Attacking Boron Nucleophiles:  NMR Properties of Five-Membered Diazaborole Rings

2007 ◽  
Vol 111 (3) ◽  
pp. 419-421 ◽  
Author(s):  
Janet E. Del Bene ◽  
José Elguero ◽  
Ibon Alkorta ◽  
Manuel Yáñez ◽  
Otilia Mó
Keyword(s):  
Nmr Properties

scholarly journals NMR Properties of the Cyanide Anion, a Quasisymmetric Two-Faced Hydrogen Bonding Acceptor

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1298
Author(s):  
Ilya G. Shenderovich ◽  
Gleb S. Denisov
Keyword(s):  
Hydrogen Bonding ◽  
Experimental Studies ◽  
Polarizable Continuum Model ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Cyanide Anion ◽  
Molecular Systems ◽  
Polarizable Continuum ◽  
Chemical Shieldings ◽  
Nmr Properties

The isotopically enriched cyanide anion, (13C≡15N)−, has a great potential as the NMR probe of non-covalent interactions. However, hydrogen cyanide is highly toxic and can decompose explosively. It is therefore desirable to be able to theoretically estimate any valuable results of certain experiments in advance in order to carry out experimental studies only for the most suitable molecular systems. We report the effect of hydrogen bonding on NMR properties of 15N≡13CH···X and 13C≡15NH···X hydrogen bonding complexes in solution, where X = 19F, 15N, and O=31P, calculated at the ωB97XD/def2tzvp and the polarizable continuum model (PCM) approximations. In many cases, the isotropic 13C and 15N chemical shieldings of the cyanide anion are not the most informative NMR properties of such complexes. Instead, the anisotropy of these chemical shieldings and the values of scalar coupling constants, including those across hydrogen bonds, can be used to characterize the geometry of such complexes in solids and solutions. 1J(15N13C) strongly correlates with the length of the N≡C bond.

scholarly journals The long-standing relationship between Paramagnetic NMR and Iron-Sulfur proteins: the mitoNEET example. An old method for new stories or the other way around?

2021 ◽  
Author(s):  
Francesca Camponeschi ◽  
Angelo Gallo ◽  
Mario Piccioli ◽  
Lucia Banci
Keyword(s):  
The Other ◽  
Paramagnetic Nmr ◽  
Relaxation Rates ◽  
Iron Sulfur ◽  
Iron Sulfur Proteins ◽  
Metal Cofactor ◽  
Function Relationship ◽  
Nmr Properties ◽  
Nmr Signals ◽  
S Proteins

Abstract. Paramagnetic NMR spectroscopy and iron-sulfur (Fe–S) proteins have maintained a synergic relationship for decades. Indeed, the hyperfine shifts with their temperature dependencies and the relaxation rates of nuclei of cluster-bound residues have been extensively used as a fingerprint of the type and of the oxidation state of the Fe–S cluster within the protein frame. The identification of NMR signals from residues surrounding the metal cofactor is crucial for understanding the structure-function relationship in Fe–S proteins, but it is generally impaired in standard NMR experiments by paramagnetic relaxation enhancement due to the presence of the paramagnetic cluster(s). On the other hand, the availability of systems of different size and stability has, over the years, stimulated NMR spectroscopists to exploit iron-sulfur proteins as paradigmatic cases to develop experiments, models and protocols. Here, the cluster binding properties of human mitoNEET have been investigated by one-dimensional and two-dimensional 1H diamagnetic and paramagnetic NMR, in its oxidized and reduced states. The NMR spectra of both oxidation states of mitoNEET appeared to be significantly different from those reported for previously investigated [Fe2S2]2+/+ proteins. We show how the use of 1D NOE experiments, 13C direct-detected experiments, and the optimization of NMR experiments for paramagnetic systems significantly reduce the blind sphere of the protein around the paramagnetic cluster. The application of this approach provided a detailed description of the unique electronic properties of mitoNEET, that are responsible for its biological function. Indeed, the NMR properties suggested that the specific electronic structure of the cluster possibly drives the functional properties of different [Fe2S2] proteins.

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