scholarly journals Frequency offset dependence of adiabatic rotating frame relaxation rate constants: relevance to MRS investigations of metabolite dynamics in vivo

2011 ◽  
Vol 24 (7) ◽  
pp. 807-814 ◽  
Author(s):  
Silvia Mangia ◽  
Timo Liimatainen ◽  
Michael Garwood ◽  
Ivan Tkac ◽  
Pierre-Gilles Henry ◽  
...  
Keyword(s):  
Relaxation Rate ◽  
Rate Constants ◽  
Frequency Offset ◽  
Rotating Frame ◽  
Rotating Frame Relaxation

scholarly journals Quantitative Assessment of Water Pools by T1p and T2p MRI in Acute Cerebral Ischemia of the Rat

2008 ◽  
Vol 29 (1) ◽  
pp. 206-216 ◽  
Author(s):  
Kimmo T Jokivarsi ◽  
Juha-Pekka Niskanen ◽  
Shalom Michaeli ◽  
Heidi I Gröhn ◽  
Michael Garwood ◽  
...  
Keyword(s):  
Correlation Time ◽  
Continuous Wave ◽  
Vasogenic Edema ◽  
Free Water ◽  
Rotating Frame ◽  
Mri Contrast ◽  
Water Fraction ◽  
Acute Cerebral Ischemia ◽  
Rotating Frame Relaxation

The rotating frame longitudinal relaxation magnetic resonance imaging (MRI) contrast, T1ρ, obtained with on-resonance continuous wave (CW) spin-lock field is a sensitive indicator of tissue changes associated with hyperacute stroke. Here, the rotating frame relaxation concept was extended by acquiring both T1ρ and transverse rotating frame ( T2ρ) MRI data using both CW and adiabatic hyperbolic secant (HSn; n = 1, 4, or 8) pulses in a rat stroke model of middle cerebral artery occlusion. The results show differences in the sensitivity of spinlock T1ρ and T2ρ MRI to detect hyperacute ischemia. The most sensitive techniques were CW- T1ρ and T1ρ using HS4 or HS8 pulses. Fitting a two-pool exchange model to the T1ρ and T2ρ MRI data acquired from the infarcting brain indicated time-dependent increase in free water fraction, decrease in the correlation time of water fraction associated with macromolecules, and increase in the exchange correlation time. These findings are consistent with known pathology in acute stroke, including vasogenic edema, destructive processes, and tissue acidification. Our results show that the sensitivity of the spinlock MRI contrast in vivo can be modified using different spinlock preparation blocks, and that physicochemical models of the rotating frame relaxation may provide insight into progression of ischemia in vivo.

Longitudinal rotating frame relaxation time measurements in infarcted mouse myocardium in vivo

2012 ◽  
Vol 69 (5) ◽  
pp. 1389-1395 ◽  
Author(s):  
Haja-Sherief N. Musthafa ◽  
Galina Dragneva ◽  
Line Lottonen ◽  
Mari Merentie ◽  
Lyubomir Petrov ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Rotating Frame ◽  
Rotating Frame Relaxation

scholarly journals Synergistic Experimental and Computational Investigation of the Bioorthogonal Reactivity of Substituted Aryltetrazines

2021 ◽  
Author(s):  
Umberto Battisti ◽  
Rocío García-Vázquez ◽  
Dennis Svatunek ◽  
Barbara Herrmann ◽  
Andreas Löffler ◽  
...  
Keyword(s):  
Kinetic Study ◽  
Solvent Effects ◽  
Rate Constants ◽  
Biomedical Applications ◽  
Aqueous Systems ◽  
Phenyl Substituent ◽  
Computational Investigation ◽  
Radiation Burden ◽  
Intrinsic Reactivity

Tetrazines (Tz) have been applied as bioorthogonal agents for various biomedical applications including pretargeted imaging approaches. In radioimmunoimaging, pretargeting increases the target-to-background ratio while simultaneously reducing the radiation burden. We have recently reported a strategy to directly 18F-label highly reactive tetrazines based on a 3-(3-fluorophenyl)-Tz core structure. Herein, we report a kinetic study on this versatile scaffold. A library of 40 different tetrazines was prepared, fully characterized, and investigated with emphasis on second order rate constants for the reaction with trans-cyclooctene (TCO). Our results reveal the effects of various substitution patterns and moreover demonstrate the importance of measuring reactivities in the solvent of interest, as click rates in different solvents do not necessarily correlate well. In particular, we report that tetrazines modified in 2-position of the phenyl substituent show high intrinsic reactivity towards TCO, which is diminished in aqueous systems by unfavorable solvent effects. The obtained results enable the prediction of the bioorthogonal reactivity and thereby facilitate the development of the next-generation of substituted aryltetrazines for in vivo application.

