An original phylogenetic approach identified mitochondrial haplogroup T1a1 as inversely associated with breast cancer risk in BRCA2 mutation carriers

Introduction: Individuals carrying pathogenic mutations in the BRCA1 and BRCA2 genes have a high lifetime risk of breast cancer. BRCA1 and BRCA2 are involved in DNA double-strand break repair, DNA alterations that can be caused by exposure to reactive oxygen species, a main source of which are mitochondria. Mitochondrial genome variations affect electron transport chain efficiency and reactive oxygen species production. Individuals with different mitochondrial haplogroups differ in their metabolism and sensitivity to oxidative stress. Variability in mitochondrial genetic background can alter reactive oxygen species production, leading to cancer risk. In the present study, we tested the hypothesis that mitochondrial haplogroups modify breast cancer risk in BRCA1/2 mutation carriers.

Methods: We genotyped 22,214 (11,421 affected, 10,793 unaffected) mutation carriers belonging to the Consortium of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected or unaffected individuals.

Results: We discovered that subclade T1a1 was depleted in affected BRCA2 mutation carriers compared with the rest of clade T (hazard ratio (HR) = 0.55; 95% confidence interval (CI), 0.34 to 0.88; P = 0.01). Compared with the most frequent haplogroup in the general population (that is, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk.

Conclusions: This study illustrates how original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects.

Dual interfacial modifications of hierarchically structured iodine-doped ZnO photoanodes for high-efficiency dye-sensitized solar cells

A nanocomposite porous electrode structure consisting of hierarchical iodine-doped zinc oxide (I-ZnO) aggregates combined with the two simple solution-processed interfacial modifications i.e. a ZnO compact layer (CL) and a TiO2 protective layer (PL) has been developed in order to understand electron transport and recombination in the photoanode matrix, together with boosting the conversion efficiency of I-ZnO based dye-sensitized solar cells (DSCs). Electrochemical impedance spectra demonstrate that ZnO CL pre-treatment and TiO2 PL post-treatment synergistically reduce charge-transfer resistance and suppress electron recombination. Furthermore, the electron lifetime in two combined modifications of IZnO + CL + PL photoelectrode is the longest in comparison with the other three photoelectrodes. As a consequence, the overall conversion efficiency of I-ZnO + CL + PL DSC is significantly enhanced to 6.79%, with a 36% enhancement compared with unmodified I-ZnO DSC. Moreover, the stability of I-ZnO + CL + PL cell is improved as compared to I-ZnO one. The mechanism of electron transfer and recombination upon the introduction of ZnO CL and TiO2 PL is also proposed in this work.

Effects of large anphiphilic ligands upon the spectra and kinetics of cytochrome C oxidase

Cytoch ro me c oxidase (ferrocytochrome c : 02 oxidoreductase ; EC 1.9. 3.1) is the terminal enzyme in the mitochondrial electron transport chain, catalyzing the transfer of electrons from ferrocytochrome c to molecular oxygen. The effects of two large amphiphilic molecules .. valinomycin and dibucaine upon the spectra of the isolated enzyme and upon the activity of both isolated enzyme and enzyme in membrane systems are investigated by using spectrophotometric and oxygen electrode techniques. The results show that both valinomycin and dibucaine change the Soret region of the spectrum and cause a partial inhibition in a concentration range higher than that in which they act as ionophores. It is concluded that both valinomycin and dibucain~ binding induce a conformational change of the protein structure which modifies the spectrum of the a3 CUB centre and diminishes the rate of electron transfer between cytochrome a and the binuclear centre.

Heterogeneity of photosystem II as it occurs in domain specific regions of the thylakoid membrane of spinach (spinacia oleracia L.)

