N.M.R. spectra of the carbolines. II. 14N quadrupolar and exchange broadening of spectral lines

1973 ◽  
Vol 26 (7) ◽  
pp. 1523 ◽  
Author(s):  
F Balkau ◽  
ML Heffernan
Keyword(s):  
Pyridine Ring ◽  
Chemical Exchange ◽  
Spectral Lines ◽  
Line Broadening ◽  
Quadrupolar Relaxation ◽  
Line Widths ◽  
Exchange Broadening

The n.m.r, spectra of carbazole and the carbolines were previously reported to show unusual line broadening effects under certain conditions. It is found that for the proton in position 9 both chemical exchange and 14N quadrupolar relaxation are responsible for the large line widths observed, while for protons in the ?pyridine? ring chemical exchange is the more important effect. The nature of this exchange is still uncertain, the rate being critically dependent on solvent and sample purity as well as temperature.

Detection of Chemical Exchange in Methyl Groups of Macromolecules

2019 ◽  
Author(s):  
Michelle Gill ◽  
Andrew Hsu ◽  
Arthur G. Palmer, III
Keyword(s):  
Relaxation Rate ◽  
Chemical Exchange ◽  
Double Quantum ◽  
Methyl Groups ◽  
Multiple Quantum ◽  
Relaxation Data ◽  
E Coli ◽  
Methyl Trosy ◽  
Dynamics Simulations ◽  
Exchange Broadening

<div> <div> <div> <p>The zero- and double-quantum methyl TROSY Hahn-echo and the methyl <sup>1</sup>H-<sup>1</sup>H dipole- dipole cross-correlation nuclear magnetic resonance experiments enable estimation of multiple quantum chemical exchange broadening in methyl groups in proteins. The two relaxation rate constants are established to be linearly dependent using molecular dynamics simulations and empirical analysis of experimental data. This relationship allows chemical exchange broadening to be recognized as an increase in the Hahn-echo relaxation rate constant. The approach is illustrated by analyzing relaxation data collected at three temperatures for <i>E. coli </i>ribonuclease HI and by analyzing relaxation data collected for different cofactor and substrate complexes of <i>E. coli </i>AlkB. </p> </div> </div> </div>

scholarly journals Toward Engineering Intrinsic Line Widths and Line Broadening in Perovskite Nanoplatelets

ACS Nano ◽  
2021 ◽  
Vol 15 (4) ◽  
pp. 6499-6506
Author(s):  
Albert Liu ◽  
Gabriel Nagamine ◽  
Luiz G. Bonato ◽  
Diogo B. Almeida ◽  
Luiz F. Zagonel ◽  
...  
Keyword(s):  
Line Broadening ◽  
Line Widths

CRDS study of auto-ionizing Rydberg states of argon in a microwave discharge This article is part of a Special Issue on Spectroscopy at the University of New Brunswick in honour of Colan Linton and Ron Lees.

2009 ◽  
Vol 87 (5) ◽  
pp. 575-581 ◽  
Author(s):  
B. M. van der Ende ◽  
C. Winslade ◽  
R. L. Brooks ◽  
R. H. deLaat ◽  
N. P.C. Westwood
Keyword(s):  
New Brunswick ◽  
Excited States ◽  
Microwave Discharge ◽  
Rydberg States ◽  
Spectral Lines ◽  
Optical Transitions ◽  
Single Source ◽  
Special Issue ◽  
Line Widths ◽  
The University

Optical transitions from two microwave discharge excited states of argon have been observed using cavity ring-down spectroscopy. These transitions originate on the high-lying levels, 3d[1/2] 1° and 3d[3/2] 2° , and terminate on the nf ′[5/2] Rydberg (n = 8 to 22) levels, which, except for n = 8, lie between the 2P3/2 and 2P1/2 ionization thresholds. In total, 24 such spectral lines have been observed. The quantum defect for the f ′ series has been measured and is compared to previously measured values. We observe a nearly threefold jump in line width in going from n = 8 to n = 9, below and above the 2P3/2 threshold, respectively. The line widths are broad and increase monotonically with n (above 9), in contrast to the narrowing of line widths usually observed. We cannot attribute this to a single source but conclude that collisional, quasielastic l-mixing of the nf ′[5/2] Rydberg states plays a significant role.

Notizen: Binding and Kinetics of 1-Methylimidazol on Fe(III)-Protoporphyrin(IX)dimethylester and Fe(III)-Tetraphenylporphyrin in Chloroform

1976 ◽  
Vol 31 (2) ◽  
pp. 242-245 ◽  
Author(s):  
Eberhard V. Goldammer ◽  
Herbert Zorn
Keyword(s):  
Spin State ◽  
Chemical Exchange ◽  
Phase 1 ◽  
Protoporphyrin Ix ◽  
Bulk Phase ◽  
Paramagnetic Species ◽  
Solvent Exchange ◽  
Line Broadening ◽  
Axial Ligands ◽  
Kinetics Of

Nuclear magnetic line widths data have been used to determine the rate of solvent exchange between the coordination sphere of Fe(III)-protoporphyrin(IX)dimethylester or Fe(III)-tetraphenylporphyrin and the bulk phase of 1-methylimidazol/chloroform. At temperatures below 322 K both porphyrins are in the low-spin state and separate PMR absorption caused by the methyl protons of two 1-methylimidazol molecules complexed in fifth and sixth position of ferri-porphyrins is detected. At T ≳ 320 K an accelerated exchange of these ligands was observed and the underlying kinetic parameters have been extracted. It was found that this exchange takes place when the paramagnetic species is in its low-spin state. For 240 K ≲ T ≲ 290 K dynamic line broadening of bulk phase 1-methylimidazol indicates occurrence of chemical exchange attributed to 1-methylimidazol interacting with ferri-porphyrin in addition to the strongly bound axial ligands.

