Two-jet production inp\bar p collisions

The production of two quark/gluon jets in \(p\bar p\) collisions is analyzed. We determine the cross section dependence on the transverse momentum, the rapidities, and on the two-jet invariant mass, and we evaluate the sensitivity of the results on the theoretical input assumptions and the experimental cuts. We extrapolate these results into the TeV energy region.     

Un substrat pour le dosage chimique de la rénine

A fluorogenic renin substrate, N-CBO-L -prolyl-L -phenylalanyl-L -histidyl-L -leucyl-L -leucyl-L -valyl-L -tyrosyl-L -seryl-β-naphthylamide, has been synthesized. Upon incubation at pH 5,6 with renin and an excess of the auxiliary enzyme aminopeptidase M, it gives rise to β-naphthylamine at a rate related to the quantity of renin.     

NMR spectra of a microcrystalline protein at 30 kHz MAS

Proteins are not always available in amounts desirable for solid-state magic-angle spinning (MAS) nuclear-magnetic resonance (NMR) spectroscopy. To maximize the signal-to-noise ratio achievable with small samples, the filling factor must be optimized by using small-diameter MAS rotors. These rotors have the added benefit of allowing higher radio frequency field amplitudes during polarization transfer steps and during decoupling periods as well as allowing higher spinning frequencies. We demonstrate the advantages of relatively fast MAS (30 kHz using a 2.5 mm rotor) compared to MAS at 12 kHz for the 10.4 kDa model protein Crh with 93 residues and show that the signal-to-noise ratio in two-dimensional correlation spectra can be significantly improved by taking advantage of optimized pulse sequences available with rapid MAS.     

ψψ production at collider energies

We estimate ψψ production at collider energies in the framework of perturbative QCD. TheO(α _s ² )?(α _s ⁴ ) parton cross-sections, with the non-relativistic approximation for the heavy quark bound states, are used. This first insight into the characteristics of the kinematical distributions allows predictions on the predominance of the quark, gluon orB meson production mechanisms in particular kinematical regions.     

On theQ 2-extrapolations of AF-corrected Drell-Yan processes

TheQ ²-dependence of the integrated Drell-Yan cross sections with asymptotic freedom (AF) corrections is investigated forQ ²≦ 10⁷ GeV². Existing AF-parametrizations lead to widely differing predictions. Lowest order QCD indicates a strong dependence on thex-behaviour of the input momentum distributions (atQ ²=Q ₀ ² ) which for sea quarks and gluons are guesses. Consequently, AF-corrected Drell-Yan extrapolations toW-energies and beyond involve considerable uncertainties.     

Pharmacomodulation of a ligand targeting the HBV capsid hydrophobic pocket

Hepatitis B virus (HBV) is a small enveloped retrotranscribing DNA virus and an important human pathogen. Its capsid-forming core protein (Cp) features a hydrophobic pocket proposed to be central notably in capsid envelopment. Indeed, mutations in and around this pocket can profoundly modulate, and even abolish, secretion of enveloped virions. We have recently shown that Triton X-100, a detergent used during Cp purification, binds to the hydrophobic pocket with micromolar affinity. We here performed pharmacomodulation of pocket binders through systematic modifications of the three distinct chemical moieties composing the Triton X-100 molecule. Using NMR and ITC, we found that the flat aromatic moiety is essential for binding, while the number of atoms of the aliphatic chain modulates binding affinity. The hydrophilic tail, in contrast, is highly tolerant to changes in both length and type. Our data provide essential information for designing a new class of HBV antivirals targeting capsid–envelope interactions.

Small-molecule binding to the Hepatitis B virus core protein hydrophobic pocket, a possible strategy for targeting viral particle assembly.     

Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

Background  

In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types.     

The influence of nitrogen-15 proton-driven spin diffusion on the measurement of nitrogen-15 longitudinal relaxation times

The effect of nitrogen-15 proton-driven spin diffusion on quantitative (15)N T(1) measurements in solid proteins is investigated, and the impact on the measurement of dynamic parameters is assessed. A simple model of exchange between neighboring nitrogens is used to reproduce the evolution of (15)N spin systems whose longitudinal relaxation rates and exchange rates are compatible with experimental measurements. We show that the induced error in the measured T(1) and its effect on the determination of dynamics parameters is likely to be less than the current experimental error. The use of deuterated protein samples is shown to have a small but sometimes visible effect, and may also considerably slow down or even suppress the exchange of magnetization due to spin diffusion.