Studies on the enzyme α-glucan phosphorylase

ac-qlncnn phosphorylsse is en ilportent enzyme in glycoiysis. It is the first used knows to exhibit ellosteric properties and lance its inhibition end ectivetion have significant effect on the rete ot qlycolysis. The thesis deals with 11 detailed study of the structure. inhibition and control or this snlrlls from rabbit uncle and troll e merino eninelo ‘the thesis is divided into two parts. Port 1 deals with studies on rabbit uncle glycogen phospherylese. After e review of the relevant literetnre (Chapter 1) the inhibition and chancel sodiiicetion studies on rabbit ensyle ere discussed in chepters 2 to 5. Chapter 6. gives the methods used for the study

GABA and 5-HT chitosan nanoparticles enhanced liver cell proliferation and neuronal survival in partially hepatectomised rats: GABAB and 5-HT2A receptors functional

Nanoparticulate drug delivery systems provide wide opportunities for solving problems associated with drug stability or disease states and create great expectations in the area of drug delivery (Bosselmann & Williams, 2012). Nanotechnology, in a simple way, explains the technology that deals with one billionth of a meter scale (Ochekpe, et al., 2009). Fewer side effects, poor bioavailability, absorption at intestine, solubility, specific delivery to site of action with good pharmacological efficiency, slow release, degradation of drug and effective therapeutic outcome, are the major challenges faced by most of the drug delivery systems. To a great extent, biopolymer coated drug delivery systems coupled with nanotechnology alleviate the major drawbacks of the common delivery methods. Chitosan, deacetylated chitin, is a copolymer of β-(1, 4) linked glucosamine (deacetylated unit) and N- acetyl glucosamine (acetylated unit) (Radhakumary et al., 2005). Chitosan is biodegradable, non-toxic and bio compatible. Owing to the removal of acetyl moieties that are present in the amine functional groups of chitin, chitosan is readily soluble in aqueous acidic solution. The solubilisation occurs through the protonation of amino groups on the C-2 position of D-glucosamine residues whereby polysaccharide is converted into polycation in acidic media. Chitosan interacts with many active compounds due to the presence of amine group in it. The presence of this active amine group in chitosan was exploited for the interaction with the active molecules in the present study. Nanoparticles of chitosan coupled drugs are utilized for drug delivery in eye, brain, liver, cancer tissues, treatment of spinal cord injury and infections (Sharma et al., 2007; Li, et a., 2009; Paolicelli et al., 2009; Cho et al., 2010). To deliver drugs directly to the intended site of action and to improve pharmacological efficiency by minimizing undesired side effects elsewhere in the body and decrease the long-term use of many drugs, polymeric drug delivery systems can be used (Thatte et al., 2005).

Crystal Structures and Spectral Aspects of Mixed Ligand Transition Metal Chelates Derived from Aldehyde based ONS Donor Thiosemicarbazones

Thiosemicarbazones have emerged as an important class of ligands over a period of time, for a variety of reasons, such as variable donor properties, structural diversity and biological applications. Interesting as the coordination chemistry may be, the driving force for the study of these ligands has undoubtedly been their biological properties and the majority of the 3000 or so publications on thiosemicarbazones since 2000 have alluded to this feature. Thiosemicarbazones with potential donor atoms in their structural skeleton fascinate coordination chemists with their versatile chelating behavior. The thiosemicarbazones of aromatic aldehydes and ketones form stable chelates with transition metal cations by utilizing both their sulfur and azomethine nitrogen as donor atoms. They have been shown to possess a diverse range of biological activities including anticancer, antitumor, antibacterial, antiviral, antimalarial and antifungal properties owing to their ability to diffuse through the semipermeable membrane of the cell lines. The enhanced effect may be attributed to the increased lipophilicity of the metal complexes compared to the ligand alone.