Thylakoid membrane fractions were prepared from specific regions of thylakoid membranes of spinach (Spinacia oleracea). These fractions, which include grana (83), stroma (T3), grana core (8S), margins (Ma) and purified stroma (Y100) were prepared using a non-detergent method including a mild sonication and aqueous two-phase partitioning. The significance of PSlla and PSII~ centres have been described extensively in the literature. Previous work has characterized two types of PSII centres which are proposed to exist in different regions of the thylakoid membrane. a-centres are suggested to aggregate in stacked regions of grana whereas ~-centres are located in unstacked regions of stroma lamellae. The goal of this study is to characterize photosystem II from the isolated membrane vesicles representing different regions of the higher plant thylakoid membrane. The low temperature absorption spectra have been deconvoluted via Gaussian decomposition to estimate the relative sub-components that contribute to each fractions signature absorption spectrum. The relative sizes of the functional PSII antenna and the fluorescence induction kinetics were measured and used to determine the relative contributions of PSlla and PSII~ to each fraction. Picosecond chlorophyll fluorescence decay kinetics were collected for each fraction to characterize and gain insight into excitation energy transfer and primary electron transport in PSlla and PSII~ centres. The results presented here clearly illustrate the widely held notions of PSII/PS·I and PSlIa/PSII~ spatial separation. This study suggests that chlorophyll fluorescence decay lifetimes of PSII~ centres are shorter than those of PSlIa centres and, at FM, the longer lived of the two PSII components renders a larger yield in PSlIa-rich fractions, but smaller in PSIlr3-rich fractions.

Effects of large anphiphilic ligands upon the spectra and kinetics of cytochrome C oxidase

Cytoch ro me c oxidase (ferrocytochrome c : 02 oxidoreductase ; EC 1.9. 3.1) is the terminal enzyme in the mitochondrial electron transport chain, catalyzing the transfer of electrons from ferrocytochrome c to molecular oxygen. The effects of two large amphiphilic molecules - valinomycin and dibucaine upon the spectra of the isolated enzyme and upon the activity of both isolated enzyme and enzyme in membrane systems are investigated by using spectrophotometric and oxygen electrode techniques. The results show that both valinomycin and dibucaine change the Soret region of the speetrum and cause a partial inhibition in a concentration range higher than that in which they act as ionophores. It is concluded that both valinomycin and dibucaine binding induce a conformational change of the protein structure which modifies the spectrum of the a3 CUB centre and diminishes the rate of electron transfer between cytochrome a and the binuclear centre.

Spin labile conducting metallopolymers : a new architecture for hybrid multifunctional materials

The synthesis of 3-ethynylthienyl- (2.07), 3-ethynylterthienyl- (2.19) substituted qsal [qsalH = N-(8-quinolyl)salicylaldimine] and 3,3' -diethynyl-2,2' -bithienyl bridging bisqsal (5.06) ligands are described along with the preparation and characterization of eight cationic iron(III) complexes containing these ligands with a selection of counteranions [(2.07) with: SCN- (2.08), PF6- (2.09), and CI04- (2.10); (2.19) with PF6 - (2.20); (5.06) with: cr (5.07), SeN- (5.08), PF6- (5.09), and CI04- (5.10)]. Spin-crossover is observed in the solid state for (2.08) - (2.10) and (5.07) - (5.10), including a ve ry rare S = 5/2 to 3/2 spin-crossover in complex (2.09). The unusal reduction of complex (2.10) produces a high-spin iron(I1) complex (2.12). Six iron(II) complexes that are derived from thienyl analogues of bispicen [bispicen = bis(2-pyridylmethyl)-diamine] [2,5-thienyl substituents = H- (3.11), Phenyl- (3.12), 2- thienyl (3.13) or N-phenyl-2-pyridinalimine ligands [2,5-phenyl substituents = diphenyl (3.23), di(2-thienyl) (3.24), 4-phenyl substituent = 3-thienyl (3.25)] are reported Complexes (3.11), (3.23) and (3.25) display thermal spin-crossover in the solid state and (3.12) remains high-spin at all temperatures. Complex (3.13) rearranges to form an iron(II) complex (3.14) with temperature dependent magnetic properties be s t described as a one-dimensional ferromagnetic chain, with interchain antiferromagnetic interactions and/or ZFS dominant at low temperatures. Magnetic succeptibility and Mossbauer data for complex (3.24) display a temperature dependent mixture of spin isomers. The preparation and characterization of two cobalt(II) complexes containing 3- ethynylthienyl- (4.04) and 3-ethynylterhienyl- (4.06) substituted bipyridine ligands [(4.05): [Co(dbsqh(4.04)]; (4.07): [Co(dbsq)2(4.06)]] [dbsq = 3,5-dbsq=3,5-di-tert-butylI ,2-semiquinonate] are reported. Complexes (4.05) and (4.07) exhibit thermal valence tautomerism in the solid state and in solution. Self assembly of complex (2.10) into polymeric spheres (6.11) afforded the first spincrossover, polydisperse, micro- to nanoscale material of its kind. . Complexes (2.20), (3.24) and (4.07) also form polymers through electrochemical synthesis to produce hybrid metaUopolymer films (6.12), (6.15) and (6.16), respectively. The films have been characterized by EDX, FT-IR and UV-Vis spectroscopy. Variable-temperature magnetic susceptibility measurements demonstrate that spin lability is operative in the polymers and conductivity measurements confirm the electron transport properties. Polymer (6.15) has a persistent oxidized state that shows a significant decrease in electrical resistance.

