scholarly journals 1H-NMR characterization of l-tryptophan binding to TRAP, the trp RNA-binding attenuation protein of Bacillus subtilis

1996 ◽  
Vol 315 (3) ◽  
pp. 895-900 ◽  
Author(s):  
Vasudevan RAMESH ◽  
Tom BROWN
Keyword(s):  
Bacillus Subtilis ◽  
Complex Formation ◽  
1H Nmr ◽  
Rna Binding ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Large Change ◽  
Binding Pocket ◽  
Nmr Study ◽  
Nmr Characterization

A 1H-NMR study of the binding of L-tryptophan to the trp RNA-binding attenuation protein of Bacillus subtilis (TRAP), an ondecamer (91.6 kDa), has been implemented. The assignment of the aromatic indole ring proton resonances of the bound tryptophan ligand has been successfully carried out by two-dimensional chemical exchange experiments. The observation of only a single set of chemical shifts of the bound ligand demonstrates that the tryptophan binding site is identical in all the 11 subunits of the protein. Further, the large change in ligand chemical shifts suggests that the conformation of tryptophan ligand undergoes a significant rearrangement after complex formation with TRAP. This is further substantiated by the extensive ligand-induced chemical shift changes observed to the protein resonances and identification of several strong ligand–protein intermolecular nuclear Overhauser effects. A correlation of these preliminary NMR data with the X-ray crystal structure of the TRAP–tryptophan complex also suggests, tentatively, that the observed changes to the NMR spectra of the protein might correspond to changes associated with residues surrounding the tryptophan binding pocket owing to complex formation.

Thermodynamic and 1H NMR study of proton complex formation of histidine-containing cyclodipeptides in aqueous solution

1992 ◽  
pp. 371 ◽  
Author(s):  
Giuseppe Arena ◽  
Giuseppe Impellizzeri ◽  
Giuseppe Maccarrone ◽  
Giuseppe Pappalardo ◽  
Domenico Sciotto ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
1H Nmr ◽  
Nmr Study

109Ag NMR-Study of the Selective Solvation of the Ag+ Ion in Solvent Mixtures of Water and the Organic Solvents: Pyridine, Acetonitrile, and Dimethyl Sulfoxide

1984 ◽  
Vol 39 (1) ◽  
pp. 83-94 ◽  
Author(s):  
L. Guinand. K. L. Hobt. E. Mittermaier ◽  
E. Rößler ◽  
A. Schwenk ◽  
H. Schneider
Keyword(s):  
Chemical Shift ◽  
Dimethyl Sulfoxide ◽  
Organic Solvents ◽  
Mole Fraction ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Solvent Mixtures ◽  
Nmr Study ◽  
Solvent Molecules

In mixtures of water (W) and one of the organic solvents pyridine, acetonitrile, and dimethyl sulfoxide (O), the silver ion forms the following solvate complexes: AgW2, AgWO, and Ag02. The chemical shift of 109Ag is strongly affected by the ligating solvent molecules, and replacing the ligand W by one of the three organic ligands yields a higher Larmor frequency. In solvent mixtures, only a single resonance line has been observed because of rapid chemical exchange. The measured chemical shifts in the range up to 400 ppm are mean values of the chemical shifts of the different solvate species in a given mixture, weighted with their relative concentrations. The 109Ag chemical shifts were determined for 0.05 to 0.15 molal solutions of AgNO3, as functions of the mole fractions of the solvent components. Using a Gaussian least squares fitting routine, the individual chemical shifts of the Ag+ solvate complexes and the corresponding equilibrium constants were determined. This fit was successful for the whole mole fraction range of DMSO, while in the solvent systems with acetonitrile and with pyridine at higher concentrations of the organic component the chemical shift is influenced by more than two solvent molecules. In these cases equilibrium constants were calculated from chemical shift data for solutions of low mole fraction of acetonitrile and pyridine.

scholarly journals 14N, 13C, and 119Sn solid-state NMR characterization of tin(II) carbodiimide Sn(NCN)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Aleksander Jaworski ◽  
Jędrzej Piątek ◽  
Liuda Mereacre ◽  
Cordula Braun ◽  
Adam Slabon
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Chemical Shifts ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Quadrupolar Coupling ◽  
Nmr Study ◽  
Nmr Characterization ◽  
Angle Spinning ◽  
High Level

Abstract We report the first magic-angle spinning (MAS) nuclear magnetic resonance (NMR) study on Sn(NCN). In this compound the spatially elongated (NCN)2− ion is assumed to develop two distinct forms: either cyanamide (N≡C–N2−) or carbodiimide (−N=C=N−). Our 14N MAS NMR results reveal that in Sn(NCN) the (NCN)2− groups exist exclusively in the form of symmetric carbodiimide ions with two equivalent nitrogen sites, which is in agreement with the X-ray diffraction data. The 14N quadrupolar coupling constant | C Q | $\vert {C}_{\text{Q}}\vert $  ≈ 1.1 MHz for the −N=C=N− ion in Sn(NCN) is low when compared to those observed in molecular compounds that comprise cyano-type N≡C– moieties ( | C Q | $\vert {C}_{\text{Q}}\vert $  > 3.5 MHz). This together with the information from 14N and 13C chemical shifts indicates that solid-state NMR is a powerful tool for providing atomic-level insights into anion species present in these compounds. The experimental NMR results are corroborated by high-level calculations with quantum chemistry methods.

