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.

Kinetics of protoporphyrin IX formation in rat oral mucosa and skin after application of 5-aminolevulinic acid and its methylester

2004 ◽  
Author(s):  
Stefan Kristiansson ◽  
Asta Juzeniene ◽  
Petras Juzenas ◽  
Vladimir Iani ◽  
Lennart Löfgren ◽  
...  
Keyword(s):  
Oral Mucosa ◽  
Aminolevulinic Acid ◽  
Protoporphyrin Ix ◽  
Kinetics Of

Recent 31 P n.m.r. studies of myocardium

1980 ◽  
Vol 289 (1037) ◽  
pp. 437-439 ◽  
Keyword(s):  
Mechanical Performance ◽  
Normal Values ◽  
Chemical Exchange ◽  
Exchange Reactions ◽  
Perfused Heart ◽  
Time Intervals ◽  
Non Invasive ◽  
Biochemical State ◽  
Perfused Hearts ◽  
Kinetics Of

Earlier work from this laboratory has concerned the possible use of phosphorus n.m.r. as a method to monitor, in a non-invasive manner, the biochemical state of the perfused heart as a function of its mechanical performance. We showed that a simulated coronary infarction could be detected by 31 P n.m.r. (Hollis et al 1978 a and that hypothermia and KC1 arrest could preserve the pH and the ATP levels at more nearly normal values than in a non-arrested heart during long periods (40 min) of ischaemia (Hollis et al . 1978 b ).More recently it was shown that multiple doses of KC1, given at intervals, were more effective in this respect than was a single dose (Flaherty et al . 1979). These studies essentially followed the kinetics of transitions of the heart between two or more distinct physiological states (i.e. normoxic and ischaemic, with or without KC1 arrest) by observation of the 31 P n.m.r. spectra at various time intervals over periods of up to 1 h. As described in detail and demonstrated in Dr Truman Brown’s contribution to these discussions, the rates of chemical exchange reactions occurring in a steady state can be measured by the techniques of saturation transfer in various biological systems, including perfused hearts.

Application of two-dimensional NMR to kinetics of chemical exchange

1990 ◽  
Vol 90 (6) ◽  
pp. 935-967 ◽  
Author(s):  
Charles L. Perrin ◽  
Tammy J. Dwyer
Keyword(s):  
Chemical Exchange ◽  
Two Dimensional ◽  
Kinetics Of
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