“Investigations on Vibrational Overtones in the NIR region and Laser Induced Fluorescence in some selected compounds”

The central theme of this research concerns the study of vibrationally excited molecules. We have used the local mode description of such vibrational states, and this -model has now gained general acceptance. A central feature of the model is the Wloealizafion of vibrational energy. A study of these high—energy localized states provides example, becauseof this localization, overtone spectra, which measure the absorption of T vibrational energy, are extremely sensitive to the properties of X-H bonds. We also use -overtone spectra to study the conformation of molecules, i.e., the relative internal orientation of their bonds. The thesis comprises six chapters

“A comparative study of medium and large pore zeolites in alkylation reactions”

Zeolites have established themselves as industrial catalysts for over two decades for a variety of hydrocarbon processing reactions where acidity and shape selectivity are important factors. As solid catalysts, zeolites may be advantageous and superior compared to their homogenous counterparts due to their characteristic properties. It is only in recent years that the utility of zeolites for organic synthesis is recognized for producing specific organic intermediates and fine chemicals in high selectivity. In this thesis an attempt has been made to compare the catalytic activity of some medium and large pore zeolites in a few alkylation and acylation reactions. The work reported in the present study is basically centered around the following zeolites namely, ZSM-5, mordenite, zeolite Y and beta. The major reactions carried out were benzoylation of o-xylene, propionylation of toluene and anisole and benzylation of oxylene. . The programme involves the synthesis, modifications and characterization of the zeolite catalysts by various methods. The influence of various parameters such as non-framework cations, Si/Al ratio of zeolites, temperature of the reaction, catalyst concentration, molar ratio of the reactants and recycling of the catalysts were also examined upon the conversion of reactants and the formation of the desired products in the alkylation/ acylation reactions. The general conclusions drawn by us from the results obtained are summarized in the last chapter of the thesis. Zeolite beta ofi'ers interesting opportunities as a potential catalyst in alkylation reactions and the area of catalysis by medium and large pore zeolites is very fascinating and there is plenty of scope for further research in this field. Moreover, zeolite based catalysts are effective in meeting current industrial processing and more stringent environment pollution limits.

Vibrational spectroscopic studies and computational study of quinoline-2-carbaldehyde benzoyl hydrazone

FT-IR spectrum of quinoline-2-carbaldehyde benzoyl hydrazone (HQb H2O) was recorded and analyzed. The synthesis and crystal structure data are also described. The vibrational wavenumbers were examined theoretically using the Gaussian03 package of programs using HF/6-31G(d) and B3LYP/6-31G(d) levels of theory. The data obtained from vibrational wavenumber calculations are used to assign vibrational bands obtained in infrared spectroscopy of the studied molecule. The first hyperpolarizability, infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non-linear optics. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated values. The changes in the CAN bond lengths suggest an extended p-electron delocalization over quinoline and hydrazone moieties which is responsible for the non-linearity of the molecule

Characterization of low dielectric constant polyaniline thin film synthesized by ac plasma polymerization technique

Polyaniline thin films were prepared by ac plasma polymerization technique. Capacitance, dielectric loss, dielectric constant and ac conductivity of these films were investigated in the frequency range from 100 Hz to 1MHz and in the temperature range from 300 to 373 K. Capacitance and dielectric loss decreased with frequency and increased with temperature. This type of behaviour was found to be in good agreement with an existing model. The ac conductivity σ(ω) was found to vary as ωs with the index s 1. Annealing of polyaniline thin films in high vacuum at 373K for 1 h was found to reduce the dielectric loss. FTIR studies reveal that the aromatic ring is retained in the polyaniline thin films, which enhances the thermal stability of the polymer films

Investigations on the electrical and structural properties of polyaniline doped with camphor sulphonic acid

Polyaniline is chemically synthesised and doped with camphor sulphonic acid. FTIR studies carried out on these samples indicate that the aromatic rings are retained after polymerisation. The percentage of crystallinity for polyaniline doped with camphor sulphonic acid has been estimated from the X-ray diffraction studies and is around 56% with respect to polyaniline emeraldine base. The change in dielectric permittivity with respect to temperature and frequency is explained on the basis of interfacial polarisation. AC conductivity is evaluated from the observed dielectric permittivity. The values of AC and DC conductivity and activation energy are calculated. The activation energy values suggested that the hopping conduction is the prominent conduction mechanism in this system.

Biodegradation Of Phenol Using Spent Substrate Of Pleurotus Sp.

