The theory of the quadrupole interaction in nuclear magnetic resonance spectroscopy and relaxation measurements is presented in detail, with applications to ²H-NMR studies of order and dynamics in bilayers of deuterated lipids. Investigations of lipid-protein interactions in reconstituted membrane systems and intact biological membranes are reviewed. An experimental program is described which uses a synthetic amphiphilic polypeptide, with known geometry and variable length, to isolate questions about the geometrical interpretation of orientational order in lipid-protein interactions. A report is presented of an investigation of the effects of this polypeptide, Lys₂-Gly-Leu₂₀-Lys₂-Ala-amide, on the mixed bilayer system: Dimyristoylphosphatidylcholine Di-per-deuterio-myristoylphosphatidic Acid. The addition of the peptide was found to have little effect (≤5%) on the first and second moments of the distribution of quadrupole splittings in the liquid crystalline phase. Similarly, the spin-lattice relaxation time constants were affected by ≤10% in the liquid crystalline phase. The time constant for the decay of the quadrupole echo decreased dramatically above the phase transition with the addition of peptide, a phenomenon which is explained in terms of the presence of a new slow motion in the lipid-peptide systems. A simple model of the slow motion induced by the peptide is proposed, in which the lipid molecules undergo a rapid exchange between boundary and bulk sites. An effective correlation time is determined from an average over the rotations on each of these sites. Using this model, estimates are made of the change in the second moment brought about by the onset of the rotations, and. of the number of binding sites on the peptide. These estimates are found to be in agreement with independent measurements of the change in the second moment, and the number of binding sites is within the range predicted by simple considerations of charge balance. The change in the lineshape with the variation of the spacing of the pulses in the quadrupole echo experiment was investigated, and it was determined that the transverse relaxation time constants have a slight orientation dependence. It was also determined that the addition of the peptide has no significant effect on the variation of the lineshape. Some experiments which could answer some of the questions raised by these results are suggested. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The electric quadrupole splitting of the 11B nuclear magnetic resonance signal have been studied in a single crystal of datolite (H Ca B SiO5) placed in a magnetic field of 6350 Gauss and the methods developed by Volkoff and coworkers have been used to analyse the data. The space group of datolite, P 2 1/C, permits two different orientations of the otherwise identical quadrupole coupling tensors existing at the four boron sites in the unit cell. The observed five line 11B (I = 3/2) spectrum is consistent with the crystal symmetry. The quadrupole coupling constant, eqQ/h, and asymmetry parameter, η, at the unique boron site have been determined as well as the orientation of the principal axes of the electric field gradient tensor. The value of 172±1 Kc/sec found for eqQ/h in datolite is consistent with the overall range of values observed for BO4 tetrahedra in other crystals. / Thesis / Master of Science (MSc)

No description available.

M.S.

M.S.

No description available.

The focus of this dissertation is the introduction of surface-induced dissociation (SID) into a commercially available quadrupole time-of-flight mass spectrometer as an alternative ion fragmentation method. The performance of the SID device was characterized and its applications were demonstrated by dissociating peptides, proteins, inorganic salt clusters and non-covalent protein complexes. The SID setup allowed direct comparison of SID with conventional collision-induced dissociation (CID) on the same instrument, taking advantage of the characteristics of Q-TOF instrumentation, including extended mass range, high sensitivity and resolution. With the SID setup installed, no significant reduction of the ion transmission was evident. SID fragmentation patterns of peptides are, in general, similar to CID, with slight differences in the relative intensities of immonium ions, backbone cleavage b- versus y- type ions, and y- versus y-NH3 ions. This suggests enhanced accessibility to high energy/secondary fragmentation channels with SID. SID studies on cesium iodide clusters (CsI) also revealed that SID deposits more internal energy.The utility of mass spectrometric methods to probe the gas phase cyclization process was studied with [D-Ala2]-Leucine Enkephalin amide. This peptide showed prominent formation of the [M-NH3]+ ion which is believed to be the linear b5 ion with a C-terminal oxazolone structure. Other fragments in the spectra indicate that the linear b5 ion undergoes cyclization, subsequent ring opening and further dissociation to rearranged fragments that cannot be explained by the initial sequence. The similarities between the cyclic and b5-ion from the linear peptide indicated the formation of a heterogeneous ion population and this is further supported by gas-phase H/D exchange experiments. An ion funnel interface to improve ion transmission at high pressures was tested in a custom built quadrupole-surface-quadrupole instrument. The ion transmission efficiency for selected bio-molecules such as YGGFLR, insulin chain-B, ubiquitin and cytochrome c showed to approach almost 90%, with the funnel interface installed. The ion transmission efficiency was effected by several factors including: the size of the analyte, the DC gradient, the RF frequency, and the RF amplitude. The higher fragmentation efficiencies for SID in the presence of the funnel interface indicated higher internal energy deposition for the funnel interface.

