scholarly journals Thermodynamic and Kinetic Aspects on the Biosorption of Cadmium by Low Cost Materials: A Review

2006 ◽  
Vol 3 (6) ◽  
pp. 400 ◽  
Author(s):  
Pablo Lodeiro ◽  
Roberto Herrero ◽  
Manuel E. Sastre de Vicente
Keyword(s):  
Low Cost ◽  
Kinetic Studies ◽  
Chemical Precipitation ◽  
Point Of View ◽  
Biological Origin ◽  
Biosorption Process ◽  
Low Concentrations ◽  
Passive Adsorption ◽  
High Concentrations

Environmental Context. The toxicity of cadmium in waters can be decreased by using a wide variety of low-cost biomaterials. A number of such investigations are reviewed here and the models used to describe the process of biosorption discussed. Fundamental investigations that probe the thermodynamics and kinetics of the biosorption process are essential for a strong understanding of all biosorption processes. Areas that still need addressing are highlighted, in particular with regard to cadmium biosorption, some models for which are ready to be tested in pilot plants. Abstract. Cadmium is internationally recognized as an important pollutant in the environment, and different methods for its removal from wastewaters (chemical precipitation being the most commonly used) have been reported in the literature. Those methods are in most cases oriented to situations with high concentrations of the pollutant. Thus, alternative removal and recovery methods are being considered for removing very low concentrations of cadmium. These methods are all based on biosorption, the passive adsorption and sequestration of metals by several natural materials of biological origin. In this review we have considered the biosorption of cadmium onto biomaterials from a physicochemical, thermodynamic, and kinetic perspective. The thermodynamic perspective is based on the characterization of the interactions of the binding sites of the biosorbents with cadmium species in aqueous solution. Traditionally, this approach has been quantified using different kinds of isotherms. In addition, the description is completed by taking into account electrostatic effects, and the influence of pH and ionic strength, which are associated with the negative charge developed, in most cases, by the biomaterial. The other point of view in this review is the kinetic one, which is necessary for a full physicochemical description of the sorbate–biosorbent system. Consequently, an updated description of the various approaches commonly employed in kinetic studies in biosorption has been carried out.

scholarly journals The enzymology of short-chain fatty acyl-coenzyme A synthetase from seeds of Pinus radiata. Kinetic studies and a proposed reaction mechanism

1974 ◽  
Vol 137 (3) ◽  
pp. 435-442 ◽  
Author(s):  
Owen A. Young ◽  
John W. Anderson
Keyword(s):  
Fatty Acid ◽  
Pinus Radiata ◽  
Kinetic Studies ◽  
Single Species ◽  
Competitive Inhibitor ◽  
Fatty Acyl ◽  
Short Chain ◽  
Low Concentrations ◽  
High Concentrations ◽  
Acyl Coenzyme A

1. Short-chain fatty acyl-CoA synthetase from seeds of Pinus radiata was examined by acetate- and propionate-dependent PPi–ATP exchange. Reaction mixtures came to equilibrium almost instantly as judged by rates of exchange and analysis of an incubation mixture. 2. The activity of the enzyme was correlated with the concentration of MgP2O72- but not with the concentration of Mg2+, as judged by PPi–ATP exchange and fatty acyl AMP-dependent synthesis of ATP in the presence of PPi. In PPi–ATP exchange assays, no clear relationship between activity and any single species of ATP was apparent. 3. High concentrations of fatty acid inhibited PPi–ATP exchange. PPi–dATP exchange was less than PPi–ATP exchange at low concentrations of fatty acid, but at higher concentrations PPi–dATP exchange exceeded PPi–ATP exchange. The rate of synthesis of fatty acyl-CoA in the presence of dATP was less than with ATP. 4. ATP and propionate inhibited the synthesis of ATP from propionyl-AMP and PPi. The inhibition by ATP was competitive with respect to propionyl-AMP and non-competitive with respect to PPi. The inhibition by propionate was non-competitive with respect to propionyl-AMP and PPi. 5. AMP was a competitive inhibitor of propionyl-AMP-dependent synthesis of ATP and competitively inhibited propionate-dependent PPi–ATP exchange when ATP was the variable substrate. 6. It was concluded that the first partial reaction catalysed by the enzyme is ordered; ATP is the first substrate to react with the enzyme and PPi is probably the only product released.

scholarly journals The binding of oxidized coenzymes by glutamate dehydrogenase and the effects of glutarate and purine nucleotides

1972 ◽  
Vol 126 (4) ◽  
pp. 975-984 ◽  
Author(s):  
K. Dalziel ◽  
R. R. Egan
Keyword(s):  
Glutamate Dehydrogenase ◽  
Dissociation Constants ◽  
Equilibrium Dialysis ◽  
Kinetic Studies ◽  
Binding Studies ◽  
Purine Nucleotides ◽  
Active Centre ◽  
Sodium Phosphate Buffer ◽  
Low Concentrations ◽  
High Concentrations

