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Retrospective Theses and Dissertations

Physical chemistry

Biophysics

Articles 1 - 9 of 9

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Distance-Based Nmr Structure Determination And Refinement, Feng Cui Jan 2005

Distance-Based Nmr Structure Determination And Refinement, Feng Cui

Retrospective Theses and Dissertations

Protein structures play a pivotal role in understanding protein functions. X-ray crystallography and nuclear magnetic resonance spectroscopy (NMR) are two main experimental approaches for protein structure determination. The structures determined by NMR are not as accurate as those by X-ray crystallography in general, due to limited distance data (e.g. NOEs) that can be generated from NMR experiments. The NMR modeling algorithms are not well developed either, to produce high-quality structures with desired accuracy and efficiency. To address the NMR modeling issues, a so-called geometric build-up approach for NMR modeling has been developed, which remarkably reduces computing time in determining ...


Photophysics And Light Induced Photobiology Of Antiviral And Antitumor Agents, Hypericin And Hypocrellin , Jaehun Park Jan 2001

Photophysics And Light Induced Photobiology Of Antiviral And Antitumor Agents, Hypericin And Hypocrellin , Jaehun Park

Retrospective Theses and Dissertations

The dissertation mainly focuses on the excited-state photophysics and the light-induced biological activity of hypericin and its analogs.;Femtosecond laser technology has provided the opportunity to investigate the rapid dynamics of these molecules. Fluorescence upconversion measurements, which monitor only emission from the fluorescent singlet state, demonstrate that hexamethoxy hypericin, which possesses no labile protons, has an instantaneous rise time for its transient response. On the other hand, hypericin shows a clear 10-ps rise time. This confirms excited-state H-atom transfer as the primary photophysical process in hypericin.;Femtosecond transient absorption spectroscopy technique is used to determine if excited state H-atom transfer ...


Primary Photoprocesses Of Light-Activated Antiviral And Antitumor Agents, Hypericin And Hypocrellin , Alexandre V. Smirnov Jan 1999

Primary Photoprocesses Of Light-Activated Antiviral And Antitumor Agents, Hypericin And Hypocrellin , Alexandre V. Smirnov

Retrospective Theses and Dissertations

The dissertation focuses on the ultrafast primary photoprocesses of the title anti-viral and anti-cancer agents, whose activity depends on light which is also accompanied by photoacidification in vesicles and living cells;By complementing the techniques of time-resolved absorption spectroscopy with those of fluorescence upconversion and applying them to hypericin, hypocrellin A and B, and their methylated analogs that are unable to execute proton transfer, it was demonstrated that intramolecular excited-state hydrogen atom transfer is a dominant primary nonradiative process;For hypocrellin A in viscous solvents such as octanol and ethylene glycol, an absorption transient of ∼10-ps duration, similar to the ...


Application Of Spectral Hole Burning To The Study Of In Vitro Cellular Systems , Nebojsa Milanovich Jan 1999

Application Of Spectral Hole Burning To The Study Of In Vitro Cellular Systems , Nebojsa Milanovich

Retrospective Theses and Dissertations

The high resolution spectroscopic technique of nonphotochemical hole burning (NPHB) was applied to the study of in vitro cellular systems. Suspensions of two well-characterized cell lines were used for these studies: (1) MCF-10F cells, a normal human breast epithelial cell line, and (2) MCF-7 cells, a human breast adenocarcinoma cell line. Both cell lines were stained with the dye aluminum phthalocyanine tetrasulfonate (APT) and prepared for spectroscopic study at liquid helium temperatures. Routinely measured hole burning parameters were obtained for the two cell types and compared in order to differentiate between physical properties of normal and cancer cells;A comparison ...