HUMAN MEIZOTHROMBIN 1, ITS ISOLATION AND PROPERTIES

1987 ◽  
Author(s):  
Zbigniew S Latallo ◽  
Craig M Jackson
Keyword(s):  
Rate Constants ◽  
Antithrombin Iii ◽  
Order Rate Constant ◽  
Red Cross ◽  
Apparent Lack ◽  
First Order ◽  
Order Rate ◽  
Matching Grant ◽  
Echis Carinatus

Meizothrombin (MT) and meizothrombin des Fragment 1 (MT1) are intermediates in the conversion of prothrombin to α-thrombin (αTH). Due to their transient character, properties of these enzymes are difficult to establish. Isolation of MT1 was achieved by affinity chromatography on D-Phe-Pro-Arginal (FPRal)immobilized on Affi-Gel 10 as originally employed for thrombin purification (Patel et al. Biochim.Biophys. Acta 748,321 (1983)). Human prethrombin 1 was activated with the purified activator from Echis carinatus venom in the presence of Ca++;, benzamidine and FPRal gel at pH 7.8. After exhaustive washing the MT1 was eluted with 0.1 M hydroxylamine in 0.15 M Na acetate buffer, pH 5.5. Under these conditions the MT1 is stable and can bestored at -70°C. Upon changing the pH of the preparation to 8.0, complete conversion into aTH occurred atroom temperature within 48 hours. Homogeneity of both preparations wasdemonstrated by PAGE. The Km and ke, values for MT1 measured on Tos-Gly-Pro-Arg pNA(0.1 M NaCl, 0.01 M TRIS, 0.01 M HEPES, 0.1% PEG, pH 7.8, 25°C) were 15.7 /iM and 126 s-1. The kinetic con stants for the aTH resulting from autocatalytic degradation of MT1 were indistinguishable from those previously established forαTH obtained by Xa activation i.e. 4.77 /μM and 126 s-1. Clotting activity of MT1 was found to be only one fifth as high as that of the resulting μTH(746 u/mg vs. 3900 u/mg as tested using the NIH standard) .Inhibitionof MTl by antithrombin III was alsomuch less rapid than αTH andmost importantly, it was not affected by high affinity heparin( Mr20,300). Under conditions of the experiment (0.3 M NaCl, 0.0rl M TRIS, 0.01 M HEPES, 2.5 mM EDTA, 0.1% PEG, pH 7.8, 25°C; [ATIII] 100 nM, [E] 10 nM), the pseudo first order rate constants in the absence of heparin were 4.04 × 10-3V1 (MTl) and 1.13 × 10-3V1 (αTH), giving apparent second order rate constants of 4.04 × 103 and 1.13 × 10-4M-1s-1. In the presence of 4.5 nM of heparin the observed first order rate constant for MTl remained unchanged whereas it increased to 6.241 × 10-3s-1 (5.5 fold) for αTH. This apparent lack of an effect of heparin may be of significance in vivo.Supported by a Matching Grant from the American National Red Cross and by the Southeastern Michigan Blood Service.

scholarly journals State-to-state rotational relaxation rate constants for CO+Ne from IR–IR double-resonance experiments: Comparing theory to experiment

2004 ◽  
Vol 120 (16) ◽  
pp. 7483-7489 ◽  
Author(s):  
David A. Hostutler ◽  
Tony C. Smith ◽  
Gordon D. Hager ◽  
George C. McBane ◽  
Michael C. Heaven
Keyword(s):  
Relaxation Rate ◽  
Rate Constants ◽  
Double Resonance ◽  
Rotational Relaxation

scholarly journals Balanced spin‐lock preparation for B 1 ‐insensitive and B 0 ‐insensitive quantification of the rotating frame relaxation time T 1ρ

2020 ◽  
Author(s):  
Maximilian Gram ◽  
Michael Seethaler ◽  
Daniel Gensler ◽  
Johannes Oberberger ◽  
Peter M. Jakob ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Rotating Frame ◽  
Spin Lock ◽  
Rotating Frame Relaxation
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