Micellar laccase-catalyzed synthesis of electroconductive polyaniline

A method of enzymatic synthesis of electroconductive polyaniline on the micelles of dodecylbenzenesulfonic acid sodium salt (DBSNa) is proposed. The high potential laccase from the basidiomycete Trametes hirsuta was used as a biocatalyst. The conditions for polyaniline synthesis were optimized (pH 4.0; reagent concentrations, 10–20 mM; and aniline/DBSNa ratio, 2 : 1). The resulting product was electrochemically active in the range of potentials from ?200 to 600 mV, electroconductive, and capable of reversible dedoping with a change in pH of solution.     

Enzymatic synthesis of a conducting complex of polyaniline and poly(2-arcylamido-2-methyl-1-propanesulfonic ACID) using palm tree peroxidase and its properties

An enzymatic method of producing a conducting polyelectrolyte complex of polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) was developed. Acidic stable peroxidase isolated from royal palm tree (Roystonea regia L.) leaves was used as a catalyst in the oxidative polymerization of aniline at pH 2.8. The synthesis procedure was optimized. Spectroscopic and electrochemical characteristics of nanoparticles of obtained PANI/PAMPS complexes at different pH were studied. It was shown that the acidity of the medium affects their properties.     

Enzymatic synthesis of electroconductive biocomposites based on DNA and optically active polyaniline

Electroconductive interpolymer polyaniline complexes are synthesized on the DNA matrix, using the method of oxidative polymerization of aniline with two different biocatalyzers: horseradish root peroxidase and micropiroxidase-11 biomimetic. The spectral characteristics and morphology of the acquired biocomposites have been studied. The stereospecificity of the acquired samples of interpolymer complexes is shown, depending on the biocatalyzers used. The results acquired indicate the important role of a biocatalyzer in the formation of the twist direction of an electroconductive polymer spiral on the DNA matrix; i.e., the optical activity of the polymer samples acquired is apparently associated with the biocatalyzer properties.     

Enzymatic synthesis of electroconductive biocomposites based on DNA and optically active polyaniline

Electroconductive interpolymer polyaniline complexes are synthesized on the DNA matrix, using the method of oxidative polymerization of aniline with two different biocatalyzers: horseradish root peroxidase and micropiroxidase-11 biomimetic. The spectral characteristics and morphology of the acquired biocomposites have been studied. The stereospecificity of the acquired samples of interpolymer complexes is shown, depending on the biocatalyzers used. The results acquired indicate the important role of a biocatalyzer in the formation of the twist direction of an electroconductive polymer spiral on the DNA matrix; i.e., the optical activity of the polymer samples acquired is apparently associated with the biocatalyzer properties.     

Enzymatic synthesis of a conducting complex of polyaniline and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) using palm tree peroxidase and its properties

An enzymatic method of producing a conducting polyelectrolyte complex of polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) was developed. Acidic stable peroxidase isolated from royal palm tree (Roystonea regia L.) leaves was used as a catalyst in the oxidative polymerization of aniline at pH 2.8. The synthesis procedure was optimized. Spectroscopic and electrochemical characteristics of nanoparticles of obtained PANI/PAMPS complexes at different pH were studied. It was shown that the acidity of the medium affects their properties.__________Translated from Prikladnaya Biokhimiya i Mikrobiologiya, Vol. 41, No. 3, 2005, pp. 283–287.Original Russian Text Copyright © 2005 by Mazhugo, Caramyshev, Shleev, Sakharov, Yaropolov.     

Synthesis of electroconductive polyaniline using immobilized laccase

A new method for synthesis of the conductive complex between polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (PAMPS) was proposed; in this method, the immobilized laccase from the basidiomycete Trametes hirsuta is used as a biocatalyst for aniline oxidative polymerization. The conditions for laccase immobilization on CM cellulose by bifunctional Woodward’s reagent were optimized. The catalytic properties of immobilized and native laccases were compared. The immobilized laccase appeared an efficient catalyst for the oxidative radical polymerization of aniline on polysulfonic acid matrix at 4°C. It was demonstrated that the immobilized enzyme could be repeatedly used for enzymatic synthesis of this polymer. Several spectral characteristics of the PANI/PAMPS complexes synthesized at various pH values were studied. The conductance of PANI specimens produced using immobilized laccase as a catalyst was 13 mS/cm.     

