190
ERNEST SCHOFFENIELS
With a monomolecular film of stearic acid, it is possible to show
that, if the solution supporting the film contains Na and Ca in a concentration ratio of 100, Na exchanges for Ca in the film. These results are
best explained if we postulate the formation of complexes having different dissociation constants according to the ion considered. This therefore
explains satisfactorily the so-called balance required for the various
cations.
VIII. Chemical Nature of the Structure Responsible for the
Permeability Characteristics of Living Membranes
It is actually impossible to analyze quantitatively, in the light of the
scheme presented in the preceding section, the results concerning the
action of various compounds on the permeability characteristics of a
living membrane. The chemical nature of X, i.e., the molecular architecture responsible for the permeability characteristics, is still unknown.
This is one of the major obstacles over which we stumble.
From the results of indirect experiments, various compounds have
been proposed as being part of the chemical architecture responsible for
the permeability characteristics of the membrane. Cephalin and chondroitin sulfuric acid are able to form complexes with Ca: thus the
amount of Ca bound would control the permeability (203, 204). This
hypothesis finds an experimental support in the results obtained while
studying the permeability of connective tissue of vertebrates under various conditions: the diffusion of P0 4 increases in the absence of Ca (205).
Nucleic acids have also been proposed as being responsible for the
permeability characteristics of living membranes, on the basis of the
following observations (200): (a) presence of ribonucleic acid at the
surface of some cells; (b) ribonucleic acid complexes with Ca; (c)
inhibitory action of ribonuclease on the fixation of Ca by Elodea cells.
Let us now examine, in the light of available experimental findings,
how we could characterize the molecular architectures responsible for the
permeability characteristics of a membrane. The substance subjected to
transport is generally assumed to form a complex with some membrane
component. A reactive site for transport must therefore be assumed.
On the basis of the fact that nitrogen, argon, and other rare gases are
concentrated in the swim bladder of some fishes, it has however been
argued that such a step is not necessary, as the rare gases do not enter
into any known chemical reactions because of the saturation of their
electronic shells. However, it should be borne in mind that the concentration process in this case seems to result from a countercurrent system
in the rete mirabile and from the removal of oxygen (206).
Before attempting to isolate the molecule bearing the transport sites,
ERNEST SCHOFFENIELS
With a monomolecular film of stearic acid, it is possible to show
that, if the solution supporting the film contains Na and Ca in a concentration ratio of 100, Na exchanges for Ca in the film. These results are
best explained if we postulate the formation of complexes having different dissociation constants according to the ion considered. This therefore
explains satisfactorily the so-called balance required for the various
cations.
VIII. Chemical Nature of the Structure Responsible for the
Permeability Characteristics of Living Membranes
It is actually impossible to analyze quantitatively, in the light of the
scheme presented in the preceding section, the results concerning the
action of various compounds on the permeability characteristics of a
living membrane. The chemical nature of X, i.e., the molecular architecture responsible for the permeability characteristics, is still unknown.
This is one of the major obstacles over which we stumble.
From the results of indirect experiments, various compounds have
been proposed as being part of the chemical architecture responsible for
the permeability characteristics of the membrane. Cephalin and chondroitin sulfuric acid are able to form complexes with Ca: thus the
amount of Ca bound would control the permeability (203, 204). This
hypothesis finds an experimental support in the results obtained while
studying the permeability of connective tissue of vertebrates under various conditions: the diffusion of P0 4 increases in the absence of Ca (205).
Nucleic acids have also been proposed as being responsible for the
permeability characteristics of living membranes, on the basis of the
following observations (200): (a) presence of ribonucleic acid at the
surface of some cells; (b) ribonucleic acid complexes with Ca; (c)
inhibitory action of ribonuclease on the fixation of Ca by Elodea cells.
Let us now examine, in the light of available experimental findings,
how we could characterize the molecular architectures responsible for the
permeability characteristics of a membrane. The substance subjected to
transport is generally assumed to form a complex with some membrane
component. A reactive site for transport must therefore be assumed.
On the basis of the fact that nitrogen, argon, and other rare gases are
concentrated in the swim bladder of some fishes, it has however been
argued that such a step is not necessary, as the rare gases do not enter
into any known chemical reactions because of the saturation of their
electronic shells. However, it should be borne in mind that the concentration process in this case seems to result from a countercurrent system
in the rete mirabile and from the removal of oxygen (206).
Before attempting to isolate the molecule bearing the transport sites,