14N NMR Studies on Cyclic Nitramines. Correlations of Chemical Shifts with Nitrogen Partial Atomic Charge and .pi.-Orbital Overlap

1994 ◽  
Vol 59 (19) ◽  
pp. 5623-5626 ◽  
Author(s):  
Michael Kony ◽  
Ian J. Dagley ◽  
D. Ralph Leslie
Keyword(s):  
Chemical Shifts ◽  
Atomic Charge ◽  
Nmr Studies ◽  
Partial Atomic Charge ◽  
Cyclic Nitramines ◽  
14N Nmr

14N-NMR-Untersuchungen an Aminophosphinen / 14N NMR Studies on Aminophosphines

1978 ◽  
Vol 33 (5) ◽  
pp. 515-520 ◽  
Author(s):  
K. Barlos ◽  
H. Nöth ◽  
B. Wrackmeyer
Keyword(s):  
Chemical Shifts ◽  
Steric Effects ◽  
Nmr Studies ◽  
Π Interactions ◽  
Nuclear Shielding ◽  
14N Nmr

Abstract14N chemical shifts of a series of cyclic and noncyclic aminophosphines are reported. The nuclear shielding of nitrogen decreases with increasing number of halogen substituents at phosphorus as well as with increasing number of phosphinyl groups attached to nitrogen. In addition to the influence of electronegativity PN(π)-interactions may account for the observed shielding. Steric effects are discussed.

Synthesis and characterization of 19F NMR chelators for measurement of cytosolic free Ca

1987 ◽  
Vol 252 (4) ◽  
pp. C441-C449 ◽  
Author(s):  
L. A. Levy ◽  
E. Murphy ◽  
R. E. London
Keyword(s):  
Chemical Shifts ◽  
Cell Types ◽  
Free Calcium ◽  
Tetraacetic Acid ◽  
Nmr Studies ◽  
Cytosolic Free Calcium ◽  
Fluorine Nmr ◽  
Dissociation Constant Kd

Fluorine 19 nuclear magnetic resonance (NMR) studies of intracellular fluorinated calcium chelators provide a useful strategy for the determination of cytosolic free calcium levels in cells and perfused organs. However, the fluorinated chelator with the highest affinity for calcium ions which has been described to date. 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), exhibits a dissociation constant (Kd) value 5- to 10-fold greater than the intracellular calcium concentration levels in most cell types, thus limiting the ability of fluorine NMR to report these concentrations reliably. We have consequently designed and synthesized several fluorinated calcium chelators with higher affinity for calcium. The best of these, 2-(2-amino-4-methyl-5-fluorophenoxy)-methyl-8 aminoquinidine-N,N,N',N'-tetraacetic acid (quinMF), has a Kd value approximately 10 times lower than that of 5FBAPTA. Several of the newly synthesized indicators have different chemical shifts for the calcium complexed and uncomplexed chelators to allow the simultaneous use of two indicators. In addition to providing information about the level of cytosolic free calcium, chelators containing a quinoline ring exhibit considerable sensitivity to magnesium levels and hence have potential application for the determination of cytosolic-magnesium concentrations. Application of these chelators is illustrated by determination of the cytosolic-free calcium level in erythrocytes. Use of quinMF, the chelator with the lowest Kd value, gives a calcium value of 25-30 nM.

NMR studies of tandem WW domains of Nedd4 in complex with a PY motif-containing region of the epithelial sodium channel

1998 ◽  
Vol 76 (2-3) ◽  
pp. 341-350 ◽  
Author(s):  
Voula Kanelis ◽  
Neil A Farrow ◽  
Lewis E Kay ◽  
Daniela Rotin ◽  
Julie D Forman-Kay
Keyword(s):  
Chemical Shift ◽  
Sodium Channel ◽  
Chemical Shifts ◽  
Epithelial Sodium Channel ◽  
Chemical Shift Assignment ◽  
Nmr Studies ◽  
Ww Domains ◽  
Ww Ii ◽  
Py Motif ◽  
Shift Assignment

