Ammonia Fragments Research Articles

Effects of syngas and methanol fuel substitution on ammonia counterflow diffusion flames

Ammonia (NH3) is increasingly recognized as a promising alternative fuel. Various blending options have been proposed that are aimed at improving its flammability and applicability across diverse energy systems. This study conducts a comprehensive investigation, employing both experimental and numerical approaches, to understand the impact of blending ammonia with CH3OH or syngas, at various H2:CO ratios, on flame extinction limits, structure, and NOx emissions in counterflow laminar diffusion flames. Concentration profiles of ammonia and intermediate species (O2, CO, CO2, H2, NO, and N2O) were measured using Fourier-transformed infrared (FTIR) and gas chromatographic (GC) techniques. The findings indicate that increasing the H2:CO ratio in syngas-blended flames increases the extinction limits and reduces NO and N2O emissions. Compared with ammonia/methanol flames the ammonia/syngas flames exhibit higher extinction limits, flame temperatures, and lower NO and N2O emissions. Multiple kinetic models were found to underestimate the extinction strain limits, with Wang et al.’s 2021 model offering the closest predictions. Notably, discrepancies in ammonia dissociation and oxygen leakage to the rich side of stoichiometry impact reaction zone characteristics, extinction limits, and NOx predictions. Further kinetic analyses reveal that reactivity in syngas-blended flames is dominated by heat and radicals-producing reactions, while methanol-blended flames are sensitive to reactions involving ammonia fragments, resulting in decreased reactivity compared to syngas-blended flames. The results and findings from this study yield valuable insights into optimizing ammonia blends for enhanced flame stability and reduced emissions across various energy applications. It also provides data for chemical kinetics model validation in non-premixed diffusion environment where both species chemistry and transport are encountered.

Modification of the surface energy and morphology of GaN monolayers on the AlN surface in an ammonia flow

Based on theoretical predictions, it has been demonstrated that it is possible to purposefully change the elemental composition and position of the adsorbed particles on the GaN surface, thereby controlling the surface energy and morphology of GaN. Comparison of experimental data obtained by reflected high-energy electron diffraction and the calculated concentration of ammonia fragments on the GaN surface, and surface energy showed that the movement of adsorbed ammonia fragments into strongly bound states is an effective mechanism to control the GaN morphology. The minimum value of equivalent NH3 beam pressure at different temperatures to prevent the conversion of the two-dimensional (2D) GaN layer to three-dimensional (3D) islands has been established. It was shown that the boundary between the 2D and 3D states on the surface is defined by the elemental composition of adsorbed particles on the surface and the temperature dependence of the surface energy of the facets of islands.

Exploring the Interaction of Ammonia with Supported Vanadia Catalysts by Continuous Wave and Pulsed Electron Paramagnetic Resonance Spectroscopy

Continuous wave (CW) and pulsed electron paramagnetic resonance (EPR) spectroscopy are used to investigate the nature of vanadium species on V2O5/TiO2 catalysts prepared via wet impregnation and gas-phase grafting routes. CW EPR experiments show in both cases the formation of VO2+ vanadyl ions upon reaction with ammonia; moreover, phase memory time filtered echo-detected EPR experiments at X- and Q-band frequencies provide direct experimental evidence for the reduction of the TiO2 substrate and the formation of Ti3+ ions. X-band hyperfine sublevel correlation (HYSCORE) experiments are used to investigate the local environment of VO2+ ions. The direct nitrogen coordination of residual ammonia fragments in the equatorial plane of the vanadyl ion is demonstrated.

Interaction of ammonia and hydrogen with tungsten at elevated temperature studied by gas flow through a capillary

The interaction of ammonia and hydrogen (H2 and D2) was studied by flowing pure gas or gas mixture through a hot tungsten capillary. The composition of the gas after passing the capillary was analyzed by mass spectrometry as a function of capillary temperature. Specific temperatures were identified where changes in mass spectra take place indicating thermal decomposition and isotope exchange channels. Measurements with pure ammonia and deuterium provided new data for the thermal decomposition of these molecules on hot tungsten. Ammonia gets effectively decomposed at around 900 K in the tungsten capillary, and only 7% of ammonia survives through the capillary at temperatures above 1100 K. By studying the production and desorption of HD in ammonia and deuterium mixture, the authors show that D2 molecules can get adsorbed on tungsten dissociatively only at temperatures above 1300 K in the presence of nitrogen or ammonia fragments. An adsorption barrier of 0.17 eV is determined for this case. A comparison of ...