Microbial electron uptake in microbial electrosynthesis: a mini-review

Journal of Industrial Microbiology & Biotechnology - Microbial electron uptake (EU) is the biological capacity of microbes to accept electrons from electroconductive solid materials. EU has...     

β-(1→4)-d-glucan synthesis from UDOP-[14C]-d- glucose by a solubilized enzyme from Lupinus albus

The particulate enzyme responsible for the synthesis of β-(1→4)-d-glucans from UDP-[¹⁴C-d-glucose has been solubilized and some of its properties have been characterized. Mg²⁺ markedly enhanced synthesis of β-(1→4)-d-glucans and inhibited synthesis of β-(1→3)-d-glucans. The optimal pH for synthesis of β-(1→4)-d-glucans is near pH 8 and the synthesis was enhanced in these preparations by d-glucose, methyl-β-d-glucopyranoside and cellobiose.     

The influence of the culture pH value on the direct glucose oxidative pathway in Klebsiella pneumoniae NCTC 418

Klebsiella pneumoniae NCTC 418 was cultured aerobically in chemostat cultures (D=0.3 h^-1; 35°C) under respectively carbon-, phosphate-, potassium-, sulphate-, and ammonia-limited conditions with glucose as the sole carbon and energy source. The effect of the external pH value on glucose metabolism and on the enzymes of the direct glucose oxidative pathway was examined. The pH value of the medium had a profound influence on both the activity and the synthesis of the glucose dehydrogenase and the gluconate dehydrogenase. At pH values ranging from pH 5.5 to pH 6.0 maximal activity and synthesis of these enzymes resulted in a more than 80% conversion of the glucose consumed into gluconate and 2-ketogluconate under potassium-or phosphate-limited conditions. On the other hand, no gluconate and/or 2-ketogluconate production could be detected when K. pneumoniae was cultured at pH 8.0. Whereas the synthesis of gluconate dehydrogenase seemingly was completely repressed, still some glucose dehydrogenase was present. The lack of glucose dehydrogenase activity at pH 8.0 was shown not to be due to the dissociation of the cofactor PQQ from the enzyme.Abbreviations DCIP dichlorophenol indophenol - PQQ pyrroloquinoline quinone [2,7,9-tricarboxy-1H-pyrrolo (2,3-f) quinoline-4,5-dione] - WB Wurster's Blue [1,4-bis-(dimethylamino)-benzene perchlorate]     

Oxidative phosphorylation by membrane vesicles from Bacillus alcalophilus

ADP and Pi-loaded membrane vesicles from t-malate-grown Bacillus alcalophilus synthesized ATP upon energization with ascorbate/N,N,N',N'-tetra-methyl-P-phenylenediamine. ATP synthesis occurred over a range of external pH from 6.0 to 11.0, under conditions in which the total protonmotive force delta-mu-H+ was as low as -30 mV. The phosphate potentials (delta Gp) were calculated to be 11 and 12 kcal/mol at pH 10.5 and 9.0, respectively, whereas the delta-mu-H+ values in vesicles at these two pH values were quite different (-40 +/- 20 mV at pH 10.5 and -125 +/- 20 mV at pH 9.0). ATP synthesis was inhibited by KCN, gramicidin, and by N,N1-dicyclohexylcarbodiimide. Inward translocation of protons, concomitant with ATP synthesis, was demonstrated using direct pH monitoring and fluorescence methods. No dependence upon the presence of Na+ or K+ was found. Thus, ATP synthesis in B. alcalophilus appears to involve a proton-translocating ATPase which functions at low delta-mu-H+.     

