This research is directed towards developing a more sensitive and rapid electrochemical sensor for enzyme labeled immunoassays by coupling redox cycling at interdigitated electrode arrays (IDA) with the enzyme label b-galactosidase. Coplanar and comb IDA electrodes with a 2.4 mm gap were fabricated and their redox cycling currents were measured. ANSYS was used to model steady state currents for electrodes with different geometries. Comb IDA electrodes enhanced the signal about 3 times more than the coplanar IDAs, which agreed with the results of the simulation. Magnetic microbead-based enzyme assay, as a typical example of biochemical detection, was done using the comb and coplanar IDAs. The enzymes could be placed close to the sensing electrodes (~10 mm for the comb IDAs) and detection took less than 1 min with a limit of detection of 70 amole of b-galactosidase. We conclude that faster and more sensitive assays can be achieved with the comb IDA. A paramagnetic bead assay has also been demonstrated for detection of bacteriophage MS2, used as a simulant for biothreat viruses, such as small pox. The immunoassay was carried out in a microfluidic format with the IDA, reference and counter electrodes integrated on the same chip. Detection of 90 ng/mL MS2 or 1.5x1010 MS2 particles/mL was demonstrated.

Mixed-valence compounds are of interest as model systems for the study of electron transfer reactions. The intramolecular electron transfer processes and patterns of charge delocalization in such compounds depend on the interplay between the electronic (V) and the vibronic (L) coupling. One can obtain both parameters from a Hush analysis of the intervalence band that arises upon optical intramolecular electron transfer if the band is intense and well-separated from other bands. This is quite often the case for mixed-valence triarylamines. As such, both Hush analysis and simulation of the intervalence band are widely used to classify these compounds as charge localized (class-II) or delocalized (class-III). Yet one must estimate the diabatic electron transfer distance (R) to calculate V in the Hush formalism. For mixed-valence triarylamines, R is commonly taken as the N-N distance; we show this to be a poor approximation in many cases. The activation barrier to thermal intramolecular electron transfer in a class-II mixed-valence compound is also related to the parameters V and L. Thus, if one can capture the rate of thermal electron transfer at multiple temperatures, then two experimental methods exist by which to extract the microscopic parameters. One technique that is widely used for organic mixed-valence compounds is variable-temperature electron spin resonance (ESR) spectroscopy. But this method is only rarely used to determine thermal electron transfer rates in mixed-valence triarylamines, as the electron transfer in most of the class-II compounds with distinct intervalence bands is too fast to observe on the ESR timescale. We show, for the first time, that one can use ESR spectroscopy to measure thermal electron transfer rates in such compounds. Simulation of ESR spectra based on density functional theory calculation and comparison with optical data also uncover the nature (i.e., adiabatic or nonadiabatic) of the electron transfer process.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 148 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 124 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 81-87).

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains x, 210 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 154-185).

D. Tech. Chemistry. / Demonstrates the possibility of preparing large surface coatings of monodispersed spherical particles of chromium(III) oxide by using the ACG method for solar heating and magneto-optic technologies. t is aimed in the current study to investigate the photo-induced ESR phenomena in a-Cr2O3 mono-dispersed spherical particles using elimination of 160mW Nd:YAG laser of ˜1064 nm and a pulse repetition frequency of 30Hz, in the temperature range of 150 up to 315 K.

