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A new florescent oligo(aminopyrene) (OAP) was successfully synthesized by enzymatic approach. For this, H2O2and Horse Radish peroxidase (HRP) were used as catalyst and oxidant, respectively. The structures of monomer and oxidation product were confirmed by NMR, FT-IR and UV-Vis measurements. The oxidation product was characterized by gel permeation chromatography (GPC), thermogravimetry (TG), differential scanning calorimetry (DSC), cyclic voltammetry (CV), photoluminescence (PL) and scanning electron microscopy (SEM) analyses. OAP was soluble in a wide range of organic solvents. UV-Vis spectrum of the OAP showed a dramatic red shift compared to that of the monomer. The optical and electrochemical band gaps of OAP were found to be 1.65 and 1.56 eV, respectively. OAP emitted turquoise color in THF and green color in toluene. SEM observations indicated the presence of a heterogeneous cauliflower like morphology. [ABSTRACT FROM PUBLISHER]

Quercetin is a flavonol found in fruits, onions and wine. Recently, quercetin has been extensively investigated for its antioxidant behavior in food such as poultry and fish. While quercetin has been shown to be a good stabilizer for several oils, the thermal stability and solubility at neutral and slightly alkaline conditions continue to be an area of huge concern. However, increasing the stability and the antioxidant potency of this flavonol would be beneficial to the food industry. We utilized horseradish peroxidase, a phytochemical enzyme, to polymerize quercetin in biocompatible water/ethanol mixtures. This unique, one pot procedure has provided a method to synthesize polyquercetin under mild conditions. The final polymer is soluble in a water/ethanol mixture. Preliminary data were presented in the Material Research Society fall meeting in Boston on December 3, 2008. However, in this article, enzymatically synthesized polyquercetin has also been characterized by a variety of techniques. Using UV-Vis FTIR, GPC, NMR and TGA we have deduced certain aspects of the structure. Structural elucidation was further refined by results from molecular modeling. Density functional theory calculations predict that the UV-Vis spectra of polyquercetin can show high conjugation relative to those of quercetin monomer. This was confirmed by the experimental results. This novel thermally stable polymer, synthesized using Green Chemistry principles, can be used as a potent antioxidant in the highly regulated food industry. [ABSTRACT FROM AUTHOR]

Hematin, a hydroxyferriprotoporphyrin, is the stable, oxidized form of heme. Heme has been reported to be the active catalytic center of naturally occurring peroxidases such as horseradish peroxidase (HRP). While there have been reports on the use of hematin as a catalyst for oxidative polymerization reactions, these reactions could be carried out only at high pH conditions due to limited aqueous solubility of hematin at lower pH conditions. We report here the biocatalytic modification of hematin using a lipase, Novozyme-435. Hematin has been modified by tethering monomethoxy polyethylene glycol (mPEG) chains which provide aqueous solubility over a fairly wide range of pH conditions. This pegylated Hematin (PEG-Hematin) is synthesized via a one-step solventless reaction and the products formed can be isolated with minimal purification. The PEG-Hematin synthesized serves as a robust alternative to HRP for the polymerization of aniline and phenol. [ABSTRACT FROM AUTHOR]

In aqueous solution, both amphiphilic decyl esters of the amino acids D & L-Tyrosine have been shown to self-assemble at identical low mM range c.m.c. values to form similar rod or plate-like fibers a few microns wide and with lengths ranging from tens to hundreds of microns [Mat. Sci. Eng. C11 2000 155-163]. These monomers have only slightly different rates of polymerization with horseradish peroxidase below their c.m.c. and have been shown to possess pH dependent self-assembly properties, as well as significantly increased binding to the gold surface of a quartz crystal microbalance with increasing pH [Biotech. Progress 15 1999 522-528]. In the present study, we quantitate the pH dependence and gold surface adsorption kinetics of the decyl ester of L-tyrosine using X-ray photoelectron spectroscopy (XPS) and then correlate these data with monomer solution titration studies. These data support the notion of increasing gold surface adsorption with increasing pH in the range from 5-8. We present evidence that this involves the lowered solubility of the neutral charged species resulting from the deprotonation of the α-NH3+ in each monomer unit. At 24 h adsorption at pH 7.0, we observed XPS evidence for complete coverage of the Au surface. From these data for the Au 4f photoelectron signal attenuation, we estimate a film thickness of 5.89 nm from the attenuation of the Au4f photoelectron intensity by the growing film. [ABSTRACT FROM AUTHOR]

