Permanent URI for this collection
Browse
Recent Submissions
Publication Synthesis of Monomers for New Conjugated Polymers(2012-02) Jadhav, Kedar GirishABSTRACT SYNTHESIS OF MONOMERS FOR NEW CONJUGATED POLYMERS This dissertation addresses the problem of synthesis of different monomers for donor and acceptor polymers in photovoltaic applications. In general, functionalization of conjugated polymers and understanding of molecular packing of electron donors and electron acceptors are very important to produce efficient solar cells. As a result, it is important to design and synthesize novel monomers which will require making new π-conjugated donors and acceptors polymers and understand the influence of these new polymers in bulk heterojunction to design polymer solar cells. In this study, two different monomers were synthesized. The first monomer was designed and synthesized to investigate the effect of π-conjugated linker directly attached to the polymer backbone where the polymer backbone was based on thiophene unit and conjugated linker was 1,2,3-triazole. In a different study, a conjugated monomer based on benzthiadiazole was designed and synthesized in order to synthesize new acceptor homopolymers and alternating copolymers. Two different monomers with different alkyl side chains based on benzthiadiazole were synthesized and subject to Suzuki and Stille polymerization to get respective polymers.Publication The Study of Inter and Intramolecular Interactions in Gas Phase Protein Ions by Electron Transfer Dissociation(2012-02) Browne, Shaynah JMass spectrometry (MS) is emerging as an important tool for studying protein and protein complexes. When applying this tool, it is important to understand and investigate whether some of the intramolecular and intermolecular interactions of proteins in solution and are maintained in the gas phase. To investigate if some of these interactions are maintained in the gas phase, we develop and use a method in which the electron-transfer dissociation (ETD) spectra of native proteins are compared with spectra from ETD followed by low amplitude collisional induced dissociation (CID). From these experiments, we find that some intramolecular interactions from solution are maintained in the gas phase for ubiquitin and beta-2-microglobulin (β2m). However, using these approaches, cytochrome c’s structure in the gas phase appears to be quite different than its structure in solution. We also investigated if ETD spectra of intact protein complexes reflect contact site information in these complexesPublication Selective Inhibition Studies of Factor Inhibiting Hif (fih)(2011-09) Holmes, Breanne EThe control of oxygen delivery to cells in the body is the result of a small group of primary oxygen sensors, one of the most important of which is the hypoxia-inducible transcription factor-1 (HIF-1). Two alpha-ketoglutarate dependent non-heme iron dioxygenases are responsible for the regulation of HIF-1 through hydroxylation of residues on the HIF-1a subunit. One of these enzymes, known as the factor inhibiting HIF-1 (FIH-1) is responsible for hydroxylating residue Asn803 on HIF-1a, preventing the transcription of hypoxia related genes controlled by HIF-1. It was hypothesized that there would be a difference in inhibition of FIH-1 from the other HIF-1 regulating enzyme, the prolyl hydroxylase domain-2 (PHD2), when testing a series of ten small molecule inhibitors. The ten inhibitors chosen fell into three classes: pyrones, pyridines, and catechols. Of these inhibitors, it was found that catechols produced a significant inhibitory difference between PHD2 and FIH, and may provide useful in further inhibitor design and synthesis work.Publication Electronic and Vibrational Spectroscopy of Ni+(H2O)(2011-05) Daluz, Jennifer S.The electronic and vibrational spectra of Ni+(H2O) were measured using photofragment spectroscopy. In the electronic spectrum, photodissociation is observed at photon energies above 16875 cm-1. The only fragment observed is Ni+. The electronic spectrum consists of well-resolved peaks spaced by ~340 cm-1, due to a vibrational progression in the excited electronic state. These peaks have complex sub-structure, consisting of a triplet, spaced by ~30 cm-1. The sub-structure is due to rotational structure in a perpendicular transition of a prolate top molecule. In addition to this major progression, there is a series of less intense, single peaks spaced by ~340 cm-1. These may be due to a vibrational progression in a second electronic state, this time due to a parallel transition. The O-H stretching vibrations of Ni+(H2O) were measured using vibrationally