Nuclear spin-lattice relaxation of192Ir in ferromagnetic amorphous alloy Fe-B studied by nuclear orientation

The nuclear spin-lattice relaxation of¹⁹²Ir in the glassy alloy Ir_3.1Fe_80.5B_16.4 has been studied by low-temperature nuclear orientation technique. The thermal cycling method has been used. No dependence on extermal magnetic field in the range 0.25–1.2 T has been observed. Weger’s mechanism seems to play a crucial role.     

Surface characterization and catalytic CO + H2 reaction on Fe82.2B17.8 amorphous alloy

Fe_82.2B_17.8 amorphous ribbon has been used as a catalyst for the Fischer-Tropsch-type reaction of CO+H₂. Specific activity has been found to be at least an order of magnitude higher than that of either the crystallized ribbon of identical composition or the supported iron catalyst. Before and after the catalytic tests the ribbons were characterized by XRD, XPS, UPS and Mössbauer spectroscopy in transmission and in conversion electron modes. Conversion electron Mössbauer spectroscopy and UPS proved that the surface of the amorphous ribbons is being partially crystallized during 8000 min reaction time at a maximum reaction temperature of 560 K. The superior catalytic activity has been explained by stabilization of the small iron particles and Fe₂O₃ by boron atoms at the surface and by suppressed carbide formation.     

Synthesis and Tritium Labelling of 6β-Amino-4,5α-epoxymorphinans and their 14-hydroxy derivatives as potential affinity labelling probes with μ opioid agonist activity

The synthesis of 6β-(methylfumaramido) and 6β-chloroacetamido derivatives 1b and 1c of 6β-amino-7,8- didehydromorphinan and the corresponding 14-hydroxy derivatives 1e and 1f are described. The 7,8-dihydro derivatives of these compounds were synthesized in inactive ( 2b,c,e,f ) as well as in tritiated form ( 3b,c,e,f ).     

Calculation of weakly polar interaction energies in polypeptides using density functional and local Møller-Plesset perturbation theory

The interaction energies of ubiquitous weakly polar interactions in proteins are comparable with those of hydrogen bonds, consequently, they stabilize local, secondary, and tertiary structures. However, the most widely-used density functionals fail to describe the weakly polar interactions. Thus, it is important to find and test functionals which adequately describe and quantify the energetics of such interactions. For this purpose, interaction energies in the hydrophobic core of rubredoxin (PDB id: 1rb9) and in the S22 subset of the JSCH-2005 benchmark database were computed with the BHandHLYP and PWPW91 functionals and with the pseudospectral implementation of the local MP2 (PS-LMP2) method. The cc-pVDZ, cc-pVTZ(-f), cc-pVTZ, cc-pVQZ(-g), aug-cc-pVDZ, aug-cc-VTZ(-f), and aug-cc-pVTZ basis sets were used for the calculations. In the S22 subset the PS-LMP2 results were extrapolated to the complete basis set limit. Furthermore, the a posteriori counterpoise method of Boys and Bernardi was used to correct the basis set superposition errors in the calculation of interaction energies. Calculations using the BHandHLYP functional, both for the various weakly polar interactions in rubredoxin and for the dispersion interactions in the S22 subset, were in good agreement with those using the coupled cluster (CCSD(T)) and the resolution of identity MP2 (RIMP2) methods and clearly outperformed both the PWPW91 functional and the PS-LMP2 method. The results for the S22 hydrogen bonded subset, obtained with PWPW91 calculations, were closest to those of the reference high level calculations. For the "mixed" (hydrogen bonded and dispersive) interactions in the S22 subset, results obtained with the BHandHLYP and PS-LMP2 calculations agreed well with the reference calculations.     

Characterization of the conformational probability of N-acetyl-phenylalanyl-NH2 by RHF, DFT, and MP2 computation and AIM analyses, confirmed by jet-cooled infrared data

Computational and experimental determinations were carried out in parallel on the conformational probability of N-Acetyl-Phenylalanine-NH2 (NAPA). Ab initio computations were completed at the BLYP/6-311G(df,p), B3LYP/6-31G(d), B3LYP/6-31G(d,p), and B3LYP/6-31+G(d) levels of theory, labeled L/61fp, B/6, B/6p, and B/6+, respectively. Three experimentally identified conformers were compared with theoretical data, confirming their identities as the betaLanti, gammaLgauche+, and gammaLgauche- (BACKBONESIDECHAIN) conformers. Evidence comes from matching experimental and theoretical data for all three constituent N-H stretches of NAPA, with a Delta(Experimental-Theoretical) = approximately 1-3 cm(-1), approximately 0-5 cm(-1), and approximately 1-6 cm(-1), at the L/61fp and B/6+ levels, respectively. Corrected-ZPE relative energies were computed to be 0.14, 0.00, 0.26 and 0.00, 0.67, 0.57 (kcal*mol(-1)) for the betaLanti, gammaLgauche+, and gamma(Lgauche- conformers, respectively, at the L/61fp and B/6+ levels, respectively. The MP2/6-31+G(d) level of theory was subsequently found to give similar relative energies. Characterization of the intramolecular interactions responsible for red and blue shifting of the N-H stretches showed the existence of the following intramolecular interactions: C=O[i]- - -HN[i], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-Cdelta-H- - -O=C[i-1] for betaLanti; C=O[i-1]- - -HN[i+1], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-C-H- - -O=C[i] for gammaLgauche+; and C=O[i-1]- - -HN[i+1] for gammaLgauche-. Each of these interactions were further investigated and subsequently characterized by orbital population and Atoms-In-Molecules (AIM) analyses, with the identity of overlap and bond critical points (BCP) serving as 'scoring criteria', respectively. Experimental and theoretical carbonyl stretches were also compared and showed good agreement, adding further strength to the synergy between experiment and theory.