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Tetrakis(2,6-diisopropylphenyl)diphosphine and related compounds : an electrochemical and EPR spectroscopic study of radical cationsTaghavikish, Mona January 2012 (has links)
In this thesis the synthesis and full characterization of a new bulky diphosphine, tetrakis-(2,6-diisopropylphenyl)diphosphine, are described. This compound displays facile oxidation and a thorough investigation of its redox properties has been studied by combining solution electrochemical techniques such as cyclic voltammetry (CV) and rotating disk electrode (RDE) voltammetry, with spectroscopic methods such as electron paramagnetic resonance (EPR) and Simultaneous Electrochemical Electron Paramagnetic Resonance (SEEPR) spectroscopy over a wide temperature range. Density functional theory (DFT) calculations were carried out to aid in structural characterization of the radical cation that is produced and to provide computed hyperfine splitting (HFS) constants for comparison with experimental results. For comparison to this species with bulky aromatic substituents, similar studies were conducted that have identified the previously unreported radical cation of tetrakis-tert-butyldiphosphine with a bulky aliphatic substituent that provides even higher steric pressure than the 2,6-diisopropylphenyl group. DFT calculations are reported, as is full characterization with fluid and frozen-solution EPR spectroscopy.
Further CV and EPR (SEEPR) studies are reported that led to the identification of radical cations of tris(2,6-diisopropylphenyl)arsine and bis(2,4,6-triisopropylphenyl)(2,6-diisopropylphenyl)phosphine. DFT calculations are reported, as is full characterization with fluid and frozen-solution EPR spectroscopy. / xix, 172 leaves : ill (some col.) ; 29 cm
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Imaging of tissue injury-repair addressing the significance of oxygen and its derivativesOjha, Navdeep, January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 223-247).
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A site-directed spin labelling study of the human alpha-lactalbumin molten globuleYoung, Matthew Alexander January 2013 (has links)
The human α-lactalbumin (α-LA) molten globule formed at low pH is a model for the study of protein folding intermediates. The molten globule lacks native-like side-chain interactions, resulting in a fluctuating ensemble of tertiary structures, characterisation of which has been precluded by severe line-broadening in NMR spectra and a lack of long-range NOEs. Paramagnetic relaxation enhancements (PREs) have been measured in a variant of α-LA in which all native cysteines have been mutated to alanine (all-Ala α-LA). Cysteine residues have been mutated into regions of interest and spin labelled with MTSL. These measurements have confirmed that all-Ala α-LA forms a compact molten globule. Transient, long-range interactions that are stabilising the compact fold have also been identified using PREs measured in urea-denatured states. This has identified several interactions formed by hydrophobic residues from both the α- and β-domain, which could be important for initiating and driving folding. The molten globule’s 3D topology has been probed by measuring long-range distances between MTSL pairs using Double Electron-Electron Resonance (DEER). Broad distance distributions have been identified between elements of secondary structure, indicative of a fluctuating but compact fold. By contrast, a narrower distance distribution has been measured within one of the major helices, indicative of native-like secondary structure. The surface accessibility of all-Ala α-LA and that of two other variants ([28-111] α-LA and 4SS α-LA) has been probed using solvent PREs obtained using TEMPOL, a paramagnetic co-solute. This has revealed differences in the solvent-exposure of hydrophobic residues due to the removal of disulphide bonds. This method has also identified buried hydrophobic residues that contribute to forming the molten globule’s stable, native-like core.
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Estudo espectroscópico da interação entre as proteínas séricas humanas Albumina e transferrina com o potencial agente quimioterapêutico cloreto de cis-tetraminodiclorutênio (III) / Spectroscopic study of the interaction between human serum proteins albumin and transferrin with the potential chemotherapeutic agent cis-tetraminodiclororutênio chloride (III)Guedes, Adriana Pereira Mundim 13 September 2013 (has links)
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Previous issue date: 2013-09-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Motivated by the perspective of ruthenium complexes to be used in cancer treatment,
our research group has tested the hipotesis that some complexes of Ru (III) are able
to interact with serum proteins, particularly albumin and transferrin. The Complex cis-
[RuCl2(NH3)4]Cl (CTRu(III)) have been tested against different kind of tumor cells,
obtaining good results. Starting from promising results obtained with this compound,
subsequent studies are required to understanding the mechanism by which it exerts
specificity for tumor cells. In this article, we report the first application of absorption
UV-Vis, Fluorescence and Electron Paramagnetic Resonance (EPR) spectroscopy,
to study the complex CTRu(III) interaction with human serum albumin (hsA) and
bovine serum albumin (bsA). Fluorescence measurements revealed strong proteinsbound
complex with Ksv of 1.32 x 105 and 3.71 x 105 for hsA and bsA, respectively.
