FRUCTOSE DIPHOSPHATE ALDOLASE FROM FUSARIUM OXYSPORUM f. LYGOPERSICI: II. CHARACTERISTICS OF THE EXCHANGE REACTION

1967 ◽  
Vol 45 (10) ◽  
pp. 1505-1511 ◽  
Author(s):  
J. M. Ingram
Keyword(s):  
Methylene Blue ◽  
Fusarium Oxysporum ◽  
Exchange Reaction ◽  
Active Site ◽  
Reaction Rates ◽  
Exchange Capacity ◽  
Proton Exchange ◽  
Dihydroxyacetone Phosphate ◽  
Cleavage Reaction ◽  
Twofold Decrease

Fruetose-1,6-diphosphate aldolase purified from extracts of Fusarium oxysporum f. lycopersici was examined in detail. The different pH optima obtained for the proton exchange (pH 6.0) and cleavage (pH 7.5) reactions indicate that this enzyme resembles the yeast FDP-aldolase rather than the aldolase from muscle. When the enzyme was dialyzed extensively, in the absence of Cleland's reagent, it was found that neither the cleavage nor the exchange reaction rates were increased appreciably after addition of mercaptan. Treatment of the enzyme with either methylene blue in the presence of light or with diazosulfanilic acid, two known inhibitors of the cleavage reaction, resulted in almost complete inhibition of FDP cleavage but only a twofold decrease in the exchange capacity. These results substantiate our previous findings that the inhibitors react with residues involved in the D-glyceraldehyde-3-phosphate rather than the dihydroxyacetone phosphate active site.

PURIFICATION AND PROPERTIES OF FRUCTOSE DIPHOSPHATE ALDOLASE FROM FUSARIUM OXYSPORUMF. LYCOPERSICI

1967 ◽  
Vol 45 (6) ◽  
pp. 929-936 ◽  
Author(s):  
J. M. Ingram ◽  
R. M. Hochster
Keyword(s):  
Methylene Blue ◽  
Active Site ◽  
Inhibitory Action ◽  
Sulfhydryl Group ◽  
Dihydroxyacetone Phosphate ◽  
Tyrosine Residues ◽  
Crude Extracts ◽  
Purification And Properties

Fructose-1,6-diphosphate (FDP) aldolase obtained from crude extracts of the mycelium of Fusarium lycopersici was purified approximately 35-fold. The properties of the enzyme indicate that it resembles the FDP aldolase commonly found in yeast and bacteria rather than that found in animals or plants. The inhibitory action of p-hydroxymercuribenzoate, N-ethylmaleimide, and iodosobenzoate suggests that a sulfhydryl group may be involved in an active site. The inhibitions caused by methylene blue in the presence of light and of diazosulfanilic acid suggest that histidine and (or) tyrosine residues may also be involved in the active site. The importance of this site has been established by demonstrating that fructose diphosphate and D-glyceraldehyde-3-phosphate prevent inactivation by diazosulfanilic acid whereas dihydroxyacetone phosphate is without effect.

FRUCTOSE DIPHOSPHATE ALDOLASE FROM FUSARIUM OXYSPORUM f. LYCOPERSICI: III. STUDIES ON THE MECHANISM OF REACTION

1967 ◽  
Vol 45 (12) ◽  
pp. 1909-1917 ◽  
Author(s):  
J. M. Ingram
Keyword(s):  
Fusarium Oxysporum ◽  
Proton Exchange ◽  
Base Catalysis ◽  
Dihydroxyacetone Phosphate ◽  
Amino Acid Residues ◽  
Cleavage Rate ◽  
General Base ◽  
Mechanism Of Reaction ◽  
Cleavage Reactions ◽  
Rate Limiting