The effect of synthesis media on the properties of substituted polyaniline/chitosan composites

Substituted polyaniline/chitosan (sPANI/Ch) composites were chemically synthesized in H₂SO₄ and CH₃COOH synthesis media. Structural and physical properties of the composites were characterized by using FTIR, SEM, TGA, UV–vis, XRD techniques, and conductivity measurements. The effect of synthesis media on morphology, thermal stability, conductivity, and crystalline properties was investigated. Chemical interactions between substituted polyanilines and chitosan were explained using FTIR spectra results. The different morphological surfaces were observed in SEM images of the composites. The size of the substituted polyaniline/chitosan (sPANI/Ch) composites was in nanoscale, and the composites synthesized in acetic acid media showed smaller structures than those of H₂SO₄ media and pure chitosan. It was interpreted from XRD results that the composites have amorphous structure and the PNEANI/Ch–CH₃COOH composite has the highest crystallinity.     

Enzymatically Synthesized Polyaniline Doped with Copper Ions: Physico-Chemical and Antimicrobial Properties of the Product

Applied Biochemistry and Microbiology - Enzymatic synthesis of the polyaniline (PANI)/sodium polystyrenesulfonate (PSS) interpolyelectrolyte complex, in which PANI is doped with Cu(II) ions, has...     

Green synthesis of conductive polyaniline by Trametes versicolor laccase using a DNA template

The green synthesis of highly conductive polyaniline by using two biological macromolecules, i.e laccase as biocatalyst, and DNA as template/dopant, was achieved in this work. Trametes versicolor laccase B (TvB) was found effective in oxidizing both aniline and its less toxic/mutagenic dimer N‐phenyl‐p‐phenylenediamine (DANI) to conductive polyaniline. Reaction conditions for synthesis of conductive polyanilines were set‐up, and structural and electrochemical properties of the two polymers were extensively investigated. When the less toxic aniline dimer was used as substrate, the polymerization reaction was faster and gave less‐branched polymer. DNA was proven to work as hard template for both enzymatically synthesized polymers, conferring them a semi‐ordered morphology. Moreover, DNA also acts as dopant leading to polymers with extraordinary conductive properties (～6 S/cm). It can be envisaged that polymer properties are magnified by the concomitant action of DNA as template and dopant. Herein, the developed combination of laccase and DNA represents a breakthrough in the green synthesis of conductive materials.     

Hepatic urea synthesis and pH regulation. Role of CO2, HCO3-, pH and the activity of carbonic anhydrase

In isolated perfused rat liver, urea synthesis from ammonium ions was dependent on extracellular HCO3- and CO2 concentrations when the HCO3-/CO2 ratio in the influent perfusate was constant (pH 7.4). Urea synthesis was half-maximal at HCO3- = 4 mM, CO2 = 0.19 mM and was maximal at HCO3- and CO2 concentrations above 20 mM and 0.96 mM, respectively. At physiological HCO3- (25 mM) and CO2 (1.2 mM) concentrations in the influent perfusate, acetazolamide, the inhibitor of carbonic anhydrase, inhibited urea synthesis from ammonium ions (1 mM) by 50-60% and led to a 70% decrease in citrulline tissue levels. Acetazolamide concentrations required for maximal inhibition of urea synthesis were 0.01-0.1 mM. At subphysiological HCO3- and CO2 concentrations, inhibition of urea synthesis by acetazolamide was increased up to 90%. Inhibition of urea synthesis by acetazolamide was fully overcome in the presence of unphysiologically high HCO3- and CO2 concentrations, indicating that the inhibitory effect of acetazolamide is due to an inhibition of carbonic-anhydrase-catalyzed HCO3- supply for carbamoyl-phosphate synthetase, which can be bypassed when the uncatalyzed intramitochondrial HCO3- formation from portal CO2 is stimulated in the presence of high portal CO2 concentrations. With respect to HCO3- supply of mitochondrial carbamoyl-phosphate synthetase, urea synthesis can be separated into a carbonic-anhydrase-dependent (sensitive to acetazolamide at 0.5 mM) and a carbonic-anhydrase-independent (insensitive to acetazolamide) portion. Carbonic-anhydrase-independent urea synthesis linearly increased with the portal 'total CO2 addition' (which was experimentally determined to be CO2 addition plus 0.036 HCO3- addition) and was independent of the perfusate pH. At a constant 'total CO2 addition', carbonic-anhydrase-dependent urea synthesis was strongly affected by perfusate pH and increased about threefold when the perfusate pH was raised from 6.9 to 7.8. It is concluded that the pH dependent regulation of urea synthesis is predominantly due to mitochondrial carbonic anhydrase-catalyzed HCO3- supply for carbamoyl phosphate synthesis, whereas there is no control of urea synthesis by pH at the level of the five enzymes of the urea cycle. Because HCO3- provision for carbamoyl phosphate synthetase increases with increasing portal CO2 concentrations even in the absence of carbonic anhydrase activity, susceptibility of ureogenesis to pH decreases with increasing portal CO2 concentrations. This may explain the different response of urea synthesis to chronic metabolic and chronic respiratory acidosis in vivo.     

