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As emerging chiral metamaterials, plasmonic nanospirals (NSs) show strong optical activity that is expected to enhance the enantiodiscrimination of chiral molecules or help in the design of a new generation of integrated optical devices. The study of the optical activity of plasmonic NSs is still in its infancy, and no analytical model exists to describe their chiroptical mechanism. In this study, numerical and analytical simulations are devised to investigate the optical activity of plasmonic NSs that are generated by glancing-angle deposition. The findings will pave the way for the development of novel optical and optoelectronic devices with integrated functions. The CD spectrum of a closely packed random AgNS array has two CD peaks in the UV and visible regions with opposite signs. The pitch-normalized CD in the UV regime tends to be independent of the helical pitch, but that in the visible regime decreases in amplitude as helical pitch increases. The difference can be explained using an analytical LC circuit model and finite-element method simulation. The LC circuit model is used to quantitatively evaluate the chiroptical contribution. It is revealed that radiative loss makes an important chiroptical contribution to the two CD modes and that the visible CD mode receives a greater contribution from radiative loss than does the UV CD mode. Finally, the heterochiral biaxial AgNS arrays alter the sign of the visible CD by switching the incident direction, which shows that the arrays can function as circular polarizers in the visible regime. Furthermore, when AgNSs are deposited on a polymer substrate coated with indium tin oxide, the chiroptical flexible thin film has excellent chiroptical stability when exposed to forward mechanical bending, paving the way for the development of flexible or wearable chiroplasmonic devices.

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Thesis (Ph. D.)--Carleton University, 1992. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references (leaves 308-309).

In this study we have used isothermal titration calorimetry, ITC, and circular dichroism spectropolarimetry, CD, to directly measure the thermodynamics and the structural changes for binding histones, H11 and H14, to DNA. The ITC data have been used to estimate the binding constant, (K ≈ 108) and the enthalpy change (ΔH ≈ + 5 (H11 at 25ºC), ΔH ≈ +20 kcal/mol (H14 at 15 ºC) for formation of the H1/DNA complex. CD data indicate that both H1 and DNA are partially unfolded in the H1/DNA complex. Protein and DNA unfolding must contribute to the large unfavorable endothermic enthalpy change for complex formation. The ITC data indicate that the H11 binding site is comprised 30 DNA base pairs while H14 interacts with approximately 36 DNA base pairs. At saturation, our data are consistent with 100% of the H1 binding sites being occupied in the H1/DNA complex.

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Made available in DSpace on 2014-06-11T19:31:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-19Bitstream added on 2014-06-13T20:21:35Z : No. of bitstreams: 1 vicente_ef_dr_araiq_parcial.pdf: 165362 bytes, checksum: 96b2cf2b3ae74363a4b5898b957a3b6a (MD5) Bitstreams deleted on 2015-06-03T11:42:42Z: vicente_ef_dr_araiq_parcial.pdf,. Added 1 bitstream(s) on 2015-06-03T11:44:08Z : No. of bitstreams: 1 000721605_20150819.pdf: 147542 bytes, checksum: f5cc64495e4f5a562a1e11d2ae711ce3 (MD5) Bitstreams deleted on 2015-08-20T11:58:40Z: 000721605_20150819.pdf,. Added 1 bitstream(s) on 2015-08-20T11:59:13Z : No. of bitstreams: 1 000721605.pdf: 4723399 bytes, checksum: 29bea79ab4fbb0c39fdce178c6b55872 (MD5) / A diidroorotato desidrogenase é uma enzima que apresenta um papel central na biossíntese de pirimidinas e catalisa a oxidação do diidroorotato a orotato. A enzima atua durante a via “de novo” de síntese de pirimidinas e está presente em quase todos os organismos vivos. A diidroorotato desidrogenase humana (HsDHODH) pode representar um importante alvo para o tratamento de doenças hiperproliferativas e inflamatórias, já que sua inibição bloqueia a síntese de ácidos nucléicos, impedindo a sua proliferação. Esta enzima tem uma estrutura monomérica e está associada com a membrana interna das mitocôndrias pela sua extensão N-terminal. Assim, entender em detalhes como esta enzima interage com a membrana poderia elucidar um alvo seletivo para drogas antiproliferativas, antiparasíticas e imunossupressivas. Esta região está também envolvida com a catálise central da enzima, sequestrando moléculas de ubiquinona presentes na membrana, fundamentais para as reações de oxirredução feitas pela enzima. Deste modo, para um melhor entendimento destes aspectos, neste trabalho foram sintetizados, por meio da Síntese de Peptídeos em Fase Sólida (SPFS) o peptídeo Ac-GDERFYAEHLMPTLQGLLDPESAHRLAVRFTSLG-NH2, que corresponde ao microdomínio existente na porção N-terminal da HsDHODH, entre os resíduos 33 e 66. Três análogos marcados com o aminoácido paramagnético TOAC nas posições 0, 12 ou 20, além de dois análogos duplamente marcados também foram obtidos. Ambos os peptídeos com dupla marcação possuem uma cisteína ligada ao spin MTSSL na posição 35 (C-terminal) se diferenciando pela posição do segundo marcador: um contendo outra cisteína ligada ao MTSSL na posição 12 e o segundo possuindo o TOAC na posição 0 (ou N-terminal). Estes peptídeos foram estudados por técnicas... / The dihydroorotate dehydrogenase is an enzyme that has a central role on the pyrimidine biosynthesis and catalyses the oxidation of dihydrorotate to orotate. The enzyme acts on de novo pyrimidines nucleotides pathway and it is present in almost all the live organisms. The human dihydroorotate dehydrogenase (HsDHODH) can represent an important target for the treatment of hiperproliferative and inflammatory diseases, since its inhibition blocks the nucleic acid synthesis, which restrains the cell proliferation. This enzyme has a monomeric structure and it is associated into the inner mitochondrial membrane by the N-terminal extension. Thus, understanding in details how this enzyme interacts with the membrane could help to elucidate a selective target for antiproliferative, antineoplasic and immunosuppressive drugs. This region is also involved with the central enzyme catalysis, harboring quinones molecules that are in the membranes, which is essential for the oxidation-reduction reactions made by the HsDHODH. In this way, for a better evaluation of these aspects, in this work we synthesized through the Solid Phase Peptide Synthesis (SPPS) the peptide Ac-GDERFYAEHLMPTLQGLLDPESAHRLAVRFTSLG-NH2, which corresponds to the HsDHODH N-terminal microdomain, between the residues 33 to 66. Three analogues labeled with the paramagnetic amino acid TOAC in the positions 0, 12 or 20 and two doubly labeled analogues were also synthesized. Both doubly labeled peptides contain a MTSSL-attached cysteine residue bounded to the position 35 (C-terminus), differing by the position of the second spin label: one possessing a cysteine with MTSSL at position 12 and the other contains TOAC at position 0 (N-terminus). These peptides were studied by spectroscopy techniques in order to obtain information about... (Complete abstract click electronic access below)