xv, 153 p. : ill. (some col.) / Lead sulfide nanocrystals (PbS-NCs) are an important class of semiconductor nanomaterials that are active in the near-infrared and exhibit unique properties distinct from their bulk analogues, notably, size tunability of the band gap and solution processability. One factor influencing PbS-NC properties is the presence of an organic ligand shell, which forms the interface between the nanocrystal core and its environment. The specific focus of this dissertation is how ionic functionalization of the ligand shell alters the physical and chemical properties of the resulting PbS-NC/ligand complex. Short-chain ligands can improve photoconductivity in PbS-NC thin films, but there are few solution-based preparations available. Chapter II demonstrates how ionic groups can enable functionalization of PbS-NCs with two short- chain thiol ligands - sodium 3-mercaptopropanesulfonate (MT) and sodium 2,3-dimercaptopropanesulfonate (DT) - via a solution-phase exchange procedure. Despite a structural similarity, DT-functionalized PbS-NCs (PbS-DT) are more stable to oxidation than MT-functionalized PbS-NCs (PbS-MT). The relative stabilities are explained in terms of different binding modes to the nanocrystal surface (bidentate vs. monodentate) and oxidation pathways (intermolecular vs. intramolecular). Toxicology studies on nanomaterials have been limited by the availability of water-soluble samples with systematically controlled structures. As examples of such materials, PbS-DT and PbS-MT nanocrystals are studied in Chapter III for their toxicological impacts on embryonic zebrafish. PbS-DT solutions induce less toxicity than PbS-MT solutions, which is explained in terms of the relative stabilities of the nanocrystal solutions. Finally, Chapter IV investigates the hitherto unexplored effects of ionic functionalization on the optical/electrical properties of PbS-NC thin films, with an emphasis on understanding how counter ions affect the photoconductivity of PbS-DT thin films. Films containing small counter ions exhibit increased dark conductivity and responsivity with time under an applied bias, whereas films containing larger or multivalent counter ions show a suppression of this behavior. These results are discussed in terms of ion motion and ion-assisted carrier injection at the PbS-NC/electrode interface. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: David R. Tyler, Chair; Mark C. Lonergan, Advisor; Catherine J. Page, Inside Member; Andrew Marcus, Inside Member; Hailin Wang, Outside Member

abstract: InAsBi is a narrow direct gap III-V semiconductor that has recently attracted considerable attention because its bandgap is tunable over a wide range of mid- and long-wave infrared wavelengths for optoelectronic applications. Furthermore, InAsBi can be integrated with other III-V materials and is potentially an alternative to commercial II-VI photodetector materials such as HgCdTe. Several 1 μm thick, nearly lattice-matched InAsBi layers grown on GaSb are examined using Rutherford backscattering spectrometry and X-ray diffraction. Random Rutherford backscattering measurements indicate that the average Bi mole fraction ranges from 0.0503 to 0.0645 for the sample set, and ion channeling measurements indicate that the Bi atoms are substitutional. The X-ray diffraction measurements show a diffraction sideband near the main (004) diffraction peak, indicating that the Bi mole fraction is not laterally uniform in the layer. The average out of plane tetragonal distortion is determined by modeling the main and sideband diffraction peaks, from which the average unstrained lattice constant of each sample is determined. By comparing the Bi mole fraction measured by random Rutherford backscattering with the InAsBi lattice constant for the sample set, the lattice constant of zinc blende InBi is determined to be 6.6107 Å. Several InAsBi quantum wells tensilely strained to the GaSb lattice constant with dilute quantities of Bi are characterized using photoluminescence spectroscopy. Investigation of the integrated intensity as a function of carrier excitation density spanning 5×1025 to 5×1026 cm-3 s-1 indicates radiative dominated recombination and high quantum efficiency over the 12 to 250 K temperature range. The bandgap of InAsBi is ascertained from the photoluminescence spectra and parameterized as a function of temperature using the Einstein single oscillator model. The dilute Bi mole fraction of the InAsBi quantum wells is determined by comparing the measured bandgap energy to that predicted by the valence band anticrossing model. The Bi mole fraction determined by photoluminescence agrees reasonably well with that estimated using secondary ion mass spectrometry. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2016

