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Reactions of Chloroketenes with Ketene Acetals (open access)

Reactions of Chloroketenes with Ketene Acetals

The first objective of this investigation was to conduct a systematic study into the reactions of chloroketenes with ketene acetals. The second objective was to explore the synthetic utility of these reaction products and offer a rational explanation for these reaction products.
Date: May 1981
Creator: Watts, Ronald David, 1943-
System: The UNT Digital Library
Spectroscopic and Physical Effects of Highly Polar Groups (open access)

Spectroscopic and Physical Effects of Highly Polar Groups

Since the development of the understanding that the electron distribution within a molecule is chiefly responsible for its properties and behavior, factors influencing this charge distribution have been of interest to scientists. The chemical reactivity of a molecule, the physical properties, and to a large extent, structure and geometry, are all functions of the electron distribution. This study examines the issue of electronic structure from two points of view, each of them focussing on a specific component within the molecules studied. In the present work, the effects of the highly polar carbonyl group on spectroscopic parameters and physical behavior are investigated. An additional area of study is the effect of fluorine substitution on the energy levels of some halogenated ethylenes. The specific parameters examined are the ionization potentials, the absorption frequencies, and the energies of a class of excited states known as molecular Rydberg states. It was during the study of these halogenated ethylenes that the observations leading to the carbonyl compound investigations were made, so that the two areas examined are connected both experimentally and chemically.
Date: December 1981
Creator: Schander, Judith Turner
System: The UNT Digital Library
The Regulation of HMG-CoA Reductase by Enzyme-Lipid Interactions (open access)

The Regulation of HMG-CoA Reductase by Enzyme-Lipid Interactions

The temperature-dependent catalytic activity of rat liver 3-hydroxy-3 -methylglutaryl coenzyme A reductase (HMG-CoA reductase) displays the nonlinear Arrhenius behavior characteristic of many membrane-bound enzymes. A two-conformer equilibrium model has been developed to characterize this behavior. In the model, HMG-CoA reductase undergoes a conformational change from a low specific activity to a high specific activity form. This conformation change is apparently driven by a temperature-dependent phase transition of the membrane lipids. It has been found that this model accurately describes the data from diets including rat chow, low-fat, high-carbohydrate, and diets supplemented with fat, cholesterol or cholestyramine. The effects characterized by the model are consistent with the regulation of HMG-CoA reductase by enzyme-lipid interactions.
Date: May 1981
Creator: Smith, Vana L.
System: The UNT Digital Library
The Analysis of Fire Debris Using Nuclear Magnetic Resonance Spectroscopy (open access)

The Analysis of Fire Debris Using Nuclear Magnetic Resonance Spectroscopy

This paper describes a new technique for analyzing fire debris using nuclear magnetic resonance (NMR) spectroscopy. Petroleum distillates, which are commonly used accelerants, were weathered, burned, and steamdistilled. These, as well as virgin samples of the accelerants, were analyzed by gas chromatography and nuclear magnetic resonance spectroscopy. In addition, solvent studies and detectibility limit studies were conducted. The use of NMR is described as a valuable adjunct to the existing methods of analysis.
Date: August 1981
Creator: Bryce, Kenneth L.
System: The UNT Digital Library
The Effect of Ozonation in Reducing Trihalomethane Formation Potential (open access)

The Effect of Ozonation in Reducing Trihalomethane Formation Potential

Trihalomethanes such as chloroform, dichlorobromomethane, dibromochloromethane, and bromoform are formed when natural water is chlorinated in water treatment. This investigation explores the use of ozone to remove organic precursors from natural water, thus decreasing trihalomethane formation potential. The data suggest a mechanism involving formation of secondary precursors after prolonged contact with ozone, suggesting that trihalomethane precursors may be minimized by using low doses of ozone and short contact time.
Date: May 1981
Creator: Lin, Simon H.
System: The UNT Digital Library
Studies on Lipoprotein Specificity of Human Plasma Lecithin Cholesterol Acyltransferase (open access)

Studies on Lipoprotein Specificity of Human Plasma Lecithin Cholesterol Acyltransferase