Catechins are polyphenolic compounds found in green tea. These flavonoids possess anti‐oxidant, anti‐carcinogenic, and anti‐inflammatory properties. The primary goal of this work is to synthesize water‐soluble oligomers of catechins. Although, oxidative polymerization of catechins catalyzed by enzymes such as Horseradish Peroxidase (HRP) have been reported, the polymeric products have limited solubility. This restricts their compatibility with biological systems and their effectiveness as antioxidants or anti‐carcinogenic agents. Here we report a unique enzymatic approach for the synthesis of water‐soluble oligo(catechins). Polyelectrolytes such as Sulfonated Polystyrene (SPS) and surfactants such as sodium dodecylbenzenesulphonate (SDS) have been used as templates for the HRP catalyzed polymerization of (+)‐, (-)‐catechins and (-)‐epicatechin. Oligocatechins synthesized exhibit enhanced anti‐tumorigenic activity to human colon cancer cells as compared with the monomeric catechins. [ABSTRACT FROM AUTHOR]

The chiral conducting polyaniline (PANI) nanocomposites [polyacrylic acid/polyaniline/(−) camphorsulphonic acid (CSA)] were synthesized using enzyme, horseradish peroxidase (HRP) in the aqueous buffer solution at pH 4.3. It appears that the enzyme HRP apart being a biocatalyst, plays an important role during the polymerization, which allows PANI to prefer a specific helical conformation whether the induced chirality in the monomer-CSA complex is either by (+)CSA or (−)CSA. In this paper, we report, the structural characterization of these nanocomposites by solid-state 13C cross-polarization with magic angle spinning (CP/MAS) NMR techniques. The structural features of PANI in the conducting form of nanocomposite (as-synthesized) are similar to that of enzymatically and chemically synthesized PANI. Preliminary data also suggest that some portion of nanocomposite samples are not completely doped. Dedoping of as-synthesized PANI nanocomposite with aqueous NH4OH shows the spectral features that of the emeraldine base form. Solid-state 13C NMR data suggest that it is possible to detach PAA and CSA from PANI in the nanocomposite material. [ABSTRACT FROM AUTHOR]

Peroxidase-catalyzed polymerization of a hydroxy substituted polynuclear aromatic compound, 1-hydroxypyrene, is reported. The fluorescence spectrum of the synthesized polymer shows a dramatic red shift compared to that of the monomer. The enzymatic polymerization of 1-hydroxypyrene demonstrates the capability of peroxidase in catalyzing the oxidation of polynuclear aromatic molecules, and offers new possibilities for the design and synthesis of polymers with interesting electrical and optical properties in an environmentally friendly way. [ABSTRACT FROM AUTHOR]

The effect of temperature on the concentration of the major reactive species as a function of H2O2 addition in the enzymatic polymerization of 4‐propylphenol was investigated using in situ 1H‐NMR spectroscopy. We have studied the trend of monomer depletion and the formation of predominant dimers with an incremental addition of H2O2 at different temperatures. The trends for depletion of monomer are very similar while the trends for the dimers display dramatic differences at the investigated temperatures. The dynamic equilibrium stage of dimers was observed only in the case of low reaction temperature. The comparison of the in situ spectra recorded at different reaction temperatures suggests that less undesired side reactions occurred at low temperature. #Dedicated to the memory of Professor Sukant K. Tripathy. [ABSTRACT FROM AUTHOR]

Poly(4-hydroxybenzyl alcohol) was synthesized enzymatically starting with 4-hydroxybenzyl alcohol using hydrogen peroxide as the oxidizing agent in methanol and 0.01 M phosphate buffer (pH 7.0) mixture (1:1, v/v) and at room temperature (25°C). Polymerization reaction was catalyzed by horseradish peroxidase (HRP). The polymer formed was characterized by UV-Vis, FT-IR, 1H and 13C-NMR spectroscopic studies, which revealed that HRP catalyzed polymer is composed of a mixture of phenylene and oxyphenylene units and alcoholic hydroxyl groups are not participating in the polymerization. The resulting poly(4-hydroxybenzyl alcohol) contains pendant primary hydroxyl groups which provide an opportunity to further functionalize the polymer. The post-functionalization of enzymatically synthesized polymers with photoresponsive chromophores provides new molecularly engineered materials that are useful in photonics and sensor applications. [ABSTRACT FROM AUTHOR]