The purpose of this study was to evaluate the effects of sodium hypochlorite on the organic and inorganic composition of enamel. Background: With the advent of enamel bonding for orthodontic appliances in the late 1970s, it has been shown that traditional phosphoric acid etching affects the inorganic portion of the enamel.1, 2 In an attempt to enhance the acid etching pattern and, furthermore, the bond strength, additional pretreatment techniques that target the organic components of the enamel biofilm have been proposed. One such method is the non-invasive enamel pretreatment with 5.25% sodium hypochlorite (NaOCl) prior to phosphoric acid etching.3, 4 It has been suggested that the mechanism by which sodium hypochlorite enhances the etching pattern is enamel deproteinization, in which organic elements, including the acquired film, are removed from the enamel surface.3, 5 This presumption is based on the multitude of endodontic literature supporting the use of NaOCl as an effective irrigant in root canal therapy6-13. In contrast to dentin and pulpal tissue, enamel is comprised of minimal organic matter.14, 15 As a result of this fact and the limited amount of experimentation of the effect of NaOCl on the enamel surface, the true mechanism by which sodium hypochlorite enhances the etching pattern of enamel is questionable.5, 16 The objective of this study was to determine the compositional effects of sodium hypochlorite on human enamel. Methods: Following IRB approval, 120 enamel sections from 22 extracted human premolar teeth were randomly divided into three experimental groups and one control group.17 The control group (E = enamel) received no treatment. The first experimental group (A = phosphoric acid) received a 15-second treatment with 37% phosphoric acid, rinsed with distilled water and air sprayed for 20 seconds, then dried with oil free compressed air. The second experimental group (H = sodium hypochlorite) received a treatment of 5.25% sodium hypochlorite for 60 seconds, washed with distilled water for 10 seconds, and dried. The third experimental group (HA = sodium hypochlorite + phosphoric acid) received a treatment of 5.25% sodium hypochlorite for 60 seconds, washed with distilled water for 10 seconds, dried, then receive the 15-second treatment with 37% phosphoric acid as in Group A.3 Following treatment preparations of the four groups, scanning electron microscopy (SEM)/energy-dispersive X-ray spectrometer (EDX) analysis was performed for all groups.18 For elemental concentration, a one-way ANOVA and Tukey’s post hoc statistical tests were applied.17, 19, 20 ANOVA and Tukey tests were performed at a significance level of p ≤ 0.05. Results: There were no significant effects of treatment on the enamel elements carbon (C), calcium (Ca) sodium (Na), oxygen (O), and phosphorous (P). There was a significant effect of treatment on the amount of chlorine (Cl) in enamel between groups acid (A) and hypochlorite + acid (HA) as well as between groups hypochlorite (H) and hypochlorite + acid (HA) (p = 0.004). The amount of variation of iodine (I) in the enamel composition between untreated enamel (E) and enamel treated with sodium hypochlorite + phosphoric acid (HA) was significant (p = 0.004). Additionally, there was a significant decrease in the quantity of antimony (Sb) found in the control group (E) versus the hypochlorite + acid (HA) experimental group (p = 0.002). Lastly, tin (Sn) was significantly reduced from the enamel surface (E) when treated with hypochlorite + acid (HA) (p = 0.008). Conclusions: The various treatments minimally affected the elemental concentrations of C, Ca, Na, O, and P. The amount of chlorine present in enamel significantly increased following treatment with sodium hypochlorite (H) alone and even more so following treatment with phosphoric acid and sodium hypochlorite (AH). In contrast, elements I, Sb, and Sn demonstrated a congruent reduction in concentration after treatment with hypochlorite and acid (HA). Although it has been hypothesized that sodium hypochlorite targets the organic pellicle present on the surface of enamel via a process known as deproteinization, the findings presented here suggest that pre-treatment with NaOCl impacts the inorganic components of enamel more so than the organic constituents. These quantitative findings corroborate the enhanced etching pattern that can be visualized under scanning electron microscopy in this as well as previous studies.

