Article: Modulation of hippocampal synaptic transmission by low concentrations of cell-permeant Ca2+ chelators: effects of Ca2+ affinity, chelator structure and binding kinetics.
Table 1Ca2+ affinities and binding rates of the Ca2+ chelators employed in this study
Chelator
Kd (nM)*
References
kon (M−1s−1, ×10−7)
References
EGTA
160
17[17]
0.15
53[53]
BAPTA
700
38[38]
60
20[20]†
5NO2BAPTA
94,000
38[38]
60
20[20]†
APTRA
25,000
24[24]
8
24[24]‡
4F-APTRA
167,000
24[24]
8
24[24]
*Kd=dissociation constant for Ca2+=koff/kon. These Kd values may shift under conditions simulating the neuronal cytoplasm, and as such cannot be considered exact. However, these Kd values illustrate the rank order of calcium affinities of the chelators used in this study, and are presumed to reflect the order of magnitude of the true Ca2+ affinity of the compound.†Based on the kon estimate for fura-2.‡Based on the kon estimate for 4-FAPTRA.