Synthesis of conducting polyelectrolyte complexes of polyaniline and poly(2-acrylamido-3-methyl-1-propanesulfonic acid) catalyzed by pH-stable palm tree peroxidase

Comparison of the stability of five plant peroxidases (horseradish, royal palm tree leaf, soybean, and cationic and anionic peanut peroxidases) was carried out under acidic conditions favorable for synthesis of polyelectrolyte complexes of polyaniline (PANI). It demonstrates that palm tree peroxidase has the highest stability. Using this peroxidase as a catalyst, the enzymatic synthesis of polyelectrolyte complexes of PANI and poly(2-acrylamido-3-methyl-1-propanesulfonic acid) (PAMPS) was developed. The template polymerization of aniline was carried out in aqueous buffer at pH 2.8. Varying the concentrations of aniline, PAMPS, and hydrogen peroxide as reagents, favorable conditions for production of PANI were determined. UV-vis-NIR absorption and EPR demonstrated that PAMPS and PANI formed the electroactive complex similar to PANI doped traditionally using low molecular weight sulfonic acids. The effect of pH on conformational variability of the complex was evaluated by UV-vis spectroscopy. Atomic force microscopy showed that a size of the particles of the PANI-PAMPS complexes varied between 10 and 25 nm, depending on a concentration of PAMPS in the complex. The dc conductivity of the complexes depends also on the content of PAMPS, the higher conductivity being for the complexes containing the lower content of the polymeric template.     

Power production enhancement with a polyaniline modified anode in microbial fuel cells

In this paper, an approach of improving power generation of microbial fuel cells (MFCs) by using a HSO(4)(-) doped polyaniline modified carbon cloth anode was reported. The modification of carbon cloth anode was accomplished by electrochemical polymerization of aniline in 5% H(2)SO(4) solution. A dual-chamber MFC reactor with the modified anode achieved a maximum power density of 5.16 Wm(-3), an internal resistance of 90 Ω, and a start-up time of 4 days, which was respectively 2.66 times higher, 65.5% lower, and 33.3% shorter than the corresponding values of the MFC with unmodified anode. Evidence from X-ray photoelectron spectroscopy and scanning electron microscopy results proved that the formation of biofilm on the anode surface could prevent the HSO(4)(-) doped polyaniline to be de-doped, and the results from electrochemical tests confirmed that the electrochemical activity of the modified anode was enhanced significantly after inoculation. Charge transfer was facilitated by polyaniline modification. All the results indicated that the polyaniline modification on the anode was an efficient approach of improving the performance of MFCs.     

Effect of extracellular ph on matrix synthesis by chondrocytes in 3D agarose gel

In cartilage tissue engineering, the determination of the most appropriate cell/tissue culture conditions to maximize extracellular matrix synthesis is of major importance. The extracellular pH plays an important role in affecting energy metabolism and matrix synthesis by chondrocytes. In this study, chondrocytes were isolated from bovine articular cartilage, embedded in agarose gel, and cultured at varied pH levels (7.3-6.6). Rate of lactate production, total glycosaminoglycan (GAG) and collagen synthesis, as well as total cell numbers and cell viability were evaluated after culturing for up to 7 days. The results showed the rate of lactic acid production over the 7-day culture was significantly affected by extracellular pH; acidic pH markedly inhibited the production of lactate. Also, a biphasic response to extracellular pH in regard to total GAG synthesis was observed; the maximum synthesis was seen at pH 7.2. However, the collagen synthesis was not pH-dependent within the pH range explored. In addition, within the conditions studied, total cell numbers and cell viability were not significantly affected by extracellular pH. In conclusion, even minor changes in extracellular pH could markedly affect the metabolic activities and biosynthetic ability of chondrocytes. Consequently, the control of extracellular pH condition is crucially important for successful cartilage tissue engineering and for the study of chondrocyte physiology and functions.     

