A solid-state NMR investigation of orexin-B

2004 ◽  
Vol 82 (10) ◽  
pp. 1554-1563 ◽  
Author(s):  
Guy M Bernard ◽  
Mark Miskolzie ◽  
George Kotovych ◽  
Roderick E Wasylishen
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Dipolar Coupling ◽  
Double Resonance ◽  
Solution Nmr ◽  
Carbonyl Carbon ◽  
Distance Measurements ◽  
Nmr Study ◽  
Amide Carbonyl

Some key aspects of the secondary structure of solid orexin-B, a 28 amino-acid peptide, have been investigated by solid-state NMR spectroscopy. The 13C–15N dipolar coupling between the carbonyl carbon of Leu11 and the nitrogen of Leu15, as determined by rotational echo double resonance (REDOR) experiments, is 35 Hz, indicating that these nuclei are separated by approximately 4.5 Å. This distance is consistent with the α-helical structure determined for this segment of orexin-B by solution NMR measurements. REDOR measurements of the dipolar coupling between the carbonyl carbon of Ala17 and the nitrogen of Ala22 support the contention in an earlier solution NMR study that a bend exists between the two α helices of orexin-B. However, in the solid state the internuclear distance (6.4 Å) is significantly greater than that observed for orexin-B in aqueous solution. In addition to the distance measurements, the principal components of the amide carbonyl carbon chemical shift (CS) tensors for Leu11 and Ala17 and of the amide nitrogen CS tensors for Leu15 and Ala22 are reported. There are only minor differences between the amide carbonyl carbon CS tensors for Leu11 and Ala17 and between the nitrogen CS tensors for Leu15 and Ala22.Key words: orexin-B, solid-state NMR, REDOR, chemical shift tensors.

13C Chemical Shift and 13C–14N Dipolar Coupling Tensors Determined by 13C Rotary Resonance Solid-State NMR

2001 ◽  
Vol 148 (2) ◽  
pp. 298-308 ◽  
Author(s):  
Louise Odgaard ◽  
Mads Bak ◽  
Hans J. Jakobsen ◽  
Niels Chr. Nielsen
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Dipolar Coupling ◽  
13C Chemical Shift

scholarly journals Linear dicoordinate beryllium: a 9Be solid-state NMR study of a discrete zero-valent s-block beryllium complex

2018 ◽  
Vol 96 (7) ◽  
pp. 646-652 ◽  
Author(s):  
C. Leroy ◽  
J.K. Schuster ◽  
T. Schaefer ◽  
K. Müller-Buschbaum ◽  
H. Braunschweig ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Chemical Shift Tensor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Quadrupolar Coupling ◽  
Nmr Study ◽  
Tensor Data

Beryllium-9 (9Be) quadrupolar coupling and chemical shift tensor data are reported for bis(1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidine-2-ylidene)beryllium (Be(CAAC)2). These are the first such data for beryllium in a linear dicoordinate environment. The 9Be quadrupolar coupling constant, 2.36(0.02) MHz, is the largest recorded in the solid state to date for this isotope. The span of the beryllium chemical shift tensor, 22(2) ppm, covers about half of the known 9Be chemical shift range, and the isotropic 9Be chemical shift, 32.0(0.3) ppm, is the largest reported in the solid state to our knowledge. DFT calculations reproduce the experimental data well. A natural localized molecular orbital approach has been used to explain the origins and orientation of the beryllium electric field gradient tensor. The single-crystal X-ray structure of a second polymorph of Be(CAAC)2 is also reported. Inspection of the powder X-ray diffraction data shows that the new crystal structure is part of the bulk product next to another crystalline phase. Therefore, experimental X-ray powder data for the microcrystalline powder sample and the SSNMR data do not fully match either the originally reported crystal structure (Arrowsmith et al. Nat. Chem. 2016, 8, 890–894) or the new polymorph. The ability of solid-state NMR and powder X-ray diffraction to characterize powdered samples was thus particularly useful in this work.

scholarly journals Structure and Orientation of Pardaxin Determined by NMR Experiments in Model Membranes

2004 ◽  
Vol 279 (44) ◽  
pp. 45815-45823 ◽  
Author(s):  
Fernando Porcelli ◽  
Bethany Buck ◽  
Dong-Kuk Lee ◽  
Kevin J. Hallock ◽  
Ayyalusamy Ramamoorthy ◽  
...  
Keyword(s):  
Solid State ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Solid State Nmr ◽  
Double Resonance ◽  
Slow Motion ◽  
Solution Nmr ◽  
Helical Conformation ◽  
Hydrophobic Core ◽  
Nmr Studies

Pardaxins are a class of ichthyotoxic peptides isolated from fish mucous glands. Pardaxins physically interact with cell membranes by forming pores or voltage-gated ion channels that disrupt cellular functions. Here we report the high-resolution structure of synthetic pardaxin Pa4 in sodium dodecylphosphocholine micelles, as determined by1H solution NMR spectroscopy. The peptide adopts a bend-helix-bend-helix motif with an angle between the two structure helices of 122 ± 9°, making this structure substantially different from the one previously determined in organic solvents. In addition, paramagnetic solution NMR experiments on Pa4 in micelles reveal that except for the C terminus, the peptide is not solvent-exposed. These results are complemented by solid-state NMR experiments on Pa4 in lipid bilayers. In particular,13C-15N rotational echo double-resonance experiments in multilamellar vesicles support the helical conformation of the C-terminal segment, whereas2H NMR experiments show that the peptide induces considerable disorder in both the head-groups and the hydrophobic core of the bilayers. These solid-state NMR studies indicate that the C-terminal helix has a transmembrane orientation in DMPC bilayers, whereas in POPC bilayers, this domain is heterogeneously oriented on the lipid surface and undergoes slow motion on the NMR time scale. These new data help explain how the non-covalent interactions of Pa4 with lipid membranes induce a stable secondary structure and provide an atomic view of the membrane insertion process of Pa4.

scholarly journals Solid state NMR study of 1,3imidazolidine-2-thione, 1,3-imidazolidine-2-selenone and some of their N-substituted derivatives

2004 ◽  
Vol 18 (1) ◽  
pp. 113-119 ◽  
Author(s):  
Mohamed I. M. Wazeer ◽  
Anvarhusein A. Isab ◽  
Ali El-Rayyes
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
Methyl Derivative ◽  
Nmr Spectrum ◽  
Nmr Study ◽  
Molecular Computations

Solid‒state NMR spectra were recorded for 1,3-imidazolidine-2-thione, 1,3-imidazolidine-2-selenone and some of their N-substituted derivatives. Spinning side-bands of thione and selenone carbons were analysed to yield chemical shift anisotropies for these carbons. The NMR spectrum of imidazolidine-2-thione (Imt) showed some evidence for the presence of thiol tautomer. Molecular computations were carried out for Imt and its N-methyl derivative to yield relative energies of various tautomers.

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