters is briefly discussed. An approach little-used, but which may provide more accurate estimates, is the simultaneous analysis of two assays differing from one another in the order of addition of reactants.

The effect of the GABA A receptor antagonists bicuculline and SR 95531 was compared with that of the antidepressants amoxapine and amitriptyline on GABA-stimulated 36 CL − uptake using membrane vesicles from the rat cerebral cortex. The interaction of Ro15–1788 with these drugs and the effect of Ro15–1788 on GABA-stimulated uptake of 36 Cl − were also investigated. GABA A receptor antagonists and the antidepressants inhibited 30 μM GABA-mediated uptake of 36 Cl − with the rank order of potency of SR 95531 > bicuculline > amoxapine > amitriptyline. Ro15–1788 potentiated the effect of these inhibitors on 30 μM GABA-stimulated chloride uptake. Ro15–1788 alone did not alter the effect of 30 μM GABA on 36 Cl − uptake. However, it did inhibit the 36 Cl − uptake produced by 100 μM GABA, and enhanced 36 Cl − uptake mediated by 10 μM GABA. The data show variations in the apparent intrinsic efficacy of Ro15–1788 at the chloride channel with respect to different experimental conditions. It is suggested that the activity of Ro15–1788 depends on changes in the conformational state of benzodiazepine-GABA A receptor chloride-ionophore complex produced by GABA and GABA receptor antagonists.

Comparison of MeO-Suc-Val-Pro-Phe-CO2Me (29) and MeO-Suc-Ala-Ala-Pro-Phe- CO2Me (25) with their corresponding trifluoromethyl ketones 9a and 9b, respectively, in rat and human neutrophil cathepsin G assays showed the alpha-keto esters to be more potent inhibitors. Likewise, Ac-Pro-Ala-Pro-Ala-CO2Me (21) was more potent than its corresponding trifluoromethyl ketone (9c) in both porcine pancreatic elastase and human neutrophil elastase assays. Within a set of Ala-Ala-Pro-Val-CF3 elastase inhibitors, the carbobenzyloxy (Cbz) N-protecting group conferred greater potency as a P5 site recognition unit for elastase than did dansyl, methoxysuccinyl, or tert-butyloxycarbonyl. Initial inhibition of elastase was greater when trifluoromethyl ketone 9f was added from a stock solution of dimethyl sulfoxide than when it had been buffer-equilibrated prior to assay, which suggests that the nonhydrated ketone is the more effective form of the inhibitor. The most potent elastase inhibitor we report is Na-(Ad-SO2)-N epsilon-(MeO-Suc)Lys-Pro-Val-CF3 (16) which has a Ki of 0.58 nM.

Glycinamide ribonucleotide transformylase (GART; 10-formyltetrahydrofolate:5'-phosphoribosylglycinamide formyltransferase, EC 2.1.2.2), an essential enzyme in de novo purine biosynthesis, has been a chemotherapeutic target for several decades. The three-dimensional structure of the GART domain from the human trifunctional enzyme has been solved by X-ray crystallography. Models of the apoenzyme, and a ternary complex with the 10-formyl-5,8-dideazafolate cosubstrate and a glycinamide ribonucleotide analogue, hydroxyacetamide ribonucleotide [alpha,beta-N-(hydroxyacetyl)-d-ribofuranosylamine], are reported to 2.2 and 2.07 A, respectively. The model of the apoenzyme represents the first structure of GART, from any source, with a completely unoccupied substrate and cosubstrate site, while the ternary complex is the first structure of the human GART domain that is bound at both the substrate and cosubstrate sites. A comparison of the two models therefore reveals subtle structural differences that reflect substrate and cosubstrate binding effects and implies roles for the invariant residues Gly 133, Gly 146, and His 137. Preactivation of the DDF formyl group appears to be key for catalysis, and structural flexibility of the active end of the substrate may facilitate nucleophilic attack. A change in pH, rather than folate binding, correlates with movement of the folate binding loop, whereas the phosphate binding loop position does not vary with pH. The electrostatic surface potentials of the human GART domain and Escherichia coli enzyme explain differences in the binding affinity of polyglutamylated folates, and these differences have implications to future chemotherapeutic agent design.

