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INVITROGEN/MOLECULAR PROBES CONSTANTS?

CALCIUM

See: http://probes.invitrogen.com/handbook/sections/1900.html

They have been adapted to the MAXC format assuming that, being derived from BAPTA, the hydrogen disassociation constants are the same (admittedly a "wild" assumption, but we have to start somewhere?).

SPECIAL NOTE FROM DONALD BERS [4/28/1999]:

"My only concern is with the exact values of some of the fluorescent indicator Kd values. Most of these Ca indicators have a higher Kd in the cellular environment than in a cuvette with simple salt solutions. This is at least partly due to binding to cellular proteins (e.g. Hove-Madsen & Bers Biophys J 63:89-97, 1992). Typically, this increases Kd by 2-4 fold so we get Kd for indo-1 of 844-1000 nM (Bassani et al, Biophys J 68:1453-1460, 1995) and for Fluo3 we use 1-1.1 uM (based on work of Harkins et al BJ 65:865-881, 1993)."

Here are the Kds in order of decreasing Ca affinity:

CHELATOR/INDICATOR

Kd (nM)

MAXC CONSTANT

Intracellular Constant
as per above

BAPTA

136

6.970

 

Fura Red

140

6.957

 

Fura 2

145

6.942

 

Oregon Green 488

170

6.873

 

Calcium Orange

185

6.836

 

Calcium Crimson

185

6.836

 

Calcium Green-1

190

6.824

 

Indo-1

230

6.742

6.103 - 6.177

Fluo-4

345

6.565

 

Bis-fura

370

6.535

 

Texas Red-Calcium Green

370

6.535

 

Fluo-3

390

6.513

6.062 - 6.103

Caclium Green-2

550

6.363

 

Rhod-2

570

6.348

 

Oregon Green 488-BAPTA-2

580

6.340

 

X-rhod-1

700

6.258

 

The rest of the MAXC constants for BAPTA are: [Fura and related compouinds have only (3) H constants, so only use H1, H2 and H3, leaving H4 at ZERO, check Molecular Probes handbook for individual formulas]

H1

H2

H3

H4

6.360

5.470

1.000

1.000

 

 

 

 

dH1

dH2

dH3

dH4

0.01

0.01

0.00

0.00

The Ca-BAPTA constants are:

CaM

CaHM

6.970

0.000

 

 

dCaM

dCaHM

4.70

0.00

If anyone has more precise values for any of the above, please let me know, cpatton@stanford.edu

These values are more likely to be valid the closer they are to the experimental conditions that Molecular Probes used to assess the Kd in the first place, 22C, pH 7.2, 0.110N

 

Chris Patton: cpatton@stanford.edu