Some time ago Art Chadwick presented a series of objections to proteinoids
being proto-proteins. One was that only pure amino acids could be used and
another that the percentages carboxylic animo acids (glutamate and aspartate)
required to make proteinoids did not reflect the percentages made under
actual simulated prebiotic conditions. At the time I offered evidence that
showed that these objections were wrong, but since then I have found
additional information that reinforces that conclusion.
Saunders MA and Rohlfing DL. "Polyamino Acids: Preparation from Reported
Proportions of 'Prebiotic' and Extraterrestrial Amino Acids." _Science_
1972; 176:172-3. This paper describes how proteinoids were made from
mixtures of amino acids whose percentages reflect those produced by several
simulated prebiotic experiments. One conducted by Miller consisting of using
electricity to create amino acids from a gaseous mixture of ammonia, methane,
hydrogen and water. The resulting mixture obtained consisted of 50.6%
glycine, 27.3% alpha-alanine, 21.3% other amino acids and only 0.3% aspartate
and 0.5% glutamate; in other words only 0.8% carboxylic amino acids. Yet a
mixture of amino acids with these same exact proportions still made
proteinoids. So it would seem that proteinoids can be made with less than 1%
glutamate/aspartate, which in turn conforms to virtually any simulated
prebiotic scenario. This same paper also demonstrated that proteinoids can
be made from mixtures of amino acids representing amino acid proportions
found in lunar soil samples and meteorites.
Rohlfing DL. "Evolution of Models for Evolution." In k Dose, SW Fox, GA
Deborin and TE Pavlovskaya, eds., _The Origin of Life and Evolutionary
Biochemistry_ . Plenum Publishing, New York, 1974. This article provides
evidence that proteinoids can be made even when mixed with 8 times as much
finely ground basalt as total amino acid weight. It also reports that (at
that time) more recent unpublished experiments showed that sea sand could
actually increase the yield of proteinoids produced. So not only do the
amino acids not have to be pure or even the major constituent, some
impurities can actually stimulate the formation of proteinoids as well.
This same paper also provided evidence that demonstrated that proteinoids can
be made under a range of atmospheric presures from 1.0 to 0.0004 atm, and
under a wide range of different atmospheric compositions, including pure
hydrogen, pure oxygen and pure carbon dioxide. So it would appear that, far
from requiring very specific conditions, proteinoids can in fact be formed
using almost any simulated prebiotic scenario.
Kevin L. O'Brien