EPR spectra from mono-nuclear Ru(III) complexes in buffer, showed a significant
decrease in the overall signal intensity following the first aquation step, is consistent
with the formation of oxo-bridged Ru(III) dimers. EPR spectra revealed that the BSA
very rapid binding to the protein via covalent binding through ligand-exchange with
protein side chains, likely with histidine imidazoles. On the other hand, the complex
binds non-covalently in hsA, probably as a product of the oligomerization of the
complex in hemin-biding pocket. Furthermore, two species are slowly formed by
covalent binding of the complex with the histidine residues, producing a species of
axial symmetry and the other rhombic symmetry. These bonds seem to arise from
the interaction of the complex with the histidine residue located in the binding
Sudlow’s site II. / Motivado pela perspectiva de complexos de rutênio podem ser utilizados no
tratamento do câncer, o nosso grupo de pesquisa testou a Hipótese que alguns
complexos de Ru (III) são capazes de interagir com as proteínas do soro,
particularmente albumina e transferrina. O complexo de cis-[RuCl2(NH3)4]Cl
(CTRu(III)) foi testado contra diferentes tipos de células tumorais, obtendo bons
resultados. A partir de resultados promissores obtidos com este composto, estudos
subsequentes são necessários para a compreensão do mecanismo pelo qual ele
exerce sua especificidade para células de tumor. Neste artigo, apresentamos a
aplicação de espectroscopia de absorção UV-vis, fluorescência e ressonância
paramagnética eletrônica (RPE), para estudar a interação do complexo CTRu(III)
com albumina sérica humano (hsA) e a albumina sérica bovina (bsA). Medidas de
fluorescência revelaram uma forte ligação do complexo com as proteínas com Ksv de
1,32 x 105 e 3,71 x 105 para hsA e bsA, respectivamente. Espectros de RPE de
complexos de Ru (III) mono-nucleares em tampão mostraram um decréscimo
significativo na intensidade do sinal global após a primeira passo de aquação, que é
consistente com a formação de dímeros de oxo complexos de Ru (III). Os espectros
de RPE revelaram que a ligação à bsA é muito rápida, a ligação covalente à proteína
ocorre através de troca dos ligantes com cadeias laterais de proteínas,
provavelmente com o imidazol da histidina. Por outro lado, o complexo se liga não
covalentemente na hsA, provalente como produto da oligomerização do complexo
no bolso de ligação hemin. Além disso, duas espécies são formadas lentamente por
ligação covalente do complexo com os resíduos histidina, produzindo uma espécie
de simetria axial e a outra de simetria rômbica. Essas ligações parecem surgir pela
interação do complexo com o resíduo histidina localizado no sítio de ligação Sudlow
II.
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Probing the mechanism of Bacillus subtilis oxalate decarboxylaseZhu, Wen 01 December 2015 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Oxalate decarboxylase (EC 4. 1. 1. 2 OxDC) from Bacillus subtilis is a manganese-dependent enzyme that catalyzes the cleavage of the chemically inactive C-C bond in oxalate to yield formate and carbon dioxide. A mechanism involving Mn(III) has been proposed for OxDC, however no clear spectroscopic evidence to support this mechanism has yet been obtained. In addition, a recent study has shown that N-terminal metal binding site loop variants of OxDC were able to catalyze the oxidation of oxalate to yield hydrogen peroxide and carbon dioxide, which makes OxDc function as another oxalate degradation protein in the cupin superfamily, oxalate oxidase (EC 1.2.3.4 OxOx). In this work, wild-type (WT) Bacillus subtilis OxDC and a series of variants with mutations on conserved residues were characterized to investigate the catalytic mechanism of OxDC. The application of membrane inlet mass spectrometry (MIMS), electronic paramagnetic resonance (EPR) spectroscopy and kinetic isotope effects (KIEs) provided information about the mechanism. The Mn(III) was identified and characterized under acidic conditions in the presence of dioxygen and oxalate. Mutations on the second shell residues in the N-terminal metal binding site affected the enzyme activity properties of the metal. In the N-terminal domain, the functional importance of the residues in the active site loop region, especially Glu162, was confirmed, and evidence for the previously proposed mechanism in which OxDC and the OxDC/OxOx chimeric variant share the initial steps has been found. In addition, the mono-dentate coordination of oxalate in the N-terminal metal binding site was confirmed by X-ray crystallography. A proteinase cleavable OxDC was constructed and characterized, revealing the interaction between the N-terminal and C-terminal domains.