Impacts des réarrangements génomiques chloroplastiques sur l'apparition des phénotypes de variégation chez Arabidopsis thaliana

Contrairement à la plupart des eucaryotes non-photosynthétiques, les végétaux doivent assurer la stabilité d’un génome additionnel contenu dans le plastide, un organite d’origine endosymbiotique. Malgré la taille modeste de ce génome et le faible nombre de gènes qu’il encode, celui-ci est absolument essentiel au processus de photosynthèse. Pourtant, même si ce génome est d’une importance cruciale pour le développement de la plante, les principales menaces à son intégrité, ainsi que les conséquences d’une déstabilisation généralisée de sa séquence d’ADN, demeurent largement inconnues. Dans l’objectif d’élucider les conséquences de l’instabilité génomique chloroplastique, nous avons utilisé le mutant why1why3polIb d’Arabidopsis thaliana, qui présente d’importants niveaux de réarrangements génomiques chloroplastiques, ainsi que la ciprofloxacine, un composé induisant des brisures double-brins dans l’ADN des organites. Ceci nous a permis d’établir qu’une quantité importante de réarrangements génomiques provoque une déstabilisation de la chaîne de transport des électrons photosynthétique et un grave stress oxydatif associé au processus de photosynthèse. Étonnamment, chez why1why3polIb, ces hautes concentrations d’espèces oxygénées réactives ne mènent ni à la perte de fonction des chloroplastes affectés, ni à la mort cellulaire des tissus. Bien au contraire, ce déséquilibre rédox semble être à l’origine d’une reprogrammation génique nucléaire permettant de faire face à ce stress photosynthétique et conférant une tolérance aux stress oxydatifs subséquents. Grâce à une nouvelle méthode d’analyse des données de séquençage de nouvelle génération, nous montrons également qu’un type particulier d’instabilité génomique, demeuré peu caractérisé jusqu’à maintenant, constitue une des principales menaces au maintien de l’intégrité génomique des organites, et ce, tant chez Arabidopsis que chez l’humain. Ce type d’instabilité génomique est dénommé réarrangement de type U-turn et est vraisemblablement associé au processus de réplication. Par une approche génétique, nous démontrons que les protéines chloroplastiques WHY1, WHY3 et RECA1 empêchent la formation de ce type d’instabilité génomique, probablement en favorisant la stabilisation et le redémarrage des fourches de réplication bloquées. Une forte accumulation de réarrangements de type U-turn semble d’ailleurs être à l’origine d’un sévère trouble développemental chez le mutant why1why3reca1. Ceci soulève de nombreuses questions quant à l’implication de ce type d’instabilité génomique dans de nombreux troubles et pathologies possédant une composante mitochondriale.

