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We present a detailed analysis of the production efficiency of weakly bound heteronuclear KRb-Feshbach molecules using radio frequency association in a harmonic trap. The efficiency was measured in a wide range of temperatures, binding energies and radio frequencies. A comprehensive analytical model is presented, explaining the observed asymmetric spectra and achieving good quantitative agreement with the measured production rates. This model provides a deep understanding of the molecule association process and paves the way for future experiments which rely on Feshbach molecules e.g. for the production of deeply bound molecules., Comment: 5 pages, 4 figures

Previous studies from our laboratory have indicated that the lipopolysaccharide (LPS) from Mannheimia haemolytica serotype A1 contains both L- glycero -D- manno -heptose and D- glycero -D- manno -heptose residues. NMR methods making use of 1D 1H selective excitation and 2D (1H, 13C) and (1H, 31P) heteronuclear experiments were used for the structural determination of the major core oligosaccharide components of the deacylated low-molecular-mass LPS obtained following sequential treatment with anhydrous hydrazine and aq KOH. The core oligosaccharide region was found to be composed of a branched octasaccharide linked to the deacylated lipid A moiety via a 3-deoxy-4-phospho-D- manno -oct-2-ulosonate residue having the structure (see text). Heterogeneity was found to be present at several linkages. NMR methods were devised to distinguish between the diastereomeric forms of the heptose residues. Synthesized monosaccharides of L-D- and D-D-heptose were used as model compounds for analysis of the 1H and 13C NMR chemical shifts and proton coupling constants. Molecular modeling using a Monte Carlo method for conformational analysis of saccharides was used to determine the conformation of the inner core of the oligosaccharide and to establish the stereochemical relationships between the heptoses.

One dimensional steady-state selective intermolecular C-13, H-1 Overhauser effect study of tert-butylformamide provides the first experimental evidence of differentical hydration of the Z isomer, compared to the E isomer, due to the presence of the bulky tert-butyl group; the significant decrease in the population of the Z isomer should be attributed to steric effects and deformation of the amide bond with hydration differences playing a significant role. Copyright (C) 1996 Elsevier Science Ltd Tetrahedron Lett

The cytochromes c′ are paramagnetic heme proteins generally consisting of two identical 14 kDa subunits. The recent assignment of the 'H and15N resonances of the Rhodobacter capsulatus ferricytochrome c' has allowed characterization of the dynamic properties by measurement of the heteronuclear NOE for each resolved amide group. The relative importance of fast local motion and paramagnetic effect on nuclear relaxation were distinguished by comparison of the measured heteronuclear NOE with that of the overall experimental average. We show that the average experimental value of -0.16 corresponds to the rigid body motion expected for a spherical complex of 28 kDa. Residues 3–5, 50–55 and 69–70 exhibit decreased heteronuclear NOE due to local motions on a fast time scale with respect to molecular tumbling. Based on the X-ray crystal structure of the homologous cytochrome c′ from Chromatium vinosum, the mobile regions correspond to the N-terminus of helix-1 and 2 regions of nonregular secondary structure located between helices-2 and -3.

Full assignment of the H-1 and C-13 NMR spectra of ent-atisane-3 beta,16 alpha-diol, a cytotoxic diterpene isolated from the Caribbean sponge Spirastrella cunctatrix, was achieved by extensive use of two-dimensional NMR spectroscopy and spectral simulation. This is the first complete NMR characterization af an atisane terpene.

The capsular polysaccharide of Actinobacillus pleuropneumoniae serotype 5b (strain L20) was found to be a high molecular mass polymer composed of 2-acetamido-2-deoxy-D-glucose, D-glucose, and 3-deoxy-D-manno-octulosonic acid (KDO). Methylation analysis, partial hydrolysis and a combination of homonuclear and 1H-detected heteronuclear shift-correlated nuclear magnetic resonance experiments showed the polysaccharide to be a branched polymer of a trisaccharide repeating unit, having the structure: [formula; see text]

A method for the quantitative determination of interproton distances from H-1 NOE relayed heteronuclear correlation is presented. Model compounds are investigated. Accurate distances are obtained if all the factors affecting such distance measurements, such as the local mobility and the presence of strong coupling in heteronuclear systems, are properly taken into account.

Department of Chemistry, University College of Science, Calcutta-700 009 Manuscript received 12 April 1989, revised 15 November 1989, accepted 21 November 1989 Complete carbon-13 and proton spectral analyses of friedelin have been made using INADEQUATE (or CCCP) and heteronuclear (13C-1H) correlation experiments.