Bulletin of the American Physical Society
2006 Texas Section of the APS Joint Fall Meeting
Thursday–Saturday, October 5–7, 2006; Arlington, Texas
Session BP1: Biophysics |
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Chair: Wei Chen, University of Texas at Arlington Room: UT Arlington, University Center Palo Pinto |
Friday, October 6, 2006 10:30AM - 10:42AM |
BP1.00001: ABSTRACT WITHDRAWN |
Friday, October 6, 2006 10:42AM - 10:54AM |
BP1.00002: Dynamics of beta-amyloid peptide in cholesterol superlattice domain Anton Smirnov, Qing Zhu, Mark Vaughn, Rajesh Khare, K. Cheng Presence of beta-amyloid peptide (beta-A) plagues in membranes of neuron cells is a clinical signature of Alzheimer disease. The onset of beta-A peptide aggregation occurs via a conformational transition from an alpha-helix state to a beta-sheet state. A gradual build-up of beta-A content in the neuronal extracellular space is another characteristic of the beta-A plague formation. Hypothetically, both the pathological conformation and the predominant localization of the beta-A can be a result of specific dynamic characteristics of the interphase between cellular membrane and extracellular milieu. In this study, the beta-A interphase problem has been investigated using a virtual membrane model implemented on the base of GROMACS molecular dynamics simulation package. The detailed folding pattern of beta-A has been examined using a novice interphase model comprised of a cholesterol supperlattice membrane and two water layers. [Preview Abstract] |
Friday, October 6, 2006 10:54AM - 11:06AM |
BP1.00003: Matrix Vector-Pade Approximations in Medical Imaging Daniel Bessis Thus far, the conventional theoretical framework for data analysis in biomedical imaging including MRS (Magnetic Resonance Spectroscopy) and MRSI (Spectroscopic Imaging) has been the Fast Fourier Transform (FFT). Many of the limitations can be directly related to the reliance upon FFT, which has low resolution, poor signal-to-noise ratio (S/N), supplies only a shape spectrum and requires fitting, which is non-unique, such that the number of metabolites must be guessed in advance. This can lead both to spurious peaks (over-fitting) and true metabolites being undetected (under-fitting). Clearly, the potential of MRSI in oncology has yet to be realized. In order to achieve this goal, one must go beyond technical (hardware) improvements, important as these are. The fundamental realization is that the measurement contains far more information than heretofore appreciated, and conventionally extracted. A key breakthrough can be made by applying recent mathematical advances in signal processing. It has been conclusively demonstrated within in vivo MRS that the fast Pade transform (FPT) can circumvent the above-described limitations of the FFT As a high resolution, non-linear, parametric method, the FPT substantially improves S/N (signal to noise ratio) and fulfils the most stringent requirements for tumor diagnostics. Here, we propose to go one step further than FPT by introducing Matrix Vector-Pade Approximations. [Preview Abstract] |
Friday, October 6, 2006 11:06AM - 11:18AM |
BP1.00004: Time-resolved fluorescence spectroscopic study of flavin fluorescence in purified enzymes of bioluminescent bacteria Elena Vetrova, N. Kudryasheva, K. Cheng Time-resolved fluorescence intensity and anisotropy decay measurements have been used to study the environment and rotational mobility of endogenous flavin in two purified enzymes of bioluminescent bacteria, Luciferase from \textit{Photobacterium leiognathi} and NAD(P)H:FMN-oxidoreductase from \textit{Vibrio fischeri}. We compared the time-resolved fluorescence parameters, intensity decay lifetimes, rotational correlation times, and their fractional contribution, of the endogeneous flavin fluorescence in each of the two enzymes in the presence or absence of quinones of different structures and redox potentials. The endogeneous flavin exhibited multi-exponential decay characteristics as compared to a single decay lifetime of around 5 ns for free flavin, suggesting a complex and heterogeneous environment of flavin bound to the enzyme. In addition, a significant increase in the rotational correlation time and a certain degree of ordering of the molecule were observed for endogenous flavin when compared to a single and fast rotational correlation time of 150 ps of free flavin. Quinone significantly altered both the lifetime and rotational characteristics of endogenous flavin suggesting specific interactions of quinones to the endogeneous flavin in the bacterial enzyme. [Preview Abstract] |
Friday, October 6, 2006 11:18AM - 11:30AM |
BP1.00005: Fluorescence spectroscopic and microscopic study of beta-amyloid peptide interaction with lipid bilayers John Como, Liming Qiu, Anthony Lewis, Jacob Ajimo, J. Huang, K. Cheng Beta-amyloid is a short peptide with only 39 to 42 amino acids. Aggregated beta-amyloid on neuronal membrane surface has been implicated with the pathogenesis of Alzheimer disease. The detailed mechanism of interactions of this peptide with neuronal membranes is still not clear. Using a model bilayer system, the association of this peptide with lipid bilayer containing charged headgroup and varying amount of cholesterol has been studied using fluorescence spectroscopy and microscopy. Fluorescence anisotropy of a cholesterol analog, DHE, energy transfer from peptide to DHE, and the surface binding of labeled peptide with membrane surface were measured systematically as a function of the cholesterol content in the lipid bilayer. Our results revealed an interesting biphasic behavior of peptide/lipid interaction. We conclude that cholesterol strongly regulates the binding of beta-amyloid to cholesterol containing membranes. [Preview Abstract] |
Friday, October 6, 2006 11:30AM - 11:42AM |
BP1.00006: Nanoparticle Based Photodynamic Therapy for Cancer Wei Chen This presentation describes research into a new approach to cancer treatment through a combination of radiation and photodynamic therapy. Under this concept, scintillation or persistent luminescence nanoparticles with attached photosensitizers, such as porphyrins, are used as an in vivo agent for photodynamic therapy. The nanoparticle PDT agents are delivered to the treatment site. Upon exposure to ionizing radiation such as X-rays, the nanoparticles emit scintillation or luminescence, which in turn activates the photosensitizers; as a consequence, singlet oxygen ($^1$O$_2$) is produced. Studies have shown that $^1$O$_2$ can be effective in killing cancer cells. The innovation described in this study involves the use of in vivo luminescent nanoparticles so that an external light source is not required to support PDT. Consequently, application of the therapy can be more localized and the potential of damage to healthy cells is reduced. This new modality will provide an efficient, low-cost approach to PDT while still offering the benefits of augmented radiation therapy at lower doses. [Preview Abstract] |
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