As part of a Department of Defense project, the US Environmental Protection Agency was responsible for designing, building and field operating a pilot-scale pervaporation unit. The field site was an active dry cleaning facility on the grounds of Marine Corps Base Camp Lejeune in Jacksonville, NC. The overall goal of the project was to remove tetrachloroethylene (PCE) from the soil beneath the dry cleaning shop using a surfactant-based soil remediation fluid and to recycle/reuse the surfactant. In order to reinject the recovered surfactant, the pervaporation unit was required to achieve an average 95% removal of contaminants from the extracted fluid over the duration of the test period. PCE removal averaged 95.8% during peak surfactant levels and exceeded 99.9% in the absence of surfactant, thereby meeting the reinjection requirement. Removal of a group of secondary contaminants at the site, termed Varsol compounds, was monitored via concentrations of three Varsol marker compounds: decane, undecane and 1,3,5-trimethylbenzene. The pervaporation system processed 100,000 gal of groundwater and surfactant solution over a period of 70 days. In order to evaluate and validate process performance, a variety of process variables and properties were monitored over the course of the demonstration. Pervaporation costs are projected to be on the order of $20 per 1000 gal of surfactant solution treated for a moderate size system (10 gpm).

Glycinamide ribonucleotide transformylase catalyzes the third reaction of de novo purine biosynthesis, namely, the conversion of glycinamide ribonucleotide to N -formylglycinamide ribonucleotide, with concomitant conversion of 10-formyltetrahydrofolate to tetrahydrofolate. This activity has been shown to be a target for cancer chemotherapy, which has generated renewed interest in both the enzyme and the pathway. Moreover, in higher eukaryotes this activity constitutes the C-terminal domain of a monomeric protein which also catalyzes two additional reactions of de novo purine biosynthesis. In this study, the human glycinamide ribonucleotide transformylase domain has been expressed to high levels in Escherichia coli and purified to homogeneity. Our improved expression–purification system produces the desired activity exclusively in a soluble form and in higher abundance than previously achieved. The kinetic constants have been determined and the kinetic mechanism has been established as ordered–sequential, with the folate substrate binding first. The correspondence of these data to those obtained for the glycinamide ribonucleotide transformylase activity of the mammalian trifunctional enzyme indicates that the recombinant enzyme is fully functional.

During the R-->T transition in the tetrameric pig kidney fructose-1,6-bisphosphatase (Fru-1,6-P2ase, EC 3.1.3.11) a major change in the quaternary structure of the enzyme occurs that is induced by the binding of the allosteric inhibitor AMP (Ke HM, Liang JY, Zhang Y, Lipscomb WN, 1991, Biochemistry 30:4412-4420). The change in quaternary structure involving the rotation of the upper dimer by 17 degrees relative to the lower dimer is coupled to a series of structural changes on the secondary and tertiary levels. The structural data indicate that Lys-42 is involved in a complex set of intersubunit interactions across the dimer-dimer interface with residues of the 190's loop, a loop located at the pivot of the allosteric rotation. In order to test the function of Lys-42, we have replaced it with alanine using site-specific mutagenesis. The kcat and K(m) values for Lys-42-->Ala Fru-1,6-P2ase were 11 s-1 and 3.3 microM, respectively, resulting in a mutant enzyme that was slightly less efficient catalytically than the normal pig kidney enzyme. Although the Lys-42-->Ala Fru-1,6-P2ase was similar kinetically in terms of K(m) and kcat, the response to inhibition by AMP was significantly different than that of the normal pig kidney enzyme. Not only was AMP inhibition no longer cooperative, but also it occurred in two stages, corresponding to high- and low-affinity binding sites. Saturation of the high-affinity sites only reduced the activity by 30%, compared to 100% for the wild-type enzyme. In order to determine in what structural state the enzyme was after saturation of the high-affinity sites, the Lys-42-->Ala enzyme was crystallized in the presence of Mn2+, fructose-6-phosphate (Fru-6-P), and 100 microM AMP and the data collected to 2.3 A resolution. The X-ray structure showed the T state with AMP binding with full occupancy to the four regulatory sites and the inhibitor Fru-6-P bound at the active sites. The results reported here suggest that, in the normal pig kidney enzyme, the interactions between Lys-42 and residues of the 190's loop, are important for propagation of AMP cooperativity to the adjacent subunit across the dimer-dimer interface as opposed to the monomer-monomer interface, and suggest that AMP cooperativity is necessary for full allosteric inhibition by AMP.

The active site of pig kidney fructose-1,6-bisphosphatase (EC 3.1.3.11) is shared between subunits, Arg-243 of one chain interacting with fructose-1,6-bisphosphate or fructose-2,6-bisphosphate in the active site of an adjacent chain. In this study, we present the X-ray structures of the mutant version of the enzyme with Arg-243 replaced by alanine, crystallized in both T and R allosteric states. Kinetic characteristics of the altered enzyme showed the magnesium binding and inhibition by AMP differed slightly; affinity for the substrate fructose-1,6-bisphosphate was reduced 10-fold and affinity for the inhibitor fructose-2,6-bisphosphate was reduced 1,000-fold (Giroux E, Williams MK, Kantrowitz ER, 1994, J Biol Chem 269:31404-31409). The X-ray structures show no major changes in the organization of the active site compared with wild-type enzyme, and the structures confirm predictions of molecular dynamics simulations involving Lys-269 and Lys-274. Comparison of two independent models of the T form structures have revealed small but significant changes in the conformation of the bound AMP molecules and small reorganization of the active site correlated with the presence of the inhibitor. The differences in kinetic properties of the mutant enzyme indicate the key importance of Arg-243 in the function of fructose-1,6-bisphosphatase. Calculations using the X-ray structures of the Arg-243-->Ala enzyme suggest that the role of Arg-243 in the wild-type enzyme is predominantly electrostatic in nature.