The thesis aims at developing techniques in solid state nuclear magnetic resonance (ssNMR) of paramagnetic metal-organic and inorganic systems in combination with electron paramagnetic resonance (EPR) spectroscopy and quantum chemical methods such as density functional theory (DFT).Solid state NMR signals of paramagnetic systems suffer from severe loss of sensitivity and resolution due to large hyperfine interactions. Among all the interactions seen in ssNMR, the interaction between the unpaired electron(s) and the observed nucleus leading to hyperfine interaction in paramagnetic solids is large in magnitude. Large broadening due to fast relaxation in paramagnetic systems on the one hand limits the excitation of the nuclei using conventional probes thereby causing severe loss in sensitivity and resolution of ssNMR signals. On the other hand the large shifts due to Fermi-contact interaction mask the diamagnetic chemical shifts (which are rich source of chemical group information) and make signal assignment difficult. The conventional techniques developed for solid state NMR of diamagnetic systems are inefficient for paramagnetic systems. These factors have led ssNMR of paramagnetic systems to be an unexplored topic for decades.Recently Ishii and co-workers have circumvented some of these problems using very-fast magic angle spinning (VFMAS).1 Spinning the sample at MAS frequencies >30 kHz drastically enhances the sensitivity and resolution of ssNMR signals in paramagnetic complexes. We have used the VFMAS approach and have shown how to cope with moderate hyperfine interactions in ssNMR of organic (cyclam and acetylacetonate) and inorganic (alkaline-copper pyrophosphates) systems with transition metal ions such as CuII, NiII and VIV as paramagnetic center. On the one hand Fermi-contact interaction which is responsible for large shifts up to 100 ppm in 1H and 1000 ppm in 13C and 31P cause severe problems for signal assignment. But on the other hand it also leads to better spectral dispersion and hence improve the resolution of the ssNMR signals. We were able to exploit this idea and a well resolved 13C and even 1H solid state NMR spectrum in paramagnetic metal-organic systems was obtained using a simple Hahn-echo experiment. This is usually not possible, since 1H NMR in diamagnetic solids suffer from large broadening of 100 kHz due to 1H-1H homonuclear dipolar coupling. Furthermore fast relaxation in paramagnetic systems allows one to reduce the interscan delay and thereby repeat the experiments several times in a given time and improve the signal to noise ratio. This compensates for loss in sensitivity more often due to fast relaxation in paramagnetic systems.Fermi-contact shifts are characteristics of unpaired electron spin density in a molecule. Using quantum chemical methods such as DFT one can calculate the theoretical Fermi-contact shifts.2 We have compared the experimental 13C ssNMR shifts with shifts from DFT calculation in paramagnetic metal -cyclam and -acetylacetonate complexes and have assigned the 13C signals. For assignment of 1H, a 2D version of dipolar INEPT (insensitive nuclei enhancement by polarization transfer) was used. In some cases such as the Cu-cyclam complex, a very well resolved 1H ssNMR spectrum motivated us to try 1H-1H homonuclear correlation experiment. We obtained several important cross peaks with a relatively simple pulse sequence. We used the dipolar connectivity information from it to complete the 1H assignment.One of the important aims of the thesis was to find a way to measure the metal-carbon distances using solid state NMR relaxation rates. In paramagnetic metal-organic complexes the carbon-13 relaxation caused by the dipolar interaction with the unpaired electron depends on the distance of the carbon atoms to the central metal ion, therefore its rates in principle contain structural information...

The topology and dynamics of biomolecules are intricately linked with their biological function. The focus of this thesis is the NMR-based measurement of topology and dynamics in biomolecular systems, and methods of measuring immersion depth and orientation of membrane-associated molecules. In detergent micelles and lipid bilayers, the local concentrations of hydrophobic and hydrophilic molecules are a function of their bilayer immersion depth. For paramagnetic molecular oxygen or metal cations, the magnitudes of the associated paramagnetic isotropic contact shifts and relaxation rate enhancements (PREs) are therefore depth-dependent. NMR measurements of these effects reveal the immersion depth of bilayer- or detergent-associated molecules. This work first explores transbilayer oxygen solubility and thermodynamics, as measured from contact shifts and PREs of the constituent lipid molecules in the presence of 30 bar oxygen. Contact shifts revealed the transmembrane O2 solubility profile spans a factor of seven across the bilayer, while PREs indicated that oxygen partitioning into bilayers and dodecylphosphocholine (DPC) micelles is entropically driven. Next, this work describes how paramagnetic effects from molecular oxygen and Ni(II) cations may be employed to study the immersion depth and topology of drug and protein molecules in DPC micelles. In one study, the positioning of the amphipathic drug imipramine in micelles was determined from O2- and Ni(II)-induced contact shifts. A second study, relying solely on O2-induced PREs, determined the tilt angles and micelle immersion depths of the two alpha helices in a monomeric mutant of the membrane protein phospholamban. A third study utilized 19F NMR to explore the importance of juxtamembraneous tryptophans on the topology of the membrane protein synaptobrevin, via O2-induced contact shifts and solvent-induced isotope shifts of a juxtamembraneous 19F-phenylalanine. Comparison of synaptobrevin constructs with zero, one, and two juxtamembraneous tryptophans revealed that while one tryptophan is sufficient to ‘anchor’ the protein in micelle, the addition of a second tryptophan dampens local dynamics. These solution state NMR studies demonstrate how paramagnetic effects from dissolved oxygen, complemented with measurements of local water exposure, provide detailed, accurate descriptions of membrane immersion depth and topology. These techniques are readily extended to the study of a wide range of biomolecules.

