255
14
BOX: The Miller–Urey Experiment
The so-called Miller–Urey
experiment shows that under
the conditions of a hypothetical
“ancient atmosphere” of our
earth organic molecules like
amino acids can form from
simple and inorganic substrates.
This hypothesis is the basis of
chemical evolution and thus
of the emergence of living
beings from simpler organic
building blocks. Stanley Miller
carried out the corresponding
experiments with the support
of Harold C. Urey in 1952 at
the University of Chicago. They
were published in the renowned
journal Science in 1953 under the
title: “A Production of Amino Acids
Under Possible Primitive Earth
Conditions”.
In the original experiment,
water vapor, hydrogen,
methane and ammonia were
exposed to an electrical
discharge as an energy
source in a special apparatus
over a period of one week
(. Fig. 14.5). In the condensed
water phase, various organic
molecules were detected at
the end of the experiment,
including larger amounts
of the proteinogenic amino
acids glycine and alanine. It
is regarded to be certain that
these were formed by Strecker
synthesis with the intermediate
products hydrocyanic
acid, formaldehyde and
acetaldehyde, respectively.
. Fig. 14.5 Experimental
setup for the Miller–Urey
experiment
Gas feed
CH4, NH3, H2
Circulation direction
Power supply
,,Primordial
atmosphere’’
H2O, CH4, NH3, H2
Electric arc
Cooling
Collection
tube
Heat source
H2O
14.1 · Amino Acids
Arginine (Arg) was first found in lupine
shoots in 1886. It was named after the Latin
word for silver (argentum) because it was first
isolated as a silver salt. Arginine is the proteinogenic amino acid having the highest nitrogen
content. In almost all proteins, it is contained to
3–6%, in peanut protein even to 11%. Arginine is
“semi-essential” for humans, i.e. they only need it
in certain metabolic situations.
Asparagine (Asn) was the first amino acid to
be isolated from asparagus in 1805. It is found in
many plant shoots, e.g. in soybeans and in many
proteins. In the side chain, asparagine contains
an amide group.
Aspartic acid (Asp) has a similar structure
to asparagine, but contains a second carboxyl
group instead of the amide group. Aspartic acid
is found in all animal proteins in amounts of
up to 10%. It is also found in larger amounts in
the proteins of the pulses alfalfa (lucerne) and
maize. It occurs in free form in sugar cane. It is
produced by enzymatic synthesis in 10,000 t a −1 ,
14
BOX: The Miller–Urey Experiment
The so-called Miller–Urey
experiment shows that under
the conditions of a hypothetical
“ancient atmosphere” of our
earth organic molecules like
amino acids can form from
simple and inorganic substrates.
This hypothesis is the basis of
chemical evolution and thus
of the emergence of living
beings from simpler organic
building blocks. Stanley Miller
carried out the corresponding
experiments with the support
of Harold C. Urey in 1952 at
the University of Chicago. They
were published in the renowned
journal Science in 1953 under the
title: “A Production of Amino Acids
Under Possible Primitive Earth
Conditions”.
In the original experiment,
water vapor, hydrogen,
methane and ammonia were
exposed to an electrical
discharge as an energy
source in a special apparatus
over a period of one week
(. Fig. 14.5). In the condensed
water phase, various organic
molecules were detected at
the end of the experiment,
including larger amounts
of the proteinogenic amino
acids glycine and alanine. It
is regarded to be certain that
these were formed by Strecker
synthesis with the intermediate
products hydrocyanic
acid, formaldehyde and
acetaldehyde, respectively.
. Fig. 14.5 Experimental
setup for the Miller–Urey
experiment
Gas feed
CH4, NH3, H2
Circulation direction
Power supply
,,Primordial
atmosphere’’
H2O, CH4, NH3, H2
Electric arc
Cooling
Collection
tube
Heat source
H2O
14.1 · Amino Acids
Arginine (Arg) was first found in lupine
shoots in 1886. It was named after the Latin
word for silver (argentum) because it was first
isolated as a silver salt. Arginine is the proteinogenic amino acid having the highest nitrogen
content. In almost all proteins, it is contained to
3–6%, in peanut protein even to 11%. Arginine is
“semi-essential” for humans, i.e. they only need it
in certain metabolic situations.
Asparagine (Asn) was the first amino acid to
be isolated from asparagus in 1805. It is found in
many plant shoots, e.g. in soybeans and in many
proteins. In the side chain, asparagine contains
an amide group.
Aspartic acid (Asp) has a similar structure
to asparagine, but contains a second carboxyl
group instead of the amide group. Aspartic acid
is found in all animal proteins in amounts of
up to 10%. It is also found in larger amounts in
the proteins of the pulses alfalfa (lucerne) and
maize. It occurs in free form in sugar cane. It is
produced by enzymatic synthesis in 10,000 t a −1 ,