H+/ATP ratio of proton transport-coupled ATP synthesis and hydrolysis catalysed by CF0F1-liposomes

The H(+)/ATP ratio and the standard Gibbs free energy of ATP synthesis were determined with a new method using a chemiosmotic model system. The purified H(+)-translocating ATP synthase from chloroplasts was reconstituted into phosphatidylcholine/phosphatidic acid liposomes. During reconstitution, the internal phase was equilibrated with the reconstitution medium, and thereby the pH of the internal liposomal phase, pH(in), could be measured with a conventional glass electrode. The rates of ATP synthesis and hydrolysis were measured with the luciferin/luciferase assay after an acid-base transition at different [ATP]/([ADP][P(i)]) ratios as a function of deltapH, analysing the range from the ATP synthesis to the ATP hydrolysis direction and the deltapH at equilibrium, deltapH (eq) (zero net rate), was determined. The analysis of the [ATP]/([ADP][P(i)]) ratio as a function of deltapH (eq) and of the transmembrane electrochemical potential difference, delta micro approximately (H)(+) (eq), resulted in H(+)/ATP ratios of 3.9 +/- 0.2 at pH 8.45 and 4.0 +/- 0.3 at pH 8.05. The standard Gibbs free energies of ATP synthesis were determined to be 37 +/- 2 kJ/mol at pH 8.45 and 36 +/- 3 kJ/mol at pH 8.05.     

Production of lovastatin examined by an integrated approach based on chemometrics and DOSY-NMR

The penicillin acylase-catalyzed synthesis of ampicillin by acyl transfer from D-(-)-phenylglycine amide (D-PGA) to 6-aminopenicillanic acid (6-APA) becomes more effective when a judiciously chosen pH gradient is applied in the course of the process. This reaction concept is based on two experimental observations: 1) The ratio of the initial synthesis and hydrolysis rates (V(S)/V(H)) is pH-dependent and exhibits a maximum at pH 6.5-7.0 for a saturated solution of 6-APA; 2) at a fixed 6-APA concentration below saturation, V(S)/V(H) increases with decreasing pH. Optimum synthetic efficiency could, therefore, be achieved by starting with a concentrated 6-APA solution at pH 7 and gradually decreasing the pH to 6.3 in the course of 6-APA consumption. A conversion of 96% of 6-APA and 71% of D-PGA into ampicillin was accomplished in an optimized procedure, which significantly exceeds the efficiency of enzymatic synthesis performed at a constant pH of either 7.0 or 6.3.     

Behavior of glucose oxidase immobilized in various electropolymerized thin films

Glucose oxidase was immobilized by electropolymerization into films of polyaniline, polyindole, polypyrrole, poly(o-phenylediamine), and polyaniline crosslinked with p-phenylenediamine. The kinetics and the behavior of the entrapped enzyme toward elevated temperature, organic solvent denaturation, and pH were investigated, along with the response of the films to electroactive species such as acetaminophen, ascorbate, cysteine, and uric acid. For most of the films, linearity to glucose extended from 7 to 10 mM. The poly(o-phenylenediamine)/glucose oxidase film gave the best signal/noise ratio and polypyrrole/glucose oxidase film gave the most reproducible current responses. No significant shift of the optimum reaction pH (5.5), except for polypyrrole (5.0), was observed after immobilization of glucose oxidase in the various films. Enzymatic activity decreased rapidly when pH was raised above 7.5. Thermodeactivation studies at 55 degrees , 60 degrees , and 65 degrees C have shown polypyrrole/and poly(o-phenylediamine)/glucose oxidase films to be the most resistant enzymatic films. Poly(o-phenylenediamine) films offered the best protection against glucose oxidase deactivation in hexane, chloroform, ether, THF, and acetonitrile when compared with the other electropolymerized films. All the enzymatic films exhibited permselection toward electroactive species. (c) 1996 John Wiley & Sons, Inc.