Structural and functional analysis of violaxanthin de-epoxidase

Non photochemical quenching (NPQ) is an important way for plants to protect themselves from photooxidative damage. In higher plants, the major and most rapid part of NPQ is qE, which is controlled by the Violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZE). VDE converts Violaxanthin (Vx) to Antheraxanthin (Ax), and then to Zeaxanthin (Zx). Several experiments were carried through to analyze functional and structural properties of VDE. All the 13 Cysteines(Cys) in VDE were mutated to Serine (Ser) to detect the Cys that contribute to VDE activity. 12 mutations were found with decreased VDE activity. The function of the region between the N-terminal domain and the lipocalin domain was investigated by expression of the peptide before and after the linker region in different lengths combination and followed activity measurement. The results showed that the two independent domains lost majority of activity and N-terminal part of linker region was more important for activity. An experiment was set up to analyze the function of C-terminal by measuring the activity of VDE after cleaving different length of C-terminal. The result showed different degrees of activity loss that was caused by removal of different lengths of the C-terminal. A number of experiments suggests that VDE acts as a dimer that is formed at low pH. These experiments will contribute to further research of the function and structure of VDE.Popular Science Summary There is a saying that the sun supports the life living on earth. In general, the sunlight supports plants living, and plants become the base of almost all forms of ecosystems. A reaction called photosynthesis exists in all kinds of plants and is the foundation of usage of sunlight energy. In the photosynthesis process, energy in the sunlight converted into the energy stored in plants, the latter is used in various kinds of biochemical reactions. And during photosynthesis, oxygen is released into the environment and supports the metabolism of all living things. In the photosynthesis process, sunlight energy is gathered by a complex called light harvesting system, and excites chlorophyll, a molecule absorbs light. The excited chlorophyll continues to transfer the energy to the following photochemical reactions. In nature, the intensity of the sunlight is changing all the time. Sometimes, plants receive more sunlight energy than they need for the biochemical reactions in photosynthesis, that means not all excited chlorophyll are in use. And excited chlorophyll will dissipate its energy and return to the ground-energy state. The release of energy can form reactive oxygen species, a molecule that is harmful to plants cells. To prevent the formation of oxidative species, plants have evolved some other ways to release the energy in the excited chlorophyll. One typical way of de-excitation of excited chlorophyll is called non-photochemical quenching; it dissipates the energy into heat. Our research is mainly about an enzyme which is important to the major component of the non-photochemical quenching in higher plants. The enzyme is called violaxanthin de-epoxidase (VDE). VDE converts violaxanthin (a chain-structure pigment which contains two epoxy groups) to zeaxanthin (a chain-structure pigment without the two epoxy groups). And zeaxanthin is believed to quench the excited chlorophyll. Our research of VDE is to investigate the structure and function of VDE by using molecular and biochemistry methods. We produce different parts of the VDE molecule and we change cysteines (one kind of amino acid which can form covalent bond to each other) in VDE into another amino acid. We measure the activity of the protein we produced. We found that cysteines are important for VDE activity. Another discovery of ours is that the VDE molecule gives its activity only when two VDE molecules contact to each other in low pH, and this contact is influenced by the end part of VDE. We also found that VDE consists of two independent functional parts; each part can form its own structure independently. We believe our discoveries may contribute to the further functional and structural research of VDE

Neutrino mixing in the seesaw model

In the seesaw model with hierarchical Dirac masses, the neutrino mixing angle exhibits the behavior of a narrow resonance. In general, the angle is strongly suppressed, but it can be maximal for special parameter values. We delineate the small regions in which this happens, for the two flavor problem. On the other hand, the physical neutrino masses are hierarchical, in general, except in a large part of the region in which the mixing angle is sizable, where they are nearly degenerate. Our general analysis is also applicable to the RGE of neutrino mass matrix, where we find analytic solutions for the running of physical parameters, in addition to a complex RGE invariant relating them. It is also shown that, if one mixing angle is small, the three neutrino problem reduces to two, two flavor problems.Comment: 19 pages, 4 figures; added new sections on RGE effects and universal seesaw; version to appear in EPJ

Plane-projection multi-photon microscopy for high-frame-rate Live Tissue Imaging

We present a wide-field multi-photon microscopy that provides optical sectioning at high frame rate under biocompatible laser dosage. Axial resolution comparable to confocal microscopy and 5-frame-per-second live tissue imaging are demonstrated

Classification and Application of Triangular Quark Mass Matrices

The hierarchical structure in the quark masses and mixings allows its ten physical parameters to be most conveniently encoded in mass matrices of the upper triangular form. We classify these matrices in the hierarchical, minimal parameter basis where the mismatch between the weak and mass eigenstates involves only small mixing angles. Ten such pairs are obtained for the up and down quarks. This analysis can be used to classify texture zeros of general mass matrices. For hermitian mass matrices with five texture zeros, this method yields immediately five pairs of textures with simple, analytic predictions for the quark mixings. Comparison with data indicates that, of the five pairs, three are disfavored, one is marginally acceptable, while the fifth fits well.Comment: 18 pages, ReVTe

Renormalization of the neutrino mass matrix

The renormalization group equations for the general 2 by 2, complex, neutrino mass matrix are shown to have exact, analytic solutions. Simple formulas are given for the physical mixing angle, complex phase and mass ratio in terms of their initial values and the energy scales. We also establish a (complex) renormalization invariant relating these parameters. The qualitative features of the physical parameters' renormalization are clearly illustrated in vector field plots. In both the SM and MSSM, maximal mixing is a saddle point.Comment: 16 pages, 5 figure

Identification of osteopontin-dependent signaling pathways in a mouse model of human breast cancer

<p>Abstract</p> <p>Background</p> <p>Osteopontin (OPN) is a secreted phosphoprotein which functions as a cell attachment protein and cytokine that signals through two cell adhesion molecules, α_vβ₃-integrin and CD44, to regulate cancer growth and metastasis. However, the signaling pathways associated with OPN have not been extensively characterized. In an in vivo xenograft model of MDA-MB-231 human breast cancer, we have previously demonstrated that ablation of circulating OPN with an RNA aptamer blocks interaction with its cell surface receptors to significantly inhibit adhesion, migration and invasion in vitro and local progression and distant metastases.</p> <p>Findings</p> <p>In this study, we performed microarray analysis to compare the transcriptomes of primary tumor in the presence and absence of aptamer ablation of OPN. The results were corroborated with RT-PCR and Western blot analysis. Our results demonstrate that ablation of OPN cell surface receptor binding is associated with significant alteration in gene and protein expression critical in apoptosis, vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF), interleukin-10 (IL-10), granulocyte-macrophage colony stimulating factor (GM-CSF) and proliferation signaling pathways. Many of these proteins have not been previously associated with OPN.</p> <p>Conclusion</p> <p>We conclude that secreted OPN regulates multiple signaling pathways critical for local tumor progression.</p