The Interaction Of Serum Albumins With Calcium Page 2
ADVERTISEMENT
1
2
3
4N. H. MARTIN AND D. J. PERKINS
to setting up the
equilibrating systems. The final molarities
ranged from 0-15 to 0-155. The only cations present
were
Ca and Na and the only anions
were
chloride and
protein.
0
4
C
2 12
3v
16
-
0
20
40
60
80 100 120 140 160 180
Ca
(mg./I.)
Fig.
1. Deviations
of the Ca concentrations found
by
the
method used in this work from the
true
Ca concentrations
determined
gravimetrically, expressed
as
percentages of
the gravimetric values.
The distribution of
freely diffusible
ions at
equilibrium
across a
semi-permeable membrane
in the presence of
one
non-diffusible ion was investigated by Donnan & Harris
(1911). They proved that if the distribution of
a
univalent
anion was
measured,
then the distribution of
a
univalent
cation present in the same system would be
inversely
pro-
portional
to that of the anion
[Na'+L
[C12]
[Na+L2
[C71
]1
Donnan & Gamer (1919) extended the
theory
to
the
study
of
bivalent ions and showed that the distribution of bivalent
cations at
equilibrium
was proportional to the ratio of the
square of the univalent ions
[Ca+], ([Na+]1)2 ([CF-]2)2
[Ca+]2 ([Na+L2)
2
([CI1 L)
2
The corrections applied in this paper have been based on the
distribution of chloride between the two chambers, assuming
that at the concentrations employed there was complete
ionization of CaCl2 and that the salt does not form complexes
when equilibrium has been established.
RESULTS
Human, bovine and equine albumins were examined.
The results are arranged in Tables 1-3. Three
specimens of bovine albumin and two of horse
albumin were examined and compared with seven
specimens of human albumin. The crude albumins
prepared by methanol fractionation of horse and ox
both had calcium-binding capacities of the order of
11 mg./g. protein nitrogen, which is markedly
different from the calcium-binding capacities of
three human albumins examined, all of which had
calcium-binding capacities of the order of 4-5 mg./g.
protein nitrogen. Two preparations of human albu-
min had no demonstrable calcium-binding capacity
and the remaining two preparations, the one crystal-
lized with the aid of decanol and the other in the
presence of mercury, had calcium-binding capacities
of the order of 1-0 and 9-0 respectively.
Tables 1 and 2 show the results on bovine and
horse albumins and on crude and purified human
albumin, respectively. Table 3 shows the results on
a human albumin
believed to have been denatured
in the course of fractionation.
Table
1.
Calcium-binding capacities of
bovine and
horse
serum
albumins
Material
Bovine albumin
Methanol fractionation
(94-97 %)
(Pillemer &
Hutchinson, 1945)
Ethanol fractionation
(95%) (Cohn
et
al.
1946)
Crystalline (100 %)
(Cohn,
Hughes
&
Weare, 1947)
Horse albumin
Methanol fractionation
(94-97 %) (Pillemer &
Hutchinson, 1945)
Crystallized
carbohydrate-
poor (100
%)
Kekwick,
1938)
N of
sample
in sac
pH
(g./l.)
6-70
6-76
6-84
6-86
6-92
6-95
6-10
6-30
0-80
0-80
2-33
2-33
9-97
9-97
4-57
9-13
6-76
1-50
6-32
6-34
6-40
6-42
6-43
1-07
1-07
2-14
3-21
4-28
Ca (mg./l.)
Outside
Inside
sac
sac
125-2
124-1
134-0
134-0
130-6
130-6
144-7
138-1
136-2
94-9
95-0
92-8
90-8
87-5
137-0
134-2
162-5
164-2
179-8
179-2
158-6
167-3
156-5
107-4
108-1
119-8
130-1
141-4
Donnan
coefficient
calculated
from
chloride
distribution
1-01
1-01
1-02
1-03
1-08
1-09
1-04
1-07
1-02
1-02
1-02
1-02
1-03
1-03
Calculated
free Ca
inside
sac
(mg./l.)
126-9
125-4
137-2
137-6
141-4
142-0
148-7
147-1
138-8
96-3
96-4
94-7
92-5
90-1
Bound Ca
N
(mg./g.)
12-6
11-0
10-9
11-5
3-9
3-7
2-2
2-2
11-8
10-4
11-0
11-8
11-8
12-0
324
I950
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Miscellaneous