Development of Absorption and Fluorescence Probes Based on Mouse Model for Molecular Optical Imaging [abstract]

Comparative Medicine - OneHealth and Comparative Medicine Poster SessionIn this work we summarize our collaborative research on a project to develop absorption and fluorescence targeting probes. Several groups from University of Missouri and Harry S. Truman Memorial Veteran's Hospital including Dr. Ma's group, Dr. Yu's group, Dr. Smith's group, Dr. Hoffman's group, and Professor Wynn Volkert have been involved in the project. Our goal is to develop probes based on mouse model for molecular optical imaging. In vivo imaging of targeted fluorescence molecular probes, or molecular imaging, is an emerging field in biomedical imaging. During the past forty years, three dimensional biomedical imaging technologies such as CT and MRI have been extensively used in human health and diseases. However, the human body is a complex and interactive biological system. A fundamental scientific barrier in previous biomedical imaging technologies is their limited ability to study physiological processes in vivo at the cellular and molecular levels. Molecular imaging technologies can overcome this barrier. Optical imaging modalities have the highest sensitivity compared to other imaging techniques. So they are good candidates for molecular imaging. We develop probes for two biomedical optical imaging techniques. The first technique is coherence domain imaging. This technique can be used to monitor interactions between targeted peptide conjugates and cancer cells at a tissue level. It requires absorption properties of the probe for effective molecular imaging. The second technique is fluorescence mediated tomographic imaging using an image-intensified CCD camera. This technique uses fluorescence of the probe for molecular imaging. Dye bombesin conjugates are synthesized for site-specific absorption and fluorescence imaging in human prostate and breast cancer cells. Bombesin (BBN), an amphibian analog to the endogenous ligand, binds to the gastrin releasing peptide receptors (GRPr) with high specificity and affinity. BBN conjugates have a specific significance in cancer detection and therapy due to high over-expression levels of GRPrs in human cancer cells. Previously, we have developed an Alexa Fluor 680 BBN peptide conjugate. This probe can not be used as an absorption probe in near-infrared imaging since its absorption peak is in the visible wavelength range. In addition, long wavelength fluorescence is desired because long wavelength photons can penetrate deeper into tissue when using the conjugates as a fluorescent probe. The new absorption and fluorescent probe we developed is based on the last eight-residues of BBN and labeled with Alexa Fluor 750 through an effective linker. The developed probe, AF750-BetaAla-BBN[7-14]NH2, exhibits optimal pharmacokinetic properties for targeting GRPr over-expressing cancer cells in mice. Absorption spectra have been measured and showed absorption peaks at 690nm, 720nm and 735nm. Fluorescent band is located at 755nm. Fluorescent microscopic imaging of the conjugates in human PC-3 prostate cancer and T-47D breast cancer cells indicated specific uptake and internalization in vitro. In vivo optical and MR imaging was performed in SCID mice bearing human breast and prostate xenografts. In vitro and in vivo studies have demonstrated the effectiveness of the fluorescent probe Alexa Fluor 750-BetaAla-BBN[7-14]NH2 to specifically target GRPr overexpressed cancer tissues

On Buffered Threshold Garch Models

published_or_final_versio

Half-metallic ferromagnetism induced by dynamic electron correlations in VAs

The electronic structure of the VAs compound in the zinc-blende structure is investigated using a combined density-functional and dynamical mean-field theory approach. Contrary to predictions of a ferromagnetic semiconducting ground state obtained by density-functional calculations, dynamical correlations induce a closing of the gap and produce a half-metallic ferromagnetic state. These results emphasize the importance of dynamic correlations in materials suitable for spintronics.Comment: Published in Phys. Rev. Lett. 96, 197203 (2006

Optical and dc conductivities of cuprates: Spin-fluctuation scattering in the t-J model

A microscopic theory of the electrical conductivity $\sigma(\omega)$ within the t-J model is developed. An exact representation for $\sigma(\omega)$ is obtained using the memory-function technique for the relaxation function in terms of the Hubbard operators, and the generalized Drude law is derived. The relaxation rate due to the decay of charge excitations into particle-hole pairs assisted by antiferromagnetic spin fluctuations is calculated in the mode-coupling approximation. Using results for the spectral function of spin excitations calculated previously, the relaxation rate and the optical and dc conductivities are calculated in a broad region of doping and temperatures. The reasonable agreement of the theory with experimental data for cuprates proves the important role of spin-fluctuation scattering in the charge dynamics.Comment: 13 pages,15 figures, v.2, publication referenc

Hamiltonian Quantization of Chern-Simons theory with SL(2,C) Group

We analyze the hamiltonian quantization of Chern-Simons theory associated to the universal covering of the Lorentz group SO(3,1). The algebra of observables is generated by finite dimensional spin networks drawn on a punctured topological surface. Our main result is a construction of a unitary representation of this algebra. For this purpose, we use the formalism of combinatorial quantization of Chern-Simons theory, i.e we quantize the algebra of polynomial functions on the space of flat SL(2,C)-connections on a topological surface with punctures. This algebra admits a unitary representation acting on an Hilbert space which consists in wave packets of spin-networks associated to principal unitary representations of the quantum Lorentz group. This representation is constructed using only Clebsch-Gordan decomposition of a tensor product of a finite dimensional representation with a principal unitary representation. The proof of unitarity of this representation is non trivial and is a consequence of properties of intertwiners which are studied in depth. We analyze the relationship between the insertion of a puncture colored with a principal representation and the presence of a world-line of a massive spinning particle in de Sitter space.Comment: 78 pages. Packages include

Strong spin-orbit splitting on Bi surfaces

Using first-principles calculations and angle-resolved photoemission, we show that the spin-orbit interaction leads to a strong splitting of the surface state bands on low-index surfaces of Bi. The dispersion of the states and the corresponding Fermi surfaces are profoundly modified in the whole surface Brillouin zone. We discuss the implications of these findings with respect to a proposed surface charge density wave on Bi(111) as well as to the surface screening, surface spin-density waves, electron (hole) dynamics in surface states, and to possible applications to the spintronics.Comment: 4 pages 2 figure

On problem of polarization tomography, I

The polarization tomography problem consists of recovering a matrix function f from the fundamental matrix of the equation $D\eta/dt=\pi_{\dot\gamma}f\eta$ known for every geodesic $\gamma$ of a given Riemannian metric. Here $\pi_{\dot\gamma}$ is the orthogonal projection onto the hyperplan $\dot\gamma^{\perp}$. The problem arises in optical tomography of slightly anisotropic media. The local uniqueness theorem is proved: a $C^1$- small function f can be recovered from the data uniquely up to a natural obstruction. A partial global result is obtained in the case of the Euclidean metric on $R^3$

The signature of subsurface Kondo impurities in the local tunnel current

The conductance of a tunnel point-contact in an STM-like geometry having a single defect placed below the surface is investigated theoretically. The effect of multiple electron scattering by the defect after reflections by the metal surface is taken into account. In the approximation of s-wave scattering the dependence of the conductance on the applied voltage and the position of the defect is obtained. The results are illustrated for a model s-wave phase shift describing Kondo-resonance scattering. We demonstrate that multiple electron scattering by the magnetic impurity plays a decisive role in the point-contact conductance at voltages near the Kondo resonance. We find that the sign and shape of the Kondo anomaly depends on the position of the defect.Comment: 13 pages, 4 figures. To be published in J. Phys.: Cond. Ma