scholarly journals Abrogation of prenucleation, transient oligomerization of the Huntingtin exon 1 protein by human profilin I

2020 ◽  
Vol 117 (11) ◽  
pp. 5844-5852 ◽  
Author(s):  
Alberto Ceccon ◽  
Vitali Tugarinov ◽  
Rodolfo Ghirlando ◽  
G. Marius Clore
Keyword(s):  
Single Molecule ◽  
Chemical Exchange ◽  
Coiled Coil ◽  
Relaxation Dispersion ◽  
Line Broadening ◽  
Exon 1 ◽  
Nmr Techniques ◽  
Mechanistic Basis ◽  
Kinetics Of ◽  
Micromolar Range

Human profilin I reduces aggregation and concomitant toxicity of the polyglutamine-containing N-terminal region of the huntingtin protein encoded by exon 1 (httex1) and responsible for Huntington’s disease. Here, we investigate the interaction of profilin with httex1using NMR techniques designed to quantitatively analyze the kinetics and equilibria of chemical exchange at atomic resolution, including relaxation dispersion, exchange-induced shifts, and lifetime line broadening. We first show that the presence of two polyproline tracts in httex1, absent from a shorter huntingtin variant studied previously, modulates the kinetics of the transient branched oligomerization pathway that precedes nucleation, resulting in an increase in the populations of the on-pathway helical coiled-coil dimeric and tetrameric species (τex≤ 50 to 70 μs), while leaving the population of the off-pathway (nonproductive) dimeric species largely unaffected (τex∼750 μs). Next, we show that the affinity of a single molecule of profilin to the polyproline tracts is in the micromolar range (Kdiss∼ 17 and ∼ 31 μM), but binding of a second molecule of profilin is negatively cooperative, with the affinity reduced ∼11-fold. The lifetime of a 1:1 complex of httex1with profilin, determined using a shorter huntingtin variant containing only a single polyproline tract, is shown to be on the submillisecond timescale (τex∼ 600 μs andKdiss∼ 50 μM). Finally, we demonstrate that, in stable profilin–httex1complexes, the productive oligomerization pathway, leading to the formation of helical coiled-coil httex1tetramers, is completely abolished, and only the pathway resulting in “nonproductive” dimers remains active, thereby providing a mechanistic basis for how profilin reduces aggregation and toxicity of httex1.

Echoes and imaging in solids

1990 ◽  
Vol 333 (1632) ◽  
pp. 427-439 ◽  
Keyword(s):  
Spin Echo ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Spectral Lines ◽  
Line Broadening ◽  
Rf Pulses ◽  
Field Gradients ◽  
Magnetic Field Gradients ◽  
Bandwidth Limitation ◽  
Successful Approach

The broad spectral lines usually encountered in solid state NMR present considerable difficulties for imaging. One successful approach to the problem is to artificially narrow the line by multipulse or sample spinning methods. An alternative is to apply sufficiently large magnetic field gradients that they dominate the line broadening and seek ways to deal with bandwidth and power requirements thereby introduced. This paper explores the second route and demonstrates that spin-echo techniques help to solve several of the inherent problems. Gradient echoes produced by periodic reversal of the field gradients have significant advantages. The addition of synchronous RF pulses can produce an extended train of ‘solid’ echoes which overcomes, at least to some extent, the bandwidth limitation of this approach and permits rapid imaging in two dimensions. Slice selection and three-dimensional back projection have also been achieved in solid-like samples. Comparison with linenarrowing methods and relative advantages of the different approaches are addressed.

Nuclear magnetic resonance spectroscopy of denatured proteins

1969 ◽  
Vol 22 (5) ◽  
pp. 1083 ◽  
Author(s):  
JH Bradbury ◽  
NLR King
Keyword(s):  
Molecular Weight ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Trifluoroacetic Acid ◽  
Guanidine Hydrochloride ◽  
Dichloroacetic Acid ◽  
Random Coil ◽  
Resonance Spectroscopy ◽  
Line Broadening ◽  
Line Widths

The proton magnetic resonance spectroscopy of 11 proteins (molecular weight range 5700-650000) has been investigated in five denaturing solvents, viz., trifluoroacetic acid-d, formic acid, dichloroacetic acid, 6M guanidine hydrochloride in D2O, and 8M urea in D2O. The chemical shifts, line-widths, and intensities of the resonances have been measured of the histidine C2 protons, the methionine SCH3 protons and methyl protons of leucine, isoleucine, and valine, the aromatic protons, and the α-CH protons. ��� It is found that, with some exceptions delineated below, the line- widths of the methyl resonances are constant for a particular solvent, independent of the molecular weight of the protein. This indicates that, in general, the proteins behave as random coil structures in these solvents, which confirms the conclusion reached by Tanford and co-workers1-4 for 6M guanidine hydrochloride. ��� However, methyl line broadening occurs in dichloroacetic acid for catalase and fibrinogen, in guanidine hydrochloride for insulin, and in urea for insulin and lysozyme. Furthermore, the C 2 histidine resonance is absent in dichloroacetic acid solutions of thyroglobulin, catalase, and fibrinogen; the SCH3 resonance is absent in myoglobin in trifluoroacetic acid-d and occurs as a doublet for trypsin in guanidine hydrochloride and in urea. A general line broadening of resonances indicates association and/or incomplete unfolding of molecules, whereas perturbations of only one particular resonance, as in the cases detailed above, are probably due to intramolecular non-covalent interactions which involve the perturbed group and another unspecified group in the protein. ��

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