Étude d'un nouveau facteur impliqué dans la biosynthèse de la paroi bactérienne : le facteur ElyC

La résistance bactérienne aux antibiotiques est de nos jours une préoccupation majeure aux acteurs du monde de la santé publique. L’identification de nouvelles cibles bactériennes en vue de développer de nouveaux antibiotiques est donc nécessaire. La paroi bactérienne est une bonne cible car l’inhibition de sa biosynthèse cause la mort des bactéries. De récents travaux de notre laboratoire ont identifié de nombreux nouveaux facteurs importants pour la biosynthèse de la paroi chez Escherichia coli. L’un de ces facteurs renommé ElyC a un domaine DUF218 extrêmement conservé à travers les espèces bactériennes. L’absence du gène elyC entraîne la lyse bactérienne à température pièce. Des études bioinformatiques indiquent qu’ElyC est une protéine membranaire avec deux domaines transmembranaires et un domaine conservé DUF218 de fonction inconnue. Étant donné que les protéines agissent souvent en complexes, nous avons émis l’hypothèse qu’ElyC interagit avec d’autres protéines afin d'exécuter sa fonction biologique. Le but de mon projet est de déterminer la topologie d’ElyC et d’identifier ses partenaires protéiques. L’étude de la topologie a été faite par l’essai de modification de cystéine sur des souches exprimant individuellement le facteur ElyC avec un résidu cystéine en position N-terminale, dans la boucle ou en position C-terminale. Les partenaires protéiques d’ElyC ont été isolés par immuno-précipitation et identifiés par spectrométrie de masse. Les résultats obtenus ont révélé qu’ElyC est une protéine membranaire chez E. coli et est impliquée dans l'assemblage de l'enveloppe bactérienne, dans la chaîne de transport d'électrons et la phosphorylation oxydative. Ils ont permis aussi de confirmer l’existence d’un lien entre ElyC et le stress oxydatif. Cependant les résultats pour la détermination de la topologie restent à être clarifiés.

Wave-vector dependence of spin and density multipole excitations in quantum dots

We have employed time-dependent local-spin density-functional theory to analyze the multipole spin and charge density excitations in GaAs-AlxGa1-xAs quantum dots. The on-plane transferred momentum degree of freedom has been taken into account, and the wave-vector dependence of the excitations is discussed. In agreement with previous experiments, we have found that the energies of these modes do not depend on the transferred wave vector, although their intensities do. Comparison with a recent resonant Raman scattering experiment [C. Schüller et al., Phys. Rev. Lett. 80, 2673 (1998)] is made. This allows us to identify the angular momentum of several of the observed modes as well as to reproduce their energies

Quantum wire with periodic serial structure

Electron wave motion in a quantum wire with periodic structure is treated by direct solution of the Schrödinger equation as a mode-matching problem. Our method is particularly useful for a wire consisting of several distinct units, where the total transfer matrix for wave propagation is just the product of those for its basic units. It is generally applicable to any linearly connected serial device, and it can be implemented on a small computer. The one-dimensional mesoscopic crystal recently considered by Ulloa, Castaño, and Kirczenow [Phys. Rev. B 41, 12 350 (1990)] is discussed with our method, and is shown to be a strictly one-dimensional problem. Electron motion in the multiple-stub T-shaped potential well considered by Sols et al. [J. Appl. Phys. 66, 3892 (1989)] is also treated. A structure combining features of both of these is investigated

Semiclassical theory of shot noise in ballistic n+in+ semiconductor structures: relevance of Pauli and long range Coulomb interactions

We work out a semiclassical theory of shot noise in ballistic n+-i-n+ semiconductor structures aiming at studying two fundamental physical correlations coming from Pauli exclusion principle and long-range Coulomb interaction. The theory provides a unifying scheme which, in addition to the current-voltage characteristics, describes the suppression of shot noise due to Pauli and Coulomb correlations in the whole range of system parameters and applied bias. The whole scenario is summarized by a phase diagram in the plane of two dimensionless variables related to the sample length and contact chemical potential. Here different regions of physical interest can be identified where only Coulomb or only Pauli correlations are active, or where both are present with different relevance. The predictions of the theory are proven to be fully corroborated by Monte Carlo simulations.

