Magnetic Resonance in Chemistry

A complete assignment of all ¹H, ¹³C and ¹⁵N resonances of Phcocyanobilin (PCB) in HMPT is presented. Utilizing ¹³C and ¹⁵N labelled PCB we establish an alternative assignment route based on the concept of triple resonance experiments known from protein NMR. This strategy is straightforward and can—as presented here—be applied to a small and highly symmetric protein co-factor and a sample of very low concentration.

Linearly conjugated benzene rings (acenes), belt shape molecules and model single wall carbon nanotubes were fully optimized at the B3LYP/6-31G* level of theory. These models were selected to get some insight into the changes of nuclear isotropic changes upon systematically changing (increasing) basic building units of single wall carbon nanotubes (SWCNT). Both geometrical and NMR parameters were approximated toward the infinity upon the increase of the studied systems size using simple two-parameter mathematical formula.

We present a filter element to observe exclusively the resonances of Asp and Glu residues in several ¹³C detected experiments, CACO, CBCACO, and CCCO. The spectra show the coupling between the carboxyl carbon and the backbone CO in Asp residues, providing information on their side chain conformation.

UHMWPE was the material of choice for the articulating surface in total joint replacements and the necessary sterilisation of UHMWPE prosthetic components was commonly carried out by high energy radiation. Formation and evolution of three different macro-radicals, produced during this process, was followed with EPR spectroscopic technique.

Stereochemical study of five sterically crowded phenylselanylalkenes obtained via the hydroselenation of either terminal or internal alkynes with benzeneselenol catalyzed by the nanosized Ni complexes has been carried out based on the experimental HMBC measurements and theoretical SOPPA calculations of their ⁷⁷Se¹H spin–spin coupling constants across double bond in combination with the energy-based theoretical conformational analysis performed at the MP2/6-311G** level. It has been found that studied phenylselanylalkenes adopt mainly skewed s-cis conformation with the noticeable out-of-plane deviations of the phenylselanyl and phenyl groups.

A novel 3D NMR experiment hNCOcanHhas been described to aid rapid sequence specific backbone assignment in ¹⁵N/¹³C-labeled proteins. The experiment in combination with the HNN experiment described previously [Panchal et al, J. Biomol. NMR 20 (2001) 135–147] leads to a robust assignment protocol than could be derived from combination of HNN and HN(C)N experiments [Bhavesh et al, Biochemistry, 40 (2001) 14727–14735].

Diffusion-edited NMR spectroscopy has been used as a tool for water suppression when determining the M/G ratio in alginate polysaccharides. The monomer composition can even be obtained upon complete overlap between water and alginate signals. The method is also suitable for automation procedures.

Isotopic effect on tautomeric behaviors of the synthesized 5-(aryloxy)-tetrazoles were investigated in DMSO-d₆ added one drop of D₂O.

The measurements of ¹³C magnetic shielding for pure liquid TMS, solution of 1% TMS in CDCl₃ and solid fullerene were performed in spherical ampoules exploring the relation between the resonance frequencies, shielding constants and magnetic moments of ¹³C and ³He nuclei. The ¹³C shielding constants of solid glycine, hexamethylbenzene and adamantane were established from their chemical shifts. All the new results are free from susceptibility effects and recommended as the reference standards of ¹³C shielding scale in MAS NMR experiments.

Theoretical calculations of isotropic hfccs and g-factors for nitrogen-oxygen-centered radicals, N-alkoxyaminyls and aminoxyls, have been performed to investigate the dependence property of hybrid DFT functionals.

Complexations between three oridonin derivatives and βCD were studied by NMR method. These studies proved the 1:1 stoichiometry inclusion complexes formation, and achieved detailed spatial interaction and the corresponding three-dimensional geometry information between each derivative and βCD. Apparent formation constants (K_a) of complexes were calculated.