mediated photodissociation (VMP) in a depletion experiment, only monitoring transitions from K’’=1. This revealed a O-H symmetric stretch at 3629 cm-1 and antisymmetric O-H stretch at 3692 cm-1. Several electronic structure calculations complement the experiments using the BHandHLYP hybrid density functional and the 6-311++G(3dp, f) basis set. At this level of theory, Ni+(H2O) is predicted to have C2v symmetry and 2A1 ground state. The Ni-O bond length is 1.95, the O-H bond lengths are .955 and the H-O-H angle is 108.2˚ The molecule is a near-prolate top, with rotational constants A=13.98 cm-1, B=0.297 cm-1 and C=0.296 cm-1 . Analysis of the electronic and vibrational spectra reveals that binding to Ni+ removes electron density from the oxygen lone pairs, increasing the H-O-H bond angle from its value in bare H2O. The electronic and vibrational spectra corresponds to 4s ¬3d transistion in Ni+. As a result of electronic excitation, the Ni-O bond stretches by .20 Å, and the H-O-H bond angle is reduced.Publication Determination Of Chemoreceptor Organization In-vitro With Site Directed Cross-linking(2010-05) Karunanayake Mudiyanselage, Aruni PKKChemoreceptor dimers mediate bacterial chemotaxis through receptor arrays that form complexes with CheW and the kinase CheA. Both kinase activity and the rate of receptor methylation have been observed to change with receptor density in the signaling complexes of an assembled system. Receptor dimers play a structural and functional important role during the signaling process. The dimer is an established unit of a functional receptor array, but the exact packing arrangement of dimers in the signaling array is not known in detail. Two different models of the packing arrangement have been proposed, based on crystal structures of receptor cytoplasmic fragments: the trimer of dimers and hedgerow models. Here, we determine the importance of CF dimer organization on density dependence of kinase activity, receptor methylation, and we probe CF trimer organization by site-directed TMEA cross-linking. CF dimers were prepared by site-directed cysteine disulfide bond formation to test for a possible monomer-dimer equilibrium process in the density-dependence of kinase activity in the vesicle-assembled system. We found that density transition observed for CF4E is similar for both reduced and disulfide-linked CF, indicating that the CF is organized as dimers even at lower densities. CheR-catalyzed methylation experiment revealed that disulfide-linked CF dimers in solution are insufficient for efficient methylation, assembly of the CFs on a vesicle surface is required. CF trimers were trapped by the trifunctional crosslinker TMEA, but only with vesicle assembled CFs. TMEA crosslinking occurred between residues that were expected to form trimer, but also those that were not. The results provide evidence that CF behavior is highly dynamic in maleimide crosslinking reaction which conducted on vesicle assembled system.Publication Fluorescence Behavior of pH-Sensitive Molecular Probe at the Single-Molecule Level with a Model Coumarin 6(2009) Kim, JinhongMy research has demonstrated the feasibility of the experimental methodologies for proton-sensitive molecular probes of proton transport at the single-molecule level where a single molecule fluorescence spectral shift was observed in poly acrylamide gel (PAAG) matrix after the addition of HCl with a grating spectrometer. Proton-sensitive molecular probes are employed for observing variations of photophysical properties as protons from acid sources transport and react with the reporter molecules such as Coumarin 6 where it has two different protonated states and then shows distinguished emission spectrum. As well, in order to understand the fluorescence properties of neutral and protonated Coumarin 6 in each emission spectrum region, dual-channel detection experiment was built where those fluorescence emission spectrum are allowed to be separated into each optical detection channel. The two-color detection will provide us with the understanding of the heterogeneities indicative of the interaction of pH-responsive probe with its environment. Based on those methodologies and results, this research will lead to investigate how proton transfer kinetics and dynamics are influenced by the geometric arrangements such as inter-functional group spacing, alignment, and flexibility in single macromolecular scaffolds which will suggest the development for future fuel cell and better understanding of biological process.Publication Integration Of Organic Electronic Materials With Semiconductor Nanoparticles(2007) Lu, TongxiangQuantum