Strukturaufklärung gehört zu den wichtigsten Gebieten der Grundlagenforschung, da sie direkte Einblicke in biologische Systeme und ihre Mechanismen liefert. Der NMR Spektroskopie kommt dabei eine besondere Bedeutung zu, denn sie ermöglicht Forschung unter physiologischen Bedingungen. Dementsprechend ist die Entwicklung neuer Techniken zur Verbesserung dieser Methode weiterhin ein zentrales Forschungsgebiet. Paramagnetische Markierung von Biomolekülen ermöglicht die Bestimmung von NMR Parametern, wie z.B. residuale dipolare Restkopplungen (RDCs) oder Pseudokontaktverschiebungen (PCSs), die für die Strukturaufklärung wertvolle Winkel- und Abstandsinformationen über das Zielmolekül beinhalten. In diesem Zusammenhang wurden Lanthanoidionen-koordinierende Tags entwickelt und erfolgreich an Proteinen angebracht. Durch die paramagnetischen Eigenschaften der Lanthanoidionen wird eine partielle Ausrichtung des Zielmoleküls im Magnetfeld des NMR Spektrometers induziert und somit das Messen residualer dipolarer Kopplungen ermöglicht. Zusätzlich werden die NMR Signale durch eine Dipol-Dipol-Wechselwirkung zwischen dem Lanthanoidion und den Kernen verschoben (PCS). In der konventionellen NMR Spektroskopie werden diese Effekte, aufgrund der Brownschen Molekularbewegung und dem Fehlen eines Metallions, nicht beobachtet. In der Fachliteratur ist ein Transfer dieser Methode auf Oligonukleotide nicht bekannt, obwohl DNA und RNA zu den wichtigsten Biomolekülen überhaupt zählen. In dieser Arbeit wurde mit Hilfe des kürzlich entwickelten Cys-Ph-TAHA Tags ein Protokoll zur Bestimmung von paramagnetischen Effekten in der DNA entwickelt. Dafür wurde eine modifizierte Nukleobase synthetisiert, die eine passende Bindungsstelle für den Tag aufweist. Mit der neu entwickelten Methode wurden zwei paramagnetische und eine diamagnetische Referenzprobe hergestellt. Mittels hochauflösender NMR Spektroskopie konnten paramagnetisch-induzierte PCSs und RDCs gemessen werden. Die Auswertung zeigte eine hohe Qualität der gemessenen PCSs in beiden paramagnetischen Proben. Die RDCs wiesen einen signifikanten Fehler auf. Die in der NMR Spektroskopie übliche Isotopenmarkierung (13C/15N) ist bei im DNA-Synthesizer hergestellten Oligonukleotiden auf Grund der teuren Ausgangsmaterialien nicht möglich, sodass die hergestellten NMR Proben eine natürliche Isotopenhäufigkeit aufwiesen. In den NMR Spektren zur Bestimmung der RDCs ist damit das Verhältnis von Signal-zu-Rausch relativ niedrig, was zusammen mit der paramagnetischen Relaxationsverstärkung zu einem größeren Messfehler führt. Dennoch konnten die erhaltenen paramagnetischen Daten mit einem Ensemblemodell beschrieben werden. In der vorliegenden Arbeit wurde die Methode der paramagnetischen Markierung erfolgreich auf die Stoffklasse der Oligonukleotide übertragen. Dabei wurde ein reproduzierbares Protokoll entwickelt, mit dem eine Bindungsstelle in einen DNA Strang eingebaut und das Zielmolekül anschließend mit dem Cys-Ph-TAHA Tag markiert wurde. Die erfolgreiche Anwendung der Methode konnte durch die erhaltenen paramagnetischen Messwerte von hoher Qualität verifiziert werden.

Variable temperature ESR studies of radicals generated photolytically from simple aliphatic alcohols and ethers in cyclopropane solution reveal complex linewidth effects. Isotropic modulation of the proton hyperfine splittings (hfs) through restricted rotation about C-0 and C-C single bonds is observable in the region 230>T>150K. Such effects can be distinguished from anisotropic viscosity-dependent line broadening. In spectra from alcohol radicals resolved 2nd order structure causes no ambiguity in the interpretation. Restricted rotation about Ca-0H modulates aaH and aBH out-of-phase with a0H in the series RCHOH [R= CH3, C2H5, C2H5CH2, (CH3)2CHCH2, (CH3)3CCH2]. A general model for the process is discussed. In cases three and four restricted Co-C rotation allows the diastereotopic inequivalence of the 6-protons to be manifested as a broadening of MB = 0 components. Preferred conformations consistent with all the foregoing modulation effects and with observed HB and HY splittings are presented. The analysis is supported by results for radicals RCHOR' from related ethers and by spectral simulation. The spectrum of the 1-hydroxycyclohexyl radical demonstrates previously unobserved fine structure and a low-temperature linewidth effect tentatively attributed to radical site inversion. A second series of alcohol-derived radicals R1R2R3CCHOH with an increasingly bulky Ca substituent has been studied. The Ha hfs provide evidence of a steric flattening not hitherto observed. This effect correlates well with literature values of steric parameters for the R1R2R3C substituent. In the case R1,R2 = CH3, R3 = C2H5 an observed specific y-H interaction is assigned to a locked conformation of the crowded system. A series of highly alkylated cyclic ethers has been examined. The dramatic temperature-dependent changes in the spectrum of the 5,5-dimethyl-l,3-dioxan-2-yl radical are attributed to restricted ring flipping. A fast exchange limit spectrum has been obtained for the first time in such systems, allowing evaluation of thermodynamic parameters. the 2,4,8,10-tetraoxyspiro[5,5]undecan-3-yl radical exhibits similar behaviour. The 2,2,5,5-tetramethyl and 5,5-diethyl-2,2-dimethyl-l,3--dioxan-4-yl radicals have fixed conformations which give rise to enhanced values of ayH in agreement with theoretical calculations. In the latter case a splitting of 4.27 G is assigned to a single y-methylene proton in behaviour analogous to R1R2R3CCHOH.