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Institute
Vertebrate life depends on renal function to filter excess fluid and remove low-molecular-weight waste products. An essential component of the kidney filtration barrier is the slit diaphragm (SD), a specialized cell-cell junction between podocytes. Although the constituents of the SD are largely known, its molecular organization remains elusive. Here, we use super-resolution correlative light and electron microscopy to quantify a linear rate of reduction in albumin concentration across the filtration barrier under no-flow conditions. Next, we use cryo-electron tomography of vitreous lamellae from high-pressure frozen native glomeruli to analyze the molecular architecture of the SD. The resulting densities resemble a fishnet pattern. Fitting of Nephrin and Neph1, the main constituents of the SD, results in a complex interaction pattern with multiple contact sites between the molecules. Using molecular dynamics simulations, we construct a blueprint of the SD that explains its molecular architecture. Our architectural understanding of the SD reconciles previous findings and provides a mechanistic framework for the development of novel therapies to treat kidney dysfunction.
Vertebrate life depends on renal function to filter excess fluid and remove low-molecular-weight waste products. An essential component of the kidney filtration barrier is the slit diaphragm (SD), a specialized cell-cell junction between podocytes. Although the constituents of the SD are largely known, its molecular organization remains elusive. Here, we use super-resolution correlative light and electron microscopy to quantify a linear rate of reduction in albumin concentration across the filtration barrier. Next, we use cryo-electron tomography of vitreous lamellae from high-pressure frozen native glomeruli to analyze the molecular architecture of the SD. The resulting densities resemble a fishnet pattern. Fitting of Nephrin and Neph1, the main constituents of the SD, results in a complex interaction pattern with multiple contact sites between the molecules. Using molecular dynamics flexible fitting, we construct a blueprint of the SD, where we describe all interactions. Our architectural understanding of the SD reconciles previous findings and provides a mechanistic framework for the development of novel therapies to treat kidney dysfunction.
In this thesis, we present a detailed consideration of both qualitative and quantitative properties of static spherically symmetric solutions of the Einstein equations with self-interacting scalar fields. Our focus is on solutions with naked singularities. We study the qualitative properties of the solutions of the Einstein equations with real static self-interacting $N$ scalar fields, making some assumptions on self-interaction. We provide a rigorous proof that the corresponding solutions will be regular up to $r=0$. Furthermore, we find the rigorous form of asymptotic solutions near the singularity and at spatial infinity. We construct some examples of spherical-like naked singularities at $r=r_s\neq0$ in curvature coordinates.
We analyze the stability of the previously considered solutions against odd-parity gravitational perturbations and also examine the fundamental quasi-normal modes spectra. For the general class of the self-interaction potential, we demonstrate well-posedness of the initial problem and stability for positively defined potentials. As an example, we numerically study the case of the scalar field with power-law self-interaction potential and find the fundamental quasi-normal modes frequencies. We demonstrate that they differ from the standard Schwarzschild black hole case.
We study in detail the motion of particles in the vicinity of previously considered solutions. Mainly, we are interested in considering properties of the distribution of stable circular orbits around the corresponding configurations and images of the accretion disk for a distant observer. For all cases, we find possible types of stable circular orbit distributions and domains of parameters where they are realized.
We also demonstrate that the presence of self-interaction can lead to a new type of circular orbit distributions, which is absent in the linear massless scalar field case. We build Keplerian disk images in the plane of a distant observer and demonstrate the possibility to mimic the shadows of black holes.
An elementary derivation of the optical potential for high energies is given. For the determination of the optical potential only the knowledge of the scattering amplitude for free nucleons and of the autocorrelation function for density fluctuations is necessary. The numerical calculation of the real- and imaginary part of the optical potential was performed using the Tabakin potential.
The convergence of the eigenchannel (EK) and R-matrix (RM) theories - depending on their free parameters - is numerically investigated by comparing with a simple, analytically solvable model. The comparison shows that the results of the EK-theory are in general closer to the exact solution than those of the RM-theory. Especially in regions of sharp resonances the dependence of the expansion of the wave functions on the interaction radius ac and on the boundary condition Bc is very strong in the RM-theory and one needs very many levels to achieve good results.
