Organophosphonates are characterized by a very stable carbon-phosphorus bond. Eshcherichia coli and many other strains of bacteria possess a multi-enzyme system called carbon-phosphorus (C-P) lyase that enables these organisms to cleave the C-P bond of organophosphonates when inorganic phosphate is scarce in the local environment. Genetic studies have demonstrated that C-P lyase is encoded by the fourteen-gene phn operon, phnCDEFGHIJKLMNOP. However, the mechanism for C-P bond cleavage is still unclear. We have expressed, purified, and characterized phnP from this operon. PhnP is a phosphodiesterase which will hydrolyze both bis-(p-nitrophenyl) phosphate and 2’:3’-cyclic nucleotides as substrates. In collaboration with Dr. Zongchao Jia and Katarenya Podzelinska (Queen’s Biochemistry), we have crystallized phnP and solved the crystal structure at a resolution of 1.3 Å. The structure displayed similarity to zinc-dependent metallo-β-lactamase family proteins. However, phnP displays unique structural features with two metal binding sites per monomer: the active site containing potentially two manganese ions, and a ‘structural’ site coordinating one zinc ion. Potential active site residues were identified and corresponding point mutations were generated by site-directed mutagenesis. Studies based on the importance of these residues and the knowledge from our high resolution structure will help elucidate the mechanism of phnP as well as its function in the C-P lyase pathway. Furthermore, we performed a broad range of ligand screening for phnH, another key member from the C-P lyase pathway, by ITC experiments, co-crystallization and high throughput ligand screening. However, all the trials for the identification of the true physiological substrate for phnH proved unsuccessful. Although the mechanism of C-P bond cleavage by C-P lyase still remains unclear, we synthesized a fluorescently labelled organophosphonate (FPn) and utilized it for probing the in vivo degradation of the C-P bond by wild type E. coli and various mutants. Analysis by TLC and mass spectrometry demonstrated the production of the expected alkane product. With this promising fluorescent probe, potential intermediates and substrates can be identified for individual C-P lyase enzymes. Taken together, our studies on the C-P lyase pathway will contribute to elucidate the still unknown mechanism of the cleavage of the stable C-P bond. / Thesis (Master, Chemistry) -- Queen's University, 2008-08-29 12:11:55.179

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: finite energy functional spaces; unbounded domains with a cut Includes bibliographical references (leaf 29).

The pancreas is a very inaccessible organ situated in the retroperitoneal space. Study of its physiology and function was first confined to animals, where it was possible to construct a pancreatic fistula and thus collect pure pancreatic juice. In addition, pancreatic tissue from animals was also obtainable relatively easily. Early attempts to study the pancreas in man was restricted to patients with pancreatic fistulae, usually the result of surgical procedures. These investigations were on the whole unsatisfactory as the conditions of the experiment were not truly physiological and the juice soon became contaminated and infected. Another method employed later used the intraduodenal tube to collect duodenal contents. The aspirate consisted of a mixture of gastric acid and contents, duodenal juice, bile and succus entericus. Various meals were used to stimulate the pancreatic secretion. Other authors have emphasized the importance of preventing contamination of duodenal contents with gastric juice, and by inserting a second tube or double lumen tube to aspirate the acid from the stomach this was attained. Meal stimulation was now no longer possible so that various drugs and later the two hormones, secretin and pancreozymin, were used to stimulate pancreatic secretion. These two hormones very soon completely replaced any other method of pancreatic simulation. The intravenous injection or infusion of secretin and/or pancreozymin is, however, not a physiological procedure. The initial enthusiasm aroused by this method was tempered due to the varied results obtained by different workers. More recently, Lund has used the test meal to stimulate pancreatic secretion. This technique has been replicated by numerous authors, with promising results reported by all. These reports are characterized by the varied nature of the test meal used, the different position of the intraduodenal tube, the type of suction employed, the period of collection, the length of the test and the type of enzymes estimated. The purpose of the present study is to investigate the physiological responses to the test meal, to define its value in the investigation of pancreatic function and to try and standardise the procedure to obtain optimal pancreatic stimulation.