Amitriptyline inhibits the GABA-mediated uptake of 36Cl− in membrane vesicles prepared from the cerebral cortices of drug-naive and saline-treated rats. In contrast, chronic in vivo treatment with amitriptyline affects an increase in the GABA-stimulated uptake of chloride ions in its presence. The benzodiazepine receptor antagonist ZK 93426 blocks the capacity of amitriptyline to augment the uptake of 36Cl− by 30 μM GABA. There is a possibility that there are two distinct effects of amitriptyline's action in the rat forebrain. The first is evident in vesicles from drug-naive animals and the second only after chronic treatment with this antidepressant. The authors discuss the pertinence of this finding to the mechanism of action of amitriptyline.

SUMMARY 1. Gavage of rats with β-aryl derivatives of α-mercaptoacrylic acid resulted in pronounced and sustained elevation of serum zinc concentration. Greater than ten-fold increases above normal zinc levels were attained 2–8 h after doses of 50 mg/kg of the phenyl and furan derivatives. 2. These compounds were rapidly absorbed from the rat gastrointestinal tract and could be detected in serum for several days after a single dose. The return of serum zinc concentration to the normal level paralleled clearance of the mercaptoacrylic acid from plasma. 3. Close to 100% of the zinc and of the α-mercapto-β-(2-furan)acrylic acid (MFA) in serum 4 h after administration of the compound were bound to serum macromolecules. 4. MFA decreased excretion of endogenous zinc; it altered neither the gastrointestinal absorption of zinc nor serum concentrations of copper, albumin and total protein. 5. These compounds appear to mobilize zinc from tissue stores and retard zinc clearance from plasma.

Addition of an equal volume of 20% ( w w ) polyethylene glycol 6000 to human serum leads to separation of two major zinc ligands. α2-Macroglobulin, a zinc metalloprotein, is precipitated, while albumin, which forms a zinc-protein complex in serum, remains soluble. Total serum zinc and albumin-bound zinc are measured; α2-macroglobulin bound zinc is obtained by difference. The following values of zinc distribution were obtained in a study of 16 normal males; serum zinc, 82 ± 9 (mean ± standard deviation) μg/100 ml; albumin-bound zinc 66 ± 7 μg/100 ml and α2-macroglobulin-bound zinc 16 ± 3 μg/100 ml.

Collagenase from Clostridium histolyticum induced haemorrhages when applied to the surface of dog lung; it exerted a similar effect on mouse lung when injected intrathoracically. Injected into rat paws, bacterial collagenase induced haemorrhage and oedema. Effects of collagenase were prevented by several procedures that inhibit collagenolytic activity (heating at various temperatures and incubation with metal-complexing agents such as EDTA, penicillamine and dithiothreitol). Protein protease inhibitors, dexamethasone and standard acidic anti-inflammatory drugs had only a slight or no effect on collagenase-induced haemorrhages; dexamethasone and acidic anti-inflammatory drugs blocked collagenase-induced oedema. Inhibition of endogenous kinin-releasing mechanisms by administration of hexadimethrine, a recognized inhibitor of the activation of clotting Factor XII, and depletion of kininogen by administration of carrageenin blocked collagenase-induced oedema. Collagenase did not increase permeability of rat skin vessels, nor did it release potential inflammatory mediators, such as bradykinin or prostaglandins, from plasma or platelets. Bacterial collagenase-induced haemorrhage presumably resulted from enzymatic destruction of membranous structures; at least a portion of the inflammatory response may be due to activation of a kinin-like system.

An ultrafiltration technique was used to study stripping by glycine of the first copper and zinc ion equivalents bound by bovine, dog, and rat serum albumins at pH 7.5. Affinity of dog serum albumin for copper was poorer than for the other albumins, consistent with the absence in the former albumin of the copper binding site present at the amino terminus of the latter albumins. Affinities of all three proteins for zinc were similar, suggesting that the albumin amino terminus is not the primary zinc ion binding site.