Self-consistent theory of current and voltage noise in multimode ballistic conductors

Electron transport in a self-consistent potential along a ballistic two-terminal conductor has been investigated. We have derived general formulas which describe the nonlinear current-voltage characteristics, differential conductance, and low-frequency current and voltage noise assuming an arbitrary distribution function and correlation properties of injected electrons. The analytical results have been obtained for a wide range of biases: from equilibrium to high values beyond the linear-response regime. The particular case of a three-dimensional Fermi-Dirac injection has been analyzed. We show that the Coulomb correlations are manifested in the negative excess voltage noise, i.e., the voltage fluctuations under high-field transport conditions can be less than in equilibrium.

Sequential interactions of Silver-silica nanocomposite (Ag-SiO2NC) with cell wall, metabolism and genetic stability of Psedomonas aeruginosa, a multiple antibiotic resistant bacterium

The study was carried out to understand the effect of silver-silica nanocomposite (Ag-SiO2NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drugresistant bacterium. Bacterial sensitivity towards antibiotics and Ag-SiO2NC was studied using standard disc diffusion and death rate assay, respectively. The effect of Ag-SiO2NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. P. aeruginosa was found to be resistant to β-lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 μgml-1 concentration of Ag-SiO2NC. The cell wall integrity reduced with increasing time and reached a plateau of 70 % in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 μgml-1 Ag-SiO2NC, followed by DNA breakage. The study thus demonstrates that Ag-SiO2NC invades the cytoplasm of the multiple drug-resistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stability

