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Search Results: 1 - 10 of 2601 matches for " Ralf Jockers "
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Biological Significance of GPCR Heteromerization in the Neuro-Endocrine System
Ralf Jockers
Frontiers in Endocrinology , 2011, DOI: 10.3389/fendo.2011.00002
Abstract: Clustering of proteins in higher order complexes is a common theme in biology and profoundly influences protein function. The idea that seven-transmembrane spanning G protein-coupled receptors (GPCRs) might form dimers or higher order oligomeric complexes has been formulated more than 20 years ago. Since then, this phenomenon has been investigated with many different biochemical and biophysical techniques. The more recent notion of GPCR heteromerization describes the specific association of two different GPCRs. GPCR heteromerization may be of primary importance in neuroendocrinology, as this may explain at least some of the functional crosstalks described between different hormonal systems. Importantly, many GPCR heteromers have distinct functional properties compared to their corresponding homomers. Heteromer-specific pharmacological profiles might be exploited for drug design and open new therapeutic options. GPCR heteromerization has been first studied in heterologous expression systems. Today, increasing evidence for the existence of GPCR heteromers in endogenous systems is emerging providing crucial evidence for the physiological function of GPCR heteromerization.
Challenges for Cellular Endocrinology: Improving the Detection Methods and Closing the Gap between in Vitro and in Vivo Observations
Ralf Jockers
Frontiers in Endocrinology , 2010, DOI: 10.3389/fendo.2010.00003
Frontiers Commentary on Tallet et al. Investigation of Prolactin Receptor Activation and Blockade Using Time-Resolved Fluorescence Resonance Energy Transfer
Ralf Jockers
Frontiers in Endocrinology , 2014, DOI: 10.3389/fendo.2014.00088
Comment on “The Use of BRET to Study Receptor-Protein Interactions”
Ralf Jockers
Frontiers in Endocrinology , 2014, DOI: 10.3389/fendo.2014.00003
Expanding the Concept of G Protein-Coupled Receptor (GPCR) Dimer Asymmetry towards GPCR-Interacting Proteins
Maud Kamal,Pascal Maurice,Ralf Jockers
Pharmaceuticals , 2011, DOI: 10.3390/ph4020273
Abstract: G protein-coupled receptors (GPCRs), major targets of drug discovery, are organized in dimeric and/or oligomeric clusters. The minimal oligomeric unit, the dimer, is composed of two protomers, which can behave differently within the dimer. Several examples of GPCR asymmetry within dimers at the level of ligand binding, ligand-promoted conformational changes, conformational changes within transmembrane domains, G protein coupling, and most recently GPCR-interacting proteins (GIPs), have been reported in the literature. Asymmetric organization of GPCR dimers has important implications on GPCR function and drug design. Indeed, the extension of the “asymmetry concept” to GIPs adds a new level of specific therapeutic intervention.
A note on colored HOMFLY polynomials for hyperbolic knots from WZW models
Jie Gu,Hans Jockers
Mathematics , 2014, DOI: 10.1007/s00220-015-2322-z
Abstract: Using the correspondence between Chern-Simons theories and Wess-Zumino-Witten models we present the necessary tools to calculate colored HOMFLY polynomials for hyperbolic knots. For two-bridge hyperbolic knots we derive the colored HOMFLY invariants in terms of crossing matrices of the underlying Wess-Zumino-Witten model. Our analysis extends previous works by incorporating non-trivial multiplicities for the primaries appearing in the crossing matrices, so as to describe colorings of HOMFLY invariants beyond the totally symmetric or anti-symmetric representations of SU(N). The crossing matrices directly relate to 6j-symbols of the quantum group U_q(su(N)). We present powerful methods to calculate such quantum 6j-symbols for general N. This allows us to determine previously unknown colored HOMFLY polynomials for two-bridge hyperbolic knots. We give explicitly the HOMFLY polynomials colored by the representation {2,1} for two-bridge hyperbolic knots with up to eight crossings. Yet, the scope of application of our techniques goes beyond knot theory; e.g., our findings can be used to study correlators in Wess-Zumino-Witten conformal field theories or -- in the limit to classical groups -- to determine color factors for Yang Mills amplitudes.