1. The binding of NAD+ and NADP+ to glutamate dehydrogenase has been studied in sodium phosphate buffer, pH7.0, by equilibrium dialysis. Approximate values for the dissociation constants are 0.47 and 2.5mm respectively. For NAD+ the value agrees with that estimated from initial-rate results. 2. In the presence of the substrate analogue glutarate both coenzymes are bound more firmly, and there is one active centre per enzyme subunit. The binding results cannot be described in terms of independent and identical active centres, and binding is stronger at low coenzyme concentrations than at high concentrations. Either the six subunits of the oligomer are not identical or there are negative interactions between them in the binding of coenzymes in ternary complexes with glutarate. The latter explanation is favoured. 3. The binding studies support the conclusions drawn from earlier kinetic studies of the glutamate reaction. 4. ADP and GTP respectively decrease and increase the affinity of the enzyme for NAD+ and NADP+, in both the presence and absence of glutarate. The negative binding interactions in the presence of glutarate are abolished by ADP, which decreases the affinity for the coenzymes at low concentrations of the latter. 5. In the presence of glutarate, GTP and NAD+ or NADP+, the association of enzyme oligomers is prevented, and the solubility of the enzyme is decreased; the complex of enzyme and ligands readily crystallizes. 6. The results are discussed in relation to earlier kinetic studies.

scholarly journals Construction and Characterization of Two Recombinant Bacteria That Grow on ortho- and para-Substituted Chlorobiphenyls

1999 ◽  
Vol 65 (5) ◽  
pp. 2163-2169 ◽  
Author(s):  
Yarek Hrywna ◽  
Tamara V. Tsoi ◽  
Olga V. Maltseva ◽  
John F. Quensen ◽  
James M. Tiedje
Keyword(s):  
Sole Carbon Source ◽  
Polychlorinated Biphenyl ◽  
Cloning And Expression ◽  
Cell Protein ◽  
Arthrobacter Globiformis ◽  
Comamonas Testosteroni ◽  
Recombinant Bacteria ◽  
Low Concentrations ◽  
High Concentrations

ABSTRACT Cloning and expression of the aromatic ring dehalogenation genes in biphenyl-growing, polychlorinated biphenyl (PCB)-cometabolizingComamonas testosteroni VP44 resulted in recombinant pathways allowing growth on ortho- andpara-chlorobiphenyls (CBs) as a sole carbon source. The recombinant variants were constructed by transformation of strain VP44 with plasmids carrying specific genes for dehalogenation of chlorobenzoates (CBAs). Plasmid pE43 carries the Pseudomonas aeruginosa 142 ohb genes coding for the terminal oxygenase (ISPOHB) of the ortho-halobenzoate 1,2-dioxygenase, whereas plasmid pPC3 contains the Arthrobacter globiformis KZT1 fcb genes, which catalyze the hydrolytic para-dechlorination of 4-CBA. The parental strain, VP44, grew only on low concentrations of 2- and 4-CB by using the products from the fission of the nonchlorinated ring of the CBs (pentadiene) and accumulated stoichiometric amounts of the corresponding CBAs. The recombinant strains VP44(pPC3) and VP44(pE43) grew on, and completely dechlorinated high concentrations (up to 10 mM), of 4-CBA and 4-CB and 2-CBA and 2-CB, respectively. Cell protein yield corresponded to complete oxidation of both biphenyl rings, thus confirming mineralization of the CBs. Hence, the use of CBA dehalogenase genes appears to be an effective strategy for construction of organisms that will grow on at least some congeners important for remediation of PCBs.

scholarly journals Cloning and Expression of the Inositol Monophosphatase Gene from Methanococcus jannaschii and Characterization of the Enzyme

1998 ◽  
Vol 64 (7) ◽  
pp. 2609-2615 ◽  
Author(s):  
Liangjing Chen ◽  
Mary F. Roberts
Keyword(s):  
Gene Product ◽  
Heat Stability ◽  
Cloning And Expression ◽  
Hyperthermophilic Archaea ◽  
Methanococcus Jannaschii ◽  
Inositol Monophosphatase ◽  
E Coli ◽  
Low Concentrations ◽  
High Concentrations