Synthesis, Characterization and Applications of Modified TiO2 Systems

This thesis is divided in to 9 chapters and deals with the modification of TiO2 for various applications include photocatalysis, thermal reaction, photovoltaics and non-linear optics. Chapter 1 involves a brief introduction of the topic of study. An introduction to the applications of modified titania systems in various fields are discussed concisely. Scope and objectives of the present work are also discussed in this chapter. Chapter 2 explains the strategy adopted for the synthesis of metal, nonmetal co-doped TiO2 systems. Hydrothermal technique was employed for the preparation of the co-doped TiO2 system, where Ti[OCH(CH3)2]4, urea and metal nitrates were used as the sources for TiO2, N and metals respectively. In all the co-doped systems, urea to Ti[OCH(CH3)2]4 was taken in a 1:1 molar ratio and varied the concentration of metals. Five different co-doped catalytic systems and for each catalysts, three versions were prepared by varying the concentration of metals. A brief explanation of physico-chemical techniques used for the characterization of the material was also presented in this chapter. This includes X-ray Diffraction (XRD), Raman Spectroscopy, FTIR analysis, Thermo Gravimetric Analysis, Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy(SEM), UV-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), Transmission Electron Microscopy (TEM), BET Surface Area Measurements and X-ray Photoelectron Spectroscopy (XPS). Chapter 3 contains the results and discussion of characterization techniques used for analyzing the prepared systems. Characterization is an inevitable part of materials research. Determination of physico-chemical properties of the prepared materials using suitable characterization techniques is very crucial to find its exact field of application. It is clear from the XRD pattern that photocatalytically active anatase phase dominates in the calcined samples with peaks at 2θ values around 25.4°, 38°, 48.1°, 55.2° and 62.7° corresponding to (101), (004), (200), (211) and (204) crystal planes (JCPDS 21-1272) respectively. But in the case of Pr-N-Ti sample, a new peak was observed at 2θ = 30.8° corresponding to the (121) plane of the polymorph brookite. There are no visible peaks corresponding to dopants, which may be due to their low concentration or it is an indication of the better dispersion of impurities in the TiO2. Crystallite size of the sample was calculated from Scherrer equation byusing full width at half maximum (FWHM) of the (101) peak of the anatase phase. Crystallite size of all the co-doped TiO2 was found to be lower than that of bare TiO2 which indicates that the doping of metal ions having higher ionic radius into the lattice of TiO2 causes some lattice distortion which suppress the growth of TiO2 nanoparticles. The structural identity of the prepared system obtained from XRD pattern is further confirmed by Raman spectra measurements. Anatase has six Raman active modes. Band gap of the co-doped system was calculated using Kubelka-Munk equation and that was found to be lower than pure TiO2. Stability of the prepared systems was understood from thermo gravimetric analysis. FT-IR was performed to understand the functional groups as well as to study the surface changes occurred during modification. EDX was used to determine the impurities present in the system. The EDX spectra of all the co-doped samples show signals directly related to the dopants. Spectra of all the co-doped systems contain O and Ti as the main components with low concentrations of doped elements. Morphologies of the prepared systems were obtained from SEM and TEM analysis. Average particle size of the systems was drawn from histogram data. Electronic structures of the samples were identified perfectly from XPS measurements. Chapter 4 describes the photocatalytic degradation of herbicides Atrazine and Metolachlor using metal, non-metal co-doped titania systems. The percentage of degradation was analyzed by HPLC technique. Parameters such as effect of different catalysts, effect of time, effect of catalysts amount and reusability studies were discussed. Chapter 5 deals with the photo-oxidation of some anthracene derivatives by co-doped catalytic systems. These anthracene derivatives come underthe category of polycyclic aromatic hydrocarbons (PAH). Due to the presence of stable benzene rings, most of the PAH show strong inhibition towards biological degradation and the common methods employed for their removal. According to environmental protection agency, most of the PAH are highly toxic in nature. TiO2 photochemistry has been extensively investigated as a method for the catalytic conversion of such organic compounds, highlighting the potential of thereof in the green chemistry. There are actually two methods for the removal of pollutants from the ecosystem. Complete mineralization is the one way to remove pollutants. Conversion of toxic compounds to another compound having toxicity less than the initial starting compound is the second way. Here in this chapter, we are concentrating on the second aspect. The catalysts used were Gd(1wt%)-N-Ti, Pd(1wt%)-N-Ti and Ag(1wt%)-N-Ti. Here we were very successfully converted all the PAH to anthraquinone, a compound having diverse applications in industrial as well as medical fields. Substitution of 10th position of desired PAH by phenyl ring reduces the feasibility of photo reaction and produced 9-hydroxy 9-phenyl anthrone (9H9PA) as an intermediate species. The products were separated and purified by column chromatography using 70:30 hexane/DCM mixtures as the mobile phase and the resultant products were characterized thoroughly by 1H NMR, IR spectroscopy and GCMS analysis. Chapter 6 elucidates the heterogeneous Suzuki coupling reaction by Cu/Pd bimetallic supported on TiO2. Sol-Gel followed by impregnation method was adopted for the synthesis of Cu/Pd-TiO2. The prepared system was characterized by XRD, TG-DTG, SEM, EDX, BET Surface area and XPS. The product was separated and purified by column chromatography using hexane as the mobile phase. Maximum isolated yield of biphenyl of around72% was obtained in DMF using Cu(2wt%)-Pd(4wt%)-Ti as the catalyst. In this reaction, effective solvent, base and catalyst were found to be DMF, K2CO3 and Cu(2wt%)-Pd(4wt%)-Ti respectively. Chapter 7 gives an idea about the photovoltaic (PV) applications of TiO2 based thin films. Due to energy crisis, the whole world is looking for a new sustainable energy source. Harnessing solar energy is one of the most promising ways to tackle this issue. The present dominant photovoltaic (PV) technologies are based on inorganic materials. But the high material, low power conversion efficiency and manufacturing cost limits its popularization. A lot of research has been conducted towards the development of low-cost PV technologies, of which organic photovoltaic (OPV) devices are one of the promising. Here two TiO2 thin films having different thickness were prepared by spin coating technique. The prepared films were characterized by XRD, AFM and conductivity measurements. The thickness of the films was measured by Stylus Profiler. This chapter mainly concentrated on the fabrication of an inverted hetero junction solar cell using conducting polymer MEH-PPV as photo active layer. Here TiO2 was used as the electron transport layer. Thin films of MEH-PPV were also prepared using spin coating technique. Two fullerene derivatives such as PCBM and ICBA were introduced into the device in order to improve the power conversion efficiency. Effective charge transfer between the conducting polymer and ICBA were understood from fluorescence quenching studies. The fabricated Inverted hetero junction exhibited maximum power conversion efficiency of 0.22% with ICBA as the acceptor molecule. Chapter 8 narrates the third order order nonlinear optical properties of bare and noble metal modified TiO2 thin films. Thin films were fabricatedby spray pyrolysis technique. Sol-Gel derived Ti[OCH(CH3)2]4 in CH3CH2OH/CH3COOH was used as the precursor for TiO2. The precursors used for Au, Ag and Pd were the aqueous solutions of HAuCl4, AgNO3 and Pd(NO3)2 respectively. The prepared films were characterized by XRD, SEM and EDX. The nonlinear optical properties of the prepared materials were investigated by Z-Scan technique comprising of Nd-YAG laser (532 nm,7 ns and10 Hz). The non-linear coefficients were obtained by fitting the experimental Z-Scan plot with the theoretical plots. Nonlinear absorption is a phenomenon defined as a nonlinear change (increase or decrease) in absorption with increasing of intensity. This can be mainly divided into two types: saturable absorption (SA) and reverse saturable absorption (RSA). Depending on the pump intensity and on the absorption cross- section at the excitation wavelength, most molecules show non- linear absorption. With increasing intensity, if the excited states show saturation owing to their long lifetimes, the transmission will show SA characteristics. Here absorption decreases with increase of intensity. If, however, the excited state has strong absorption compared with that of the ground state, the transmission will show RSA characteristics. Here in our work most of the materials show SA behavior and some materials exhibited RSA behavior. Both these properties purely depend on the nature of the materials and alignment of energy states within them. Both these SA and RSA have got immense applications in electronic devices. The important results obtained from various studies are presented in chapter 9.