The focus of this thesis is to derive analytical tools for the design of infrared nondestructive tests in single and multi layer material bodies. This requires the predetermination of the parameters of the experiment such that the infrared image has the required resolution for defect detection. Inverse heat conduction in single and multi-layer materials is investigated to determine the required frequency of excitation in order to obtain a desired temperature at the observation point. We use analytical quadrupole representation to derive a polynomial relation to estimate the frequency of the periodic excitation as a function of the temperature amplitude at a given observation point within the body. The formula includes characteristic geometric and material parameters of the system. The polynomial formula can be an e ective design tool for quick frequency predetermination in the design of non-destructive testing experiments with infrared thermography. The convergence and accuracy of the formula is assessed by comparison with the analytical thermal quadrupole solution and experimental results. We also investigate the e ect of the nite length of the material domain in order to establish the range of applicability of a simpli ed formula based on semi-in nite domain assumption. The e ect of nite length is investigated analytically by using (i) Fourier series which accounts for transients and (ii) Time varying solution associated to the steady state solution when a purely periodic excitation is applied. These results are also compared with numerical solution obtained with commercial nite element software ANSYSTM.

Neste trabalho implementamos a técnica da ressonância quadrupolar nuclear (RQN) em duas dimensões. O espectro bidimensional é obtido a partir do pseudo-FID usando o estimador autoregressivo. Como o gradiente de campo-elétrico (GCE) no sítio do núcleo é produzido pelas cargas externas ao núcleo e o tensor GCE é simétrico, bastam dois parâmetros para determinar este tensor num sistema de coordenadas dos eixos principais. Estes parâmetros podem ser obtidos a partir do espectro de RQN para todos os núcleos quadrupolares, menos os núcleos com spin 3/2. Usando o espectro bidimensional é possível determinar o parâmetro de assimetria, eta, e consequentemente o outro parâmetro do tensor GCE, mesmo para as amostras policristalinas contendo núcleos com spin 3/2. A oprientação do sistema de coordenadas do tensor GCE no sistema de coordenadas do laboratório não pode ser obtida usando apenas o espectro de RQN. Há vários métodos experimentais que permitem determinar esta orientação relativa. Em todos os casos esta determinação requer um grande esforço experimental com um equipamento muito mais caro que um simples espectrômetro de RQN. Neste trabalho apresentamos um novo método para a deterrminação da orientação do tensor GCE no sistema de coordenadas do laboratório, usando apenas a RQN em duas dimensões e o método da máxima entropia para a deconvolução dos dados experimentais / In this work we implemented the nuclear quadrupole resonance (NQR) in two dimensions. The bidimensional spectrum is obtained from pseudo FID through the auto-regressive estimator. Since the electric field gradient (EFG) at the nucleus site is produced by the external charges and the EFG tensor is symmetric, we need only two parameters to determine this tensor in the coordinate system of principal axis. These parameters can be obtained from the NQR spectra for all the nucleus possessing quadrupole moment, except the one with spin 3/2. Using the bidimensional spectra, it is possible to determine the asymmetry parameter, 7], and consequently the other parameters of the EFG tensor, even in polycrystalline samples containing nucleus with spin 3/2.

Neste trabalho implementamos a técnica da ressonância quadrupolar nuclear (RQN) em duas dimensões. O espectro bidimensional é obtido a partir do pseudo-FID usando o estimador autoregressivo. Como o gradiente de campo-elétrico (GCE) no sítio do núcleo é produzido pelas cargas externas ao núcleo e o tensor GCE é simétrico, bastam dois parâmetros para determinar este tensor num sistema de coordenadas dos eixos principais. Estes parâmetros podem ser obtidos a partir do espectro de RQN para todos os núcleos quadrupolares, menos os núcleos com spin 3/2. Usando o espectro bidimensional é possível determinar o parâmetro de assimetria, eta, e consequentemente o outro parâmetro do tensor GCE, mesmo para as amostras policristalinas contendo núcleos com spin 3/2. A oprientação do sistema de coordenadas do tensor GCE no sistema de coordenadas do laboratório não pode ser obtida usando apenas o espectro de RQN. Há vários métodos experimentais que permitem determinar esta orientação relativa. Em todos os casos esta determinação requer um grande esforço experimental com um equipamento muito mais caro que um simples espectrômetro de RQN. Neste trabalho apresentamos um novo método para a deterrminação da orientação do tensor GCE no sistema de coordenadas do laboratório, usando apenas a RQN em duas dimensões e o método da máxima entropia para a deconvolução dos dados experimentais / In this work we implemented the nuclear quadrupole resonance (NQR) in two dimensions. The bidimensional spectrum is obtained from pseudo FID through the auto-regressive estimator. Since the electric field gradient (EFG) at the nucleus site is produced by the external charges and the EFG tensor is symmetric, we need only two parameters to determine this tensor in the coordinate system of principal axis. These parameters can be obtained from the NQR spectra for all the nucleus possessing quadrupole moment, except the one with spin 3/2. Using the bidimensional spectra, it is possible to determine the asymmetry parameter, 7], and consequently the other parameters of the EFG tensor, even in polycrystalline samples containing nucleus with spin 3/2.