Abstract
The apparent calcium association constants (K′Ca) of ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) and 1,2-bis[2-bis(o-amino-5-bromophenoxy)ethane-N,N,N′,N′-tetraacetic acid (dibromo-BAPTA) were measured using the method described by Bers (Am. J. Physiol. 242 (1982) C404-408). The purity of the three ligands determined from the x-intercept of Scatchard plots were 96.3%, 79.0% and 97.3% for EGTA, BAPTA and dibromo-BAPTA, respectively. The impurity of BAPTA was found to be water by drying several samples to constant weight. Increasing temperature from 1 to 36°C led to an increase in K′Ca which was of similar magnitude for the three ligands. Increasing ionic strength from 0.104 to 0.304 M led to a reduction of K′Ca in all cases, though EGTA was affected much less than BAPTA or dibromo-BAPTA. Experimental results were compared with values of K′Ca calculated from the individual association constants of the ligands for calcium and protons which were modified for the experimental conditions using the Debye-Hückel limiting law and the Van't Hoff Isochore to correct for ionic strength and temperature, respectively. The experimental values of K′Ca of EGTA agree well with those in the literature and with the calculated values. Good agreement was also found between the experimental and calculated values of K′Ca for the temperature and ionic strength dependence of BAPTA and dibromo-BAPTA.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 133-143 |
| Number of pages | 11 |
| Journal | BBA - General Subjects |
| Volume | 925 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 13 1987 |
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Keywords
- 1,2-Bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid
- Affinity constant
- BAPTA
- Calcium binding
- Calcium chelation
- EGTA
- Ionic strength
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology
Cite this
The effect of temperature and ionic strength on the apparent Ca-affinity of EGTA and the analogous Ca-chelators BAPTA and dibromo-BAPTA. / Harrison, Simon M.; Bers, Donald M.
In: BBA - General Subjects, Vol. 925, No. 2, 13.08.1987, p. 133-143.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The effect of temperature and ionic strength on the apparent Ca-affinity of EGTA and the analogous Ca-chelators BAPTA and dibromo-BAPTA
AU - Harrison, Simon M.
AU - Bers, Donald M
PY - 1987/8/13
Y1 - 1987/8/13
N2 - The apparent calcium association constants (K′Ca) of ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) and 1,2-bis[2-bis(o-amino-5-bromophenoxy)ethane-N,N,N′,N′-tetraacetic acid (dibromo-BAPTA) were measured using the method described by Bers (Am. J. Physiol. 242 (1982) C404-408). The purity of the three ligands determined from the x-intercept of Scatchard plots were 96.3%, 79.0% and 97.3% for EGTA, BAPTA and dibromo-BAPTA, respectively. The impurity of BAPTA was found to be water by drying several samples to constant weight. Increasing temperature from 1 to 36°C led to an increase in K′Ca which was of similar magnitude for the three ligands. Increasing ionic strength from 0.104 to 0.304 M led to a reduction of K′Ca in all cases, though EGTA was affected much less than BAPTA or dibromo-BAPTA. Experimental results were compared with values of K′Ca calculated from the individual association constants of the ligands for calcium and protons which were modified for the experimental conditions using the Debye-Hückel limiting law and the Van't Hoff Isochore to correct for ionic strength and temperature, respectively. The experimental values of K′Ca of EGTA agree well with those in the literature and with the calculated values. Good agreement was also found between the experimental and calculated values of K′Ca for the temperature and ionic strength dependence of BAPTA and dibromo-BAPTA.
AB - The apparent calcium association constants (K′Ca) of ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) and 1,2-bis[2-bis(o-amino-5-bromophenoxy)ethane-N,N,N′,N′-tetraacetic acid (dibromo-BAPTA) were measured using the method described by Bers (Am. J. Physiol. 242 (1982) C404-408). The purity of the three ligands determined from the x-intercept of Scatchard plots were 96.3%, 79.0% and 97.3% for EGTA, BAPTA and dibromo-BAPTA, respectively. The impurity of BAPTA was found to be water by drying several samples to constant weight. Increasing temperature from 1 to 36°C led to an increase in K′Ca which was of similar magnitude for the three ligands. Increasing ionic strength from 0.104 to 0.304 M led to a reduction of K′Ca in all cases, though EGTA was affected much less than BAPTA or dibromo-BAPTA. Experimental results were compared with values of K′Ca calculated from the individual association constants of the ligands for calcium and protons which were modified for the experimental conditions using the Debye-Hückel limiting law and the Van't Hoff Isochore to correct for ionic strength and temperature, respectively. The experimental values of K′Ca of EGTA agree well with those in the literature and with the calculated values. Good agreement was also found between the experimental and calculated values of K′Ca for the temperature and ionic strength dependence of BAPTA and dibromo-BAPTA.
KW - 1,2-Bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid
KW - Affinity constant
KW - BAPTA
KW - Calcium binding
KW - Calcium chelation
KW - EGTA
KW - Ionic strength
UR - http://www.scopus.com/inward/record.url?scp=0023640537&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0023640537&partnerID=8YFLogxK
U2 - 10.1016/0304-4165(87)90102-4
DO - 10.1016/0304-4165(87)90102-4
M3 - Article
C2 - 3113491
AN - SCOPUS:0023640537
VL - 925
SP - 133
EP - 143
JO - Biochimica et Biophysica Acta - General Subjects
JF - Biochimica et Biophysica Acta - General Subjects
SN - 0304-4165
IS - 2
ER -