Moderne Methoden der Oberflächenbehandlung können Oberflächen mit besonderen Eigenschaften versehen. Diese Eigenschaften werden zunehmend durch ultradünne Schichten mit Schichtdicken von einigen Nanometern erzeugt, da mit minimalem Materialaufwand definierte Resultate erreichbar sind. Die meisten Metalle überziehen sich mit einer Oxidschicht, deren Eigenschaften von den herrschenden Umgebungsbedingungen bestimmt werden. Diese Oxidschicht bildet die Oberfläche des Festkörpers, und weist andere Eigenschaften auf als der Festkörper selbst. Darüber hinaus beeinflussen die Rauhigkeit sowie eventuell vorliegende Legierungsbestandteile die Oberflächenbeschaffenheit. Besonders geeignet zum Erzeugen ultradünner oder monomolekularer Schichten ist der Prozess der Selbstorganisation, bei dem man sich zu Nutze macht, dass oberflächenaktive Moleküle mit sich selbst und einem Substrat in Wechselwirkung treten können. Zum Verständnis der ablaufenden Vorgänge ist die Kenntnis der Prozesskinetik sowie die Charakterisierung der Substratoberfläche vor und nach der Adsorption erforderlich. Die Größenverhältnisse zwischen den adsorbierten Molekülen und der Rauheit der Oberfläche erschweren die Charakterisierung der vorliegenden Ordnung und Orientierung der erzeugten dünnen Schichten. In dieser Arbeit sind Untersuchung des Schichtbildungsverhaltens und die Charakterisierung der erzeugten Schichten aus Phosphon- und Phosphorsäurederivaten in Abhängigkeit verschiedener Eigenschaften der Substratoberflächen vorgenommen worden. Dabei kamen oberflächensensitive Methoden wie AFM, REM, SPR und XPS zum Einsatz. Es konnte gezeigt werden, dass sich die untersuchten Moleküle wie erwartet auf den Oberflächen orientieren und dabei einen Bedeckungsgrad von etwa 60% erreichen. Der Einfluss von unterschiedlichen Vorbehandlungsmethoden konnte ebenso charakterisiert werden.

