Partonic structure of pi and rho mesons from data on hard (semi)exclusive production of two pions off nucleon

We fitted the pi-pi mass distribution in the range 0.5 < mpipi < 1.1 GeV measured in hard exclusive positron-proton reactions at HERA by the form dictated by QCD at leading twist level. Extracted parameters are related to valence quark distribution in the pion, and to the pion and rho meson distribution amplitudes. We obtain, for the first time, a measurement of the second Gegenbauer coefficient of the rho meson distribution amplitude: $a_2^{(\rho)}= -0.10\pm 0.20$ for a photon virtuality of =21.2 GeV^2.Comment: 12 pages, two figures. References and discussion are adde

Hunting the QCD-Odderon in hard diffractive electroproduction of two pions

Charge asymmetries in diffractive electroproduction of two mesons are proportional to the interference of Pomeron and Odderon exchange amplitudes. We calculate in the framework of QCD and in the Born approximation a forward-backward charge asymmetry which turns out to be sizable in a kinematical domain accessible to HERA experiments. We predict a distinctive dependence of this asymmetry on the invariant mass of the two pions. Testing this prediction is a crucial step in the discovery of the QCD-Odderon.Comment: 13 pages LATEX, 6 .eps figures, numerical error corrected, new figures,main conclusions not change

Spin effects in diffractive QQˉ Q \bar Q production at BNL eRHIC

We discuss quark-antiquark leptoproduction within a QCD two-gluon exchange model at small $x$. The double spin asymmetries for longitudinally polarized leptons and transversely polarized protons in diffractive $Q \bar Q$ production are analysed at eRHIC energies. The predicted $A_{lT}$ asymmetry is large and can be used to obtain information on the polarized generalized gluon distributions in the proton.Comment: Some modifications of the text and graphs were done. Title is modified slightly. To be published in Phys. Rev.

Exclusive rho^0 muoproduction on transversely polarised protons and deuterons

The transverse target spin azimuthal asymmetry A_UT in hard exclusive production of rho^0 mesons was measured at COMPASS by scattering 160 GeV/c muons off transversely polarised protons and deuterons. The measured asymmetry is sensitive to the nucleon helicity-flip generalised parton distributions E^q, which are related to the orbital angular momentum of quarks in the nucleon. The Q^2, x_B and p_t^2 dependence of A_UT is presented in a wide kinematic range. Results for deuterons are obtained for the first time. The measured asymmetry is small in the whole kinematic range for both protons and deuterons, which is consistent with the theoretical interpretation that contributions from GPDs E^u and E^d approximately cancel.Comment: 20 pages, 9 figures and 4 tables, updated author lis

Double spin asymmetry in exclusive rho^0 muoproduction at COMPASS

The longitudinal double spin asymmetry A_1^rho for exclusive leptoproduction of rho^0 mesons, mu + N -> mu + N + rho, is studied using the COMPASS 2002 and 2003 data. The measured reaction is incoherent exclusive rho^0 production on polarised deuterons. The Q^2 and x dependence of A_1^rho is presented in a wide kinematical range: 3x10^-3 < Q^2 < 7 (GeV/c)^2 and 5x10^-5 < x < 0.05. The presented results are the first measurements of A_1^rho at small Q2 (Q2 < 0.1 (GeV/c)^2) and small x (x < 3x10^-3). The asymmetry is in general compatible with zero in the whole kinematical range.Comment: 6 Figures, 15 pages, version 2 with updated author list, technical latex problem fixe

Coupling of boswellic acid-induced Ca(2+) mobilisation and MAPK activation to lipid metabolism and peroxide formation in human leucocytes

1. We have previously shown that 11-keto boswellic acids (11-keto-BAs), the active principles of Boswellia serrata gum resins, activate p38 MAPK and p42/44(MAPK) and stimulate Ca(2+) mobilisation in human polymorphonuclear leucocytes (PMNL). 2. In this study, we attempted to connect the activation of MAPK and mobilisation of Ca(2+) to functional responses of PMNL, including the formation of reactive oxygen species (ROS), release of arachidonic acid (AA), and leukotriene (LT) biosynthesis. 3. We found that, in PMNL, 11-keto-BAs stimulate the formation of ROS and cause release of AA as well as its transformation to LTs via 5-lipoxygenase. 4. Based on inhibitor studies, 11-keto-BA-induced ROS formation is Ca(2+)-dependent and is mediated by NADPH oxidase involving PI 3-K and p42/44(MAPK) signalling pathways. Also, the release of AA depends on Ca(2+) and p42/44(MAPK), whereas the pathways stimulating 5-LO are not readily apparent. 5. Pertussis toxin, which inactivates G(i/0) protein subunits, prevents MAPK activation and Ca(2+) mobilisation induced by 11-keto-BAs, implying the involvement of a G(i/0) protein in BA signalling. 6. Expanding studies on differentiated haematopoietic cell lines (HL60, Mono Mac 6, BL41-E-95-A) demonstrate that the ability of BAs to activate MAPK and to mobilise Ca(2+) may depend on the cell type or the differentiation status. 7. In summary, we conclude that BAs act via G(i/0) protein(s) stimulating signalling pathways that control functional leucocyte responses, in a similar way as chemoattractants, that is, N-formyl-methionyl-leucyl-phenylalanine or platelet-activating factor

Inhibition of Heterotrimeric G Protein Signaling by a Small Molecule Acting on Gα Subunit

The simultaneous activation of many distinct G protein-coupled receptors (GPCRs) and heterotrimeric G proteins play a major role in various pathological conditions. Pan-inhibition of GPCR signaling by small molecules thus represents a novel strategy to treat various diseases. To better understand such therapeutic approach, we have characterized the biomolecular target of BIM-46187, a small molecule pan-inhibitor of GPCR signaling. Combining bioluminescence and fluorescence resonance energy transfer techniques in living cells as well as in reconstituted receptor-G protein complexes, we observed that, by direct binding to the Gα subunit, BIM-46187 prevents the conformational changes of the receptor-G protein complex associated with GPCR activation. Such a binding prevents the proper interaction of receptors with the G protein heterotrimer and inhibits the agonist-promoted GDP/GTP exchange. These observations bring further evidence that inhibiting G protein activation through direct binding to the Gα subunit is feasible and should constitute a new strategy for therapeutic intervention