Hole Burning With Pressure And Electric Field: A Window On The Electronic Structure And Energy Transfer Dynamics Of Bacterial Antenna Complexes , Hsing-Mei Wu Jan 1998

Hole Burning With Pressure And Electric Field: A Window On The Electronic Structure And Energy Transfer Dynamics Of Bacterial Antenna Complexes , Hsing-Mei Wu

Retrospective Theses and Dissertations

Light-harvesting complexes of cyclic symmetry from purple bacteria are studied using absorption and high pressure- and Stark-hole burning spectroscopies. The B800→B850 energy transfer rate of (~2 ps)-1 determined by hole burning and pump-probe spectroscopies is weakly dependent on B800-B850 energy gap varied by pressure and temperature. This resilience is explained in terms of a modified Forster theory with the spectral overlap provided by the B800 fluorescence origin band and weak vibronic absorption of B850. Explanations for the additional sub-picosecond relaxation channel of B800 with excitation on the blue side are given. Pressure and temperature dependent studies show that ...


Spectral Hole Burning Studies Of Photosystem Ii , Hai-Chou Chang Jan 1995

Spectral Hole Burning Studies Of Photosystem Ii , Hai-Chou Chang

Retrospective Theses and Dissertations

Low temperature absorption and hole burning spectroscopies were applied to the D1-D2-cyt b[subscript]559, and the CP47 and CP43 antenna protein complexes of Photosystem II from higher plants. Low temperature transient and persistent hole-burning data and theoretical calculations on the kinetics and temperature dependence of the P680 hole profile are presented and provide convincing support for the linker model. Implicit in the linker model is that the 684-nm-absorbing Chl a serve to shuttle energy from the proximal antenna complex to reaction center. The stoichiometry of isolated Photosystem II Reaction Center (PSII RC) in several different preparations is also discussed ...


Photophysics And Activity Of Biological Systems Containing The Optical Probes 7-Azatryptophan And Its Analogs , Rebecca Lynne Rich Jan 1995

Photophysics And Activity Of Biological Systems Containing The Optical Probes 7-Azatryptophan And Its Analogs , Rebecca Lynne Rich

Retrospective Theses and Dissertations

A major use of photophysical apparatus is the study of biological systems, for example, peptides, proteins, and DNA, that contain one or more chromophores. In recent years the incorporation of nonnatural fluorescent compounds into these systems has gained great popularity. A number of optical 'tags' have been suggested as detection tools of structure and function; we propose the use of the tryptophan derivative, 7-azatryptophan, as an intrinsic probe in photophysical analyses of proteins. Not only is this chromophore spectroscopically distinct from tryptophan and all other natural amino acids, but we have demonstrated the successful incorporation of 7-azatryptophan into peptide sequences ...


Monolayer Studies Of Novel Synthetic Compounds And Biological Systems , Jingyuan Wang Jan 1994

Monolayer Studies Of Novel Synthetic Compounds And Biological Systems , Jingyuan Wang

Retrospective Theses and Dissertations

A general review on preparation and methods of characterization of monolayers was given in Chapter 1. Different projects were undertaken in the research of this dissertation. Neutron and X-ray reflection studies of fullerene C[subscript]60 and its derivative monolayers were performed in Chapter 1. Neutron and X-ray reflection measurements and surface pressure isotherms of spread films of C[subscript]60-dodecylamine adduct C[subscript]60-(NH[subscript]2(CH[subscript]2)[subscript]11CH[subscript]3][subscript]x and C[subscript]60-propylamine adduct C[subscript]60-(NH[subscript]2C[subscript]3H[subscript]7][subscript]x indicate that these C[subscript]60 ...


Spectral Hole Burning Studies Of Photosystem 1, J. Kevin Gillie Jan 1989

Spectral Hole Burning Studies Of Photosystem 1, J. Kevin Gillie

Retrospective Theses and Dissertations

Persistent spectral hole burning is applied to the reaction center, P700, and the light harvesting chlorophyll protein complexes of Photosystem I. A theory for solid state spectral hole burning is developed that is valid for arbitrarily strong linear electron-phonon coupling within the Condon approximation. Persistent photochemical hole burning of the reaction center P700, reveals that a broad (~300 cm[superscript] -1) hole can be burned into the adsorption profile. The hole profile and its maximum position and intensity dependence on burn wavelength are adequately fit by the electron-phonon coupling theory. The results indicate that the absorption and hole profile are ...