Thesis (Ph. D.)--Auburn University, 2008. / Abstract. Vita. The following patent resulted from the dissertation research: Davis, V., Simonian, A.L., Nepal, D., Balasubramanian, S, "Preparation of Precisely Controlled Thin Film Nanocomposites of Carbon Nanotubes and Biomaterials", U.S. Provisional Patent Application No. 61/000,938, filed on 30 October 2007. The following peer-reviewed publications resulted from the dissertation research: Dhriti Nepal, Shankar Balasubramanian, Aleksandr Simonian, and Virginia Davis, "Mechanically Strong Antibacterial Thin Film Based on Single-Walled Carbon Nanotubes Armored with Biopolymers", Nano Letters ASAP article, May 2008 (# equal contribution) -- Shankar Balasubramanian, Iryna B. Sorokulova, Vitaly J. Vodyanoy, and Aleksandr L. Simonian, "Lytic Phage as a Specific and Selective Probe For Detection of Staphylococcus Aureus: A Surface Plasmon Resonance Spectroscopic Study", Biosensors and Bioelectronics, 2007, 22, 948-955 -- Shankar Balasubramanian, Alexander Revzin, Aleksandr Simonian, "Electrochemical Desorption of Proteins from Gold Electrode Surface", Electroanalysis, 2006, 18, 1885-1892 (Invited article) -- Vishwaprakash Nanduri, Shankar Balasubramanian, Srinivas Sista, Vitaly J. Vodyanoy, and Aleksandr L. Simonian, "Highly Sensitive Phage-based Biosensor for the Detection of ß-galactosidase", Analytica Chimica Acta, 2007, 589, 166- 172 -- H. Luckarift, Shankar Balasubramanian, S. Paliwal, G. Johnson and A. Simonian, "Enzyme-Encapsulated Silica Monolayers For Rapid Functionalization of a Gold Surface", Colloids and Surfaces B: Biointerfaces, 2007, 58, 28-33 (Invited article) -- Dong Wei, Omar Oyarzabal, Tung-Shi Huang, Shankar Balasubramanian, Srinivas Sista, Aleksandr Simonian, "Development of Surface Plasmon Resonance Biosensor For The Identification of Campylobacter jejuni", Journal of Microbiological Methods, 2007, 69, 78-85. The following conferences presentations resulted from the dissertation research: Covalent Immobilization of Organophosphorus Hydrolase on Carbon Nanotubes for Biosensor Applications, accepted for oral presentation at 12th International Meeting on Chemical Sensors, Jul. 13-16, 2008, Columbus, OH -- Electrochemical characteristics of SWNT-biopolymer nanocomposites, accepted for 213th meeting of The Electrochemical Society, May 18-23, 2008, Phoenix, AR -- Mechanically Robust Antibacterial Thin Films Composed of Single-Walled Carbon Nanotubes and Biopolymers, 2008 AIChE Spring National Meeting, Apr. 6-10, New Orleans, LA -- Production and characterization of protein and DNA based single wall carbon nanocomposites by layer-by-layer assembly, MRS Fall Meeting, Nov. 26-30, 2007, Boston, MA -- Gold surface modified with enzyme-encapsulated silica monolayers for biosensor application, The 58th Southeast Regional Meeting of the American Chemical Society, Nov. 1-4, 2006, Augusta, GA -- Electrochemical modulation of biological interfaces, 209th meeting of The Electrochemical Society, May 7-12, 2006, Denver, CO -- SPR based biosensor using lytic phage as a specific and selective probe for staphylococcus aureus detection, 57th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Mar. 12-17, 2006, Orlando, FL -- Specific & selective detection of staphylococcus aureus by lytic phage using SPR biosensor, 57th Southeast / 61st Southwest Joint Regional Meeting of the American Chemical Society, Nov. 1-4, 2005, Memphis, TN -- Prevention of non-specific binding as a way to increase sensitivity of SPR-based sensors, 206th meeting of The Electrochemical Society, October 3-8, 2004, Honolulu, HI. Includes bibliographical references.

Gold nanoparticles are excellent candidates for all the biomedical applications due to their size and shape dependent optical and physiological properties. In this study, gold nanoparticles were synthesized chemically for bio-application. It was observed that the size and shape of gold nanoparticles depend strongly on the concentration of chemical solution, type of reducing agent used in the reaction, temperature of the solution and stabilizing agent for reaction. Transmission electron microscopy (TEM) has been used extensively to determine the size and shape of the gold nanoparticles. Optical properties of the size and shape selected nanoparticles were studied using UV-vis spectrophotometer in absorption mode. The chemically synthesized gold nanoparticles were observed to show excellent absorption property which is reflected by the presence of the characteristic surface plasmon resonance (SPR) band peak. The SPR peak was found to be predominantly dependent on the size of nanoparticles. We have observed a strong red shift with increasing the size of gold nanoparticles. The position of the SPR peak was also observed to change with shape of gold nanostructures. Synthesis and characterization of the composites of gold nanoparticles and Poly (Oanisidine) (POAS) have been carried out in this thesis. Gold-POAS materials system was characterized using UV-vis spectroscopy, TEM, Fourier Transform Infrared Spectroscopy. The chemically synthesized gold nanoparticles were successfully utilized for the study of Respiratory Syncycial Virus (RSV) interaction. Gold nanoparticles were found to inhibit the RSV infection. The electrochemical behavior of gold nanoparticles was studied and their potentials for biosensing applications were tested. Cyclic voltaammetry was performed for the detection of dopamine and ascorbic acid using gold nanoparticles of different sizes. Interaction of gold nanoparticles with Bovine Serum Albumin (BSA) has been studied via absorption spectroscopy and TEM measurements. The absorption spectra of the GNP-BSA show remarkable shift in SPR band peak towards high wavelength. Catalytic properties of the gold nanoparticles were studied by using them as a catalytic activator for the gas sensing applications.

