Significant Achievements in Space Bioscience 1958-1964United States. National Aeronautics and Space Administration
Science
Significant Achievements in Space Bioscience 1958-1964
United States. National Aeronautics and Space Administration
Biology; Space flight
Fox showed that when hot saturated solutions of thermal copolymers
containing the 18 common amino acids were allowed to cool, large numbers
of uniform, relatively firm, and elastic spherules separate. These range
from 0.2µ to 60µ in diameter and are quite uniform within each
preparation. Various chemical observations suggest the presence of
peptide bonds in the structural organization of these proteinoids.
Continuing observations of these microspheres have established further
characteristics that point to the possibility of their interpretation as
a kind of primitive protein macromolecule with self-organizing
properties, such that a primitive form of cell, with boundary and other
properties, might form.
In laboratory experiments the behavior of gram-negative and
gram-positive microspheres in dilute alkali parallels that of
gram-negative and gram-positive bacteria ([ref.23]). Furthermore,
time-lapse studies indicate that the proteinoid microspheres undergo a
septate kind of fission, mimicking cell division as shown in figure 1.
Cytochemical studies show that the microsphere’s boundary is
membranelike in having a primitive selectivity. Electron micrographs of
sections of stained microspheres also indicate the presence of a
boundary.
Oparin ([ref.15]) states that the type of organization peculiar to life
could only result from the evolution of a multimolecular organic system
separated from its environment by a distinct boundary but constantly
interacting with this environment. In his concept of coacervates as
precell models, Oparin ([ref.24]) indicates that present-day protoplasm
possesses a number of features similar to coacervate structure. These
coacervates could represent the starting point for evolution leading to
the origin of life. Moreover, in the course of their evolution the
initial systems may gradually become more complex. Oparin also showed
([ref.15]) that mixing solutions of different proteins and other
substances of high molecular weight produced these coacervate droplets.
These droplets are characterized by the formation of a surface layer
with altered structure and mechanical properties, thus providing a
somewhat selective barrier in which to house a molecular system capable
of replication. However, these coacervates are unstable structurally.
[Illustration: Figure 1.—_Protenoid microspheres undergoing septate
fission. Small microspheres and filamentous associations thereof are
also shown ([ref.25])._]
The NASA program has further provided considerable impetus for
continuing research with respect to the chemical evolution of life,
since its life-detection experiments may encounter prebiological
molecules in their search for extraterrestrial life on other planetary
surfaces.
In the area of exobiological research, the significant accomplishments
to date have been—
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