Papiya Nandy

Green synthesis of zinc oxide nanoparticles using Hibiscus subdariffa leaf extract: effect of temperature on synthesis, anti-bacterial activity and anti-diabetic activity

Zinc oxide (ZnO) nanoparticles (NPs) have been synthesized using Hibiscus subdariffa leaf extract. Temperature dependent synthesis and particle growth have been studied. Formation of NPs was confirmed by UV-visible (UV-VIS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Electron microscopy has been used to study the morphology and size distribution of the synthesized particles. The synthesized ZnO nanoparticles as potential anti-bacterial agents have been studied on Escherichia coli and Staphylococcus aureus. Another study has indicated that small sized ZnO NPs, stabilized by plant metabolites had better anti-diabetic effect on streptozotocin (STZ) induced diabetic mice than that of large sized ZnO particles. It has also been observed by enzyme linked immunosorbent assay (ELISA) and real time polymerase chain reaction (RT-PCR) that ZnO can induce the function of Th1, Th2 cells and expressions of insulin receptors and other genes of the pancreas associated with diabetes.

In situ synthesis and antibacterial activity of copper nanoparticle loaded natural montmorillonite clay based on contact inhibition and ion release

Copper nanoparticle based clay composite has been synthesized by in situ reduction of a copper ammonium complex ion and characterized by different analytical instruments. The copper nanoparticles were both intercalated and adsorbed on the surface with diameters of <5nm (for intercalated) and 25-30nm (for adsorbed). The composite showed good stability for over 3 months in air. Excellent antimicrobial activity of the composite was observed on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecalis with mortality rates >90% after 12h. Cellular membrane damage permeated by direct attachment of the composite and indirect damage caused by released copper ion are the primary sources of antibacterial action. Cytotoxicity measurements showed minimal adverse effect on the two human cell lines beyond the M.B.C. value for the microorganisms studied. In the present form the clay composite shows good promise for use in therapeutic applications.

The role of cerium(III)/yttrium(III) nitrate hexahydrate salts on electroactive β phase nucleation and dielectric properties of poly(vinylidene fluoride) thin films

Electroactive poly(vinylidene fluoride) (PVDF) thin films modified with Ce(NO3)3·6H2O and Y(NO3)3·6H2O (1–30 mass%) have been prepared via a simple solution casting method. The thermal stability and microstructures of the films were investigated using thermal gravimetric analysis techniques and field emission electron microscopy respectively. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry confirmed the nucleation of the electroactive β phase in the composite films. Strong interfacial interaction i.e. ion dipole interaction via formation of hydrogen bonds between the water molecules of the salts and the polar –CF2 dipoles of the polymer chains resulted in improved electroactive β phase nucleation and a large dielectric constant in PVDF films.

Heat-induced structural changes in merocyanine dyes: X-ray and thermal studies

Abstract Certain merocyanine dyes undergo heat-induced isomerisation, which is responsible for their thermovoltage generation properties. Using these dyes, our studies reveal the correlation between their thermal properties and their crystalline structure. Differential thermal analysis of hexadecyl, decyl and pentyl dyes showed reversible phase transitions at their respective characteristic temperatures (Tc) owing to thermal isomerisation of the dyes. X-Ray diffraction patterns indicated heat-induced changes in the crystal structure of the dyes. This was also supported by the results obtained from polarising microscopy studies and thermogravimetric analysis. Further heating of these dyes caused a permanent deformation in the crystal structure, which ultimately led to total disintegration as recorded in the thermogravimetric studies.

Synthesis and characterization of Cu/Ag nanoparticle loaded mullite nanocomposite system: A potential candidate for antimicrobial and therapeutic applications.

BACKGROUND Microbial resistance to antibiotics has triggered the development of nanoscale materials as an alternative strategy. To stabilize these particles an inert support is needed. METHOD Porous nanomullite developed by sol-gel route is loaded with copper and silver nanoparticle by simple adsorption method. These nanocomposites are characterized using XRD, FTIR, TEM, SEM, EDAX and UV-visible spectrophotometer. Antibacterial activity of these nanocomposites against Gram positive and Gram negative bacteria are performed by bactericidal kinetics, flow cytometry and MTT assay. The underlying mechanisms behind the antimicrobial property and cell death are also investigated by EPR spectroscopy, intracellular ROS measurement and β-galactosidase assay. The cytocompatibility of the nanocomposites is investigated by cell viability (MTT), proliferation (Alamar blue) and wound healing assay of mammalian fibroblast cell line. RESULTS Nanocomposites show a fairly uniform distribution of metal nanoparticle within mullite matrix. They show excellent antibacterial activity. Metal ions/nanoparticle is found to be released from the materials (CM and SM). Treated cells manifested high intracellular oxidative stress and β-galactosidase activity in the growth medium. The effect of nanocomposites on mammalian cell line depends on exposure time and concentration. The scratch assay shows normal cell migration with respect to control. CONCLUSION The fabricated nanoparticles possess diverse antimicrobial mechanism and exhibit good cytocompatibility along with wound healing characteristics in mouse fibroblast cell line (L929). GENERAL SIGNIFICANCE The newly synthesized materials are promising candidates for the development of antimicrobial ceramic coatings for biomedical devices and therapeutic applications.

