Because of quantum confinement, semiconductor quantum dots have size dependent electronic states, and the corresponding optic properties. Besides, ultrasmall quantum dots have additional red-side broadband emission, which can cover visible light. Suitable controlling the size thus can be a good candidate for the white light emitting material. In the dissertation, we study broadband emission mechanism of ultrasmall CdSe/ZnS quantum dots by single molecule detection system. Photoluminescence excitation spectrum in the solution indicates that the broadband emission and band transition fluorescence come from the same excitation. In addition, we measure the emission spectrum of single quantum dot, which also shows the similar broadband red-emission. The emission is separated into red emission and blue emission by a dichroic mirror. Blue emission channel is for the band transition fluorescence and red emission channel is for broadband emission. Fluorescence from two channels have different decay dynamics, which indicate the different emission mechanism. According to Hanbury Brown and Twiss experiments, we obtain the photon anti-bunching behavior at zero delay time. The result is consisted with ensemble average results that the exciton from quantum dot would choose either blue emission or red emission to release its excitation, but only single photon were emitted at each excitation. When increasing the laser power, we observe cascade emissions from multi-exciton. Antisymmetric bunching behavior at zero delay time indicates strong correlation between the two channel¡¦s arriving photons. Summing over the results, we conclude that the red-emission is from an electron transfer state that either electron or hole trapped in the surface states, but the counter carrier delocalized in the QD, which is very similar to the emission from the type II semiconductor structure.

Most proteins residing in the mitochondrial matrix are synthesized in the cytosol and post-translationally imported into the mitochondrial matrix. The matrix-targeted preproteins traverse the outer mitochondrial membrane (OM) via the Translocase of the Outer Membrane (TOM) complex, and the inner mitochondrial membrane (IM) via the Translocase of the Inner Membrane 23 (TIM23) complex. A novel system was set up to examine the import of matrix-targeted preproteins into mitochondria using fluorescence spectroscopy. The fluorescent probe 6-(7-nitrobenz-2-oxa-1,3-diazol-4- yl)aminohexanoic acid (NBD) was site-specifically incorporated into different positions along the model matrix protein Su9-DHFR. The fluorescent-labeled polypeptides were either fully imported into isolated mitochondria or were arrested along the translocation pathway by the binding of methotrexate (MTX) to the DHFR moiety, creating NBDSu9- DHFR•MTX import intermediates. The NBD-Su9-DHFR polypeptides were able to be fully imported into the mitochondrial matrix in the absence of MTX, and were inaccessible to externally-added iodide ion quenchers. Treatment of the mitochondria with the pore-forming antibiotic alamethicin allowed the iodide ion quenchers access to the matrix through pores in the inner membrane (IM). After Alamethicin treatment the fully-imported NBD-Su9-DHFR polypeptides were accessible to the externally-added iodide ions. The extent of collisional quenching of the NBD fluorophores by the iodide ions was measured as the Stern-Volmer quenching constant, Ksv. Ksv values were obtained for the NBD-Su9-DHFR polypeptides in the presence of MTX (import intermediates) or in the absence of MTX (fully-imported). The Ksv values for NBD-Su9- DHFR import intermediates were similar, despite the location of the NBD probe along the translocation pathway. These Ksv values were similar to those obtained for the fullyimported NBD-Su9-DHFR polypeptides (-MTX). The locations of the varying probe positions along the import pathway were addressed using chemical crosslinking of Su9- DHFR Cys mutants. The use of fluorescence spectroscopy, in association with chemical crosslinking, to analyze the mitochondrial protein import pathways will prove a useful tool to probe the environment of the nascent chain as it is crossing the import pathway (the TOM, TIM23 complexes).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 153-156). Available also in a digital version from Dissertation Abstracts.

1,6-Anhydro-N-acetylmuramic acid kinase (AnmK) is a homodimeric enzyme that can convert 1,6-Anhydro-N-acetylmuramic acid into N-acetylglucosamine-6-phosphate by consuming one molecule of ATP in murein recycling in Gram-negative bacteria. Structural data indicate that each subunit of AnmK is comprised of two domains that are separated by a deep active site cleft, which bears similarity to the ATPase core of proteins belonging to the hexokinase-hsp70-actin superfamily of proteins. These data also show that binding of ATP analogue changes the structure of AnmK. Our data suggest that AnmK is an allosteric enzyme and ATP binding follows Monod-Wyman-Changeux model (MWC). The apo-AnmK has two different conformations, one is more open (R state) and the other one is closed (T state). Binding of ATP to AnmK stabilizes the more open (R state) and makes AnmK prone to bind to anhMurNAc sugar.

1,6-Anhydro-N-acetylmuramic acid kinase (AnmK) is a homodimeric enzyme that can convert 1,6-Anhydro-N-acetylmuramic acid into N-acetylglucosamine-6-phosphate by consuming one molecule of ATP in murein recycling in Gram-negative bacteria. Structural data indicate that each subunit of AnmK is comprised of two domains that are separated by a deep active site cleft, which bears similarity to the ATPase core of proteins belonging to the hexokinase-hsp70-actin superfamily of proteins. These data also show that binding of ATP analogue changes the structure of AnmK. Our data suggest that AnmK is an allosteric enzyme and ATP binding follows Monod-Wyman-Changeux model (MWC). The apo-AnmK has two different conformations, one is more open (R state) and the other one is closed (T state). Binding of ATP to AnmK stabilizes the more open (R state) and makes AnmK prone to bind to anhMurNAc sugar.

Theses (M.S.)--Marshall University, 2005. / Title from document title page. Includes abstract. Document formatted into pages: contains v, 57 p. including illustrations. Bibliography: p. 31.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1938. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 28).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 344-347).

Thesis (Ph. D.)--University of California, Berkeley, 1962. / March 1962. "UCRL-9954; UC-4 Chemistry; TID-4500 (17th ed.)." Includes bibliographical references (leaves 97-101).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 122-128.