Bei der UV-Bestrahlung (2537 Å) des Zn-Insulins beobachtet man für kleinere Dosen (bis 10 Einstein/Mol) eine direkte Korrelation zwischen der Inaktivierung und der Photoreduktion einer der drei Disulfidbrücken. Mit steigender Dosis wird die Quantenausbeute für die Reduktion der Disulfidbrücken (Bildung von SH-Gruppen) sehr klein, dagegen führen dann andere Prozesse zunehmend zur photochemischen Zerstörung der Disulfidbrücken. Für größere Strahlendosen (über 100 Einstein/Mol) ergibt die Extrapolation, daß für die völlige Inaktivierung des Insulins sämtliche drei Cystinreste zerstört werden müssen. Von den übrigen Aminosäuren wird durch Dosen um 100 Einstein/Mol nur der Tyrosin-Anteil signifikant vermindert. Mit steigender Strahlendosis ändert sich — wahrscheinlich infolge von Konformationsänderungen der Polypeptidketten — die Photosensibilität der Aminosäuren.
The anion transport protein of the human erythrocyte membrane, band 3, was solubilized and purified in solutions of the non-ionic detergent nonaethylene glycol lauryl ether and then reconstituted in spherical egg phosphatidylcholine bilayers as described earlier (U. Scheuring, K. Kollewe, W. Haase, and D. Schubert, J. Membrane Biol. 90, 123-135 (1986)). The resulting paucilamellar proteoliposom es of average diameter 70 nm were transformed into smaller vesicles by French press treatment and fractionated according to size by gel filtration. The smallest protein-containing liposomes obtained had diameters around 32 nm; still smaller vesicles were free of protein. All proteoliposome samples studied showed a rapid sulfate efflux which was sensitive to specific inhibitors of band 3-mediated anion exchange. In addition, the orientation of the transport protein in the vesicle membranes was found to be “right-side-out” in all samples. This suggests that the orientation of the protein in the vesicle membranes is dictated by the shape of the protein’s intramembrane domain and that this domain has the form of a truncated cone or pyramid.
Motivated by recent reports of a quantum-disordered ground state in the triangular lattice compound NaRuO2, we derive a jeff = 1/2 magnetic model for this system by means of first-principles calculations. The pseudospin Hamiltonian is dominated by bond-dependent off-diagonal Γ interactions, complemented by a ferromagnetic Heisenberg exchange and a notably antiferromagnetic Kitaev term. In addition to bilinear interactions, we find a sizable four-spin ring exchange contribution with a strongly anisotropic character, which has been so far overlooked when modeling Kitaev materials. The analysis of the magnetic model, based on the minimization of the classical energy and exact diagonalization of the quantum Hamiltonian, points toward the existence of a rather robust easy-plane ferromagnetic order, which cannot be easily destabilized by physically relevant perturbations.
Continued advances in quantum technologies rely on producing nanometer-scale wires. Although several state-of-the-art nanolithographic technologies and bottom-up synthesis processes have been used to engineer these wires, critical challenges remain in growing uniform atomic-scale crystalline wires and constructing their network structures. Here, we discover a simple method to fabricate atomic-scale wires with various arrangements, including stripes, X-junctions, Y-junctions, and nanorings. Single-crystalline atomic-scale wires of a Mott insulator, whose bandgap is comparable to those of wide-gap semiconductors, are spontaneously grown on graphite substrates by pulsed-laser deposition. These wires are one unit cell thick and have an exact width of two and four unit cells (1.4 and 2.8 nm) and lengths up to a few micrometers. We show that the nonequilibrium reaction-diffusion processes may play an essential role in atomic pattern formation. Our findings offer a previously unknown perspective on the nonequilibrium self-organization phenomena on an atomic scale, paving a unique way for the quantum architecture of nano-network.