The disulfide bond pattern in the galactose-specific lectin 24K from the egg jelly of the Chinook salmon Oncorhynchus tshawytscha was determined, and its previously reported amino acid sequence was confirmed by mass spectrometry. A combination of tryptic digestion, HPLC separation, and chemical, modifications was used to establish the location of seven disulfide bonds and one pair of free cysteines. After proteolysis, peptides containing one or two disulfide bonds were identified by reduction and mass spectral comparison. MALDI mass spectrometry was supported by chemical modification (iodoacetamidylation) and in silico digestion. The assignments of disulfide bonds were further confirmed by mass spectral fragmentation studies including in-source dissociation (ISD) and collision-induced dissociation (CID). Lectins of comparable biochemical functions can be found in amphibian eggs as well. Those eggs are covered with glycoproteinaceous extracellular matrix, which is known as the zonae pellucidae (ZP). The ZP consists of three major glycoproteins referred to as ZPA, ZPB, and ZPC, which contain homologous regions named "ZP domains". The ZP domain is also found in other secretory glycoproteins. Trans -membrane domains present at the C -terminus of ZP glycoproteins are removed at furin-processing sites. However, the details of this processing are unclear because of the lack of information about the precise C -termini of ZP glycoproteins. In this study, the N -termini and C -termini of the glycoprotein gp 37 (ZPB, from gp 37 precursor) and gp 41 (ZPC, from gp 43) from the clawed South African toad ( Xenopus laevis ) were determined by mass spectrometric analysis. Our results suggest that the N -terminus and C -terminus of gp 41 are generated by oviductin-mediated cleavage at GSR 55 and GSR 367 and the C -terminus of gp 37 is generated by furin-mediated cleavage at CNT 457 . These findings shed light on the biochemical processing of gp 43 to gp 41 and gp 37 precursor to gp 37.

Proteases are present in all living organisms and are involved in various biological processes. Inhibition of protease activities in disease-causing agents is one strategy for rational drug design. Characterization of the protease inhibition processes is essential for understanding the inhibition mechanisms and for developing efficient therapeutics. This work represents a major challenge in analytical biochemistry. In this study, a strategy based on mass spectrometry has been developed to characterize irreversible inhibition of proteases. Five proteases representing three of the four protease classes were irreversibly inhibited by various irreversible inhibitors, some of which are potential drug candidates. In all the cases, the stoichiometry of each of the protease/inhibitor complexes was determined by electrospray ionization mass spectrometry through measurement of the complex's molecular weight. The inhibited proteases were then enzymatically cleaved and the resulting peptides isolated for further characterization by high performance tandem mass spectrometry. Attention was focused on the determination of the site(s) of the modification and the reaction mechanisms involved. High energy collision induced dissociation mass spectra of each modified peptide provided information on the exact modification site(s) and the detailed chemical nature of the covalent complex. The serine protease trypsin, the cysteine protease cruzain, and the aspartic proteases, HIV-2 protease and SIV protease, were covalently modified only at one amino acid residue, while the aspartic protease, HIV-1 protease, was found to be modified at three sites by the haloperidol derivative compounds. In addition, mass spectrometry has been applied to characterize the plasma glycoprotein, biotinidase, and to obtain partial peptide sequences of a membrane-bound protein, UDP-GalNac:polypeptide N-acetylgalactosaminyl transferase, using a low picomole quantity of sample.

The di-O-acetyl derivative of 4,6-O-benzylidene-1-deoxy-1-nitromethyl-β-D-glucopyranose was reduced by a mixture of elemental iron and nickel in aqueous tetrahydrofuran under CO2, with concurrent O → N acetyl migration to 1-acetamido-4-O-acetyl-2,6-anhydro-5,7-O-benzylidene-1-deoxy-D-glycero-D-guloheptitol. Its 2-O-mesyl derivative was converted by base into the D-manno-2,3-epoxide. The epoxide ring was opened by NH3 to give the 3-amino-β-D-altropyranose derivative, which was subsequently N-benzoylated to 1-acetamido-2,6-anhydro-4-benzoylamino-5,7-O-benzylidene-1,4-dideoxy-D-glycero-D-glucoheptitol. Attempts to prepare 1-acetamido-2,6-anhydro-4-benzoylamino-5,7-O-benzylidene-1,4-dideoxy-3-methanesulfonyl-Dglycero-D-glucoheptitol gave spontaneously the D-allo-oxazoline derivative. However, a 3-O-mesyl derivative could be obtained by mesylation of 1,4-di-acetamido-2,6-anhydro-5,7-0-benzylidene-I,4-dideoxy-D-glycero-D-glucoheptitol. 2,6-Anhydro-5,7-O-benzylidene-1-deoxy-1-nitro-D-glycero-D-guloheptitol was reduced and N-acetylated to the acetamidomethyl derivative. 3,4-Di-O-mesylation of 1-acetamido-2,6-anhydro-5,7-O-benzylidene-1-deoxy-D-glycero-D-guloheptitol gave 1-acetamido-2,6-anhydro-5,7-O-benzylidene-1-deoxy-3,4-dimethanesulfonyl-D-glycero-D-guloheptitol, which reacted with methoxide to give the D-manno-2,3-epoxide, and mostly 2,6-anhydro-5,7-O-benzylidene-1-deoxy-D-glycero-D-gluco-heptitol [1,2,3, : 4',5',6']- 2'-methyl-2'-oxazine, presumably via a D-allo-2,3-epoxide. The condensation of 4,6-O-benzylidene-D-glucopyranose with nitroethane gave 2,6-anhydro-1,3-O-benzylidene-7,8-dideoxy-7-nitro-D-threo-L-gulooctitol and its diastereomer, which was obtained by an acetylation-deacetylation procedure. 2,6-Anhydro-1,3-O-benzylidene-7,8-dideoxy-7-nitro-L-erythro-L-gulooctitol was reduced by a mixture of elemental Fe°/Ni° in aqueous FHF under CO2 to 7-amino-2,6-anhydro-1,3-O-benzylidene-7,8-dideoxy-L-erythro-L-gulooctitol with retention of the 4,6-O-benzylidene blocking group. Acetylation of 2,6-anhydro-1,3-O-benzylidene-7,8-dideoxy-7-nitro-D-threo-L-gulooctitol produced an open chain compound. Cyclic product was not isolated. The oxime derivative, 4,5-di-O-acetyl-3,7-anhydro-6,8-O-benzylidene-1,2-dideoxy-2-oxime-D-glycero-D-guloheptitol, was separated as a byproduct from the acetylation. The condensation of nitropropane with 4,6-O-benzylidene-B-D-glucopyranose, followed by acetylation of the reaction solution, gave 4,5-di-O-acetyl-2,6-anhydro-1,3-O-benzylidene-7-nitro-7,8,9-trideoxy-D-threo-L-gulononitol and its diastereomer. Deacetylation of 4,5-di-O-acetyl-2,6-anhydro-1,3-O-benzylidene-7-nitro-7,8,9-trideoxy-D-threo-L-gulononitol gave 2,6-anhydro-1,3-O-benzylidene-7-nitro-7,8,9-trideoxy-D-threo-L-gulononitol, which could be reduced to the free amino compound by a mixture of elemental Fe°/Ni° in aqueous THF under CO2.