We present a detailed analysis of the white dwarf luminosity functions derived from the local 40 pc sample and the deep proper motion catalog of Munn et al. Many previous studies have ignored the contribution of thick disk white dwarfs to the Galactic disk luminosity function, which results in an erroneous age measurement. We demonstrate that the ratio of thick/thin disk white dwarfs is roughly 20% in the local sample. Simultaneously fitting for both disk components, we derive ages of 6.8-7.0 Gyr for the thin disk and 8.7 +/- 0.1 Gyr for the thick disk from the local 40 pc sample. Similarly, we derive ages of 7.4-8.2 Gyr for the thin disk and 9.5-9.9 Gyr for the thick disk from the deep proper motion catalog, which shows no evidence of a deviation from a constant star formation rate in the past 2.5 Gyr. We constrain the time difference between the onset of star formation in the thin disk and the thick disk to be 1.6(-0.4)(+0.3) Gyr. The faint end of the luminosity function for the halo white dwarfs is less constrained, resulting in an age estimate of 12.5(-3.4)(+1.4) Gyr for the Galactic inner halo. This is the first time that ages for all three major components of the Galaxy have been obtained from a sample of field white dwarfs that is large enough to contain significant numbers of disk and halo objects. The resultant ages agree reasonably well with the age estimates for the oldest open and globular clusters.

The usual practice in any discussion of an inner-product space is to restrict the field over which the inner-product space is defined to the field of complex numbers. In defining the inner-product function, (x,y), a second function is needed; namely the conjugate function (x,y)* so that (x,y) ± (y,x)*. We will attempt to generalize this concept by investigating the existence of a conjugate function defined on fields other than the field of complex numbers and relate this function to an inner-product function defined on a linear space L over these fields.

In this paper we analyze the behavior of the Gamma function at its critical points and points of discontinuity on the negative side of the x-axis. We will also explain the bluntness of the gamma function on this negative side.

A catalog of 8472 white dwarf (WD) candidates is presented, selected using reduced proper motions from the deep proper motion catalog of Munn et al. Candidates are selected in the magnitude range 16 < r < 21.5 over 980 square degrees, and 16 < r < 21.3 over an additional 1276 square degrees, within the Sloan Digital Sky Survey (SDSS) imaging footprint. Distances, bolometric luminosities, and atmospheric compositions are derived by fitting SDSS ugriz photometry to pure hydrogen and helium model atmospheres (assuming surface gravities log g = 8). The disk white dwarf luminosity function (WDLF) is constructed using a sample of 2839 stars with 5.5 < M-bol < 17, with statistically significant numbers of stars cooler than the turnover in the luminosity function. The WDLF for the halo is also constructed, using a sample of 135 halo WDs with 5 < M-bol < 16. We find space densities of disk and halo WDs in the solar neighborhood of 5.5 +/- 0.1 x 10(-3) pc(-3) and 3.5 +/- 0.7 x 10(-5) pc(-3), respectively. We resolve the bump in the disk WDLF due to the onset of fully convective envelopes in WDs, and see indications of it in the halo WDLF as well.

Let X. Y be compact Hausdorff spaces, and E, F be Banach spaces. A linear map T¡GC (X¡AE)¡÷C (Y¡AF) is separating if ¡üTf(y)¡ü¡üTg(y)¡ü¡×0 whenever ¡üf(x)¡ü¡üg(x)¡ü¡×0, for every x belonging to X, y belonging to Y. Gau, Jeang and Wong prove that a biseparating linear bijection T is a weighted composition oprator Tf¡×hf¡³£p where h is a function from Y into the set of inveritable linear operators from E onto F and £p is a homeomorphism from Y onto X. In this thesis, we extend this result to the case that continuous functions are defined to a locally compact Hausdorff space, which is either £m-compact or first countable. Moreover, we give a short proof of a recent result of Mrcun. Finally, we give an alternative approach to an Araujo's result concerning biseparating maps of smooth functions appeared in Adv. Math.

On the Canadian Prairies, canola is a main source for biodiesel production and wheat is the primary feedstock for bioethanol production. To raise biofuel production requires a movement of resources and land away from food and grain crops, which would cause food to become scarcer and increase its price. This paper determines the impact of more biofuels production on the food industry. It considers the simultaneous estimation of share equations from both revenue function and distance function. Econometric results exploit the non-stationary nature of the data and the correlations among shares between primal and dual models are exploited by cointegration techniques. Johansen’s maximum likelihood estimator is applied to 1971-2007 data from Manitoba, Alberta and Saskatchewan. Morishima elasticity estimates indicate high long run substitutions among crops (wheat, feed grains and canola). A rise in the production of biofuel crops could cause food prices to increase, both for meat and bread.

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