Studies of Ammonia Uptake and Loss by Lichens

1999 ◽  
Vol 31 (1) ◽  
pp. 85-93 ◽  
Author(s):  
James E. Miller ◽  
Dennis H. Brown
Keyword(s):  
Binding Sites ◽  
Cation Binding ◽  
Gaseous Ammonia ◽  
Intracellular Uptake ◽  
Competitive Effect ◽  
Ammonium Ions ◽  
Rapid Loss ◽  
Ammonia Uptake ◽  
Living Material ◽  
Ammonium Binding

AbstractThe passive uptake of ammonium ions to extracellular cation binding sites has been demonstrated for a range of lichen species. The possible competitive effect of other cations on ammonium binding is discussed. Binding of uncharged gaseous ammonia to exchange sites was also shown. The rapid loss of exchangeable ammonium from extracellular sites has been demonstrated and, because the greatest losses occur in living material, intracellular uptake is inferred. The labile nature of bound ammonium means that transfer of material to the laboratory for analysis may result in the underestimation of the amount bound.

scholarly journals First Characterization of an Archaeal GTP-Dependent Phosphoenolpyruvate Carboxykinase from the Hyperthermophilic Archaeon Thermococcus kodakaraensis KOD1

2004 ◽  
Vol 186 (14) ◽  
pp. 4620-4627 ◽  
Author(s):  
Wakao Fukuda ◽  
Toshiaki Fukui ◽  
Haruyuki Atomi ◽  
Tadayuki Imanaka
Keyword(s):  
Binding Sites ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cation Binding ◽  
Activity Levels ◽  
Binding Region ◽  
Hyperthermophilic Archaeon ◽  
Dependent Activity ◽  
Additional Role

ABSTRACT Phosphoenolpyruvate carboxykinase (PCK), which catalyzes the nucleotide-dependent, reversible decarboxylation of oxaloacetate to yield phosphoenolpyruvate and CO2, is one of the important enzymes in the interconversion between C3 and C4 metabolites. This study focused on the first characterization of the enzymatic properties and expression profile of an archaeal PCK from the hyperthermophilic archaeon Thermococcus kodakaraensis (Pck Tk ). Pck Tk showed 30 to 35% identities to GTP-dependent PCKs from mammals and bacteria but was located in a branch distinct from that of the classical enzymes in the phylogenetic tree, together with other archaeal homologs from Pyrococcus and Sulfolobus spp. Several catalytically important regions and residues, found in all known PCKs irrespective of their nucleotide specificities, were conserved in Pck Tk . However, the predicted GTP-binding region was unique compared to those in other GTP-dependent PCKs. The recombinant Pck Tk actually exhibited GTP-dependent activity and was suggested to possess dual cation-binding sites specific for Mn2+ and Mg2+. The enzyme preferred phosphoenolpyruvate formation from oxaloacetate, since the Km value for oxaloacetate was much lower than that for phosphoenolpyruvate. The transcription and activity levels in T. kodakaraensis were higher under gluconeogenic conditions than under glycolytic conditions. These results agreed with the role of Pck Tk in providing phosphoenolpyruvate from oxaloacetate as the first step of gluconeogenesis in this hyperthermophilic archaeon. Additionally, under gluconeogenic conditions, we observed higher expression levels of Pck Tk on pyruvate than on amino acids, implying that it plays an additional role in the recycling of excess phosphoenolpyruvate produced from pyruvate, replacing the function of the anaplerotic phosphoenolpyruvate carboxylase that is missing from this archaeon.

Furosemide-sensitive thallium fluxes in smooth muscle of rabbit uterus

1983 ◽  
Vol 245 (6) ◽  
pp. F778-F783
Author(s):  
A. Johns ◽  
S. V. Cutshaw
Keyword(s):  
Smooth Muscle ◽  
Binding Sites ◽  
Rank Order ◽  
Chloride Concentration ◽  
Cation Binding ◽  
Exchange System ◽  
Total Uptake ◽  
Low Concentrations ◽  
Chloride Pump ◽  
High Concentrations

The furosemide-sensitive uptake of thallium represents approximately equal to 50% of the total uptake of thallium by rabbit uterus and requires Cl- and Na+. The furosemide-sensitive uptake of thallium is stimulated by other ions at low concentrations with the rank order Li+ greater than Tl+ greater than K+ = Rb+ greater than Cs+ and is inhibited by these ions at high concentrations with the rank order Tl+ greater than K+ = Rb+ greater than Cs+ greater than Li+, suggesting multiple cation binding sites on the carrier. Uptake of 36Cl- is inhibited by furosemide in the presence of ouabain. Thallium efflux and 36Cl efflux in the presence of ouabain is inhibited by furosemide. The chloride concentration regulates the proportion of thallium uptake that is ouabain sensitive and furosemide sensitive without altering the total uptake. It is suggested that the furosemide-sensitive uptake of thallium reflects a Na+-Cl- -K+ exchange system that could be classified as a cotransport or countertransport of any two of these ions and also could be the smooth muscle chloride pump.

scholarly journals Nitrogen-containing Secondary Organic Aerosols Formation by Acrolein Reaction with Ammonia/Ammonium

2018 ◽  
Author(s):  
Zhijian Li ◽  
Sergey A. Nizkorodov ◽  
Hong Chen ◽  
Xiaohui Lu ◽  
Xin Yang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Phase ◽  
Gas Phase ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Bulk Liquid ◽  
Gaseous Ammonia ◽  
Similar Reaction ◽  
Ammonium Ions ◽  
Oligomeric Compounds

