Second order rate constants for intramolecular conversions: Application to gas‐phase NMR relaxation times

1983 ◽  
Vol 79 (6) ◽  
pp. 2808-2813 ◽  
Author(s):  
S. H. Bauer ◽  
K. I. Lazaar
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Second Order ◽  
Order Rate ◽  
Nmr Relaxation Times

AM1 calculational and experimental evidence that a β-nitroxyl group significantly enhances the thermodynamic and kinetic acidities of ketones

1994 ◽  
Vol 72 (11) ◽  
pp. 2348-2350 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Chandra Deo Roy
Keyword(s):  
Experimental Evidence ◽  
Gas Phase ◽  
Carbonyl Group ◽  
Rate Constants ◽  
Second Order ◽  
Nitroxyl Group ◽  
Order Rate ◽  
Kinetics Of

The kinetics of NaOD-catalysed H/D exchange of 3,3,5,5-tetramethylcyclohexanone (1), 1-hydroxy-4-oxo-2,2,6,6-tetrame-thylpiperidine (2), 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (3), 9-hydroxynorpseudopelletierine (4), and norpseudopelle-tierine-9-oxyl (5) have been studied in 60:40 dioxane–D2O(v/v) at 25.0 °C. The second-order rate constants are 9.20 × 10−3, 6.39 × 10−2, 1.59, 2.20 × 10−2, and 5.67 × 10−1 L mol−1 s−1 for 1, 2, 3, 4, and 5, respectively. Gas-phase enthalpies of ionization (the values are 363.0, 359.4, 352.0, 360.7, and 354.1 kcal mol−1 for 1, 2, 3, 4, and 5, respectively) calculated with AM1 correlate with the relative rates of enolization. Thus replacement of the β-hydroxylamino groups of 2 and 4 with a nitroxyl group produces sizable increases in the kinetic and thermodynamic acidities of the hydrogens α to the carbonyl group.

Inhibition in Purified Systems and in Human Plasma of Chimaeric Plasminogen Activators Consisting of the NH2-Terminal Region of Tissue-Type Plasminogen Activator and the COOH-Terminal Region of UrokinaseType Plasminogen Activator

1988 ◽  
Vol 60 (02) ◽  
pp. 247-250 ◽  
Author(s):  
H R Lijnen ◽  
L Nelles ◽  
B Van Hoef ◽  
F De Cock ◽  
D Collen
Keyword(s):  
Plasminogen Activator ◽  
Rate Constants ◽  
Plasminogen Activators ◽  
Second Order ◽  
Tissue Type ◽  
Single Chain ◽  
Chain Molecules ◽  
Order Rate ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator

SummaryRecombinant chimaeric molecules between tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator (scu-PA) or two chain urokinase-type plasminogen activator (tcu-PA) have intact enzymatic properties of scu-PA or tcu-PA towards natural and synthetic substrates (Nelles et al., J Biol Chem 1987; 262: 10855-10862). In the present study, we have compared the reactivity with inhibitors of both the single chain and two chain variants of recombinant u-PA and two recombinant chimaeric molecules between t-PA and scu-PA (t-PA/u-PA-s: amino acids 1-263 of t-PA and 144-411 of u-PA; t-PA/u-PA-e: amino acids 1-274 of t-PA and 138-411 of u-PA). Incubation with human plasma in the absence of a fibrin clot for 3 h at 37° C at equipotent concentrations (50% clot lysis in 2 h), resulted in significant fibrinogen breakdown (to about 40% of the normal value) for all two chain molecules, but not for their single chain counterparts. Preincubation of the plasminogen activators with plasma for 3 h at 37° C, resulted in complete inhibition of the fibrinolytic potency of the two chain molecules but did not alter the potency of the single chain molecules. Inhibition of the two chain molecules occurred with a t½ of approximately 45 min. The two chain variants were inhibited by the synthetic urokinase inhibitor Glu-Gly-Arg-CH2CCl with apparent second-order rate constants of 8,000-10,000 M−1s−1, by purified α2-antiplasmin with second-order rate constants of about 300 M−1s−1, and by plasminogen activator inhibitor-1 (PAI-1) with second-order rate constants of approximately 2 × 107 M−1s−1.It is concluded that the reactivity of single chain and two chain forms of t-PA/u-PA chimaers with inhibitors is very similar to that of the single and two chain forms of intact u-PA.