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Biophysical studies of cholesterol in unsaturated phospholipid model membranesWilliams, Justin A. January 2013 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Cellular membranes contain a staggering diversity of lipids. The lipids are heterogeneously
distr
ibuted to create regions, or domains, whose physical properties differ from the bulk
membrane and play an essential role in modulating the function of resident proteins. Many
basic questions pertaining to the formation of these lateral assemblies remain. T
his research
employs model membranes of well
-
defined composition to focus on the potential role of
polyunsaturated fatty acids (PUFAs) and their interaction with cholesterol (chol) in restructuring
the membrane environment. Omega
-
3 (n
-
3) PUFAs are the main
bioactive components of fish
oil, whose consumption alleviates a variety of health problems by a molecular mechanism that is
unclear. We hypothesize that the incorporation of PUFAs into membrane lipids and the effect
they have on molecular organization may be, in part, responsible. Chol is a major constituent in
the plasma membrane of mammals. It determines the arrangement and collective properties of
neighboring lipids, driving the formation of domains via differential affinity for different lipids
. T
he m
olecular organization of 1
-[
2
H
31
]palmitoyl
-2-
eicosapentaenoylphosphatidylcholine (PEPC
-
d
31
) and 1
-[
2
H
31
]palmitoyl
-2-
docosahexaenoylphosphatidylcholine (PDPC
-d
31
) in membran
es with
sphingomyelin (SM) and chol (1:1:1 mol) was compared
by solid
-
state
2
H NMR spectroscopy.
Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are the two major n
-
3 PUFAs found in
fish oil, while PEPC
-d
31
and PDPC
-d
31
are phospholipids containing the respective PUFAs
at the
sn
-
2 position and a perdeuterated palmitic acid a
t the sn
-
1 position
.
Analysis of s
pectra
recorded as a function of temperature indicate
s
that in both cases, formation of PUFA
-
rich (less
ordered) and SM
-
rich (more ordered) domains occurred. A surprisingly substantial proportion of
PUFA was found to infil
trate the more ordered domain. There was almost twice as much DHA
(65%) as EPA (30%)
. The implication is
that n
-
3 PUFA
s
can incorporate
into lipid rafts, which
are
domains
enriched in SM and chol in the plasma membrane,
and
potentially
disrupt the activity of signaling proteins that reside therein. DHA, furthermore, may be the more potent component
of fish oil.
PUFA
-
chol interactions were also examined through affinity measurements. A novel method
utilizing electron paramagnetic resonance (EPR) was develope
d, to monitor
the partitioning of a
spin
-
labeled
analog
of chol
, 3β
-
doxyl
-
5α
-
cholestane (chlstn), between large unilamellar vesicles
(LUVs) and met
hyl
-
β
-
cyclodextrin (mβCD). The EPR spectra for
chlstn in the two environments
are distinguishable due to the substantial differences in tumbling rates
, allowing
the
population
distribution
ratio to
be determined by spectral simulation. Advantages of this approach include
speed of implementation and a
vo
idance of potential
artifact
s associated with
physical
separation of LUV and mβCD
. Additionally, in a check of the method, t
he relative partition
coefficients between lipids measured for the spin label analog agree with values obtained for
chol by isothermal titration calorimetry (ITC). Results from LUV with different composition
confirmed
a hierarchy of
decreased
sterol affinity for phospholipids with increasing
acyl chain
unsaturation
, PDPC possessing half the affinity of the corresponding monounsaturated
phospholipid.
Taken together, the results of
these studies
on model membranes demonstrate the potential for
PUFA
-
driven alteration of the architecture of biomembranes, a mechanism through which
human health may be impacted.
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<b>Molecular investigation of the multi-phase photochemistry of environmental aquatic systems</b>Maria V Misovich (17553087) 08 December 2023 (has links)
<p dir="ltr">The chemical constituents of terrestrial and atmospheric waters originate from biomass burning, fertilizer runoff, and anthropogenic activity, among other sources, and their multi-phase chemistry is complex. Sunlight plays an essential role in aquatic chemistry. Photosensitizers in terrestrial and atmospheric waters absorb light to form highly reactive species such as triplet excited carbon (<sup>3</sup>C*), hydroxyl radical (•OH), and singlet oxygen (<sup>1</sup>O<sub>2</sub>), driving the photochemical transformations of dissolved organic matter (DOM) in the aqueous phase. Of note, these reactive species transform DOM compounds that do not undergo direct photolysis. DOM frequently undergoes a change in optical properties following photochemical processing, with implications for air quality, water quality, and human and animal health. The presence of inorganic minerals, such as the fertilizer compound struvite, in terrestrial or atmospheric waters introduces further complexity and impacts the photochemical processes that occur. Simplified proxy systems are created in the laboratory to simulate aquatic photochemical processes and evaluate the formation and/or photodegradation of photoproducts. These mixtures typically consist of a representative organic carbon (OC) compound and a photosensitizer, along with struvite or another inorganic mineral.</p>
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