Frnctose-1,6-diphosphate aldolase from Fusarium oxysporum f. lycopersici is inhibited by acetylimidazole. The inhibition is reduced in the presence of fructose diphosphate or DL-glyceraldehyde-3-phosphate, but not in the presence of dihydroxyacetone phosphate. Under conditions of almost total inactivation, as measured by the rate of cleavage of fructose diphosphate, the decrease in the rate of exchange is only 18%. These results indicate that the amino acid residues which are altered under these conditions are concerned with the D-glyceraldehyde-3-phosphate rather than the dihydroxyacetone phosphate active site.The rate of cleavage of fructose diphosphate in D2O decreases, with increasing pH, more rapidly than the rate in H2O and resembles the decreased rate of tritium exchange into dihydroxyacetone phosphate with increasing pH. These results suggest that a correlation exists between the isolated proton exchange and cleavage reactions and that the decreased rate of exchange and cleavage with increasing pH is due to a decreased rate of proton neutralization of the enzyme – dihydroxyacetone phosphate anion. The addition of acetaldehyde to the aldolase assays at pH 8.0 and pH 9.0 stimulates the cleavage rate of fructose diphosphate to a level normally obtained at pH 7.5, confirming the supposition that the release of dihydroxyacetone phosphate becomes rate limiting with increasing pH. The results obtained by following the cleavage in D2O also indicate that general base catalysis is involved in the proton neutralization step and that the pK of the general base is less than pH 6.0. The evidence suggests that the general base is either a β-COOH of aspartate or a γ-COOH of glutamate.

scholarly journals CFD Modelling of a Hydrogen/Air PEM Fuel Cell with a Serpentine Gas Distributor

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 564
Author(s):  
Alessandro d’Adamo ◽  
Matteo Riccardi ◽  
Massimo Borghi ◽  
Stefano Fontanesi
Keyword(s):  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Catalyst Layer ◽  
Active Surface ◽  
Reaction Rates ◽  
Transport Processes ◽  
Proton Exchange ◽  
Sustainable Mobility ◽  
Cfd Modelling ◽  
Gas Distributor

Hydrogen-fueled fuel cells are considered one of the key strategies to tackle the achievement of fully-sustainable mobility. The transportation sector is paying significant attention to the development and industrialization of proton exchange membrane fuel cells (PEMFC) to be introduced alongside batteries, reaching the goal of complete de-carbonization. In this paper a multi-phase, multi-component, and non-isothermal 3D-CFD model is presented to simulate the fluid, heat, and charge transport processes developing inside a hydrogen/air PEMFC with a serpentine-type gas distributor. Model results are compared against experimental data in terms of polarization and power density curves, including an improved formulation of exchange current density at the cathode catalyst layer, improving the simulation results’ accuracy in the activation-dominated region. Then, 3D-CFD fields of reactants’ delivery to the active electrochemical surface, reaction rates, temperature distributions, and liquid water formation are analyzed, and critical aspects of the current design are commented, i.e., the inhomogeneous use of the active surface for reactions, limiting the produced current and inducing gradients in thermal and reaction rate distribution. The study shows how a complete multi-dimensional framework for physical and chemical processes of PEMFC can be used to understand limiting processes and to guide future development.

scholarly journals Competition between excited state proton and OH− transport via a short water wire: solvent effects open the gate

2014 ◽  
Vol 16 (26) ◽  
pp. 13047-13051 ◽  
Author(s):  
Gül Bekçioğlu ◽  
Christoph Allolio ◽  
Maria Ekimova ◽  
Erik T. J. Nibbering ◽  
Daniel Sebastiani
Keyword(s):  
Excited State ◽  
Exchange Reaction ◽  
Quantum Chemical Calculations ◽  
Solvent Effects ◽  
Quantum Chemical ◽  
Proton Exchange ◽  
Acid Base

We investigate the acid–base proton exchange reaction in a microsolvated bifunctional chromophore by means of quantum chemical calculations.

scholarly journals Polymer Electrolyte Membranes Based on Nafion and a Superacidic Inorganic Additive for Fuel Cell Applications

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 914 ◽  
Author(s):  
Lucia Mazzapioda ◽  
Stefania Panero ◽  
Maria Assunta Navarra
Keyword(s):  
Fuel Cell ◽  
Ion Exchange ◽  
Proton Exchange Membrane ◽  
Sol Gel ◽  
Composite Membranes ◽  
Exchange Capacity ◽  
Proton Exchange ◽  
Thermal Transitions ◽  
Ion Exchange Capacity ◽  
Electrolyte Membranes

