Sucharita Roy

PEROXIDASE, HEMATIN, AND PEGYLATED-HEMATIN CATALYZED VINYL POLYMERIZATIONS IN WATER

Horseradish peroxidase-, hematin- and pegylated-hematin mediated polymerization of sodium styrene sulfonate and sodium acrylate in water is reported. Molecular weight and yields were influenced by the concentrations of hydrogen peroxide and initiator, 2,4-pentanedione. Hematin and pegylated-hematin were studied in lieu of peroxidase at pH 11.0 and 7.0 in aqueous solution, respectively. Polymer with a high molecular weight (Mn = 223,520) was formed when the pegylated-hematin was used as the catalyst. The results demonstrate vinyl polymerizations in an all aqueous process in high yield and molecular weight catalyzed by peroxidase as well as biomimetic catalysts.

ENZYMATIC SYNTHESIS OF MOLECULAR COMPLEXES OF POLYANILINE WITH DNA AND SYNTHETIC OLIGONUCLEOTIDES: THERMAL AND MORPHOLOGICAL CHARACTERIZATION

The assembly of electronic and photonic materials on biomacromolecules is of tremendous interest for the development of biofunctional nanocomplexes as well as highly selective biosensors. In the context of the use of electrically conducting polymers for sensing, polyaniline (Pani) and polypyrrole have received considerable interest because of their well-known electrical properties. Recently, we have reported an enzyme catalyzed synthetic procedure involving horseradish peroxidase (HRP) for the polymerization of aniline on a calf thymus DNA matrix. The mild reaction conditions involved in the synthesis have provided opportunities for the use of more delicate biomacromolecules as templates. The complexation of Pani with DNA has been found to induce reversible changes in the secondary structure of DNA leading to the formation of an over-wound polymorph. The thermal characterization (melting behavior) of the DNA in the complex and the morphological properties of the complex have provided corroborative evidence for the wrapping of Pani around the DNA matrix. Scanning probe and electron microscopy studies have indicated that the formation of Pani causes the DNA-Pani strands to agglomerate, presumably due to the neutralization of charge on the phosphate groups by the partially charged Pani. We also report the synthesis of Pani on a synthetic oligonucleotide (Poly[dA-dC].poly[dG-dT]). Demonstration of the use of a new biomimetic catalyst, polyethylene glycol modified hematin (PEG-hematin), in these reactions will also be presented. These results indicate that this biocatalytic synthetic approach is generic, versatile and can be adopted for both genomic and synthetic nucleic acids. †Deceased.

Highly efficient diastereoselective biocatalytic acylation of a diastereotopic furanose diol and synthesis of key intermediates for amino derivatized bicyclonucleosides

The selectivity of Candida antarctica lipase has been demonstrated and employed in the manipulation of a diastereotopic furanose diol as the key step in the synthesis of a novel bicyclo 3-amino-3-deoxy furanose derivative, which is an important intermediate for the synthesis of bicyclic analogs of AZT. The asymmetrization of the diol has been achieved with preferred formation of a monoacylated product with 100% diastereoselectivity. An efficient synthesis of an intermediate in the synthesis of amino derivatized bicyclonucleosides is also described, two such novel compounds containing cycloamino residues have been prepared.

Novel diastereoselective acylation of 4-C-hydroxymethyl-1,2-O-(1-methylethylidene)-3-O-(phenylmethyl)-α-d-pentofuranose: Effect of lipases and acylating agents on stereoselectivity

Abstract Amano PS and CAL catalysed prochiral asymmetrization of the title compound 1 has been studied.

Biomimetic Synthesis of Water Soluble Conductive Polypyrrole and Poly(3,4‐Ethylenedioxythiophene)

Abstract A novel biomimetic method for the synthesis of conducting molecular complexes of polypyrrole (PPYR) and poly(3,4‐ethylenedioxythiophene) (PEDOT) in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG‐Hematin) was used to catalyze the polymerization of pyrrole (PYR) and 3,4‐ethylenedioxythiophene (EDOT) in the presence of SPS to form PPYR/SPS and PEDOT/SPS complexes. UV‐VIS, FT‐IR, and electrical conductivity studies for all complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of SPS in this complex provides a unique combination of properties such as processability and water‐solubility.

BIOCATALYTIC SYNTHESIS OF A RUTHENIUM MACROMOLECULAR COMPLEX FOR PHOTOVOLTAICS

ABSTRACT A phenolic ligand, 4-([1,10] Phenanthrolin-5-yliminomethyl)-phenol (APHB) has been synthesized which was subjected to biocatalytic polymerization by Hematin. The polyligand obtained was complexed with Ru[(dcbpy)2Cl2] (where dcbpy=4,4′-dicarboxylic bipyridyl) to synthesize a macromolecular complex {Ru[(dcbpy)2(APHB)]}n (macro dye) for the sensitization of a nanocrystalline titanium dioxide based dye-sensitized photovoltaic cell. The precursor monomeric Ruthenium complex, Ru[(dcbpy)2(APHB)] was also prepared for comparison. The overall solar-to-electric conversion efficiency of the macro dye was found to be 0.33%, which is lower than the monomeric complex (1.51%), when a liquid electrolyte is used. The photophysical properties were also measured using UV-visible and luminescence spectroscopy for both the monomeric complex and the macro dye.

Novel Chemoenzymatic Synthesis of Azobenzene Functionalized Ribonucleic Acid

ABSTRACT Ribonucleic acids, often called a biological jack of all trades, contribute intimately to every aspect of gene expression, including the synthesis of other polypeptide biocatalysts. The fundamental importance of recurring structural motifs and the kinetics and energetics of the complex secondary and tertiary structure of RNA have been shown to be intimately linked with its functions in vivo. We have developed a novel enzymatic synthetic approach for covalent attachment of photoresponsive units into the RNA backbone. The synthetic conditions of this approach are extremely mild, involving the reverse micellar solubilization of nucleic acid along with lipase in apolar hydrocarbon solvents. Lipase catalyzed acylation of the 2’ hydroxyl group in the ribose sugars of the RNA molecule has been used to incorporate photo-isomerizable azobenzene groups into the RNA strands. This micellar approach was envisaged for RNA functionalization while maintaining the conformational integrity of the macromolecular backbone in neutral buffer solution. The modification of RNA using covalently attached chromophores or fluorophores can be extended to other biomacromolecular matrices leading to the development of more versatile photoactive biopolymers. The photo-isomerizable groups incorporated in the RNA molecule can serve as optical ‘handles’ for the manipulation of the conformation of RNA and open new opportunities for biophotonic device applications.