Blackbody-Radiation-Induced Population Transfer Dynamics from Highly Vibrationally Excited Levels of the E 0g+ (3P2) Ion-Pair State of I2

2019 ◽  
Vol 124 (3) ◽  
pp. 492-497
Author(s):  
Shoma Hoshino ◽  
Koichi Tsukiyama
Keyword(s):  
Ion Pair ◽  
Blackbody Radiation ◽  
Population Transfer ◽  
Vibrationally Excited ◽  
Radiation Induced ◽  
Pair State

scholarly journals Ionization characteristics of the Cys-25/His-159 interactive system and of the modulatory group of papain: resolution of ambiguity by electronic perturbation of the quasi-2-mercaptopyridine leaving group in a new pyrimidyl disulphide reactivity probe

1993 ◽  
Vol 290 (1) ◽  
pp. 289-296 ◽  
Author(s):  
G W Mellor ◽  
E W Thomas ◽  
C M Topham ◽  
K Brocklehurst
Keyword(s):  
Ph Dependence ◽  
Order Rate Constant ◽  
Ion Pair ◽  
Catalytic Site ◽  
Alkaline Media ◽  
Interactive System ◽  
Data Set ◽  
Pka Value ◽  
Compound Ii ◽  
Pair State

1. A new thiol-specific reactivity probe 4,4′-dipyrimidyl disulphide [compound (VII), m.p. 110 degrees C, pKa of its monohydronated form 0.91] was synthesized and used to resolve the ambiguity of interpretation of the behaviour of papain (EC 3.4.22.2) in alkaline media known to depend to varying extents on two ionizations with pKa values approx. 8.0-8.5 and > or = 9.5 respectively. 2. A new extensive pH-second-order rate constant (k) data set for the reaction of papain with 2-(acetamido)-ethyl 2′-pyridyl disulphide (IV) demonstrated the existence of a striking rate maximum at pH approx. 4, the independence of k around pH 8 and the increase in k with increase in pH across a pKa value of 10.0, behaviour similar to that of other 2-pyridyl disulphides (R-S-S-2-Py) that lack key substrate-like binding sites in R. 3. Although the simplest interpretation of the pKa value of 10.0 assigns it to the formation of (Cys-25)-S-/(His-159)-Im from the ion-pair state of the papain catalytic site, another interpretation may be conceived in which this pKa value is assigned to another group remote from the catalytic site, the state of ionization of which modulates catalytic-site behaviour. This alternative assignment is shown to require compensating effects in the pH region around 8 such that the formation of (Cys-25)-S-/(His-159)-Im across pKa 8.0-8.5 is without net kinetic effect in the reactions of simple 2-pyridyl disulphides such as compound (IV) and 2,2′-dipyridyl disulphide (II). 4. The lower basicity of compound (VII) relative to that of compound (II) (pKa 2.45) was predicted to diminish or abolish the compensation postulated as a possibility in reactions of 2-pyridyl disulphides because of the decreased effectiveness of reaction via a (His-159)-Im+H-assisted transition state. The characteristics of the pH-dependence of the reaction of papain with compound (VII) which are quite different from those for its reaction with compound (II) support both this prediction and the alternative assignment with a value of 8.3 for the pKa of the formation of (Cys-25)-S-/(His-159)-Im. 5. Evidence that the behaviour of papain towards both substrates and some substrate-derived time-dependent inhibitors is determined not only by the loss of the (Cys-25)-S-/(His-159)-Im+H ion-pair state by dehydronation with pKa 8.3 but also by another ionization of pKa approx. 10.0 is briefly discussed.

Direct vibrational numbering of the D0u+ ion-pair state of Br2

1988 ◽  
Vol 149 (2) ◽  
pp. 155-160 ◽  
Author(s):  
R.H. Lipson ◽  
A.R. Hoy ◽  
M.J. Flood
Keyword(s):  
Ion Pair ◽  
Pair State

Time-resolved study of the lowest optically accessible ion-pair state of IBr using synchrotron radiation

1985 ◽  
Vol 31 (1) ◽  
pp. 1-5 ◽  
Author(s):  
R.J. Donovan ◽  
G. Gilbert ◽  
M. Macdonald ◽  
J.P.T. Wilkinson ◽  
I. Munro ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Ion Pair ◽  
Time Resolved ◽  
Pair State

An analysis of the F(Ou+) ion-pair state of I2 by optical-optical double resonance

1986 ◽  
Vol 119 (2) ◽  
pp. 337-351 ◽  
Author(s):  
Takashi Ishiwata ◽  
Tatsuo Kusayanagi ◽  
Takefumi Hara ◽  
Ikuzo Tanaka
Keyword(s):  
Double Resonance ◽  
Ion Pair ◽  
Optical Double Resonance ◽  
Pair State
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