Polyanilines (PANI) were synthesized from peroxidase-catalyzed polymerization of aniline with and without the presence of a template in the aqueous buffer solution of pH 4.3. The template used was poly(vinylphosphonic acid) (PVP). Solid-state 13C and 15N CP/MAS NMR techniques were applied to characterize the structure of polyaniline in its self-doped conducting, dedoped base, and redoped conducting form of PANI. The charge distribution along the polymer backbone in the protonated form of the polyaniline is also discussed. The structural features exhibited by a template assisted enzymatically synthesized PANI is the result of linear 1,4-coupling of aniline moiety while the PANI synthesized in the absence of template contains both 1,2- and 1,4-coupled products. Solid-state NMR studies on the enzymatically-synthesized polyaniline with the aid of template (PANI-PVP) confirmed the formation of a linear polymer chain containing alternate benzenoid-quinoid repeat units. The dedoped form is in the emeraldine base state of the polyaniline. The structural features in the spectra of the PANI synthesized without a template are quite different. Solid-state NMR data suggest that the PANI synthesized without aid of the template contains structures having C-C and C-N-C coupled products indicating the presence of branching in the polymer chain. [ABSTRACT FROM AUTHOR]

Template guided enzymatic synthesis of conducting polyaniline (PANI) is a one-step reaction and more importantly, it is an environmentally friendly process. Understanding of the reaction and coupling mechanism at the molecular level is of paramount significance to improve its processability and conductivity. Solid-state NMR techniques are useful to investigate molecular structures of enzymatically synthesized polyaniline (PANI). The PANI sample in three different forms i.e., (a) as-synthesized, self-doped conducting form; (b) dedoped, base form and; (c) redoped, conducting form, are investigated by solid-state 13C and 15N CP/MAS NMR techniques. Solid-state NMR data analysis shows that the structural features of enzymatically synthesized PANI are similar to that of chemically synthesized PANI. The solid-state 13C CP/MAS NMR spectrum of the base form of PANI confirmed that benzenoid-quinoid repeating units are present in the backbone of the PANI polymer chain. The poly(vinylphosphonic acid) (PVP) template provides charge compensation during the chain growth of linear polyaniline. After the completion of template-guided synthesis of PANI, it is now possible that the PVP template can be completely removed from the complex by dedoping with aqueous NH4OH. The detached PANI from the PANI-PVP complex can then be redoped to conducting form without the presence of the template. The conductivity of the PANI and PANI-PVP complex are of the same order of magnitude. The solid-state 15N CP/MAS NMR chemical shifts are sensitive to charge distribution on the nitrogens in the backbone. The solid-state 15N CP/MAS NMR spectrum of the base form of the enzymatically derived PANI sample showed the clear signature for benzenoid-quinoid repeating units in the polymer backbone. †Deceased. [ABSTRACT FROM AUTHOR]

Azophenols with various substituents at the para position of the phenyl ring were enzymatically polymerized in the presence of H2O2. Structural characterization of the synthesized polymers by FTIR, FT-Raman, and NMR (1H and 13C) spectroscopy confirms our previous observation that this enzymatically catalyzed coupling reaction occurs primarily at the ortho positions, with some substitution at the meta position of the phenol ring. The strong constraint and poor packing of the azobenzene chromophores in the polymer leads to a significant blue shift of the π-π* transition absorption and slow photoisomerization and thermal relaxation in comparison to the monomers. Surface relief gratings (SRG) with large surface modulation have been fabricated on these enzymatically synthesized polymer films. †Deceased. [ABSTRACT FROM AUTHOR]

Peroxidase-catalyzed oxidative polymerization of fluorine-containing phenols has been performed in a mixture of a water-miscible organic solvent and buffer at room temperature under air. The monomers used were 2,6-difluorophenol, 3- and 4-fluorophenols. In the polymerization of 2,6-diflurophenol catalyzed by horseradish peroxidase (HRP), effects of an organic solvent, buffer pH, and their mixed ratio have been systematically investigated with respect to the polymer yield and molecular weight. The resulting polymer was soluble in common polar organic solvents and showed good water repellent property. From NMR and IR data, it was supposed that the polymer was of mainly 2,6-difluoro-1,4-oxyphenylene unit. Elemental analysis showed that the elimination of a small amount of the fluorine atom took place during the polymerization. HRP catalysis induced the polymerization of 3- and 4-fluorophenols, yielding a new class of fluorine-containing polyphenols. [ABSTRACT FROM AUTHOR]