Polyamines are ubiquitously present in all living cells. The abnormal metabolism of polyamines that is associated with certain types of cancers has been the focus of several investigations. Enzymes that are involved in the transacetylation of polyamines have been studied extensively, so as to develop inhibitors of these enzymes which may be used as drugs in cancer therapy. Based on indirect evidence, the nuclear spermidine acetyltransferase has been thought to be a critical enzyme that is associated with genetic derepression leading to cancerous growth. In the present study a novel, rapid, sensitive and highly reproducible radio chemical procedure has been developed for assaying spermidine (polyamine) acetylation. The study contains data showing range of linearity of the procedure, percent product recovery, as well as low interference from the unreacted acetyl coenzyme A. Rat liver nuclear spermidine acetyltransferase has been purified using the biochemical procedures annmonium sulfate precipitation, DEAE chromatography, Hydroxyapatite chromatography, Diaminobutyl agarose chromatography and Polyacrylamide P-300 gel filtration. The enzyme obtained at the end of such procedures was found to be essentially homogeneous as seen on native gel electrophoresis. The purified enzyme has been shown to have an isoelectric point of 5.2. Bicine and Hepes were found to be more suitable as buffering species for good enzyme activity. The enzymatic reaction velocity was found to increase with temperature upto 36$\sp\circ$C and was found to increase linearly up to four minutes under non limiting conditions in the presence of 20% glycerol. Using the purified enzyme it has also been established that of the three nuclear polyamines, spermidine is the preferred substrate. The apparent Km for acetyl Co A with spermidine as substrate was found to be about 5 mM. The purified enzyme does acetylate histones. All the substrate analogs containing aminobutylamino group are acetylated by the enzyme.

