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