ABSTRACT Inositol monophosphatase (EC 3.1.3.25 ) plays a pivotal role in the biosynthesis of di-myo-inositol-1,1′-phosphate, an osmolyte found in hyperthermophilic archaea. Given the sequence homology between the MJ109 gene product of Methanococcus jannaschii and human inositol monophosphatase, the MJ109 gene was cloned and expressed in Escherichia coli and examined for inositol monophosphatase activity. The purified MJ109 gene product showed inositol monophosphatase activity with kinetic parameters (Km = 0.091 ± 0.016 mM;V max = 9.3 ± 0.45 μmol of Pi min−1 mg of protein−1) comparable to those of mammalian and E. coli enzymes. Its substrate specificity, Mg2+ requirement, Li+inhibition, subunit association (dimerization), and heat stability were studied and compared to those of other inositol monophosphatases. The lack of inhibition by low concentrations of Li+ and high concentrations of Mg2+ and the high rates of hydrolysis of glucose-1-phosphate and p-nitrophenylphosphate are the most pronounced differences between the archaeal inositol monophosphatase and those from other sources. The possible causes of these kinetic differences are discussed, based on the active site sequence alignment between M. jannaschii and human inositol monophosphatase and the crystal structure of the mammalian enzyme.

Yeast actin with a subdomain 4 mutation (A204C) exhibits increased pointed-end critical concentration

2007 ◽  
Vol 85 (3) ◽  
pp. 319-325 ◽  
Author(s):  
David J. Teal ◽  
John F. Dawson
Keyword(s):  
Actin Polymerization ◽  
Critical Concentration ◽  
Structural Studies ◽  
Wild Type ◽  
Low Concentrations ◽  
Engineering Strategy ◽  
High Concentrations ◽  
Pointed End ◽  
Very High

Characterizing mutants of actin that do not polymerize will advance our understanding of the mechanism of actin polymerization and will be invaluable for the production of short F-actin structures for structural studies. To circumvent the problem of expressing dominant lethal nonpolymerizing actin in yeast, we adopted a cysteine engineering strategy. Here we report the characterization of a mutant of yeast actin, AC-actin, possessing a single pointed-end mutation, A204C. Expression of this mutant in yeast results in actin-polymerization-deficient phenotypes. When copolymerized with wild-type actin, ATP–AC-actin is incorporated into filaments. ADP–AC-actin participates in the nucleation and elongation of wild-type filaments only at very high concentrations. At low concentrations, ADP–AC-actin appears to participate only in the nucleation of wild-type filaments, suggesting that Ala-204 is involved in modulating the critical concentration of the pointed end of actin.

scholarly journals Adsorptive removal of azithromycin from aqueous solutions using raw and saponin-modified nano diatomite

2019 ◽  
Vol 80 (5) ◽  
pp. 939-949
Author(s):  
Siavash Davoodi ◽  
Behnaz Dahrazma ◽  
Nasser Goudarzi ◽  
Hajar Ghasemian Gorji
Keyword(s):  
Aqueous Solutions ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Low Cost ◽  
Maximum Adsorption Capacity ◽  
X Ray ◽  
Low Concentrations ◽  
Intra Particle Diffusion ◽  
High Concentrations

Abstract This study aims to investigate the performance and mechanism of raw (R-ND) and saponin-modified nano diatomite (M-ND) in the removal of azithromycin from aqueous solutions. Adsorbent characterization was performed using X-ray fluorescence, Brunauer–Emmett–Teller (BET), scanning electron spectroscopy, dynamic light scattering and energy-dispersive X-ray analyses. It was shown that the specific surface area of R-ND was 119.5 m2/g, 14-fold higher than that for raw diatomite, and for M-ND it was 90.1 m2/g. Various adsorption conditions, i.e. adsorbent dosage, pH, initial concentration and contact time were investigated. According to the results, despite reducing the specific surface area by 25%, modification of nano diatomite by saponin markedly enhanced its performance in the removal of azithromycin. The maximum adsorption capacity of R-ND and M-ND in the removal of azithromycin was 68 and 91.7 mg/g, respectively. Fourier transform infrared spectroscopy results revealed that azithromycin was adsorbed by O-H groups on the diatomite surface. Weber–Morris intra-particle diffusion (IPD) model suggested that while IPD is not the rate-controlling step in high concentrations of azithromycin, it is the only step that controls the rate of adsorption in low concentrations. In comparison to R-ND, M-ND showed a higher efficiency in the removal of azithromycin and, therefore, it can be used as a promising low-cost adsorbent to remove azithromycin from aqueous solutions.

scholarly journals The cellulolytic enzymes of Botryodiplodia theobromae Pat. Separation and characterization of cellulases and β-glucosidases

1979 ◽  
Vol 177 (1) ◽  
pp. 9-19 ◽  
Author(s):  
Gabriel M. Umezurike
Keyword(s):  
Molecular Weight ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Exchange Chromatography ◽  
Cellulolytic Enzymes ◽  
Botryodiplodia Theobromae ◽  
Molecular Weights ◽  
Low Concentrations ◽  
High Concentrations