Cholinesterase sensor based on glassy carbon electrode modified with Ag nanoparticles decorated with macrocyclic ligands

New acetylcholinesterase (AChE) sensor based on Ag nanoparticles decorated with macrocyclic ligand has been developed and successfully used for highly sensitive detection of organophosphate and carbamate pesticides. AChE was immobilized by carbodiimide binding on carbon black (CB) layer deposited on a glassy carbon electrode. The addition of Ag nanoparticles decreased the working potential of the biosensor from 350 to 50mV. The AChE sensor made it possible to detect 0.4nM–0.2μM of malaoxon, 0.2nM–0.2μM of paraoxon, 0.2nM–2.0μM of carbofuran and 10nM–0.20μM of aldicarb (limits of detection 0.1, 0.05, 0.1 and 10nM, respectively) with 10min incubation. The AChE sensor was tested for the detection of residual amounts of pesticides in spiked samples of peanut and grape juice. The protecting effect of new macrocyclic compounds bearing quaternary ammonia fragments was shown on the example of malaoxon inhibition.

CID,ETD and HCD Fragmentation to Study Protein Post-Translational Modifications

Copyright: © 2013 Quan L. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Gas phase biomolecule-ion chemistry has played a crucial role in mass spectrometry (MS) based proteomics study. The key step generating the structure information of a protein or a peptide is by ion dissociation or transformation to the characteristic tandem mass spectrometry spectra (MS2) fragmentation patterns. Collision-induced dissociation (CID) is the most widely applied fragmentation method for proteome identification and quantification analysis. Under CID condition, the peptide/protein precursor ion undergoes one or more collisions by interactions with neutral gas molecules, contributing to vibrational energy which will redistribute over the peptide/protein ion. The vibrational energy can result in ion dissociation occurring at amide bonds along the peptide backbone, generating band y-type fragment ions or leading to losses of small neutral molecules, such as water and/ or ammonia or other fragments derived from side chains [1].

Determining the dissociation threshold of ammonia trimers from action spectroscopy of small clusters

Infrared-action spectroscopy of small ammonia clusters obtained by detecting ammonia fragments from vibrational predissociation provides an estimate of the dissociation energy of the trimer. The product detection uses resonance enhanced multiphoton ionization (REMPI) of individual rovibrational states of ammonia identified by simulations using a consistent set of ground-electronic-state spectroscopic constants in the PGOPHER program. Comparison of the infrared-action spectra to a less congested spectrum measured in He droplets [M. N. Slipchenko, B. G. Sartakov, A. F. Vilesov, and S. S. Xantheas, J. Phys. Chem. A 111, 7460 (2007)] identifies the contributions from the dimer and the trimer. The relative intensities of the dimer and trimer features in the infrared-action spectra depend on the amount of energy available for breaking the hydrogen bonds in the cluster, a quantity that depends on the energy content of the detected fragment. Infrared-action spectra for ammonia fragments with large amounts of internal energy have almost no trimer component because there is not enough energy available to break two bonds in the cyclic trimer. By contrast, infrared-action spectra for fragments with low amounts of internal energy have a substantial trimer component. Analyzing the trimer contribution quantitatively shows that fragmentation of the trimer into a monomer and dimer requires an energy of 1700 to 1800 cm(-1), a range that is consistent with several theoretical estimates.

Theoretical study of ammonia oxidation on platinum clusters – Adsorption of ammonia and water fragments

This study examined the adsorption of reactants (NH3 and OH) and intermediates (NH2, NH, N and H2O) formed during the oxidation of ammonia by hydroxyl on platinum. Specifically, four clusters were used to model the catalytic surface in the Pt(111) orientation. Structural, electronic and vibrational properties were calculated using Density Functional Theory (DFT). The molecules resided in the favored positions predicted by prior experimental observations and DFT calculations, while the adsorption energies followed the trend: H2O<NH3<OH<NH2<NH<N, with the weakest bonds formed by charge transfer and the strongest bonds formed by orbital overlap of unpaired electrons of the radicals and the d orbital of adjacent Pt atoms. Calculated frequency vibrations in this work showed sufficient agreement with experimental observation, challenged previously assigned frequency modes for NH2, NH and H2O and predicted the correct shift in frequency vibrations upon adsorption on platinum when compared with prior DFT calculations.