Effective superpotentials for compact D5-brane Calabi-Yau geometries
Hans Jockers,Masoud Soroush
Mathematics , 2008, DOI: 10.1007/s00220-008-0727-7
Abstract: For compact Calabi-Yau geometries with D5-branes we study N=1 effective superpotentials depending on both open- and closed-string fields. We develop methods to derive the open/closed Picard-Fuchs differential equations, which control D5-brane deformations as well as complex structure deformations of the compact Calabi-Yau space. Their solutions encode the flat open/closed coordinates and the effective superpotential. For two explicit examples of compact D5-brane Calabi-Yau hypersurface geometries we apply our techniques and express the calculated superpotentials in terms of flat open/closed coordinates. By evaluating these superpotentials at their critical points we reproduce the domain wall tensions that have recently appeared in the literature. Finally we extract orbifold disk invariants from the superpotentials, which, up to overall numerical normalizations, correspond to orbifold disk Gromov-Witten invariants in the mirror geometry.
Dual Pairs of Gauged Linear Sigma Models and Derived Equivalences of Calabi-Yau threefolds
Andreas Gerhardus,Hans Jockers
Mathematics , 2015,
Abstract: In this work we study the phase structure of skew symplectic sigma models, which are a certain class of two-dimensional N = (2,2) non-Abelian gauged linear sigma models. At low energies some of them flow to non-linear sigma models with Calabi-Yau target spaces, which emerge from non-Abelian strong coupling dynamics. The observed phase structure results in a non-trivial duality proposal among skew symplectic sigma models and connects non-complete intersection Calabi-Yau threefolds, that are non-birational among another, in a common quantum Kahler moduli space. As a consequence we find non-trivial identifications of spectra of topological B-branes, which from a modern algebraic geometry perspective imply derived equivalences among Calabi-Yau varieties. To further support our proposals, we calculate the two sphere partition function of skew symplectic sigma models to determine geometric invariants, which confirm the anticipated Calabi-Yau threefold phases. We show that the two sphere partition functions of a pair of dual skew symplectic sigma models agree in a non-trivial fashion. To carry out these calculations, we develop a systematic approach to study higher-dimensional Mellin-Barnes type integrals. In particular, these techniques admit the evaluation of two sphere partition functions for gauged linear sigma models with higher rank gauge groups, but are applicable in other contexts as well.
Trends of Abundance of Salton Sea Fish: A Reversible Collapse or a Permanent Condition?  [PDF]
Ralf Riedel
Natural Resources (NR) , 2016, DOI: 10.4236/nr.2016.710045
Abstract: The Salton Sea is a closed-basin, 980 km2 salt lake in the Sonoran Desert of southern California. Three marine species, bairdiella (Bairdiella icistia), orangemouth corvina (Cynoscion xanthulus), and sargo (Anisotremus davidsoni), established from introductions of over 34 species beginning in 1929. During the late 1960s and early 1970s, a hybrid tilapia (Oreochromis mossambicus × O. urolepis hornorum) invaded the Salton Sea and became dominant by number and weight. Recent surveys show a precipitous decline of all four species above starting sometime between 2001 and 2002. Declines were more evident in nearshore than in estuarine habitats. Corvina has probably declined the soonest, followed by Gulf croaker. Tilapia declines were followed by more recent increases in population numbers. The tilapia rebound observed are probably only sustainable if a curb in Salton Sea salinity levels is realized. The marine species will likely need restocking to reach historic levels, if the salinity of the lake is managed at 40 gL1 or below. Restoration alternatives for the Salton Sea must take into consideration estuarine areas as essential fish habitats and fish refuge against high salinities.
D-Brane Monodromies, Derived Categories and Boundary Linear Sigma Models
Jacques Distler,Hans Jockers,Hyukjae Park
Physics , 2002,
Abstract: An important subclass of D-branes on a Calabi-Yau manifold, X, are in 1-1 correspondence with objects in D(X), the derived category of coherent sheaves on X. We study the action of the monodromies in Kaehler moduli space on these D-branes. We refine and extend a conjecture of Kontsevich about the form of one of the generators of these monodromies (the monodromy about the "conifold" locus) and show that one can do quite explicit calculations of the monodromy action in many examples. As one application, we verify a prediction of Mayr about the action of the monodromy about the Landau-Ginsburg locus of the quintic. Prompted by the result of this calculation, we propose a modification of the derived category which implements the physical requirement that the shift-by-6 functor should be the identity. Boundary Linear sigma-Models prove to be a very nice physical model of many of these derived category ideas, and we explain the correspondence between these two approaches
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