Showing papers by "Christian Griesinger published in 1993"

Coherence Selection by Gradients without Signal Attenuation: Application to the Three‐Dimensional HNCO Experiment

Abstract: Coherence Selection by Gradients without Signal Attenuation : Application to the 3-Dimensional Hnco Experiment

Conformational backbone dynamics of the cyclic decapeptide antamanide. Application of a new multiconformational search algorithm based on NMR data

Abstract: A general procedure for the analysis of biomolecular structures by NMR in the presence of rapid conformational dynamics has been applied to the study of the cyclic decapeptide antamanide. Two-dimensional experiments, relaxation measurements in the rotating frame, and homo- and heteronuclear coupling constant determinations have been used to characterize the dynamic properties of the molecule, in combination with a novel search algorithm for investigating multiconformational equilibria. Direct evidence for the presence of a conformational exchange process with an activation energy of approximately 20 kJ mol-1 and an exchange lifetime of approximately 25 microseconds at 320 K has been obtained from rotating frame relaxation measurements. This evidence is combined with the information derived from the multiconformational search algorithm MEDUSA to propose sets of structures that coexist in a dynamic exchange equilibrium.

Vinyllithium : dynamic behavior in tetrahydrofuran solution and comprehensive analysis of NMR spin-spin coupling constants

Abstract: Vinyllithium (ViLi; isotopically labeled with 6 Li) is an 8:1 tetramer/dimer equilibrium in tetrahydrofuran-d 8 (THF-d 8 ) at -90 o C (1.6 M solution). In the presence of equilmolar amounts of TMEDA (tetramethylethylenediamine), the tretramer:dimer ratio is 1:13 in THF-d 8 at -80 o C (1.9 M solution). Dynamic NMR phenomena are observed in the ViLi tetramer: at -90 o C in THF-d 8 , a static aggregate is found, whereas at -60 o C rapid intraaggravate exchange of the four lithium sites indicates a fluxional tetramer