Imaging the State-Specific Vibrational Predissociation of the Ammonia−Water Hydrogen-Bonded Dimer

The state-to-state vibrational predissociation (VP) dynamics of the hydrogen-bonded ammonia-water dimer were studied following excitation of the bound OH stretch. Velocity-map imaging (VMI) and resonance-enhanced multiphoton ionization (REMPI) were used to determine pair-correlated product energy distributions. Following vibrational excitation of the bound OH stretch fundamental, ammonia fragments were detected by 2 + 1 REMPI via the B1E" <-- X1A1' transition. The REMPI spectra show that NH3 is produced with one and two quanta of the symmetric bend (nu2 umbrella mode) excitation, as well as in the ground vibrational state. Each band is quite congested, indicating population in a large number of rotational states. The fragments' center-of-mass (c.m.) translational energy distributions were determined from images of selected rotational levels of ammonia with zero, one, or two quanta in nu2 and were converted to rotational state distributions of the water cofragment. All the distributions could be fit well by using a dimer dissociation energy of D0 = 1538 +/- 10 cm(-1). The rotational state distributions in the water cofragment pair-correlated with specific rovibrational states of ammonia are broad and include all the J(KaKc) states allowed by energy conservation. The rotational populations increase with decreasing c.m. translational energy. There is no evidence for ammonia products with significant excitation of the asymmetric bend (nu4) or water products with bend (nu2) excitation. The results show that only restricted pathways lead to predissociation, and these do not always give rise to the smallest possible translational energy release, as favored by momentum gap models.

The origin of inter-dimer-row correlated adsorption for NH 3 on Si(0 0 1)

We discuss the interaction between adsorbing ammonia molecules and pre-adsorbed ammonia fragments on the Si(0 0 1) surface, searching for experimental evidence of a H-bonded precursor state predicted by modelling. While correlations along dimer rows have already been identified, these mix substrate-mediated effects due to dimer buckling with ammonia–adsorbate effects. Correlations between fragments on neighbouring dimer rows are not affected by substrate effects (in this system), allowing an analysis of direct ammonia–adsorbate effects. We present an analysis of cross-row correlations in existing high-coverage STM data which shows significant correlations between NH 2 groups on neighbouring dimer rows over a significant range, providing evidence for the H-bonded precursor state with a range of around 10 Å. We discuss implications for the interpretation of STM images of ammonia on Si(0 0 1).

Co-adsorption patterns of NH 3 on Si(0 0 1): Comment on “The ordering of the adsorbed NH 3 molecules across the Si dimer rows on the Si(0 0 1) surface”

In their paper, Chung et al. [O.N. Chung, H. Kim, J.-Y. Koo, S. Chung, Surf. Sci. Lett. 602 (2008) L69.] discuss the interaction of adsorbing ammonia fragments on the Si(0 0 1) surface. We suggest that they have failed adequately to explain the correlations they observe. Using a different interpretation of the STM appearance of NH 2 fragments gives strong support for cross-dimer row interactions mediated by hydrogen bonds between NH 2 groups which is not seen with their present interpretation.

Imaging the State-Specific Vibrational Predissociation of the C2H2−NH3Hydrogen-Bonded Dimer

The state-to-state vibrational predissociation (VP) dynamics of the hydrogen-bonded ammonia-acetylene dimer were studied following excitation in the asymmetric CH stretch. Velocity map imaging (VMI) and resonance-enhanced multiphoton ionization (REMPI) were used to determine pair-correlated product energy distributions. Following vibrational excitation of the asymmetric CH stretch fundamental, ammonia fragments were detected by 2 + 1 REMPI via the B1E'' <-- X1A1' and C'1A1' <-- X1A1' transitions. The fragments' center-of-mass (c.m.) translational energy distributions were determined from images of selected rotational levels of ammonia with one or two quanta in the symmetric bend (nu2 umbrella mode) and were converted to rotational-state distributions of the acetylene co-fragment. The latter is always generated with one or two quanta of bending excitation. All the distributions could be fit well when using a dimer dissociation energy of D0 = 900 +/- 10 cm(-1). Only channels with maximum translational energy <150 cm(-1) are observed. The rotational excitation in the ammonia fragments is modest and can be fit by temperatures of 150 +/- 50 and 50 +/- 20 K for 1nu2 and 2nu2, respectively. The rotational distributions in the acetylene co-fragment pair-correlated with specific rovibrational states of ammonia appear statistical as well. The vibrational-state distributions, however, show distinct state specificity among channels with low translational energy release. The predominant channel is NH3(1nu2) + C2H2(2nu4 or 1nu4 + 1nu5), where nu4 and nu5 are the trans- and cis-bend vibrations of acetylene, respectively. A second observed channel, with much lower population, is NH3(2nu2) + C2H2(1nu4). No products are generated in which the ammonia is in the vibrational ground state or the asymmetric bend (1nu4) state, nor is acetylene ever generated in the ground vibrational state or with CC stretch excitation. The angular momentum (AM) model of McCaffery and Marsh is used to estimate impact parameters in the internal collisions that give rise to the observed rotational distributions. These calculations show that dissociation takes place from bent geometries, which can also explain the propensity to excite fragment bending levels. The low recoil velocities associated with the observed channels facilitate energy exchange in the exit channel, which results in statistical-like fragment rotational distributions.