Biobutanol from lignocellulosic biomass by a novel Clostridium sporogenes BE01

In the current study, a novel non-acetone forming butanol and ethanol producer Was isolated and identified. Based on the 16s rDNA sequence BLAST and phylogenetic analyses, it was found to have high similarity with the reported hydrogen producing strains of Clostridium sporogenes. Biochemical studies revealed that it is lipase and protease positive. The lipolytic and proteolytic properties are the very important characteristics of Clostridium sporogenes. Sugar utilization profile studies were positive for glucose, saccharose, cellobiose and weakly positive result to xylose. This study demonstrated C. sporogenes BE01, an isolate from NIIST is having potential to compete with existing, well known butanol producers with the advantage of no acetone in the final solvent mixture. Rice straw hydrolysate is a potent source of substrate for butanol production by C. sporogenes BE01. Additional supplementation of vitamins and minerals were avoided by using rice straw hydrolysate as substrate. Its less growth, due to the inhibitors present in the hydrolysate and also inhibition by products resulted in less efficient conversion of sugars to butanol. Calcium carbonate played an important role in improving the butanol production, by providing the buffering action during fermentation and stimulating the electron transport mediators and redox reactions favoring butanol production. Its capability to produce acetic acid, butyric acid and hydrogen in significant quantities during butanol production adds value to the conversion process of lignocellulosic biomass to butanol. High cell density fermentation by immobilizing the cells on to ceramic particles improved the solvents and VFA production. Reduced sugar utilization from the concentrated hydrolysate could be due to accumulation of inhibitors in the hydrolysate during concentration. Two-stage fermentation was very efficient with immobilized cells and high conversions of sugars to solvents and VFAs were achieved. The information obtained from the study would be useful to develop a feasible technology for conversion of lignocellulosic biomass to biobutanol.