Browsing by Author "Philip, R."
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Item Defect induced changes in the linear and non-linear optical properties of ZnO nanotetrapods(Materials Express, 2012-12) Egblewogbe, M.; Anand, B.; Podila, R.; Philip, R.; Sai, S.S.S.; Rao, A.M.Here, we investigate the origin of green luminescence in ZnO nanotetrapods using nonlinear optical z-scan measurements in tandem with photoluminescence measurements. To this end, we synthesized ZnO nanotetrapods using a chemical vapor deposition (CVD) process, annealed at temperatures below 200 °C in O2, Ar, and Zn metal vapor and measured the ensuing optical properties. Our z-scan measurements show that all samples exhibit an effective three-photon absorption (3PA). Furthermore, the 3PA coefficient varies with the incident laser intensity consistent with the presence of real mid-gap states. Interestingly, the rate of change for the 3PA coefficient is strongly influenced by the annealing conditions. Annealing in Zn vapor (Ar and O2) leads to an increase (decrease) in green luminescence and the 3PA coefficient, strongly suggesting that the Zn interstitials are involved in the mechanism of green luminescence. © 2012 by American Scientific Publishers. All rights reserved.Item Rational design of a multiepitope vaccine encoding T-lymphocyte epitopes for treatment of chronic hepatitis B virus infections(Virology Journal 82(1):435-50, 2008) Newman, M. J.; Depla, E.; Van der Aa A.; Livingston, B.D.; Crimi, C.; Allosery, K.; De Brabandere, V.; Krakover, J.; Murthy, S.; Huang, M.; Power, S.; Babé, L.; Dahlberg, C.; McKenney, D.; Sette, A.; Southwood, S.; Philip, R.; Meheus, L.Protein sequences from multiple hepatitis B virus (HBV) isolates were analyzed for the presence of amino acid motifs characteristic of cytotoxic T-lymphocyte (CTL) and helper T-lymphocyte (HTL) epitopes with the goal of identifying conserved epitopes suitable for use in a therapeutic vaccine. Specifically, sequences bearing HLA-A1, -A2, -A3, -A24, -B7, and -DR supertype binding motifs were identified, synthesized as peptides, and tested for binding to soluble HLA. The immunogenicity of peptides that bound with moderate to high affinity subsequently was assessed using HLA transgenic mice (CTL) and HLA cross-reacting H-2(bxd) (BALB/c x C57BL/6J) mice (HTL). Through this process, 30 CTL and 16 HTL epitopes were selected as a set that would be the most useful for vaccine design, based on epitope conservation among HBV sequences and HLA-based predicted population coverage in diverse ethnic groups. A plasmid DNA-based vaccine encoding the epitopes as a single gene product, with each epitope separated by spacer residues to enhance appropriate epitope processing, was designed. Immunogenicity testing in mice demonstrated the induction of multiple CTL and HTL responses. Furthermore, as a complementary approach, mass spectrometry allowed the identification of correctly processed and major histocompatibility complex-presented epitopes from human cells transfected with the DNA plasmid. A heterologous prime-boost immunization with the plasmid DNA and a recombinant MVA gave further enhancement of the immune responses. Thus, a multiepitope therapeutic vaccine candidate capable of stimulating those cellular immune responses thought to be essential for controlling and clearing HBV infection was successfully designed and evaluated in vitro and in HLA transgenic mice.