Nedd4 (neuronal precursor cell-expressed developmentally down-regulated 4) is a ubiquitin-protein ligase containing multiple WW domains. We have previously demonstrated the association between the WW domains of Nedd4 and PPxY (PY) motifs of the epithelial sodium channel (ENaC). In this paper, we report the assignment of backbone 1Hα, 1HN, 15N, 13C', 13Cα, and aliphatic 13C resonances of a fragment of rat Nedd4 (rNedd4) containing the two C-terminal WW domains, WW(II+III), complexed to a PY motif-containing peptide derived from the β subunit of rat ENaC, the βP2 peptide. The secondary structures of these two WW domains, determined from chemical shifts of 13Cα and 13Cβ resonances, are virtually identical to those of the WW domains of the Yes-associated protein YAP65 and the peptidyl-prolyl isomerase Pin1. Triple resonance experiments that detect the 1Hα chemical shift were necessary to complete the chemical shift assignment, owing to the large number of proline residues in this fragment of rNedd4. A new experiment, which correlates sequential residues via their 15N nuclei and also detects 1Hα chemical shifts, is introduced and its utility for the chemical shift assignment of sequential proline residues is discussed. Data collected on the WW(II+III)-βP2 complex indicate that these WW domains have different affinities for the βP2 peptide.Key words: WW domain, PY motif, Nedd4, ENaC, NMR.

scholarly journals NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

2011 ◽  
Vol 7 ◽  
pp. 1205-1214 ◽  
Author(s):  
Damjan Makuc ◽  
Jennifer R Hiscock ◽  
Mark E Light ◽  
Philip A Gale ◽  
Janez Plavec
Keyword(s):  
Conformational Changes ◽  
Chemical Shifts ◽  
Dihydrogen Phosphate ◽  
Nmr Studies ◽  
Receptor Complexes ◽  
Hydrogen Bond Interactions ◽  
Weak Binding ◽  
Oxo Anions ◽  
Induced Changes ◽  
Good Agreement

The conformational properties of 1,3-diindolylureas and thioureas were studied by a combination of heteronuclear NMR spectroscopy and quantum mechanics calculations. NOE experiments showed that the anti–anti conformer along the C7–N7α bonds was predominant in DMSO-d 6 solution in the absence of anions. Anion-induced changes in the 1H and 15N chemical shifts confirm the weak binding of chloride anions with negligible conformational changes. Strong deshielding of ureido protons and moderate deshielding of indole NH was observed upon the addition of acetate, benzoate, bicarbonate and dihydrogen phosphate, which indicated that the predominant hydrogen bond interactions occurred at the urea donor groups. Binding of oxo-anions caused conformational changes along the C7–N7α bonds and the syn–syn conformer was preferred for anion–receptor complexes. The conformational changes upon anion binding are in good agreement with energetic preferences established by ab initio calculations.

27Al-MAS-NMR-Untersuchungen des thermischen Abbaus von NH4Al(SO4)2·12H2O / 27Al-MAS-NMR Studies on the Thermolysis of NH4Al(SO4)2· 12H2O

1991 ◽  
Vol 46 (11) ◽  
pp. 1515-1518 ◽  
Author(s):  
Gerhard Wegner ◽  
Gert Blumenthal ◽  
Dirk Müller ◽  
Dirk-Henning Menz ◽  
Antje Schmalstieg
Keyword(s):  
Nmr Spectroscopy ◽  
Structural Changes ◽  
Chemical Shifts ◽  
Mas Nmr ◽  
Nmr Studies ◽  
High Stage ◽  
27Al Mas Nmr ◽  
High Resolution Nmr ◽  
First Time

Products of the thermolysis of NH4Al-alum were prepared under dried air and characterized by X-ray powder diffraction, thermogravimetry, and for the first time by solid-state 27Al-MAS-NMR spectroscopy. It was found, that high resolution NMR spectroscopy is applicable to follow up the thermal decomposition and to indicate even minor structural changes. 27Al-MAS-NMR spectra show peaks with characteristic chemical shifts for octahedral Al-units up to a high stage of thermolysis. During the decomposition of Al2(SO4)3 to γ-Al2O3 we again observed three-peak spectra with the specific signal at ≈ 35 ppm for penta-coordinated Al ions as recently proved for the thermolysis of AlCl3 · 6 H2O.

Two-dimensional solid-state NMR studies of crystalline poly(ethylene oxide): Conformations and chemical shifts

Polymer ◽  
2005 ◽  
Vol 46 (25) ◽  
pp. 11737-11743 ◽  
Author(s):  
D.J. Harris ◽  
T.J. Bonagamba ◽  
M. Hong ◽  
K. Schmidt-Rohr
Keyword(s):  
Solid State ◽  
Ethylene Oxide ◽  
Solid State Nmr ◽  
Chemical Shifts ◽  
Two Dimensional ◽  
Nmr Studies ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene
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