Study of NH Stretching Vibrations in Small Ammonia Clusters by Infrared Spectroscopy in He Droplets and ab Initio Calculations

Infrared spectra of the NH stretching vibrations of (NH3)n clusters (n = 2-4) have been obtained using the helium droplet isolation technique and first principles electronic structure anharmonic calculations. The measured spectra exhibit well-resolved bands, which have been assigned to the nu1, nu3, and 2nu4 modes of the ammonia fragments in the clusters. The formation of a hydrogen bond in ammonia dimers leads to an increase of the infrared intensity by about a factor of 4. In the larger clusters the infrared intensity per hydrogen bond is close to that found in dimers and approaches the value in the NH3 crystal. The intensity of the 2nu4 overtone band in the trimer and tetramer increases by a factor of 10 relative to that in the monomer and dimer, and is comparable to the intensity of the nu1 and nu3 fundamental bands in larger clusters. This indicates the onset of the strong anharmonic coupling of the 2nu4 and nu1 modes in larger clusters. The experimental assignments are compared to the ones obtained from first principles electronic structure anharmonic calculations for the dimer and trimer clusters. The anharmonic calculations were performed at the Møller-Plesset (MP2) level of electronic structure theory and were based on a second-order perturbative evaluation of rovibrational parameters and their effects on the vibrational spectra and average structures. In general, there is excellent (<20 cm(-1)) agreement between the experimentally measured band origins for the N-H stretching frequencies and the calculated anharmonic vibrational frequencies. However, the calculations were found to overestimate the infrared intensities in clusters by about a factor of 4.

Molecular interactions and decomposition pathways ofNH3on Si(001)

Ammonia adsorbs dissociatively on the Si(001) surface above $200\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The majority dissociation products are -H and -$\mathrm{N}{\mathrm{H}}_{2}$ groups, adsorbed on the dangling bonds of the Si dimers. At low coverages, the ammonia fragments are observed to form clumps, which extend both along and across dimer rows, suggesting interactions between molecules: either direct interactions, or those mediated by the buckled dimers on the Si(001) substrate. The detailed reactions in the adsorption and dissociation of $\mathrm{N}{\mathrm{H}}_{3}$ on Si(001) have been investigated by density functional theory calculations, and compared to data from scanning tunneling microscope images. The buckling of the Si dimers provides a mechanism for preferential adsorption next to existing adsorbed species, along a single dimer row. We find that direct H-bonding interactions between chemisorbed $\mathrm{N}{\mathrm{H}}_{2}$ groups and incoming $\mathrm{N}{\mathrm{H}}_{3}\phantom{\rule{0.3em}{0ex}}$ molecules are also significant, including an interaction across dimer rows, which explains the observed clumping behavior.

Mechanistic insights into the formation of N2O and N2 in NO reduction by NH3 over a polycrystalline platinum catalyst

The reaction pathways of N2 and N2O formation in the direct decomposition and reduction of NO by NH3 were investigated over a polycrystalline Pt catalyst between 323 and 973K by transient experiments using the temporal analysis of products (TAP-2) reactor. The interaction between nitric oxide and ammonia was studied in the sequential pulse mode applying 15NO. Differently labelled nitrogen and nitrous oxide molecules were detected. In both, direct NO decomposition and NH3–NO interaction, N2O formation was most marked between 573 and 673K, whereas N2 formation dominated at higher temperatures. An unusual interruption of nitrogen formation in the 15NO pulse at 473K was caused by an inhibiting effect of adsorbed NO species. The detailed analysis of the product distribution at this temperature clearly indicates different reaction pathways leading to the product formation. Nitrogen formation occurs via recombination of nitrogen atoms formed by dissociation of nitric oxide or/and complete dehydrogenation of ammonia. N2O is formed via recombination of adsorbed NO molecules. Additionally, both products are formed via interactions between adsorbed ammonia fragments and nitric oxide.