Phenol is an aromatic hydrocarbon which exists as a colorless or white solid in its pure state. Over the past several decades, there is growing concern about wide spread contamination of surface and ground water by phenol, due to rapid development of chemical and petrochemical industries. Phenol affects aquatic life even at relatively low concentration (5-25mg/L). Treatment for removal of phenol includes chemical as well as biological processes. Studies show that ligninases such as Lignin Peroxidase and Laccase, produced by Pleurotus sp., can degrade phenol. Spent substrate of Pleurotus mushrooms consists of ligninases. Present work was to investigate the potential of spent substrate of edible mushroom P. ostreatus for biodegradation of phenol. P. ostreatus was cultivated on paddy straw. After harvest, spent substrate was utilized for phenol degradation. According to the enzyme profile of two ligninases present in the spent substrate of P. ostreatus, maximum specific activity for Laccase was observed in 35 day old spent substrate and LiP activity was maximum in 56 day old spent substrate, which together contributed significantly for removal of phenol. Spent substrate of 35th and 56th day were each incubated with phenol sample (1:1w/v) for one day, which resulted in degradation of phenol by 48% and 45% respectively. From these results it appears that, spent substrate of P. ostreatus can be used effectively to remove phenol from industrial effluents

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.

Dipodal Ferrocene Derivatives for Nanostructured Redox-Functionalised Surfaces

Self-assembled monolayers (SAMs) on solid surfaces are of great current interest in science and nanotechnology. This thesis describes the preparation of several symmetrically 1,1’-substituted ferrocene derivatives that contain anchoring groups suitable for chemisorption on gold and may give rise to SAMs with electrochemically switchable properties. The binding groups are isocyano (-NC), isothiocyanato (-NCS), phosphanyl (-PPh2), thioether (-SR) and thienyl. In the context of SAM fabrication, isothiocyanates and phosphanes are adsorbate systems which, surprisingly, have remained essentially unexplored. SAMs on gold have been fabricated with the adsorbates from solution and investigated primarily by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The results of these analytical investigations are presented and discussed in matters of the film quality and possible binding modes. The quality of self-assembled monolayers fabricated from 1,1’-diisocyanoferrocene and 1,1’-diisothiocyanatoferrocene turned out to be superior to that of films based on the other adsorbate species investigated. Films of those absorbates as well as of dppf afforded well-defined SAMs of good quality. All other films of this study based on sulfur containing anchoring groups exhibit chemical inhomogeneity and low orientational order of the film constituents and therefore failed to give rise to well-defined SAMs. Surface coordination chemistry is naturally related to molecular coordination chemistry. Since all SAMs described in this thesis were prepared on gold (111) surfaces, the ferrocene-based ligands of this study have been investigated in their ability for complexation towards gold(I). The sulfur-based ferrocene ligands [fc(SR)2] failed to give stable gold(I) complexes. In contrast, 1,1’-diisocyanoferrocene (1) proved to be an excellent ligand for the complexation of gold(I). Several complexes were prepared and characterised utilising a series of gold(I) acetylides. These complexes show interesting structural motifs in the solid state, since intramolecular aurophilic interactions lead to a parallel orientation of the isocyano moieties, combined with an antiparallel alignment of neighbouring units. The reaction of 1 with the gold(I) acetylide [Au(C≡C–Fc)]n turned out to be very unusual, since the two chemically equivalent isocyano groups undergo a different reaction. One group shows an ordinary coordination and the other one undergoes an extraordinary 1,1-insertion into the Au-C bond. As a sideline of the research of this thesis several ferrocene derivatives have been tested for their suitability for potential surface reactions. Copper(I) mediated 1,3-dipolar cycloadditions of azidoferrocene derivatives with terminal alkynes appeared very promising in this context, but failed to a certain extent in terms of ‘click’ chemistry, since the formation of the triazoles depended on the strict exclusion of oxygen and moisture and yields were only moderate. Staudinger reactions between dppf and azidoferrocene derivatives were also tested. The nucleophilic additions of secondary amines to 1,1’-diisothiocyanatoferrocene led to the respective thiourea derivatives in quantitative yields.

