Clarification of the hole-size cation-diameter relationship in crown ethers and a new method for determining calcium cation homogeneous equilibrium binding constants

1983 ◽  
Vol 105 (23) ◽  
pp. 6786-6788 ◽  
Author(s):  
George W. Gokel ◽  
Deepa M. Goli ◽  
Carlo Minganti ◽  
Luis Echegoyen
Keyword(s):  
Crown Ethers ◽  
Binding Constants ◽  
New Method ◽  
Hole Size ◽  
Equilibrium Binding ◽  
Homogeneous Equilibrium ◽  
Calcium Cation

A Fluorescence Quenching Analysis of the Binding of Fluoroquinolones to Humic Acid

2017 ◽  
Vol 71 (11) ◽  
pp. 2512-2518 ◽  
Author(s):  
Ryan P. Ferrie ◽  
Gregory E. Hewitt ◽  
Bruce D. Anderson
Keyword(s):  
Humic Acid ◽  
Fluorescence Quenching ◽  
Water Solubility ◽  
Binding Constants ◽  
High Water ◽  
Static Quenching ◽  
Temperature Range ◽  
Equilibrium Binding ◽  
Quenching Analysis ◽  
High Water Solubility

Fluorescence quenching was used to investigate the interaction of six fluoroquinolones with humic acid. Static quenching was observed for the binding of ciprofloxacin, enoxacin, fleroxacin, levofloxacin, norfloxacin, and ofloxacin to humic acid. The equilibrium binding constants were found from Stern–Volmer plots of the data. The quenching experiments were repeated over a temperature range of 25–45 ℃ and van’t Hoff plots were generated. From these linear plots, thermodynamic values were calculated for Δ H, Δ G, and Δ S for each of the fluoroquinolones. The equilibrium binding constants were found to be <1 for all the antibiotics studied. The calculated ΔH values were all negative and ranged from −9.5 to −27.6 kJ/mol. The high water solubility of the antibiotics and low ΔH of binding suggests that the antibiotics will be transported easily through the environment. Finally, whether the fluoroquinolones are in a protonated, deprotonated, or partially protonated state is found to correlate to the strength of binding to humic acid.

Improved curve fitting procedures to determine equilibrium binding constants

The Analyst ◽  
2006 ◽  
Vol 131 (10) ◽  
pp. 1145 ◽  
Author(s):  
Frank H. Stootman ◽  
Dianne M. Fisher ◽  
Alison Rodger ◽  
Janice R. Aldrich-Wright
Keyword(s):  
Curve Fitting ◽  
Binding Constants ◽  
Equilibrium Binding ◽  
Fitting Procedures

scholarly journals Functional properties of a sarcoplasmic reticulum Ca2+-ATPase with an altered Ca2+-binding mechanism

1995 ◽  
Vol 309 (2) ◽  
pp. 499-505 ◽  
Author(s):  
F Martinez-Azorin ◽  
F Soler ◽  
J C Gomez-Fernandez ◽  
F Fernandez-Belda
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Equilibrium Constants ◽  
Binding Constants ◽  
Binding Mechanism ◽  
Protein Residues ◽  
Equilibrium Binding ◽  
Positive Cooperativity ◽  
Binding Isotherms ◽  
Fitting Procedures ◽  
Equal Amplitude

Treatment of sarcoplasmic reticulum vesicles with diethylpyrocarbonate in the presence of a large excess of reagent, at pH 6.2 and at room temperature, reveals both a fast- and a slow-reacting population of protein residues. The loss of the Ca(2+)-ATPase activity is mainly associated with the fast-reacting population being partially sensitive to hydroxylamine. There is also an effect on the Ca(2+)-binding mechanism. Shorter derivatization times (5 min) produce a loss of the positive cooperativity of Ca2+ binding. When the treatment was prolonged for 30 min there was an additional decrease in the overall Ca2+ affinity. Curve-fitting procedures applied to the non-cooperative binding isotherms provide the equilibrium constants for the two Ca2+ sites, although they cannot discriminate between interacting and independent site mechanisms. Prestationary kinetics assays show 2 Ca2+:1 ATP ratios, at any extent of Ca2+ saturation, indicating that the Ca2+ sites are not independent. The Ca2+ dissociation profile after derivatization shows a decrease in the dissociation constant for the release of the second Ca2+, which is consistent with interacting sites. Isotopic exchange experiments show fast and slow components of equal amplitude even at subsaturating Ca2+ concentrations, which is incompatible with independent binding sites. The experimental data suggest a modification of the equilibrium binding constants making them more similar, but keeping the interacting character. The structural position of the external (cytoplasmic) and the internal (lumenal) Ca2+ sites remains unaltered in the absence of positive cooperativity.

scholarly journals New Method for the Measurement of Binding Constants for Amphiphiles with a Very Small Solubility in Aqueous Media

2010 ◽  
Vol 98 (3) ◽  
pp. 478a-479a
Author(s):  
Hugo L. Filipe ◽  
Winchil L.C. Vaz ◽  
Maria João Moreno
Keyword(s):  
Aqueous Media ◽  
Binding Constants ◽  
New Method ◽  
Small Solubility
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