Reactions of vanadate with N,N- dimethylhydroxylamine: aqueous equilibria and the crystal structure of the uncharged oxygenbridged dimer of bis(N,N-dimethylhydroxamido)hydroxooxovanadate

1997 ◽  
Vol 75 (4) ◽  
pp. 429-440 ◽  
Author(s):  
Pradip C. Paul ◽  
Sarah J. Angus-Dunne ◽  
Raymond J. Batchelor ◽  
Frederick W.B. Einstein ◽  
Alan S. Tracey
Keyword(s):  
Crystal Structure ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
Crystalline Solid ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Orthorhombic Space Group ◽  
Ph Variation ◽  
Nmr Study

51V nuclear magnetic resonance spectroscopy has been utilized in the investigation of the reactions of vanadate with N,N-dimethylhydroxylamine in aqueous medium. The major components of the reaction products were mono- and bisliganded mononuclear vanadate compounds with 51V chemical shifts near −630 and −740 ppm, respectively. Variation of the concentration of the reactants enabled the determination of stoichiometry and formation constants of the products. The two major signals near −740 ppm were assigned to two stereoisomers of a bisligand product. The proton stoichiometrics and pKa values of the major products were determined from pH variation studies. A crystalline product of the type [V(O)(ONMe2)2]2O was isolated from the reaction of vanadate with dimethylhydroxylamine and its structure determined from X-ray diffraction studies. The compound possesses a dimeric oxo-bridge structure with a six-coordinate vanadium core. The arrangement about each vanadium may be described as approximately tetrahedral considering the center of the N—O bond in each dimethylhydroxamide ligand as one vertex. Hydrolysis of the crystalline solid in D2O provided two isomers that corresponded to the two bisligand products. A variable temperature 1H NMR study in D2O and 50% D2O/(CD3)2CO mixture revealed the existence of reasonably fast chemical exchange between the two predominant isomers. The nature of coordination of these and related compounds is discussed. Crystal structure of [V(O)(ONMe2)2]2O: orthorhombic, space group P22121;Z = 2;a = 7.0955(9) Å; b = 10.2313(12) Å; c = 11.5942(11) Å; V = 841.69 Å3; T = 213 K; RF = 0.021 for 1141 data (I0 ≥ 2.5σ(I0) ) and 137 variables. Keywords: bis(N,N-dimethylhydroxamido)hydroxooxovanadate, vanadate, dimethylhydroxylamine, vanadium NMR, aqueous equilibria, peroxovanadate.

A solid-state 17O NMR study of platinum-carboxylate complexes: carboplatin and oxaliplatin

2015 ◽  
Vol 93 (9) ◽  
pp. 945-953 ◽  
Author(s):  
Xianqi Kong ◽  
Victor Terskikh ◽  
Abouzar Toubaei ◽  
Gang Wu
Keyword(s):  
Solid State ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Carboxylate Oxygen ◽  
Carboxylate Groups ◽  
Nmr Study ◽  
Nmr Characterization ◽  
Orbital Electron ◽  
Isotropic Chemical Shifts ◽  
Oxygen Atoms

We report synthesis and solid-state NMR characterization of two 17O-labeled platinum anticancer drugs: cis-diammine(1,1-cyclobutane-[17O4]dicarboxylato)platinum(II) (carboplatin) and ([17O4]oxalato)[(1R, 2R)-(−)-1,2-cyclohexanediamine)]platinum(II) (oxaliplatin). Both 17O chemical shift (CS) and quadrupolar coupling (QC) tensors were measured for the carboxylate groups in these two compounds. With the aid of plane wave DFT computations, the 17O CS and QC tensor orientations were determined in the molecular frame of reference. Significant changes in the 17O CS and QC tensors were observed for the carboxylate oxygen atom upon its coordination to Pt(II). In particular, the 17O isotropic chemical shifts for the oxygen atoms directly bonded to Pt(II) are found to be smaller (more shielded) by 200 ppm than those for the non-Pt-coordinated oxygen atoms within the same carboxylate group. Examination of the 17O CS tensor components reveals that such a large 17O coordination shift is primarily due to the shielding increase along the direction that is within the O=C–O–Pt plane and perpendicular to the O–Pt bond. This result is interpreted as due to the σ donation from the oxygen nonbonding orbital (electron lone pair) to the Pt(II) empty dyz orbital, which results in large energy gaps between σ(Pt–O) and unoccupied molecular orbitals, thus reducing the paramagnetic shielding contribution along the direction perpendicular to the O–Pt bond. We found that the 17O QC tensor of the carboxylate oxygen is also sensitive to Pt(II) coordination, and that 17O CS and QC tensors provide complementary information about the O–Pt bonding.

Sign in / Sign up

Export Citation Format

Share Document