Biology Reference
In-Depth Information
Table I
Properties of photosensitive Ca chelators
Before
photolysis
After
photolysis
Before
photolysis
After
photolysis
Ca-bind-
ing on-
rate
Compound
(availability)
t
Phot
(ms)
l
max
(nm) Q.E.
Ca
Q.E.
free
K
D-Ca
(
m
M)
K
D-Mg
(mM)
K
D-Ca
(
m
M)
K
D-Mg
(mM)
e
10-Ca
(M
1
cm
1
)
e
10-free
(M
1
cm
1
)
e
10-Ca
(M
1
cm
1
)
e
10-free
(M
1
cm
1
)
Nitr-5
0.27
365
0.035
0.012
0.145
8.5
6.3
8
5450
5750
13,800
27,300
0.5
Nitr-7
1.8
365
0.042
0.011
0.054
5.4
3.0
5
5780
5540
24,700
10,000
0.2
0.026
b
Nitr-8
-
365
-
0.5
-
1370
-
11,000
1100
50,000
20,000
-
Nitr-9
-
365
0.02
0.02
1000
10
1000
10
5500
5500
15,000
25,000
-
Azid-1
<
2.0
342
1.0
0.9
0.23
8
120
8
33,000
27,000
11,500
5550
0.8
0.007
c
0.0017
c
DM-
nitrophen
0.015;1.9
370
0.18
0.18
4200;89
2.5
4330
4020
3150
3150
0.02
0.08
c
NP-EGTA
0.002
345
0.23
0.23
9
1000
9
975
975
1900
1900
0.017
0.048
d
DMNPE-4
-
347
0.09
0.09
7
1000
7
5140
5140?
5140?
5140?
0.01?
NDBF-
EGTA
0.01;0.52
330
0.7
0.7
0.1
15
1000
15
18,400
18,400?
18,400?
18,400?
-
0.057
a
0.030
a
Diazo-2
0.134
370
2.2
5.5
0.073
3.4
2080
22,200
700
2080
0.8
0.030
a,b
0.030
a,b
Diazo-4
-
370
89
-
0.055
2.6
4600
46,000
500
500
0.8
<
<
Diazo-3
0.24
375
0.048
0.048
1000
20
1000
20
2100
22,800
700
2100
0.8
>
>
t
Phot
, photolysis time constant; l
max
, absorbance maximum of Ca-loaded compound; most e
V
ective photolysis wavelength; Q.E.
Ca,free
, quantum e
Y
ciency,
Ca-bound (free); K
D-Ca,Mg
, Ca (Mg) dissociation constant (1/a
Y
nity) at 0.1-0.15 M ionic strength; and
e
10-Ca,fre
e
, decadic absorbance extinction coe
Y
cient of
Ca-bound (free) compound.
a
10% of absorbed photons produce a nonphotolyzable photoproduct similar in absorbance and a
Y
nities to unphotolyzed diazo.
b
For photolysis of each site.
c
At pH 7.2; doubles for each 0.3 pH unit reduction.
d
At pH 7.2; increases 2.5
for each 0.2 pH unit reduction.
