• A Dhathathreyan

      Articles written in Journal of Chemical Sciences

    • Adsorption of DOPC vesicles on hydrophobic substrates in the presence of electrolytes: A QCM and reflectometry study

      G Edward Gnana Jothi S Kamatchi A Dhathathreyan

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      The adsorption of lipid Dioleoylphosphatidylcholine (DOPC) vesicles on a hydrophobic substrate has been investigated in aqueous buffer solution by means of the quartz crystal microbalance (QCM) and reflectometry. DOPC vesicles were prepared by the injection method on a hydrophobic substrate using 1-octadecanethiol (ODT) self-assembled on a gold-coated AT-cut quartz. The reflection spectrometry measurements of the adsorbed vesicles showed nearly monolayer formation in few cases, while in most other experiments, the frequency changes measured suggested multilayer formation assuming the usual Sauerbrey equation to hold in the present system as well. Presence of NaCl, KCl, Na2SO4 and ethanol in the aqueous phase during the formation of vesicles suggest that the multilayer formation can be hastened in some cases. Atomic force microscopic study corroborate the thicknesses that range between 8 and 20 nm for high concentration of electrolytes or ethanol suggesting coalescence of vesicles leading to several bilayers possibly stacked over each other.

    • Supported lipid bilayers as templates to design manganese oxide nanoparticles

      J Maheshkumar B Sreedhar B U Nair A Dhathathreyan

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      This work reports on the preparation of nanoclusters of manganese oxide using biotemplating techniques. Supported lipid bilayers (SLBs) on quartz using cationic lipid [Dioctadecyldimethylammonium bromide (DOMA)] and mixed systems with neutral phospholipids dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) have been used as templates to synthesize these nanoparticles in a waterbased medium at room temperature. The Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) show manganese oxide nanostructures that are composed of crystals or small clusters in the size range of 20-50 nm in diameter. Small angle XRD showed that template removal through calcining process results in nanostructures of the manganese oxide in sizes from 30 to 50 nm. Using these organized assemblies it is possible to control the nano and mesoscopic morphologies of particles and both rod-like and spherical particles can be synthesized.

    • Langmuir and Langmuir-Blodgett films of capsules of haemoglobin at air/water and solid/air interfaces

      J Maheshkumar A Dhathathreyan

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      Organized assemblies of capsules of haemoglobin (Hb), in the size range of 0.1 to 0.3 𝜇 in Langmuir films have been studied at air/water interface below and above the isoelectric point. Spread films of these organizates suggest that there is no expulsion of individual particles or particle assemblies at the interface and the particles are stable. Dynamic surface tension and the associated dilational and shear visco-elasticity in these films suggest that the capsules are highly elastic. Multilayer films of the capsules using Langmuir-Blodgett technique have been fabricated by sequential deposition on solid surfaces. These films have been characterized by circular dichroism spectroscopy (CD), atomic force microscopy (AFM), quartz crystal microbalance (QCM) and Fourier transform infrared with reflection absorption spectroscopy (FTIR-RAS). No appreciable change in the secondary structural features of Hb is seen from CD studies indicating the stability of the protein in these organized assemblies. Sizes of these capsules change near the isoelectric point and large swollen multiwalled capsules are formed. The elastic films of capsules of Hb provide a useful post preparation approach for modification of the surface roughness, porosity, and permeability of pre-assembled polypeptide microcapsules.

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