1. Filtrates from cultures of different ages of Botryodiplodia theobromae Pat. were fractionated by gel filtration, ion-exchange chromatography and polyacrylamide-gel electrophoresis. 2. Five cellulases (C1, C2, C3, C4 and C5) were found, and their molecular weights, estimated by gel filtration, were 46000–48000 (C1), 30000–35000 (C2), 15000–18000 (C3), 10000–11000 (C4) and 4800–5500 (C5). 3. Cellulase C5 was absent from old culture filtrates. 4. Cellulase C1 had little or no activity on CM-cellulose (viscometric assay), but degraded cotton flock and Whatman cellulose powder to give cellobiose only. 5. The other components (C2–C5) produced cellobiose and smaller amounts of glucose and cellotriose from cellulosic substrates and were more active in lowering the viscosity of CM-cellulose. 6. The ratio of activities assayed by viscometry and by the release of reducing sugars from CM-cellulose increased with decrease in the molecular weights of cellulases C2–C5. 7. Cellobiose inhibited the activities of the cellulases, but glucose stimulated at low concentrations although it inhibited at high concentrations. 8. A high-molecular-weight β-glucosidase (component B1, mol.wt. 350000–380000) predominated in filtrates from young cultures, but a low-molecular-weight enzyme (B4, mol.wt. 45000–47000) predominated in older filtrates. 9. Intermediate molecular species of β-glucosidase (B2, mol.wt. 170000–180000; B3, mol.wt. 83000–87000) were also found. 10. Cellulases C2–C5 acted in synergism with C1, particularly in the presence of β-glucosidase.

Isolation and characterization of rat skeletal myoblast mutants resistant to lectins

1983 ◽  
Vol 3 (12) ◽  
pp. 2166-2171
Author(s):  
B Gilfix ◽  
J Rogers ◽  
B D Sanwal
Keyword(s):  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Wild Type ◽  
Skeletal Myoblast ◽  
Skeletal Myoblasts ◽  
Isolation And Characterization ◽  
Low Concentrations ◽  
High Concentrations ◽  
Made In

Mutants resistant to the lethal action of the lectins phytohemagglutinin A (PHA) and wheat germ agglutinin (WGA) have been made in a line of differentiating rat skeletal myoblasts. The WGA mutants are of two types, WGArII, resistant to low concentrations of the lectin, and WGArI, resistant to high concentrations of the lectin. WGArII and PHAr mutants are unable to differentiate, whereas WGArI mutants differentiate normally. WGArII mutants are not impaired in the binding of wheat germ agglutinin, but WGArI mutants bind the lectin only to the extent of about 50% of the wild-type values. All of the mutants are cross-resistant to lectins other than those used in their selection.

Radioenzymatic Assay of Catecholamines: Reversal of Aluminium Inhibition of Enzymatic O-Methylation by Desferrioxamine

1983 ◽  
Vol 20 (2) ◽  
pp. 105-111 ◽  
Author(s):  
L Mason ◽  
C Weinkove
Keyword(s):  
Complex Formation ◽  
Biological Samples ◽  
Chelating Agent ◽  
Kinetic Studies ◽  
Metal Chelating ◽  
Radioenzymatic Assay ◽  
Low Concentrations ◽  
High Concentrations

Alumina is commonly used for the purification and concentration of catecholamines in biological specimens before analysis. Acid eluates of alumina, found to contain high concentrations of A13+, interfered with O-methylation but not with N-methylation. The chemistry of the catecholamines, supported by kinetic studies, suggest that complex formation between aluminium and the substrate account for the observed inhibition of O-methylation. The addition of desferrioxamine, a metal-chelating agent, to the reaction mixture reversed this inhibition and, by allowing a preliminary alumina extraction, permits the measurement of low concentrations of catecholamines in biological samples.

scholarly journals Isolation and characterization of rat skeletal myoblast mutants resistant to lectins.

1983 ◽  
Vol 3 (12) ◽  
pp. 2166-2171 ◽  
Author(s):  
B Gilfix ◽  
J Rogers ◽  
B D Sanwal
Keyword(s):  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Wild Type ◽  
Skeletal Myoblast ◽  
Skeletal Myoblasts ◽  
Isolation And Characterization ◽  
Low Concentrations ◽  
High Concentrations ◽  
Made In

Mutants resistant to the lethal action of the lectins phytohemagglutinin A (PHA) and wheat germ agglutinin (WGA) have been made in a line of differentiating rat skeletal myoblasts. The WGA mutants are of two types, WGArII, resistant to low concentrations of the lectin, and WGArI, resistant to high concentrations of the lectin. WGArII and PHAr mutants are unable to differentiate, whereas WGArI mutants differentiate normally. WGArII mutants are not impaired in the binding of wheat germ agglutinin, but WGArI mutants bind the lectin only to the extent of about 50% of the wild-type values. All of the mutants are cross-resistant to lectins other than those used in their selection.

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