SUMMARY 1. Four, six and eight hours after gavage of rats with α-mercapto-β-(2-furan) acrylic acid (MFA) (25 mg/kg) serum zinc concentration was increased ten-fold over control levels and a mean molar ratio of 1 albumin:0.4 zinc:0.8 MFA was found for seventeen sera. 2. At pH 7.5 a maximum of 1 mole of MFA could be bound per mole of metal-free bovine serum albumin. 3. In the presence of zinc ion, albumin-zinc-MFA complexes formed, since for each mole of albumin-zinc complex an additional mole of MFA could be bound to albumin. Complexes up to a molar stoichiometry of 1 albumin:2 zinc:3 MFA were prepared. 4. MFA stabilized the albumin-zinc complex against dissociation. 5. Formation of similar complexes in vivo may account for the markedly delayed clearance of plasma zinc seen in rats administered β-aryl derivatives of α-mercaptoacrylic acid.

The photolysis of ethylene has been studied at pressures from 50 to 3000 Torr using a pulsed ArF excimer laser at 193.3 nm. Major products were acetylene, n-butane, 1-butene, ethane, and 1,3-butadiene, with smaller amounts of propane, propene, methane, and allene. Quantum yields varied with pressure and reaction time; the latter dependence is ascribed to secondary photolysis of butene and butadiene. The reaction products are accounted for by three primary processes:[Formula: see text]followed by reactions of H, [Formula: see text] and C2H5 radicals. The vibrationally excited C2H3radical can decompose to H + C2H2 or can be stabilized by collision. The pressure dependence of the quantum yields of the primary processes [1]–[3] is complex, and a photodissociation mechanism involving several intermediates and excited states of ethylene is presented to account for the present results and previous measurements at 185 nm. Keywords: ethylene, uv photolysis.

The absorption of pulsed CO2-laser radiation by ethylene has been measured at total pressures from 25 to 3000 Torr, using the P(12) and P(14) lines in the 10.6 μm band, with incident fluences from 0.1 to 0.7 J/cm2. Marked deviations from the Beer-Lambert absorption law were observed, with the effective absorption coefficient varying with pressure, fluence, absorption path-length and the addition of non-absorbing gas. Pressure broadening of the rotational lines of the ethylene absorption spectrum was shown to be the major cause of these deviations, together with lesser effects which can be attributed to the rise in temperature of the absorbing gas during the laser pulse.

The partition of zinc in human serum between two major zinc-binding proteins, albumin and alpha2-macroglobulin, was studied in 28 control subjects and in 156 hospitalized patients. Albumin-bound zinc was both the major and the more dynamic of the serum zinc components. Over a wide range of values the concentrations of albumin-bound zinc and total serum zinc were highly correlated (r=0.91) with each other, as were concentrations of albumin and albumin-bound zinc (r=0.69). alpha2-Macroglobulin-bound zinc was not strongly correlated either with total serum zinc or with the serum concentration of alpha2-macroglobulin. Twenty-four hour urinary excretion of zinc was not correlated with any of the serum zinc parameters. To a large extent it appears that total serum zinc concentration reflects serum albumin concentration.

Intraperitoneal injections of alpha-mercapto-beta-(2-furyl)acrylic acid (MFA) induced incorporation of zinc into a low-molecular-weight metalloprotein fraction in rat-liver cytosol. Cytosol of control rats contained little or none of this material. alpha-Mercapto-beta-(2-thienyl)acrylic acid induced less incorporation of zinc in this fraction than did MFA. Twenty-two hours after administration of 65ZnSO4 (50 mumol/kg) and MFA (200 mumol/kg), serum concentrations of both total and radioisotopic zinc were markedly elevated, compared to serum concentrations in rats administered only 65ZnSO4. Further, in livers of MFA-treated rats, radioisotopic zinc concentration was significantly greater in all cytosol zinc-containing proteins resolved by gel chromatography, but total zinc was elevated only in the metallothionein fraction and not in proteins of higher molecular weight. This appears to be the first example of induction of a metallothionein-like protein by a procedure not involving food restriction or administration of metal salts.

Intubation of rats with alpha-mercapto-beta-(2-furyl)-acrylic acid (MFA) for 5 days at 50 mg/kg caused a 7-fold increase in kidney copper concentration, a 2-fold increase in kidney zinc concentration, and a 20% increase in liver zinc concentration. The proteins which bound the increased metals were purified and identified as metallothioneins by their amino acid compositions. Two isoforms were isolated from each organ. Renal thioneins appeared identical to counterpart hepatic apoproteins, but the former bound Cu and Zn in a 2:1 mole ratio and the latter bound only Zn. Kidney contained over 10 times more metallothionein per g of tissue than did liver. In rats previously administered MFA, injection of cadmium sulfate resulted in rapid displacement of liver metallothionein-bound Zn by Cd under conditions where minimal metallothionein was found in Cd-dosed animals not administered MFA. We conclude that MFA induces metallothionein biosynthesis in kidney and liver of normal rats; this is a novel effect for an organic compound.