Abstract. Ammonia-driven carbonyl-to-imine conversion is an important formation pathway to the nitrogen-containing organic compounds (NOC) in secondary organic aerosols (SOA). Previous studies have mainly focused on the dicarbonyl compounds as the precursors of light-absorbing NOC. In this work, we investigated whether acrolein could also act as a NOC precursor. Acrolein is the simplest α,β-unsaturated mono-carbonyl compound, and it is ubiquitous in the atmosphere. Experiments probing gas-phase and surface reactions of acrolein as well as bulk liquid-phase experiments were carried out to study the reactivity of acrolein towards ammonia and ammonium ions. Molecular characterization of the products based on gas chromatography mass spectrometry, high resolution mass spectrometry, surface enhanced Raman spectrometry and Ultraviolet/visible spectrometry was used to propose possible reaction mechanisms. We observed 3-methyl pyridine (also called 3-picoline) in the gas phase in the Tedlar bag filled with gaseous acrolein and ammonia. In the liquid phase, oligomeric compounds with formulas (C3H4O)m(C3H5N)n and pyridinium compounds like (C3H4O)2C6H8N+ were observed as the products of acrolein reaction with ammonium ions. The 3-picoline could be the product of acrolein reaction with gaseous ammonia in the gas phase. The pathway to 3-picoline was proposed to be the intramolecular carbon-carbon addition of the hemiaminal which resulted from sequential carbonyl-to-imine conversions of acrolein molecules. The similar reaction of dissolved acrolein with ammonium ions leads to the formation of 3-methyl pyridinium (also called 3-picolinium) cations in the liquid phase. The (C3H4O)2C6H8N+ was a carbonyl-to-hemiaminal product from acrolein dimer and 3-picolinium cations, while the oligomeric products of (C3H4O)m(C3H5N)n were polymers of acroleins and propylene imines via carbonyl-to-imine conversion and condensation reactions. Part of the 3-picolinium could re-volatilize to the gas phase as 3-picoline, explaining the observation of gaseous 3-picoline in the bag filled with acrolein and ammonium sulfates (or chlorides) aerosols. The pH value effect on the liquid products was also studied in the bulk liquid-phase experiments. Compared to the oligomeric compounds forming in both acid and alkaline conditions, there is a tendency for the pyridinium products to be formed under moderately acidic conditions. Both the oligomeric products and the pyridinium salts are light absorbing materials. This work suggests a potential role for acrolein reaction with ammonia/ammonium as a source of light-absorbing heterocyclic NOC in SOA. Therefore, secondary reactions of α,β-unsaturated aldehydes with reduced nitrogen should be taken into account when evaluating climate and health effects of SOA.

Inhibition of Aspergillus flavus and Selected Gram-positive Bacteria by Chelation of Essential Metal Cations by Polyphosphates

1991 ◽  
Vol 54 (5) ◽  
pp. 360-365 ◽  
Author(s):  
S.J. KNABEL ◽  
H.W. WALKER ◽  
P.A. HARTMAN
Keyword(s):  
Aspergillus Flavus ◽  
Binding Sites ◽  
Iron Supplementation ◽  
Cation Binding ◽  
Gram Negative Bacteria ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Tetrasodium Pyrophosphate ◽  
Gram Positive Bacteria ◽  
And Staphylococcus Aureus

A simple well-plate technique was utilized to determine the effect of various metals on the growth of microorganisms in media containing different polyphosphates. Aspergillus flavus and four gram-positive bacteria were completely inhibited by media containing 1% of various alkaline polyphosphates, whereas four gram-negative bacteria were not. Significant differences were observed between the type of polyphosphate added, the type of metal added, and the species of gram-positive bacterium inhibited. The addition of Mg2+ stimulated growth of A. flavus and Bacillus cereus in the presence of tetrasodium pyrophosphate, whereas Mn2+ permitted growth of A. flavus and Staphylococcus aureus in the presence of sodium hexametaphosphate. Iron supplementation allowed the growth of S. aureus and Listeria monocytogenes on media containing 1 % tetrasodium pyrophosphate. A method for determining the amount of calcium and magnesium in water was modified to detect free Mg2+ by replacing EDTA with phosphate. The addition of free Mg2+, but not Mg2+ chelated by tetrasodium pyrophosphate, permitted the growth of B. cereus on a medium containing tetrasodium pyrophosphate. It is speculated that polyphosphates specifically inhibited A. flavus and gram-positive bacteria by removing essential metals from cation-binding sites located within their cell walls.

scholarly journals Probing ligand and cation binding sites in G-quadruplex nucleic acids by mass spectrometry and electron photodetachment dissociation sequencing

The Analyst ◽  
2019 ◽  
Vol 144 (11) ◽  
pp. 3518-3524 ◽  
Author(s):  
Dababrata Paul ◽  
Adrien Marchand ◽  
Daniela Verga ◽  
Marie-Paule Teulade-Fichou ◽  
Sophie Bombard ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Ligand Binding ◽  
Binding Sites ◽  
Cation Binding ◽  
Tandem Mass ◽  
Top Down ◽  
G Quadruplex ◽  
Ligand Binding Sites ◽  
Electron Photodetachment

Tandem mass spectrometry: native top-down sequencing by electron photodetachment dissociation (EPD) reveals ligand binding sites on DNA G-quadruplexes.

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