Correction of proton and Ca association constants of EGTA for temperature and ionic strength

S. M. Harrison, Donald M Bers

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76 Citations (Scopus)

Abstract

The association constants of ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for protons and Ca can be used to calculate the apparent association constant of EGTA for Ca (K'(CaEGTA)). This value is often used in calculating the free [Ca2+] of complex solutions such as those used to determine the Ca sensitivity of skinned muscle fibers. As association constants are usually measured at 0.1 M ionic strength and between 20 and 25°C, these constants must first be adjusted for conditions different from those at which they were measured, before calculation of K'(CaEGTA). The proton and Ca association constants (and their ΔH values) from A.E. Martell and R.M. Smith (Critical Stability Constants, New York; Plenum, vol. 1, 1974) adjusted for ionic strength and temperature using a semiempirical Debye-Huckel formalism and Van 't Hoff isochore, respectively, closely describe the influence of both ionic strength and temperature on K'(CaEGTA). Errors in the adjustment or calculation of association constants can dramatically affect the calculated value of K'(CaEGTA) and hence the calculated free [Ca2+] of complex solutions, such as those used to mimic the intracellular environment.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume256
Issue number6
StatePublished - 1989

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Egtazic Acid
Ionic strength
Osmolar Concentration
Protons
Temperature
Isochores
Ethylene Glycol
Ether
Muscle
Muscles
Acids
Fibers

ASJC Scopus subject areas

  • Cell Biology
  • Clinical Biochemistry
  • Physiology

Cite this

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abstract = "The association constants of ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for protons and Ca can be used to calculate the apparent association constant of EGTA for Ca (K'(CaEGTA)). This value is often used in calculating the free [Ca2+] of complex solutions such as those used to determine the Ca sensitivity of skinned muscle fibers. As association constants are usually measured at 0.1 M ionic strength and between 20 and 25°C, these constants must first be adjusted for conditions different from those at which they were measured, before calculation of K'(CaEGTA). The proton and Ca association constants (and their ΔH values) from A.E. Martell and R.M. Smith (Critical Stability Constants, New York; Plenum, vol. 1, 1974) adjusted for ionic strength and temperature using a semiempirical Debye-Huckel formalism and Van 't Hoff isochore, respectively, closely describe the influence of both ionic strength and temperature on K'(CaEGTA). Errors in the adjustment or calculation of association constants can dramatically affect the calculated value of K'(CaEGTA) and hence the calculated free [Ca2+] of complex solutions, such as those used to mimic the intracellular environment.",
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AU - Bers, Donald M

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N2 - The association constants of ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for protons and Ca can be used to calculate the apparent association constant of EGTA for Ca (K'(CaEGTA)). This value is often used in calculating the free [Ca2+] of complex solutions such as those used to determine the Ca sensitivity of skinned muscle fibers. As association constants are usually measured at 0.1 M ionic strength and between 20 and 25°C, these constants must first be adjusted for conditions different from those at which they were measured, before calculation of K'(CaEGTA). The proton and Ca association constants (and their ΔH values) from A.E. Martell and R.M. Smith (Critical Stability Constants, New York; Plenum, vol. 1, 1974) adjusted for ionic strength and temperature using a semiempirical Debye-Huckel formalism and Van 't Hoff isochore, respectively, closely describe the influence of both ionic strength and temperature on K'(CaEGTA). Errors in the adjustment or calculation of association constants can dramatically affect the calculated value of K'(CaEGTA) and hence the calculated free [Ca2+] of complex solutions, such as those used to mimic the intracellular environment.

AB - The association constants of ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for protons and Ca can be used to calculate the apparent association constant of EGTA for Ca (K'(CaEGTA)). This value is often used in calculating the free [Ca2+] of complex solutions such as those used to determine the Ca sensitivity of skinned muscle fibers. As association constants are usually measured at 0.1 M ionic strength and between 20 and 25°C, these constants must first be adjusted for conditions different from those at which they were measured, before calculation of K'(CaEGTA). The proton and Ca association constants (and their ΔH values) from A.E. Martell and R.M. Smith (Critical Stability Constants, New York; Plenum, vol. 1, 1974) adjusted for ionic strength and temperature using a semiempirical Debye-Huckel formalism and Van 't Hoff isochore, respectively, closely describe the influence of both ionic strength and temperature on K'(CaEGTA). Errors in the adjustment or calculation of association constants can dramatically affect the calculated value of K'(CaEGTA) and hence the calculated free [Ca2+] of complex solutions, such as those used to mimic the intracellular environment.

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