17O NMR and FT-IR study of the ionization state of peptides in aprotic solvents Application to Leu-enkephalin

AbstractThe ionization state of Leu-enkephalin in DMSO and MeCN/DMSO (4/1) solution was studied by the combined use of 17O NMR and FT-IR spectroscopy. After lyophilization or an aqueous solution at nearly neutral pH, Leu-enkephalin essentially exists in the uncharged state in MeCN/DMSO (4/1) solution. In pure DMSO, only 40% of the Leu-enkephalin molecules are in the zwitterionic state under the same conditions

A PULSE SEQUENCE FOR T1 MEASUREMENT BY INVERSION RECOVERY IN THE PRESENCE OF ACOUSTIC RINGING

none1A pulse sequence is presented which allows one to perform an inversion-recovery experiment for T1 determination on quadrupolar nuclei in the presence of acoustic ringing. The sequence is based on a modification of the reference baseline subtraction-90deg pulse sequence. Some examples of 17O and 14N relaxation are presented, including spectra with overlapping peaks from which T1 values cannot be simply extracted from line widths.noneA. BAGNOBagno, Alessandr

A new NMR method for studying the dynamic of the molecule: off-resonance ROESY

By using a strong off-resonance irradiation in the ROESY sequence, one can study the relaxation without the drawbacks of NOESY (cancelation of the dipolar cross-relaxation rates) or of ROESY (angular dispersion, coherence transfer by indirect interactions). Moreover constraints on the dynamics of the system can be obtained by an appropriate choice of the angle θ between the static and the effective field in the rotating frame. Experimental illustrations of these results are presented

A recurrent RNA-binding domain is appended to eukaryotic aminoacyl-tRNA synthetases

Aminoacyl-tRNA synthetases of higher eukaryotes possess polypeptide extensions in contrast to their prokaryotic counterparts. These extra domains of poorly understood function are believed to be involved in protein–protein or protein–RNA interactions. Here we showed by gel retardation and filter binding experiments that the repeated units that build the linker region of the bifunctional glutamyl-prolyl-tRNA synthetase had a general RNA-binding capacity. The solution structure of one of these repeated motifs was also solved by NMR spectroscopy. One repeat is built around an antiparallel coiled-coil. Strikingly, the conserved lysine and arginine residues form a basic patch on one side of the structure, presenting a suitable docking surface for nucleic acids. Therefore, this repeated motif may represent a novel type of general RNA-binding domain appended to eukaryotic aminoacyl-tRNA synthetases to serve as a cis-acting tRNA-binding cofactor

High resolution H-1-NMR study on self-complexation phenomena in cyclodextrin dimers

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