Baryon pairs production ine + e − annihilation at\sqrt s = 2.4 GeV

Search for baryon pairs production ine ⁺ e ^? annihilation at \(\sqrt s = 2386 MeV\) is reported. The data relate to a luminosity of 161 nb^?1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe ⁺ e ^? annihilation into \(\Lambda \bar \Lambda \) and ofe ⁺ e ^?→ \(p\bar p\) at this energy are presented. First observation of a goode ⁺ e ^?→ \(n\bar n\) candidate is reported and upper limits are given fore ⁺ e ^?→ \(n\bar n, \Lambda \bar \sum ^0 + c.c.\) and \(\Sigma ^0 \bar \Sigma ^0 \) .     

Neue Oxocuprate(I). Zur Kenntnis von Rb3Cu5O4 [1]

New Oxocuprates(I). On Rb₃Cu₅O₄ New obtained is Rb₃Cu₅O₄, powder as well as transparent single crystals greenish yellow. The monoclinic structur [P2₁/c, a = 9.886(1), b = 7.508(1), c = 14.401(2) Å, β = 106.85(7)°, Z = 4, four-circle diffractometer data, R = 10.6% for 1 453 hkl, MoKα] is characterized by spiralic chains ? O? Cu? O? Cu? parallel to [100], which are tied together by additional Cu⁺. Motifs of mutual adjunction, Effective Coordination Numbers, ECoN, and the Madelung Part of Lattice Energy, MAPLE, are calculated and discussed.     

Estimation of certain typical trigonometric sums encountered in radio physics

Conclusions Theorems proved in the paper provide the possibility of effective estimation of a broad class of trigonometric sums and may evidently be used in varicus fields of radio physics. Analogous estimates may also be obtained for the case when A(n)1.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 19, No. 4, pp. 615–621, April, 1976.     

Elucidating the intermolecular interactions within a desolvated protein-ligand complex. An experimental and computational study

The first detailed study of the intermolecular hydrogens bonds (H-bonds) within a desolvated, noncovalent protein-ligand complex is reported. Using both experimental and computational methods, the intermolecular H-bonds stabilizing protonated and deprotonated ions of a complex composed of a single chain fragment (scFv) of a monoclonal antibody and its native trisaccharide ligand, alphaGal[alphaAbe] alphaMan (1), are characterized. Using the blackbody infrared radiative dissociation-functional group replacement (BIRD/FGR) technique, three H-bond donor-acceptor pairs within the gaseous (scFv + 1)n+ ions are identified and quantified. Additional sites of interaction on the protein and ligand, for which the binding partner could not be elucidated, are also identified. Comparison of the gas-phase interaction maps with the crystal structure suggests that at least two of the specific H-bonds are conserved upon transfer of the complex from solution to the gas phase by electrospray ionization. However, new (nonspecific) interactions can also form in the gas phase. Notably, the nature and strength of the intermolecular interactions can vary significantly with charge state, and striking differences in the structures of the (scFv + 1)n+ and (scFv + 1)n- ions are evident. Intermolecular H-bonds are also identified from molecular dynamics (MD) simulations performed at the +8 and -8 charge states. Agreement is found for a majority of intermolecular interactions predicted for the (scFv + 1)8+ ion by the MD simulation and BIRD/FGR method; the agreement is less favorable in the case of the (scFv + 1)8- ion. However, both the computational and experimental results point to structural differences between the +8 and -8 ions. The computational results also provide insights into the structural changes that accompany the loss of interfacial waters from the complex.     

Optical phonon spectra of lutetium fluoride,oxyfluoride, and lutetium oxide nanoparticles

Nano-and microcrystalline LuF₃ phases have been synthesized with particle sizes of 30 nm and 30 μm, respectively. Analysis of the IR reflection spectra measured at T = 300 K showed that the nanophase differs from the microcrystalline phase by reduced optical phonon frequencies. It is established that annealing of the LuF₃ nanophase in air leads to the formation of nanoparticles of the LuO_{1 ? x} F_{1 + 2x} and Lu₂O₃ compositions. The IR reflection spectra of the nanophases indicate that these nanoparticles consist of an oxyfluoride core surrounded with a Lu₂O₃ shell; the latter is in the strained state.     

Dissociation energies of deoxyribose nucleotide dimer anions measured using blackbody infrared radiative dissociation

The dissociation kinetics of deprotonated deoxyribose nucleotide dimers were measured using blackbody infrared radiative dissociation. Experiments were performed with noncovalently bound dimers of phosphate, adenosine (dAMP), cytosine (dCMP), guanosine (dGMP), thymidine (dTMP), and the mixed dimers dAMP.dTMP and dGMP.dCMP. The nucleotide dimers fragment through two parallel pathways, resulting in formation of the individual nucleotide or nucleotide + HPO3 ion. Master equation modeling of this kinetic data was used to determine threshold dissociation energies. The dissociation energy of (dGMP.dCMP-H)- is much higher than that for the other nucleotide dimers. This indicates that there is a strong interaction between the nucleobases in this dimer, consistent with the existence of Watson-Crick hydrogen bonding between the base pairs. Molecular mechanics simulations indicate that Watson-Crick hydrogen bonding occurs in the lowest energy structures of (dGMP.dCMP-H)-, but not in (dAMP.dTMP-H)-. The trend in gas phase dissociation energies is similar to the trend in binding energies measured in nonaqueous solutions within experimental error. Finally, the acidity ordering of the nucleotides is determined to be dTMP < dGMP < dCMP < dAMP, where dAMP has the highest acidity (largest delta Gacid).     

Hydration of gas-phase gramicidin S (M + 2H)2+ ions formed by electrospray: The transition from solution to gas-phase structure

The hydration of doubly protonated gas-phase ions of gramicidin S formed by electrospray ionization was investigated. Under “gentle” electrospray conditions, a near Gaussian distribution of (M + 2H + nH₂O)²⁺ ions with n up to 50 can be readily formed. These extensively hydrated gas-phase ions should have structures similar to those in solution. For intermediate extents of hydration, the “naked” or unsolvated ion is present in unusually high abundance. This is attributed to a competition between solvation of the charges by water vs intramolecular self-solvation via hydrogen bonding. In addition, “magic” numbers of attached water molecules are observed for n = 8, 11, and 14. These magic numbers are attributed to favorable arrangements of water molecules surrounding the charge and surface of the peptide in the gas phase. These results are indicative of a gentle stepwise transformation from the solution-phase structure of the ion to the preferred gas-phase structure as solvent evaporates from the hydrated ions.