Sustained release of nitrofurantoin (NFT) from microspheres of propylene glycol monostearate (PGM) and of PGM and ethoxylated stearyl alcohol (ESA) prepared by the meltable dispersion and cooling process was investigated. The microspheres (30-850 mu) were nonsticky, discrete and free flowing. Both the rate and extent of in vitro release of NFT (from NFT-PGM microspheres in distilled water at 37 degrees C under constant agitation at 50 rpm) declined with decreasing NFT/PGM ratio. The effect of incorporating ESA over the range of 0.01 to 0.05% w/w of PGM in formulations with NFT/PGM ratios of 1:1, 1:1.5 and 1:4, studied under similar experimental conditions revealed that NFT release was maximum in the range of 0.02 to 0.035% ESA. The effect of pH on NFT release from microspheres with 0.03% ESA and without ESA at NFT/PGM ratios of 1:1 and 1:4, was investigated in buffer solutions at pH values of 1.2, 5.8 and 7.2. The pH-dependent solubility and dissolution of NFT and PGM, in addition to NFT/PGM ratio, were found to control the rate and extent of NFT release. Both scanning electron photomicrography and contact angle measurements suggested that about 0.03% ESA was critical for the formulations studied. The in vitro evaluation of adhesion of various polymers to rabbit stomach tissue was investigated. The polymers, CLD, ACDISOL, polycarbophil and calcium polycarbophil were investigated for potential use as bioadhesives. The modified balance method developed and used to evaluate the polymers adhesion to rabbit stomach tissue in vitro at different pH levels was reproducible and could detect change in adhesive force as little as 10 mg weight. Maximum adhesion for polymers CLD and polycarbophil was observed at pH 5.8, while that of ACDISOL was at pH 7.2. The polymer, calcium polycarbophil, showed essentially no adhesion at all. The results revealed that CLD was superior and ACDISOL was inferior to polycarbophil under all three pH conditions investigated. In vitro release studies of the drug from microspheres mixed in various proportions with bioadhesive polymer CLD in phosphate buffer at pH 5.8 indicated that the presence of the polymer did not significantly hinder the drug release. (Abstract shortened with permission of author.)

In the present study, a 8 x 4 mm biodegradable device was formulated using poly(ortho ester) and metronidazole for treatment of periodontitis. Investigation focussed upon determination of formulation parameters in the form of drug (metronidazole) and adjuvant concentrations (oleic acid and palmitic acid) and device thickness necessary to achieve constant release of 0.6 μg/hr over a period of 7 days and complete degradation of the device over a period of 11 to 13 days. Presence of oleic or palmitic acid influenced the release and erosion profile considerably. Thickness of the device did not have significant influence on the drug release. The DSC and NMR studies indicated absence of interaction between drug and polymer. Computer optimization studies indicate that the optimum formulation for 7 day constant drug delivery and disappearance in 13 days should contain 0.28% w/w of oleic acid and 5.26% w/w of metronidazole at the thickness of 400-450 or 500-550 μm. This is in close agreement with the optimum formulation which was obtained with the experimental data.

Microencapsulated forms of procainamide hydrochloride (PA) were formulated and evaluated for in vitro release against Procan SR('R) tablet. Both ethylcellulose as well as Eudragit-S microcapsules were prepared by a phase separation coacervation technique. The ethylcellulose or Eudragit-S coat-to-core (PA) ratios studied were 1:1, 1:1.33, 1:2 and 1:4, while the coat-to-polyethylene ratios investigated were 3:1, 5:1, 10:1 and 30:1. Treatment of microcapsules with four different concentrations (5, 10, 15 and 20% w/v) of paraffin wax in cyclohexane was also evaluated for effects on drug release. Ethylcellulose microcapsules and Eudragit-S microcapsules with coat to core ratio of 1:4 and 1:2 respectively and a coat-to-polyethylene ratio of 30:1, after treatment with 5% paraffin wax solution, were selected for a biphasic in vitro release study in hydrochloric acid buffer, pH 1.2 for first hour, and phosphate buffer, pH 7.8 for the remaining period. The mixed blends of ethylcellulose and Eudragit-S microcapsules in the proportions of their PA content were also considered for biphasic in vitro release study. While ethylcellulose microcapsules were insensitive to pH changes, Eudragit-S microcapsules gave faster drug release in phosphate buffer pH 7.8 as expected. The time for release of 50% PA was 2.05, 5.85, 2.30, 2.70, 3.00 and 3.90 hours for Procan SR tablets, ethylcellulose microcapsules, Eudragit-S microcapsules, mixed blends MX-1, MX-2 and MX-3 respectively. The ethylcellulose microcapsules (XXI) and mixed blend (MX-3) provided more effective sustained release of PA over several hours than commercially available product Procan SR tablets. Three promising formulations (XXI, XXII and MX-3) were further evaluated for in vivo bioavailability in dogs. On the basis of area under the plasma concentration-time curve (0-10 hrs.) and total cumulative amount of drug excreted (0-30 hrs.), three formulations were found to be bioequivalent to Procan SR('R) tablets. The plasma concentration-time curve data for each formulation was analyzed pharmacokinetically by an open, one-compartment model. Mechanism of drug release from these microcapsules was also studied. The analysis of in vitro release data strongly suggests a diffusion-controlled release of PA from ethylcellulose microcapsules and possibly Procan SR tablets. The release of PA from Eudragit-S microcapsules was shown to be dissolution-controlled.