dots coated with electronically active ligands-TTF derivatives were synthesized through one step place exchange reaction. The “ON/OFF” switching of fluorescence was facilitated through manipulation of quantum dots. Furthermore, quantum dots coated with TTF derivatives will be assembled on device platforms, which will bridge between inorganic semiconductor nanoparticles and organic conductors/semiconductors, with the ultimate goal being the fabrication of devices.Publication Biosynthesis of Arsenic by E. coli(2007) Callahan, Marissa KA method was developed for pre-concentration, speciation and determination of arsenic species (As(III), As(V), MMA and DMA) in various water samples by solid phase extraction flow injection hydride generation atomic absorption spectrometry (SPE-FI-HG-AAS). The packing materials used for SPE included strong cation-exchange and strong anion-exchange silica beads. The devised method was successfully applied to the quantification of arsenic species in the University of Massachusetts campus pond water. A new method was developed for the determination of methylation and reduction of arsenic species (As(III), As(V) and DMA) in Mueller-Hinton growth media by E. coli based on anion-exchange chromatography with post column hydride generation and inductively coupled plasma optical emission spectrometry (HPLC-HG-ICP-OES). The method was successfully applied to the determination of metabolism of arsenic by E. coli by analyzing the growth media and the cell extracts. The investigations suggested that E. coli did not methylate any of the arsenic species but simply reduced As(V) to As(III). The media created a “split peak” effect for DMA, resulting in shorter retention time for the majority of the bulk and longer retention time for the rest of the species. This effect is most likely due to the reaction of DMA with the protein present in the media, generating a positive complex, which resulted in the shifts in retention times. Although the presence of hydride generation help enhances the arsenic signal by almost 30 times, it also affects the intensities of each arsenic species differently, some, such as As(III), benefit from the reaction than others, such as As(V). The studies revealed that when measuring different arsenic species in the absence of hydride generation, the ICP-OES sensitivity is not the same for all. Results from t- and F-tests suggested that AsB, DMA and As(V) are statistically the same, whereas As(III) and MMA, which are statistically indistinguishable, are from a different distribution.Publication A study of 2,3-dimethylbutadiene-1,3 and related compounds(1933) Wendell, Charles ButlerPublication A study of the properties of inulin and its quantitative determination in artichoke tubers(1933) Wanegar, Melvin HaroldPublication A study of chloretone and related compounds(1933) Tompkins, Earle AlexanderPublication A further study of the synthesis of 5,5-Alkylphenylbarbituric acids(1935) Taylor, Marion R.Publication A comparative study of the Mt. Holyoke diabase and the dike at Dry Brook(1937) Stevens, Nelson PiercePublication A study of compounds related to Luminal(1933) Spaulding, Lucian BayardPublication The relation of hydrogen-ion activity to the rate of inversion of sucrose(1930) Smith, Walter RussellPublication Publication The viscosity and surface tension of the principal proteins in ice cream(1926) Percival, Gordon PittingerIce cream has been defined as » frozen dairy-product, with or without natural flavoring, containing sugar, and a specified amount of butter fat as required by the laws or regulations of the various states and the Federal government. Ordinarily ice cream consists of cream, sugar, flavoring, and some stabilizer which is usually gelatin. These are the principal ingredients, but rich cream may be thinned by the addition of skim milk, or skim-milk powder may be added, to build up the solid s-not- fat and thus improve the body. Ice cream is truly a frozen dairy-product, although other products than cream may enter into its makeup. The different ingredients that enter into an ice cream mix exist in different grades, concentrations and forms. It is desirable, therefore, in order to obtain constructive data, to follow a logical approach which would be to study first, simple isolated portions of the system m that is, the different types of dispersed phases in the dispersion medium taken singly - and then the effects of the combinations of such systems, gradually increasing the complexity.Publication The determination of lactic acid(1937) Pease, George RaymondPublication The preparation of alkyl iodides(1932) Parrott, Ernest Milford