Food poisoning is mainly caused by pathogenic microorganisms and is now a severe problem worldwide. Therefore, rapid and sensitive methods are required to detect foodborne pathogens. A locally isolated bacterium, Bacillus licheniformis B38 was selected for this study. The spores of B. licheniformis B38 were induced by Schaeffer’s sporulation medium containing KCl, MgSO4.7H2O, Ca(NO3)4, MnCl2 and FeSO4. Schaeffer-Fulton endospore staining was used to differentiate spores and vegetative cells, where spores were stained green and vegetative cells were stained red. In order to separate the spores from the cells, a two-phase system was used to obtain pure spore suspension for following experiments. Spore coat proteins were extracted by SDS-8 M urea sample buffer and visualized by two different types of coomassie brilliant blue staining solutions. One of the staining solutions was more suitable for gel elution by diffusion. An ~10 kDa spore coat protein was selected for protein purification. Based on the given results, the protein purification by liquid chromatography was less convincing than using gel elution by diffusion technique. The two hypothetical protein sequences, P06552 and P45693, from the ~10 kDa spore coat protein were identified. In the preliminary study of B. licheniformis B38 spores detection by surface plasmon resonance, several binding parameters were studied. Dot blot was done to verify the reaction between the Bacillus spores polyclonal antibody against the B. licheniformis B38 spore coat protein. The most promising result was the binding of 0.1 mg/mL polyclonal antibody (analyte) to the 0.2 mg/mL spore coat protein at pH 2 (ligand) which showed 5.74 RU. The differences between a dot blot and a SPR detection techniques are described.

Optical whispering-gallery mode (WGM) cavities, which exhibit extraordinary spatial and temporal confinement of light, are one of the leading transducers for examining molecular recognition at low particle counts. With the advent of hybrid photonic-plasmonic and increasingly sophisticated forms of these resonators, the importance of supporting numerical methods has correspondingly become evident. In response, we adopt a full-vector finite difference approximation in order to solve for WGM's in terms of their field distributions, resonant wavelengths, and quality factors in the context of naturally discontinuous permittivity structure. A segmented Taylor series and alignment/rotation operator are utilized at such singularities in conjunction with arbitrarily spaced grid points. Simulations for microtoroids, with and without dielectric nanobeads, and plasmonic microdisks are demonstrated for short computation times and shown to be in agreement with data in the literature. Constricted surface plasmon polariton (SPP) WGM's are also featured within this document. The module of this thesis is devised as a keystone for composite WGM models that may guide experiments in the field. / Graduate

Small molecules interacting with DNA is an emerging theme in scientific research due to its specificity and minimal side-effect. Moreover, a large amount of research has been done on finding compounds that can stabilize G-quadruplex DNA, a non-canonical secondary DNA structure, to inhibit cancerous cell proliferation. G-quadruplex DNA is found in the guanine-rich region of the chromosome that has an important role in protecting chromosomes from unwinding, participate in gene expression, contribute in the control replication of cells and more. In this research, rationally designed, synthetic cyanine dye derivatives, which were tested under physiologically relevant conditions, were found to selectively bind to G-quadruplex over duplex DNA and are favored to one structure over another. The interactions were observed using UV-Vis thermal melting, fluorescence titration, circular dichroism titration, and surface plasmon resonance analysis. For fluorescence and selectivity properties, cyanine dyes, therefore, have the potential to become the detections and/or therapeutic drugs to target cancers and many other fatal diseases.