Dye-sensitized solar cells based on perylene derivatives

The oil price rises more and more, and the world energy consumption is projected to expand by 50 percent from 2005 to 2030. Nowadays intensive research is focused on the development of alternative energies. Among them, there are dye-sensitized nanocrystalline solar cells (DSSCs) “the third generation solar cells”. The latter have gained attention during the last decade and are currently subject of intense research in the framework of renewable energies as a low-cost photovoltaic. At present DSSCs with ruthenium based dyes exhibit highest efficiencies (ca 11%). The objective of the present work is to fabricate, characterize and improve the performance of DSSCs based on metal free dyes as sensitizers, especially on perylene derivatives. The work begins by a general introduction to the photovoltaics and dye-sensitized solar cells, such as the operating principles and the characteristics of the DSSCs. Chapter 2 and 3 discuss the state of the art of sensitizers used in DSSCs, present the compounds used as sensitizer in the present work and illustrate practical issues of experimental techniques and device preparation. A comparative study of electrolyte-DSSCs based on P1, P4, P7, P8, P9, and P10 are presented in chapter 4. Experimental results show that the dye structure plays a crucial role in the performance of the devices. The dye based on the spiro-concept (bipolar spiro compound) exhibited a higher efficiency than the non-spiro compounds. The presence of tert-butylpyridine as additive in the electrolyte was found to increase the open circuit voltage and simultaneously decrease the efficiency. The presence of lithium ions in the electrolyte increases both output current and the efficiency. The sensitivity of the dye to cations contained in the electrolyte was investigated in the chapter 5. FT-IR and UV-Vis were used to investigate the in-situ coordination of the cation to the adsorbed dye in the working devices. The open-circuit voltage was found to depend on the number of coordination sites in the dye. P1 with most coordination sites has shown the lowest potential drop, opposite to P7, which is less sensitive to cations in the working cells. A strategy to improve the dye adsorption onto the TiO2 surface, and thus the light harvesting efficiency of the photoanode by UV treatment, is presented in chapter 6. The treatment of the TiO2 film with UV light generates hydroxyl groups and renders the TiO2 surface more and more hydrophilic. The treated TiO2 surface reacts readily with the acid anhydride group of the dye that acts as an anchoring group and improves the dye adsorption. The short-circuit current density and the efficiency of the electrolyte-based dye cells was considerably improved by the UV treatment of the TiO2 film. Solid-state dye-sensitized solar cells (SSDs) based on spiro-MeOTAD (used as hole transport material) are studied in chapter 7. The efficiency of SSDs was globally found to be lower than that of electrolyte-based solar cells. That was due to poor pore filling of the dye-loaded TiO2 film by the spin-coated spiro-MeOTAD and to the significantly slower charge transport in the spiro-MeOTAD compared to the electrolyte redox mediator. However, the presence of the donor moieties in P1 that are structurally similar to spiro-MeOTAD was found to improve the wettability of the P1-loaded TiO2 film. As a consequence the performance of the P1-based solid-state cells is better compared to the cells based on non-spiro compounds.

Elektrochemische und spektroelektrochemische Untersuchungen symmetrischer und unsymmetrischer Spiroverbindungen

In dieser Arbeit wurden elektronische Eigenschaften der sogenannten Spiroverbin-dungen untersucht, die aus zwei durch ein gemeinsames Spiro-Kohlenstoffatom miteinander verbundenen π-Systemen bestehen. Solche Untersuchungen sind notwendig, um die gezielte Synthese organischer Materialien mit bestimmten optischen, elektrischen, photoelektrischen oder magnetischen Eigenschaften zu ermöglichen. Im einzelnen wurden mit Hilfe der Cyclovoltammetrie, Square-Wave-Voltammetrie und Spektroelektrochemie eine Reihe homologer Spiro-p-oligophenyle, sowie symmetrisch und unsymmetrisch substituierte Spiroverbindungen und Spirocyclopentadithiophene unter-sucht. Dabei ergaben sich folgende Einflussfaktoren: Kettenlänge, verschiedene Substituenten (Trimethylsilyl, tert-Butyl, Fluor, Pyridyl, perfluoriertes Pyridyl, Dimethylamino-Gruppe), verschiedene Positionen der Substitution, Lage der Spiroverknüpfung und Art des π-Systems im Spirokern. Die elektronischen Eigenschaften der untersuchten Verbindungen variieren systema-tisch mit der Kettenlänge. So vermindert sich der Betrag der Redoxpotentiale der Spiroverbin-dungen mit Zunahme der Kettenlänge, während die Anzahl der übertragenen Elektronen mit zunehmender Kettenlänge wächst. Die Absorption der neutralen und geladenen Spezies ver-schiebt sich mit steigender Kettenlänge bathochrom. Der Substituenteneinfluss auf die Poten-tiallage hängt davon ab, welcher der Effekte +I, -I, +M, -M überwiegt; dabei spielt auch die Position der Substitution eine Rolle. Weiter lässt sich der Einfluss der Lage der Spiroverknüpfung auf die Redoxpotentiale mit der verschiedenen Coulomb-Abstoßung innerhalb oder/und zwischen Phenylketten bei symmetrisch und unsymmetrisch verknüpften Spiroverbindungen begründen. Schließlich wurden die Redoxmechanismen der untersuchten Spiroverbindungen er-mittelt. Die meisten Verbindungen werden zum Bis(radikalion) reduziert bzw. oxidiert (Me-chanismus A). Nur wenige Verbindungen werden nach Mechanismus B reduziert, in dem das Elektron unter Bildung eines Dianions in die schon einfach reduzierte Molekülhälfte über-geht. Die Unterschiede der Redoxpotentiale, der Lage der Absorption, des Reduktionsme-chanismus der Verbindungen mit unterschiedlichen Spirokernen (Spirobifluoren und Spiro-cyclopentadithiophen) konnten mit den unterschiedlichen elektronischen Strukturen von Phe-nyl- und Thiophenring (aromatisches und heteroaromatisches π System) erklärt werden.

