Browsing by Author "Thomas, TJ"

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    Liquid crystalline phase behavior of high molecular weight DNA: A comparative study of the influence of metal ions of different size, charge and binding mode
    (BIOMACROMOLECULES, 2008) Sundaresan, N; Suresh, CH; Thomas, T; Thomas, TJ; Pillai, CKS
    The ability of Li+, Na+, K+, Rb+, CS+, Mg2+, Ca2+, Sr2+, Ba2+, Cu2+, Cd2+, Al3+, V4+, Hg2+, Pd2+, Au3+, and Pt4+ to provoke liquid crystalline (LC) phases in high molecular weight DNA was investigated. The alkali and alkaline earth metal ions provoked typical cholesteric/columnar structures, whereas transition metal ions precipitated DNA into solid/translucent gel-like aggregates. Heavy metal ions reduced viscosity of DNA solution, disrupting rigid, rod-like DNA structure necessary for LC textures. Three-layer quantum mechanical-molecular mechanical (QM/MM) studies of Li+, Na+, K+, Mg2+, and Ca2+ binding DNA fragment suggested several possible binding modes of these ions to the phosphate groups. The dianion mode of metal binding, involving the phosphate groups of both strands of DNA, allowed for higher DNA binding affinity of the alkaline earth metal ions. These results have implications in understanding the biological role of metal ions and developing DNA-based sensors and nanoelectronic devices.
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    Synthesis and characterization of novel water-soluble polyamide based on spermine and aspartic acid as a potential gene delivery vehicle
    (EXPRESS POLYMER LETTERS, 2008) Viola, BM; Abraham, TE; Arathi, DS; Sreekumar, E; Pillai, MR; Thomas, TJ; Pillai, CKS
    We developed a novel and convenient method for the synthesis of a potentially safe non-viral gene delivery vehicle based on the cationic block copolymer of spermine and aspartic acid ( ASSP) and coupled it with polyethylene glycol (PEG). The copolymer ASSP was prepared by direct polycondensation in the ionic liquid, butylmethylimidazolium hexafluorophosphate, using triphenyl phosphite as the condensing agent under mild reaction conditions. The highly hydrophobic ASSP was transformed into a water soluble hydrophilic micelle by coupling ASSP with polyethylene glycol (PEG) using the same ionic liquid and 1,1-carbonyl diimidazole as the condensing agent without harsh conditions. The polycationic ASSP-PEG was then used to condense calf thymus and plasmid deoxyribonuclceic acids (DNAs) in Tris-HCl buffer (pH 7.4) to get a series of block ionomer complexes with various charge ratios. The physicochemical properties of the copolymer micelle and the DNA polyplexes were studied using fourier transform-infrared (FTIR), nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy, matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and particle size measurements. It was observed that the DNA was condensed to compact particles by its interaction with the copolymer. Since DNA condensation to nano/micrometer sized particles is essential for gene delivery, our results indicate a potential use of the copolymer for gene delivery applications.