Physics. -
The spreading of proteins. By E. GORTER and F . GRENDEL.
(Cammunicated by Prof. P. EHRENFEST. )
(Communicated at the meeting of June 29, 1929.)
From the beautiful experiments of The Svedberg 1) it has resulted that
the molecular weights of several proteins are simple multiples of 34500 (A) .
Eggalbumin
Bence Jones protein
Hemoglobin
Serum albumin
Serum globulin
R. Fycoerythrin
R. Fycocyan
C. Fycocyan
Amandin
2
2
3
6
6
6
6
A
A
A
A
A
A
A
A
A
Only hemocyanins have higher molecular weights.
I have studied since several years with GRENDEL 2) the spreading of
several proteins, of which hemoglobin and casein in a pure state. Recently
I was able through the kindness of The Svedberg to study the spreading
of several proteins in his laboratory. The results of those experiments hav~
fully confirmed our former results.
.
Without entering into details of the last mentioned experiments which
have only a provisional character, I wish to emphasize the important fact
that all these proteins have a remarkably constant " spreading~number" ,
when in the tray of Langmuir's apparatus 1/10 norm al hydrochloric acid is
used . This number indicating the surface occupied by 1 mgr. of the sub~
stance was : ± 1.0 square meter.
Not only the smaller molecules but also the proteins of the 6 A . ~group
showed this same surface under these conditions. What does this
value mean?
It seems probable that in a watery solution of a protein all the molecules
have their polar groups orientated to the outer surface. When spread on
an acid solution alle these groups are however drawn to the surface and
placed in an horizontal plane.
I) The 8vedberg Colloïd Chemistry, The chemical Catalog Company, New York 1928
p, 164 and Nature 123, 871 June 8. 1929.
2) GORTER & GRENDEL, These Proceedings, Bd. 29, 1926, NO. 9 .
. Transact. of the Paraday Soc. Bd. 22. Dec 1926.
. Biochem. Ztschr. Bd. 201. 1928. pag. 391.
771
Supposing this to be the case it is easy to calculate the radius of J
molecule. According to measurements in Svedberg's laboratory the specific
volume of most of the protzins is about 0.75.
We have:
volume of 1 mgr. of protein 0.75
and outer surface of 1 mgr. of protein
X 10-3 cm 3 .
10 4
The volume of the molecules of 1 mgr. of protein is 4/3
surface of the molecules is 4 II r:!n. We therefore get :
11
_ 0.75
3
r-
~0-3
10"
cm 2 •
II
r 3 n and the
cm.
o
r=
22.5 A.
Now, Svedberg has shown that under the conditions of his measurements
a protein molecule of mass 34500, is sphericaI. and has a radius r = 22 À.
This close correspondance seems to indicate that the spherical molecules
are transformed into flat plates: the polar groups being brought from the
surface of a sp here into an horizontal plane.
The proteins, casein, hemoglobin, ovalbumin that we were able to examine
in a very pure state, showed the same transformation at the isoelectrical
point: the phenomenon is reversible.
The spreading of the proteins having a molecular weight of 208.000 gin
the same spreading number. This would indicate that they con sist or
groups of 6 spherical units, and that at the spreading under these conditions
the bonds between these units are loosened.
This modification of the form of the proteins gives an explanation of
the striking fact that the same substance which is more or Ie ss easily
soluble in a watery-buffer solution can be brought to spread under slightly
different conditions.