DFT Characterization of Adsorbed NHx Species on Pt(100) and Pt(111) Surfaces

Periodic density functional theory (DFT) calculations using plane waves have been performed to systematically investigate the adsorption and relative stability of ammonia and its dehydrogenated species on Pt(111) and Pt(100) surfaces. Different adsorption geometries and positions have been studied, and in each case, the equilibrium configuration has been determined by relaxation of the system. The vibrational spectra of the various ammonia fragments have been computed, and band assignments have been compared in detail with available experimental data. The adsorption of NH3 (on top) and NH2 (bridge) is more favorable on Pt(100) than on Pt(111), while similar adsorption energies were computed for NH (hollow) and N (hollow) on both surfaces. The remarkably lower adsorption energy of NH2 over Pt(111) as compared with Pt(100) (the difference being approximately 0.7 eV) can be related to different geometric and electronic factors associated with this particular intermediate. Accordingly, the type of platinum surface determines the most stable NH(x) fragment: Pt(100) has more affinity for NH2 species, whereas NH species are preferred over Pt(111).

Copper, nickel, and cobalt production: Impurity control and removal

An ongoing challenge in the smelting and refi ning of copper, nickel, and cobalt has been to produce high-purity metals from a diverse range of concentrates containing various impurities at different concentration levels. This purifi cation challenge has been met by using pyro-, hydro-, and electrometallurgy either individually or in combination. In pyrometallurgy, the removal of impurities—invariably to a slag phase for discard—is limited by equilibrium conditions; in hydrometallurgy, impurities are removed by precipitation, ion exchange (IX), and solvent extraction (SX). The precipitation step produces a residue for disposal in an environmentally acceptable manner, while IX and SX enable the possible recovery of the impurity metal either as a metal or salt. In electrometallurgy—both electrorefi ning and electrowinning—the treatment of a bleed stream results in the removal of the impurities either as a product or residue thereby providing control of the same in the main circuit. This issue of JOM includes four articles on removing impurities in the production of electrolytic copper. Two of the articles address electrorefi ning, the third focuses on the topic of electrowinning, and the fourth discusses control of oxygen and sulfur in blister copper. In “The Purifi cation of Copper Refi nery Electrolyte” author J. Hoffmann discusses the following impurities: As, Sb, Bi, Ni, Ca, ammonia, and organic fragments (decomposition products?). The paper describes the removal, and hence, control of arsenic, antimony, and bismuth using techniques such as precipitation, SX, and IX. Nickel is normally recovered as a nickel sulfate product from the decopperized electrolyte. Calcium precipitates as calcium sulfate on cathodes while bismuth tends to co-precipitate as a sulfate with gypsum, thus contaminating the cathode. The bleed of the electrolyte should normally control calcium levels, ensuring that it does not reach its solubility limit in the electrolyte. Ammonia and organic fragments rarely pose a problem in the tankhouse. In the second paper, author S. Wang discusses the same topic, but with some description of specifi c processes. Wang emphasizes the need to maintain a high level of arsenic in the electrolyte (about 12 g/L and above) to control antimony and bismuth by precipitation of antimonous arsenate and bismuth arsenate into the slimes. In one plant, the decopperized electrolyte is treated by IX technology to remove sulfuric acid for return to the tankhouse. Afterward, impurities (arsenic, antimony, and bismuth) are removed and nickel carbonate is precipitated as a product. The paper also reviews the use of molecular recognition technology (MRT) for Bi removal, SX for Sb and Bi control, and IX for Sb, Bi, and partial As control. Of these, MRT and SX have been evaluated at the pilot-plant level, while IX has been used at a few plants on a commercial scale for several years. In the only paper on impurity control in copper electrowinning circuits, D.R. Shaw et al. describe a unique ironcontrol system (FENIX) in which iron is loaded onto a resin followed by stripping with a cuprous sulfate solution. This has considerably reduced the bleed from the circuit. Other benefi ts are reduced acid and cobalt sulfate usage and lower usage of lime in bleed neutralization. This process operated successfully at the Mt. Gordon copper plant in Australia from September 2002 until July 2003. Unfortunately, the plant was shut down due to fi nancial issues and the FENIX process will no longer be needed at that site. In the only contribution describing pyrometallurgical methods for refi ning blister copper, authors P. Coursol and P. Larouche describe a new concept for removal of oxygen and sulfur from blister copper using alkali carbonates to produce anode copper and a molten carbonate/sulfate salt for disposal. The main variables affecting the thermodynamics of the reaction are temperature, furnace atmosphere, composition of blister copper, and carbonate/sulfate salt ratio. Copper containing 2–145 ppm sulfur and 1,100–3,700 ppm O 2 was produced in laboratory tests. Additional laboratory tests and possible pilot-plant tests are planned to evaluate kinetics of the process. In spite of the broad title encompassing a wide area of the subject, only four papers were contributed over a very narrow subject of copper metallurgy with none from the nickel and cobalt industry. The author fails to see the reason for the reluctance on the part of the nickel and cobalt industry to come forward and share information that is not proprietary in nature with the metallurgical community. One paper—a review of the topic in general—did not make the deadline for this issue. However, it will be published in a future issue of JOM in 2004.