Metallische Nanopartikel auf Quarz

This work presents the developement of an chemically stable and easy to produce in situ sensor for fast and reliable detection of polycyclic aromatic hydrocarbons (PAH) in low nanomolar concentrations. Metallic nanoparticles on dielectric substrates werde used for the rst time with surface enhanced Raman spectroscopy (SERS) in combination with shifted excitation Raman difference spectroscopy (SERDS). The preparation of the metallic nanoparticle ensembles with Volmer-Webergrowth is described first. The nanoparticles are characterized with both, optical spectroscopy and atomic force microscopy. The morphological properties of the nanoparticle ensembles are de ned by the mean axial ratio (a/b) and the mean equivalent radius (R Äq), respectively. The prepared and characterized nanoparticles were then used for intensive Raman spectroscopy measurements. Two sophisticated diode laser systems were used in cooperation with the TU Berlin, to carry out these experiments. The first step was to establish the ideal combination of excitation wavelength of the diode laser and the maximum of the surface plasmon resonance of the nanoparticle ensembles. From these results it was deduced, that for an optimum Raman signal the plasmon resonance maximum of the nanoparticle ensemble has to be red-shifted a few nanometeres in respect to the excitation wavelength. Different PAHs werde detected in concentrations of only 2 and 0.5 nmol/, respectively. Furthermore, the obtained results show an excellent reproducability. In addition the time dependence of the Raman signal intensity was investigated. The results of these measurements show, that only 2 minutes after placing the substrates in the molecular solution, a detectable Raman signal was generated. The maximum Raman signal, i.e. the time in which the molecular adsorption process is finished, was determined to about 10 minutes. In summary it was shown, that the used metallic nanoparticle ensembles are highly usable as substrates for SERS in combination with SERDS to detect PAHs in low nanomolar concentrations.

SCAPA (Spacially Addressable Protein Array) – a Novel Protein Array for the Differential Profiling of Ligand-receptor Induced Signalling

While protein microarray technology has been successful in demonstrating its usefulness for large scale high-throughput proteome profiling, performance of antibody/antigen microarrays has been only moderately productive. Immobilization of either the capture antibodies or the protein samples on solid supports has severe drawbacks. Denaturation of the immobilized proteins as well as inconsistent orientation of antibodies/ligands on the arrays can lead to erroneous results. This has prompted a number of studies to address these challenges by immobilizing proteins on biocompatible surfaces, which has met with limited success. Our strategy relates to a multiplexed, sensitive and high-throughput method for the screening quantification of intracellular signalling proteins from a complex mixture of proteins. Each signalling protein to be monitored has its capture moiety linked to a specific oligo ‘tag’. The array involves the oligonucleotide hybridization-directed localization and identification of different signalling proteins simultaneously, in a rapid and easy manner. Antibodies have been used as the capture moieties for specific identification of each signaling protein. The method involves covalently partnering each antibody/protein molecule with a unique DNA or DNA derivatives oligonucleotide tag that directs the antibody to a unique site on the microarray due to specific hybridization with a complementary tag-probe on the array. Particular surface modifications and optimal conditions allowed high signal to noise ratio which is essential to the success of this approach.