160Tb nuclear orientation in yttrium single crystal

First experimental results of¹⁶⁰Tb nuclear orientation in yttrium single crystal matrix are described. The influence of external magnetic field in combination with the crystal field interaction is discussed.     

Hyperfine anomalies and nuclear γ-factors of56Co,57Co and60Co isotopes studied by NMR/ON

The results of NMR/ON measurements on^56,57,60Co isotopes in iron are presented in the paper. To avoid the uncertainties caused by local demagnetizing field inhomogeneities the measurements on two cobalt isotopes in one sample have been carried out. The values of nuclear-factors ratios ⁵⁷/ ⁶⁰=1·805(20), ⁶⁰/ ⁵⁶ = 0·761(20), ⁵⁶/ ⁵⁷ = 0·726(20) and hyperfme anomalies^{56 60} = –0·036(10),^{60 57} = 0·017(10) and^{57 56} = 0·018(10) have been calculated from the experimental results.Dedicated to the 30th anniversary of the Joint Institute for Nuclear Research.     

Ab initio study of the NMR shielding constants and spin-spin coupling constants in cyclopropene

Summary Ab initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.Dedicated to Professor Werner Kutzelnigg on the occasion of his 60th birthday     

A vanadium-51 NMR study of the binding of vanadate and peroxovanadate to proteins

51V quadrupolar central transition NMR spectra of buffered (pH 7.6-8.0) solutions of bovine apo-transferrin (Tf) and bovine prostatic acid phosphatase (Pp) treated with vanadate show normal features (chemical shifts between -515 and -542 ppm) corresponding to the complexation of VO2+ to the Tf binding site and the Pp active centre, respectively. Addition of H2O2 leads to the temporary formation of complexed VO(O2)+ (delta approximately -595). Vanadate-dependent bromoperoxidase from the alga Ascophyllum nodosum exhibits an unusually high shielding both for the native (delta = -931) and the peroxo form (delta = -1135) of the enzyme. A resonance at -471 ppm is traced back to an inactive form with oxovanadium(V) in a trigonal-bipyramidal array.     

Cinnamaldehyde hydrogenation using ruthenium-tin catalyst type

Bimetallic ruthenium-tin catalysts were prepared using the sol-gel method and the method of carrier impregnation. Two different procedures were used for their reduction — reduction in hydrogen atmosphere under an increased temperature, and reduction using an aqueous solution of sodium borohydride. Hydrogenation of 3-phenylpropenal (cinnamaldehyde) in tetrahydrofuran at 433 K and the total pressure 7 MPa was used as the model reaction for comparing the catalytic properties of the prepared catalysts. It was demonstrated that a tin addition notably affected catalytic properties of ruthenium in the sense of a selectivity increment related to the production of an unsaturated alcohol.     

Ligand-modulated stereo- and regioselective tandem addition reactions of rhenium-bound naphthalene

A series of complexes of the form TpRe(CO)(L)(eta(2)-naphthalene) (Tp = hydridotris(pyrazolyl)borate) undergoes tandem electrophile/nucleophile addition reactions with a high degree of regiocontrol depending on the auxiliary ligand, L. When L = PMe(3), the reaction of the eta(2)-naphthalene complex with triflic acid followed by a silyl ketene acetal favors the 1,4-addition product, whereas when L = pyridine, N,N-dimethylaminopyridine, N-methylimidazole, or NH(3) the 1,2-addition product is favored. These reactions proceed with excellent stereocontrol: both electrophile (H(+), D(+)) and nucleophile (silyl ketene acetal) add anti to the face of metal coordination, and a single coordination diastereomer can be isolated for each reaction. One-electron oxidation of the Re complex affords the corresponding free dihydronaphthalene in good yield.     

Development of piezoelectric immunosensors for measurement of albuminuria

The development of piezoelectric immunosensors for human serum albumin (HSA) is reported. The piezoelectric crystals were modified either with monoclonal antibody AL-01 (direct assay) or with HSA (competitive assay). Measurements were carried out in the flow-through mode. Affinity interaction between albumin and the antibody was characterised. With immobilised antibody and HSA in solution, the kinetic association rate constant k(a) was 18 100 l mol(-1) s(-1) and the dissociation constant k(d) was 0.00369 s(-1). For the opposite arrangement (immobilised HSA), a slower dissociation was observed, k(d) was 0.00085 s(-1). A competitive assay for HSA was developed with working range of 1-5 mug ml(-1) and a total time for one analysis equal to 17 min. Samples of urine were analysed after tenfold dilution. The developed system was successfully evaluated on real samples from diabetic patients and the obtained results correlated well with the standard reflectometric assay of proteins in urine.