Huian plasma high-density lipoprotein (HDL) were isolated by a procedure employing polyanion precipitation and column chromatography. Lipid and protein composition of the HDL isolated by this method was found to be similar to another HDL preparation isolated by ultracentrifugation. However, minor differences were noted, including a higher phospholipid and apoproteinE content and lower triglyceride content of the HDL isolated by column chromatography. Four subfraction of HDL were obtained following chromatography on an anion exchange column. The subfraction four had the highest esterified to free cholesterol ratio, the second highest phospholipid to unesterified cholesterol, and the lowest molecular weight. In addition it was consistently coincided with lecithin: cholesterol acyltransferase (LCAT) activity and found to be the best substrate for the enzyme.
Date: May 1981
Creator: Jahani, Mehrnoosh
System: The UNT Digital Library
Picosecond Spectroscopy of Rhodamine B (open access)

Picosecond Spectroscopy of Rhodamine B

A series of picosecond excite-probe experiments was performed on various concentrations of aqueous and ethanolic solutions of rhodamine B in order to determine the existence of dimerization in those solutions. The goals of the research presented in this dissertation were twofold. Initially, various techniques of time-resolved spectroscopy were to be employed to further characterize the ground and excited-state molecular properties of the aqueous RB dimer. The information obtained, and the techniques developed in that study would then be utilized in an effort to secure evidence which would support or refute the claims of rhodamine B dimerization in an ethanolic solution.
Date: December 1981
Creator: Clark, James Burton
System: The UNT Digital Library
Poly(ADP-ribose) Synthesis as a Function of Growth and DNA Fragmentation (open access)

Poly(ADP-ribose) Synthesis as a Function of Growth and DNA Fragmentation

This work examines the synthesis of poly(ADP-ribose) in normal and SV40-transformed monolayer cultures of 3T3 cells as a function of growth and DNA fragmentation. A review of the relevant literature is given in the introduction of this work. Poly(ADP-ribose) synthesis has been implicated in transcription, replication, repair, differentiation and regulation of cell growth. The results of this study suggest that poly(ADP-ribose) synthesis is involved in some aspect of cell-growth control and DNA repair.
Date: December 1981
Creator: Levi, Viktorya
System: The UNT Digital Library
Synthesis of Aziridine Analogues of Pyrethroids (open access)

Synthesis of Aziridine Analogues of Pyrethroids

Rules which correlate structure and insecticidal activity of pyrethroids have evolved over the last thirty years from the results obtained in the testing of various synthetic pyrethroids. The major portion of these rules have dealt either with the development of new alcohol moieties or variations in the unsaturated side chain of the cyclopropane ring. There has been very little work done concerning modifications of the cyclopropane ring. This study was initiated to discover the affect of substituting an aziridin ring for the cyclopropane ring found in pyrethroids.
Date: May 1981
Creator: Sheppard, Rex Gerald
System: The UNT Digital Library
Isolation, Physical and Chemical Characterization of Lecithin:Cholesterol Acyltransferase from Human Plasma (open access)

Isolation, Physical and Chemical Characterization of Lecithin:Cholesterol Acyltransferase from Human Plasma

The physiological role of LCAT has been the subject of a number of recent articles (Glomset, 1979; Nilsson-Ehle et al., 1980). According to most current theories, the enzyme functions in combination with high-density lipoproteins in the reverse cholesterol transport pathway which presumably returns peripheral cholesterol to the liver where cholesterol catabolism takes place. Despite the exciting potential for studies on the catalytic function and the nature of the enzyme-substrate complex, the mechanism of action of LCAT remains largely unexplored. The relatively slow progress in the elucidation of the LCAT reaction mechanism is likely to be due to the difficulties in the isolation of the enzyme in sufficient quantities. Consequently, considerably less is known about the physical and chemical properties of the enzyme. Therefore, the first objective of this investigation was to isolate and purify sufficient amount of enzyme for subsequent characterization studies. The second objective of this investigation was to characterize the physical properties of the enzyme by techniques including analytical ultracentrifugation, ultraviolet spectroscopy, and circular dichroism and fluorescence spectroscopy. The third objective of this investigation was to characterize the chemical properties of the enzyme which deals with the amino acid and carbohydrate composition and with some basic structural features …
Date: December 1981
Creator: Chong, Kui Song
System: The UNT Digital Library