Nafion composite membranes, containing different amounts of mesoporous sulfated titanium oxide (TiO2-SO4) were prepared by solvent-casting and tested in proton exchange membrane fuel cells (PEMFCs), operating at very low humidification levels. The TiO2-SO4 additive was originally synthesized by a sol-gel method and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and ion exchange capacity (IEC). Peculiar properties of the composite membranes, such as the thermal transitions and ion exchange capacity, were investigated and here discussed. When used as an electrolyte in the fuel cell, the composite membrane guaranteed an improvement with respect to bare Nafion systems at 30% relative humidity and 110 °C, exhibiting higher power and current densities.

scholarly journals Preparation and Study of Sulfonated Co-Polynaphthoyleneimide Proton-Exchange Membrane for a H2/Air Fuel Cell

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5297
Author(s):  
Ulyana M. Zavorotnaya ◽  
Igor I. Ponomarev ◽  
Yulia A. Volkova ◽  
Alexander D. Modestov ◽  
Vladimir N. Andreev ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Proton Exchange Membrane ◽  
Maximum Output Power ◽  
Exchange Capacity ◽  
Proton Exchange ◽  
Molar Ratio ◽  
Disulfonic Acid ◽  
Membrane Electrode ◽  
Maximum Output ◽  
Practical Applications

The sulfonated polynaphthoyleneimide polymer (co-PNIS70/30) was prepared by copolymerization of 4,4′-diaminodiphenyl ether-2,2′-disulfonic acid (ODAS) and 4,4’-methylenebisanthranilic acid (MDAC) with ODAS/MDAC molar ratio 0.7/0.3. High molecular weight co-PNIS70/30 polymers were synthesized either in phenol or in DMSO by catalytic polyheterocyclization in the presence of benzoic acid and triethylamine. The titration reveals the ion-exchange capacity of the polymer equal to 2.13 meq/g. The membrane films were prepared by casting polymer solution. Conductivities of the polymer films were determined using both in- and through-plane geometries and reached ~96 and ~60 mS/cm, respectively. The anisotropy of the conductivity is ascribed to high hydration of the surface layer compared to the bulk. SFG NMR diffusometry shows that, in the temperature range from 213 to 353 K, the 1H self-diffusion coefficient of the co-PNIS70/30 membrane is about one third of the diffusion coefficient of Nafion® at the same humidity. However, temperature dependences of proton conductivities of Nafion® and of co-PNIS70/30 membranes are nearly identical. Membrane–electrode assemblies (MEAs) based on co-PNIS70/30 were fabricated by different procedures. The optimal MEAs with co-PNIS70/30 membranes are characterized by maximum output power of ~370 mW/cm2 at 80 °C. It allows considering sulfonated co-PNIS70/30 polynaphthoyleneimides membrane attractive for practical applications.

Synthesis and Characterization of Sulfonated Poly(diphenyl ether ketone sulfone)s Containing Dibenzoylbenzene Moiety for Proton Exchange Membrane Fuel Cell

2012 ◽  
Vol 724 ◽  
pp. 412-415
Author(s):  
Md. Awlad Hossain ◽  
Young Don Lim ◽  
Dong Wan Seo ◽  
Soon Ho Lee ◽  
Hyun Chul Lee ◽  
...  
Keyword(s):  
Proton Exchange Membrane ◽  
Diphenyl Ether ◽  
Chlorosulfonic Acid ◽  
Exchange Capacity ◽  
Proton Exchange ◽  
H Nmr ◽  
Ft Ir ◽  
Ether Ketone ◽  
Exchange Membrane ◽  
Sulfonated Poly

Sulfonated poly (diphenyl ether ketone sulfone) s, SPDPEKSs were successfully synthesized for proton exchange membranes (PEMs). Poly (diphenyl ether ketone sulfone) s, PDPEKSs were prepared by the polycondensation of 4,4'-sulfonyldiphenol with 1,2-bis (4-fluorobenzoyl)-3,6-diphenylbenzene (BFBDPB) and 4-fluorophenylsulfone respectively, at 210 °C using anhydrous potassium carbonate as catalyst in sulfolane. PDPEKSs were followed by sulfonation using chlorosulfonic acid and concentrated sulfuric acid at two step reactions. Different contents of sulfonated unit of SPDPEKS (25, 35, 45 mol% of BFBDPB) were studied by FT-IR, 1H NMR spectroscopy, and thermogravimetric analysis (TGA). The ion exchange capacity (IEC), water uptake and proton conductivity of SPDPEKS were evaluated with increase of degree of sulfonation.

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