Temperature effects on xanthone–β-cyclodextrin binding dynamics

2011 ◽  
Vol 89 (3) ◽  
pp. 395-401 ◽  
Author(s):  
Tamara C. S. Pace ◽  
Cornelia Bohne
Keyword(s):  
Excited State ◽  
Complex Formation ◽  
Ground State ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Equilibrium Constants ◽  
Dissociation Rate ◽  
Activation Entropy ◽  
Triplet Excited State ◽  
Dissociation Rate Constants

The complexation dynamics of the triplet excited state of xanthone with β-cyclodextrin were studied at various temperatures between 10 and 50 °C. Association and dissociation rate constants were determined using the laser flash photolysis quenching methodology with Cu2+ as a quencher. The rate constants for the association and dissociation of triplet xanthone with β-cyclodextrin increased with temperature, while the equilibrium constant for the triplet excited state remained relatively constant. Equilibrium constants for the ground-state complexation of xanthone with β-cyclodextrin were determined from fluorescence studies at various temperatures. The ground-state binding efficiency decreased with temperature and was markedly greater than that of the triplet excited state at all temperatures. The enthalpy and entropy for the β-cyclodextrin complex formation of the ground and triplet excited states fall on the enthalpy–entropy compensation relationship previously established for cyclodextrin complexes. The activation enthalpies for the association and dissociation rate constants for triplet xanthone are similar. The activation entropy is favorable for the association process, whereas a negative activation entropy was measured for the dissociation process, suggesting that solvation plays a key role in the complex formation between xanthone and β-cyclodextrin.

Calculations of cross-sections, dissociation rate constants and transport coefficients of Xe2+ colliding with Xe

2019 ◽  
Vol 21 (13) ◽  
pp. 7029-7038 ◽  
Author(s):  
Cyril Van de Steen ◽  
Malika Benhenni ◽  
René Kalus ◽  
Rajko Ćosić ◽  
Silvie Illésová ◽  
...  
Keyword(s):  
Cross Sections ◽  
Hybrid Method ◽  
Ground State ◽  
Rate Constants ◽  
Transport Coefficients ◽  
Dissociation Rate ◽  
Quantum Formalism ◽  
Dissociation Rate Constants ◽  
State Ionic

A quantum formalism and classical treatment have been used for electrons and nuclei, respectively, in a hybrid method in order to study the dynamics of electronically ground-state ionic xenon dimer, Xe2+, in its parent gas.

scholarly journals The kinetics of antibody binding to membrane antigens in solution and at the cell surface

1980 ◽  
Vol 187 (1) ◽  
pp. 1-20 ◽  
Author(s):  
D W Mason ◽  
A F Williams
Keyword(s):  
Cell Surface ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Surface Antigens ◽  
Dissociation Rate ◽  
Simple Relationship ◽  
Dissociation Kinetics ◽  
Cell Surface Antigens ◽  
Dissociation Rate Constants ◽  
Kinetics Of

The reaction kinetics of 125I-labelled mouse monoclonal antibodies binding to three cell-surface antigens of rat thymocytes (Thy-1.1, W3/25) were studied. The differences between bivalent and univalent interactions were determined by using antibody in the F(ab′)2 or Fab′ form and by using antigen in polymeric or monomeric forms. Association rate constants (k+1), dissociation rate constants (k-1) and equilibrium constants were determined. Also, the dissociation kinetics of rabbit antibodies against rat Thy-1 antigen were studied. The major findings were as follows. (i) With F(ab′)2 antibody there was no simple relationship between antigen density at the cell surface and extent of bivalent binding. Extensive univalent binding was observed unless the antibody had a high k-1 for the univalent interaction, in which case all binding was bivalent. (ii) k+1 values were similar for F(ab′)2 or Fab′ antibody, and for the different antibodies were in the range 0.8 × 10(5)–1.1 × 10(6) M-1.s-1. These differences were sufficient to affect the interpretation of serological assays with the different antibodies. (iii) Antibody bound bivalently dissociated much more slowly than that bound univalently. However, the k-1 values for the univalently bound antibody were sufficiently low in most cases that the lifetime of the univalent complex was similar to or greater than the time needed for the assay. Thus the results could be interpreted on the basis of irreversible reactions. The overall conclusion from the study is that for an understanding of the binding of antibody to cell-surface antigens the kinetics of the interaction are of major importance and theories based on equilibrium binding are inappropriate.

scholarly journals Ligand binding kinetics and dissociation of the human embryonic haemoglobins

1996 ◽  
Vol 315 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Oliver HOFMANN ◽  
Thomas BRITTAIN
Keyword(s):  
Ligand Binding ◽  
Flash Photolysis ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
General Scheme ◽  
Dissociation Rate ◽  
Oxygen Binding ◽  
Dissociation Kinetics ◽  
Oxygen Dissociation ◽  
Dissociation Rate Constants

The three human embryonic haemoglobins have been studied using a range of stopped-flow and flash photolysis experiments. The association and dissociation kinetics and equilibrium constants for the tetramer–dimer reactions of the deoxy and oxygenated forms have been investigated and found to be characterized by constants similar to those of the human adult protein. The rates of oxygen dissociation from the embryonic haemoglobins have been measured and appear to be responsible for the high oxygen-binding affinity associated with the embryonic proteins compared with the adult protein. The pH dependence of the oxygen dissociation rate constants also accounts for the rather unusual, previously described, Bohr effects characteristic of the embryonic haemoglobins. A general scheme has been developed coupling both the dimer–tetramer equilibria and ligand-binding steps observed following photolysis of the liganded forms of the human embryonic haemoglobins.

scholarly journals Dissociation Rate Constants of Human Fibronectin Binding to Fibronectin-binding Proteins on LivingStaphylococcus aureusIsolated from Clinical Patients

2012 ◽  
Vol 287 (9) ◽  
pp. 6693-6701 ◽  
Author(s):  
Nadia N. Casillas-Ituarte ◽  
Brian H. Lower ◽  
Supaporn Lamlertthon ◽  
Vance G. Fowler ◽  
Steven K. Lower
Keyword(s):  
Rate Constants ◽  
Binding Proteins ◽  
Dissociation Rate ◽  
Human Fibronectin ◽  
Fibronectin Binding ◽  
Dissociation Rate Constants
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