The purification of copper refinery electrolyte

The phrase “purification of copper refinery electrolyte” is misleading since typically, impurities are controlled by withdrawing a bleedstream of the circulating electrolyte. However, solvent extraction and ion exchange have also found some application in impurity control. This article describes conventional practice, including treatment of the bleedstream, and other attempts at electrolyte purification. Impurities to be discussed include Sb, Bi, As, Ni, Ca, ammonia, and organic fragments generated from hydrolysis of conventional cathode growth-modifying addition agents.

Thermal decomposition behaviour of polyamide fire-retardant compositions containing magnesium hydroxide filler

The thermal analysis of polyamides modified with magnesium hydroxide fire retardant filler is studied. Using combined TGA, DSC EGA and on-line FTIR techniques, it is shown that on thermal breakdown magnesium hydroxide exerts a significant pro-degraditive action on polyamides, attributed to water release and resulting hydrolysis of the polymer chain. Evolved gases released are shown to be water, carbon monoxide, carbon dioxide, ammonia and various hydrocarbon fragments. Similar results are obtained for both filled and unfilled PA compositions. However it is evident that in PA-6,6, polymer degradation occurs before magnesium hydroxide breakdown, whereas there is much greater overlap between thermal decomposition of PA-6 and the fire retardant filler.

Isolation from rat kidney of a cytosolic high molecular weight cysteine-S-conjugate beta-lyase with activity toward leukotriene E4.

A cytosolic high M(r) cysteine-S-conjugate beta-lyase (apparent M(r) of approximately 330,000) has been partially purified from rat kidneys. The high M(r) lyase is also present in the mitochondria. The purified enzyme contains at least two proteins with apparent M(r) values of approximately 50,000 and approximately 70,000. Activity is stimulated by dithiothreitol, alpha-keto acids, and pyridoxal 5'-phosphate; aminooxyacetate is an inhibitor. The enzyme catalyzes a competing (half) transamination reaction between pyridoxal 5'-phosphate cofactor and cysteine-S-conjugate substrate; added alpha-keto acids promote conversion of active site pyridoxamine 5'-phosphate to pyridoxal 5'-phosphate. The enzyme also catalyzes a full (but weak) transamination between L-phenylalanine and alpha-keto-gamma-methiolbutyrate. The purified enzyme is not recognized by polyclonal rabbit antibodies to cytosolic rat kidney glutamine transaminase K (another cysteine-S-conjugate beta-lyase of rat kidney) and has no obvious similarities to other pyridoxal 5'-phosphate-containing enzymes. In addition to catalyzing elimination reactions with S-(1,2-dichlorovinyl)-L-cysteine and S-(1,1,2,2-tetrafluoroethyl)-L-cysteine, the enzyme reacts with leukotriene E4 and 5'-S-cysteinyldopamine. Finally, the cytosolic and mitochondrial enzymes are activated by alpha-ketoglutarate. Thus, the possibility must be considered that, in kidneys of animals exposed to various cysteine conjugates, the high M(r) lyase contributes to the generation of pyruvate, ammonia, and reactive fragments in vivo. Many cysteine conjugates are nephrotoxic, and the high M(r) lyase(s) may be involved.