Binding of 4-methylumbelliferyl α-D-mannopyranoside to dimeric concanavalin A: fluorescence temperature-jump relaxation study

Biochemistry ◽  
1977 ◽  
Vol 16 (2) ◽  
pp. 167-175 ◽  
Author(s):  
Robert M. Clegg ◽  
Frank G. Loontiens ◽  
Thomas M. Jovin
Keyword(s):  
Concanavalin A ◽  
Temperature Jump ◽  
Relaxation Study

scholarly journals Binding of 4-Methylumbelliferyl alpha-d-Mannopyranoside to Tetrameric Concanavalin A. Fluorescence Temperature-Jump Relaxation Study

1977 ◽  
Vol 78 (2) ◽  
pp. 465-469 ◽  
Author(s):  
Frank G. LOONTIENS ◽  
Anita LANDSCHOOT ◽  
Robert M. CLEGG ◽  
Thomas M. JOVIN
Keyword(s):  
Concanavalin A ◽  
Temperature Jump ◽  
Relaxation Study

Kinetics of the equilibration of 3-hydroxyphthalide and o-formylbenzoic acid. Hemiacetal breakdown with a carboxylic acid leaving group

1986 ◽  
Vol 64 (6) ◽  
pp. 1196-1200 ◽  
Author(s):  
Robert A. McClelland ◽  
Poule E. Sørensen
Keyword(s):  
Carboxylic Acid ◽  
Ring Opening ◽  
Temperature Jump ◽  
Acid Catalyst ◽  
Concerted Mechanism ◽  
Leaving Group ◽  
Relaxation Study ◽  
Acid Catalyzed ◽  
Kinetics Of ◽  
Conjugate Base

A temperature-jump relaxation study is reported for the equilibration: 3-hydroxyphthalide (SH) [Formula: see text]o-formylbenzoate (R−) [Formula: see text]o-formylbenzoic acid (RH). A kinetic analysis is carried out in which SH and R− interconvert with catalysis in the ring opening direction by water and by added general bases. Excellent Brønsted plots based upon a series of oxyacid buffer catalysts are obtained. These have slopes β for the base-catalyzed ring opening of 0.81 and α for the reverse acid-catalyzed ring closing of 0.19. A mechanism where S−, the conjugate base of SH, is a discrete intermediate can be ruled out on the basis of the Brønsted values and the magnitudes of the rate constants. The lifetime of S− is estimated to lie in the range 10−11–10−15 s. Two mechanisms can be proposed. A fully concerted mechanism "enforced" by lifetimes less than 10−13 s involves direct interconversion of SH and R− with no intermediate. A preassociated mechanism "enforced" by lifetimes in the 10−11–10−12 s range requires, in the ring closing direction, that an acid catalyst be hydrogen bonded to the carbonyl in R−.

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