Determination of the Nucleophilicity of Tricarbonyliron Coordinated Cyclohepta-1,3,5-triene

1999 ◽  
Vol 64 (11) ◽  
pp. 1770-1779 ◽  
Author(s):  
Herbert Mayr ◽  
Karl-Heinz Müller
Keyword(s):  
Gibbs Energy ◽  
Ambient Temperature ◽  
Rate Constants ◽  
Second Order ◽  
Order Rate ◽  
Electrophilic Additions ◽  
Kinetics Of

The kinetics of the electrophilic additions of four diarylcarbenium ions (4a-4d) to tricarbonyl(η4-cyclohepta-1,3,5-triene)iron (1) have been studied photometrically. The second-order rate constants match the linear Gibbs energy relationship log k20 °C = s(E + N) and yield the nucleophilicity parameter N(1) = 3.69. It is concluded that electrophiles with E ≥ -9 will react with complex 1 at ambient temperature.

scholarly journals Proton NMR relaxation times in ischemic brain edema.

Stroke ◽  
1986 ◽  
Vol 17 (6) ◽  
pp. 1149-1152 ◽  
Author(s):  
Y Horikawa ◽  
S Naruse ◽  
C Tanaka ◽  
K Hirakawa ◽  
H Nishikawa
Keyword(s):  
Brain Edema ◽  
Relaxation Times ◽  
Proton Nmr ◽  
Nmr Relaxation ◽  
Ischemic Brain ◽  
Ischemic Brain Edema ◽  
Nmr Relaxation Times

Effects of hydrophobic treatments of stone on pore water studied by continuous distribution analysis of NMR relaxation times

2001 ◽  
Vol 19 (3-4) ◽  
pp. 509-512 ◽  
Author(s):  
L. Appolonia ◽  
G.C. Borgia ◽  
V. Bortolotti ◽  
R.J.S. Brown ◽  
P. Fantazzini ◽  
...  
Keyword(s):  
Pore Water ◽  
Relaxation Times ◽  
Continuous Distribution ◽  
Nmr Relaxation ◽  
Distribution Analysis ◽  
Nmr Relaxation Times

Reduction in the proton NMR relaxation times of dystrophic muscles following functional improvement

1984 ◽  
Vol 2 (3) ◽  
pp. 250-251 ◽  
Author(s):  
L.K. Misra ◽  
P.A. Narayana ◽  
D. Bearden ◽  
T. Egan ◽  
R.P. Munjaal ◽  
...  
Keyword(s):  
Relaxation Times ◽  
Proton Nmr ◽  
Nmr Relaxation ◽  
Functional Improvement ◽  
Nmr Relaxation Times

Luminescence Quenching of Rhodamines by Cyclooctatetraene

1987 ◽  
Vol 42 (9) ◽  
pp. 1009-1013 ◽  
Author(s):  
P. Targowski ◽  
B. Ziętek ◽  
A. Bączyński
Keyword(s):  
Rhodamine B ◽  
Rate Constants ◽  
Internal Conversion ◽  
Rhodamine 6G ◽  
Second Order ◽  
Luminescence Quenching ◽  
Intersystem Crossing ◽  
Order Rate ◽  
Quenching Process

Cyclooctatetraene (COT) as a quencher of fluorescence of a series of Rhodamine solutions was studied. The second order rate constants for the quenching process of Rhodamine 110, Rhodamine 19 pchl., Rhodamine 6G pchl., Rhodamine 6G, Tetramethylrhodamine, Rhodamine B and Rhodamine 3B pchl. are given. It was found that COT enhances rather intersystem crossing than internal conversion.

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