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Nonthermal Mg I Emission At 12 Micron From Procyon
We report on stellar Mg i emission at 12 mu m from alpha CMi (Procyon), a star slightly hotter than the Sun. Solar Mg i emission is well known, and its formation was successfully explained in detail by Carlsson et al. Here, for the first time, we successfully model and compare synthetic spectra of the emission lines at 12 mu m with observations of a star other than the Sun. The use of these lines as stellar diagnostics has been anticipated for 10 years or more (see, e.g., Carlsson et al.). We find that the model reproduces the observed emission in Procyon quite well. We expect that high-resolution spectrographs on 8-10 m telescopes will finally be able to exploit these new diagnostics.Swedish Research Councils VRSTINTNSF AST 03-07497Texas Advanced Research ProgramAstronom
G-quadruplexes and G-quadruplex ligands: targets and tools in antiviral therapy
G-quadruplexes (G4s) are non-canonical nucleic acids secondary structures that form within guanine-rich strands of regulatory genomic regions. G4s have been extensively described in the human genome, especially in telomeres and oncogene promoters; in recent years the presence of G4s in viruses has attracted increasing interest. Indeed, G4s have been reported in several viruses, including those involved in recent epidemics, such as the Zika and Ebola viruses. Viral G4s are usually located in regulatory regions of the genome and implicated in the control of key viral processes; in some cases, they have been involved also in viral latency. In this context, G4 ligands have been developed and tested both as tools to study the complexity of G4-mediated mechanisms in the viral life cycle, and as therapeutic agents. In general, G4 ligands showed promising antiviral activity, with G4-mediated mechanisms of action both at the genome and transcript level. This review aims to provide an updated close-up of the literature on G4s in viruses. The current state of the art of G4 ligands in antiviral research is also reported, with particular focus on the structural and physicochemical requirements for optimal biological activity. The achievements and the to-dos in the field are discussed
Highly Improved Electrospray Ionization-Mass Spectrometry Detection of G-Quadruplex-Folded Oligonucleotides and Their Complexes with Small Molecules
G-quadruplexes are nucleic acids structures stabilized by physiological concentration of potassium ions. Because low stability G-quadruplexes are hardly detectable by mass spectrometry, we optimized solvent conditions: isopropanol in a triethylamine/hexafluoroisopropanol mixture highly increased G-quadruplex sensitivity with no modification of the physiological G-quadruplex conformation. G-quadruplexes/G-quadruplex-ligand complexes were also correctly detected at concentration as low as 40 nM. Detection of the physiological conformation of G4s and their complexes opens up the possibility to perform high-throughput screening of G-quadruplex ligands for the development of drug molecules effective against critical human diseases
Discrete symmetries from hidden sectors
We study the presence of abelian discrete symmetries in globally consistent
orientifold compactifications based on rational conformal field theory. We
extend previous work [1] by allowing the discrete symmetries to be a linear
combination of U(1) gauge factors of the visible as well as the hidden sector.
This more general ansatz significantly increases the probability of finding a
discrete symmetry in the low energy effective action. Applied to globally
consistent MSSM-like Gepner constructions we find multiple models that allow
for matter parity or Baryon triality.Comment: 20 page
Frustrated spin ladder with alternating spin-1 and spin-1/2 rungs
We study the impact of the diagonal frustrating couplings on the quantum
phase diagram of a two-leg ladder composed of alternating spin-1 and spin-1/2
rungs. As the coupling strength is increased the system successively exhibits
two gapped paramagnetic phases (a rung-singlet and a Haldane-like
non-degenerate states) and two ferrimagnetic phases with different
ferromagnetic moments per rung. The first two states are similar to the phases
studied in the frustrated spin-1/2 ladder, whereas the magnetic phases appear
as a result of the mixed-spin structure of the model. A detailed
characterization of these phases is presented using density-matrix
renormalization-group calculations, exact diagonalizations of periodic
clusters, and an effective Hamiltonian approach inspired by the analysis of
numerical data. The present theoretical study was motivated by the recent
synthesis of the quasi-one-dimensional ferrimagnetic material
FeFe (trans-1,4-cyclohexanedicarboxylate) exhibiting a similar
ladder structure.Comment: 10 pages, 8 figure
Preparation and photoemission investigation of bulk-like a-Mn films on W(110)
We report the successful stabilization of a thick bulk-like, distorted
-Mn film with (110) orientation on a W(110) substrate. The observed
overstructure for the Mn film with respect to the original W(110)
low-energy electron diffraction pattern is consistent with the presented
structure model. The possibility to stabilize such a pseudomorphic Mn film is
supported by density functional total energy calculations. Angle-resolved
photoemission spectra of the stabilized -Mn(110) film show weak
dispersions of the valence band electronic states in accordance with the large
unit cell.Comment: 11 pages; 5 figure
CaII and NaI absorption signatures from the circumgalactic gas of the Milky Way
We combine CaII/NaI absorption and HI 21 cm emission line measurements to
analyse the metal abundances, the distribution, the small-scale structure, and
the physical conditions of intermediate- and high-velocity gas in the Galactic
halo.Comment: 2 pages, 1 figure, to appear in proceeding of "Galaxies in the Local
Volume" Sydney 8-13 July 200
Surface Plasmon Resonance kinetic analysis of the interaction between G-quadruplex nucleic acids and an anti-G-quadruplex monoclonal antibody
Background
G-quadruplexes (G4s) are nucleic acids secondary structures formed in guanine-rich sequences. Anti-G4 antibodies represent a tool for the direct investigation of G4s in cells. Surface Plasmon Resonance (SPR) is a highly sensitive technology, suitable for assessing the affinity between biomolecules. We here aimed at improving the orientation of an anti-G4 antibody on the SPR sensor chip to optimize detection of binding antigens.
Methods
SPR was employed to characterize the anti-G4 antibody interaction with G4 and non-G4 oligonucleotides. Dextran-functionalized sensor chips were used both in covalent coupling and capturing procedures.
Results
The use of two leading molecule for orienting the antibody of interest allowed to improve its activity from completely non-functional to 65% active. The specificity of the anti-G4 antobody for G4 structures could thus be assessed with high sensitivity and reliability.
Conclusions
Optimization of the immobilization protocol for SPR biosensing, allowed us to determine the anti-G4 antibody affinity and specificity for G4 antigens with higher sensitivity with respect to other in vitro assays such as ELISA. Anti-G4 antibody specificity is a fundamental assumption for the future utilization of this kind of antibodies for monitoring G4s directly in cells.
General significance
The heterogeneous orientation of amine-coupling immobilized ligands is a general problem that often leads to partial or complete inactivation of the molecules. Here we describe a new strategy for improving ligand orientation: driving it from two sides. This principle can be virtually applied to every molecule that loses its activity or is poorly immobilized after standard coupling to the SPR chip surface
Magnetic phase diagram of a frustrated ferrimagnetic ladder: Relation to the one-dimensional boson Hubbard model
We study the magnetic phase diagram of two coupled mixed-spin
Heisenberg chains as a function of the frustration parameter related to
diagonal exchange couplings. The analysis is performed by using spin-wave
series and exact numerical diagonalization techniques. The obtained phase
diagram--containing the Luttinger liquid phase, the plateau phase with a
magnetization per rung , and the fully polarized phase--is closely
related to the generic phase diagram of the one-dimensional boson
Hubbard model.Comment: 4 pages, 2 figure
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