Numerical Characterization of Protein Sequences and Application to Voltage-Gated Sodium Channel α Subunit Phylogeny

We propose a new method to compare sequences of protein families by generating numerical characterizations through a 20D representation. Using a walk along the axes representing the amino acids we generate a vector for each sequence whose components can be used to derive distance matrices between sequences and whose magnitudes can be used to compare the similarities/dissimilarities between the different sequences. The distance matrices enable creation of phylogenetic trees without need for multiple alignments or any other model dependencies. In this paper we test this technique with human globin gene sequences and then apply the method to a contemporary issue of evolutionary relationships of rat and human voltage-gated sodium channel alpha subunits and compare with published literature. The close match of the results demonstrates the reliability and ease of use of this method.

Liposome formation of egg lecithin and its interaction with iodine

The sonicated dispersion of egg lecithin (phosphatidylcholine) in water forms 1:1 molecular complex with iodine, when its concentration is above 1.6 X 10(-5) M. The thermodynamic and spectrophotometric properties of this complex have been determined. The thermodynamic values are: K (25 degrees C) = 1.6 X 10(3) 1 X mol-1, delta G degrees = -18.4 KJ X mol-1, delta H degrees = -27.4 KJ X mol-1 and delta S degrees = -30.0 J X mol-1 X deg-1. The complex shows two absorption bands: one at 293 nm, which is the charge transfer band and the other at 370 nm, which is the blue shifted visible iodine band at 460 nm in water.

Computational study of dispersion and extent of mutated and duplicated sequences of the H5N1 influenza neuraminidase over the period 1997-2008.

Study of mutational changes in neuraminidase (NA) gene sequences is important to track the effectiveness of the inhibitors to the H5N1 avian flu virus that targets this component of the viral apparatus. Our analysis based on numerical characterization studies of 682 complete neuraminidase gene and protein sequences available in the database, updated to March 2009, and which extends our previous work based on a sample of 173 sequences has revealed several interesting features. We have noticed that identical sequences have appeared over significant distances in space and time, raising the need for a deeper understanding of the longevity of such viral strains in the environment. Structural sections like transmembrane, stalk, body, and C-terminal tail regions have shown independent recombinations between strains from various species including human and avian hosts highlighting influenzas flexibility in host selection and recombination. Our analysis confirmed a biased nature in mutational accumulation in structural segments: a highly conserved 50-base C-terminal tail section identified in our earlier paper seems to accumulate mutational changes at a rate of about a fifth to an eighth of transmembrane and stalk regions, although the length is about half of these. Parallel study of the equivalent section to the C-terminal region in protein sequences reveals only 13 separate varieties, and all the other 669 sequences are duplicates to three of these varieties showing the highly conserved nature of this segment. Our analysis of active site related bases and amino acids showed highly conserved characteristic of those constructs, whereas the rest of the segments demonstrated rather large mutational changes. These kinds of high level of mutation in major part of the H5N1 NA sequences and recombinations within structural segments coupled with strong conservation of a few select segments show that the potential of rapid mutations to more virulent forms of this variety of avian flu continue to remain of concern, especially with the possibility of long duration dormancy of some of these viral strains, whereas islands of highly conserved segments could signify potential regions for inhibitor designs.

Improvement of electroactive β phase nucleation and dielectric properties of WO3·H2O nanoparticle loaded poly(vinylidene fluoride) thin films

Tungsten oxide hydrate (WO3·H2O) nanoparticles (NPs) have been prepared by simple hydrazine hydrate reduction. X-ray diffraction, UV-Visible spectroscopy and field emission electron scanning microscopy confirm the formation of phase pure orthorhombic WO3·H2O NPs. Thereafter, poly(vinylidene fluoride) (PVDF) thin films doped with different amounts of WO3·H2O NPs (1–15 mass%) have been prepared via a simple solution-casting method to verify the role of the NPs on the enhancement of electroactive β phase crystallization and dielectric properties of WO3·H2O NP–PVDF thin films. The interface between the NPs and the polymer matrix takes a vital role in improving β phase nucleation and dielectric properties of the WO3·H2O NP modified PVDF thin films. Strong electrostatic or ion–dipole interaction between the negatively charged NP surfaces and –CH2 dipoles of the polymer matrix at the interface effectively improves the electroactive β phase nucleation and dielectric properties of the nanocomposite thin films.

Lipid perturbation by corticosteroids: an anisotropic study

Abstract Corticosteroids are the group of steroid hormones which influence the intermediary metabolism. Normal membrane fluidity, necessary for normal functioning of cells, is affected by different drugs. It has been reported previously by us and by other workers that the nature of membrane perturbation by drugs is closely related to their biochemical actions. In this paper we have studied the nature of liquid perturbation by some corticosteroids (hydrocortisone, prednisolone, betamethasone and dexamethasone) in the liposomal membrane of dipalmitoyl phosphatidyl choline using fluorescence polarisation of 1,6-diphenyl-1,3,5-hexatriene. Our result shows that all the corticosteroids fluidise or disorder the liposomal membrane only before phase transition. The two stereoisomers, betamethasone and dexamethasone, have the same effect on the fluidity throughout the experimental temperature range. An explanation for the observed results has been sought in terms of interaction between the lipid and drug molecules at the molecular level.