Calpains are a family of intracellular cysteine proteases activated by calcium. They participate in many processes including cell motility, cell cycle progression and cell death, in response to calcium signaling. Because calpain over-activation as a result of calcium dysregulation is a contributing factor to many disease states, these enzymes are important therapeutic targets. Within the cell, calpains 1 and 2 are regulated by the protein inhibitor calpastatin. This unstructured protein is specific for calpain, binds tightly, and recognizes only the activated form of the enzyme. Detailed kinetic data obtained using surface plasmon resonance allowed the association and dissociation rates of each of the four calpastatin inhibitory domains to be measured. Based on this, inhibitory domain 4 was selected to be co-crystallized bound to calpain 2. The X-ray crystal structure of this complex provided both the first view of the active enzyme, as well as the first view of how it is inhibited. Calpastatin wraps around the enzyme making contact with each domain. It lies in the active site as a contiguous polypeptide chain and escapes cleavage by forming a loop away from the catalytic cysteine. In addition to inhibiting substrate cleavage, calpastatin protects calpain in two ways; it prevents autoproteolysis, and it prevents calcium-dependent aggregation. The crystal structure of the calpastatin:calpain complex revealed no obvious reason for this stabilization. To elucidate how this protection occurs, peptides were synthesized corresponding to conserved subdomains of calpastatin. Surprisingly, each peptide alone was capable of preventing aggregation in vitro, by blocking hydrophobic patches exposed upon activation. The increased hydrophobic surface of the activated enzyme may alter calpain’s affinity for other proteins such as substrates. By binding across many domains of calpain, calpastatin could act to block protein-protein interactions. These studies have characterized calpastatin’s interaction with calpain, which will further our understanding of the enzyme’s regulation and aid in the development of better calpain inhibitors. / Thesis (Ph.D, Biochemistry) -- Queen's University, 2010-04-29 15:27:16.208

No description available.

No description available.

Angiotensinogen is a blood protein that plays a critical role in the regulation of blood pressure in the body. This protein exists in two forms, oxidised and reduced, determined by the presence or absence of a disulfide bridge between Cys 18 and Cys 138. The ratio of oxidised to reduced angiotensinogen is 60:40 in the blood of healthy individuals - an equilibrium that is disrupted in women who develop pre-eclampsia, leading to a higher proportion of oxidised angiotensinogen in the blood. Pre-eclampsia, one of the leading causes of premature births, is a severe and potentially fatal pregnancy condition characterised by the sudden onset of symptoms such as high blood pressure and proteinuria typically during the third trimester. This condition is responsible for an estimated 550,000 deaths globally each year, and with no available treatment or cure other than early delivery of the child, there is a desperate need for a reliable and predictive diagnostic test for this condition. Can we use angiotensinogen as a biomarker for the early diagnosis of pre-eclampsia? Being able to distinguish between reduced and oxidised angiotensinogen and determine the relative amounts of each in blood samples would be of a huge diagnostic value for this condition. This thesis outlines the expression and purification of recombinant human angiotensinogen in Escherichia coli, and the development of an antibody-based SPR assay for angiotensinogen that was subsequently used to probe whether reduced and oxidised angiotensinogen can be distinguished experimentally. The assay developed was sensitive and reproducible, and demonstrated that the reduced and oxidised forms can be distinguished experimentally. The antibody bound the two forms with differential affinity, due to differences in both the association and dissociation rates of the two forms with the monoclonal antibody. Finally, in an attempt to further elucidate the differences between the two redox states of angiotensinogen, molecular dynamic simulations were carried out on angiotensinogen in the presence or absence of the disulfide bond between Cys 18 and Cys 138. These simulations revealed some quite striking differences in the dynamics between the two forms. Reduced angiotensinogen was found to be more dynamic in regions critical for binding to renin, providing a possible explanation for the reported differential affinity that renin displays for the two forms.1 Thus, reduced and oxidised angiotensinogen show some quite distinct differences and can be distinguished in an SPR-based assay, highlighting their potential for use as a biomarker in a diagnostic bioassay.