Prebiotic organic molecule synthesis
Want to get involved in research?Come hear Dr. Ostrowskis talk,
Oct 31, 1:00 pmEstess Library in the Honors College, 2nd floor of
MD Anderson Library*** Her lab tour on 11/7 is already full, so
this will be a great chance for a 1-on-1 discussion***
http://ostrowski-lab.org/A production of amino acids under
possible primitive Earth conditions. Stanley L. Miller. 1953.
Science 117:528-529.What are your pre-conceptions about this
experiment?None, Ive never heard of it.Ive heard of it, but have no
idea what its about. Miller showed that amino acids can be
synthesized from inorganic molecules.Miller showed that life began
in the primordial soup.Miller proved that life was spontaneously
generated from air and water.
A. Observationsorganic cpds synthesized from inorganic
cpdsWohler 1828synthesized ureaStrecker 1850synthesized
alanineButlerov 1861synthesized sugarsLate 1800sfatty acids &
sugars synthesized from electric discharge and gas mixture1900
1920synthesis glycine
Reducing atmosphere can reduce compounds, ie add H to them52.
Structure of simple organic cpdsglycinealanineB.
Hypothesis1920s:Oparin and Haldane independently proposed:Organic
compounds could form in absence of living things.
C. ObservationsAtmosphere of primitive Earth thought to be
reducing (Urey, 1952)To contain: methane, ammonia, water, and
hydrogenWhat atom is abundant in a reducing atmosphere?HOCNS
D. TestStanley L. Miller, organic chemistry graduate
studentExperimental Design: build an apparatus that simulates
conditions on Earth before life (1st 1 billion years)Apparatus
1
to vacuumb. Experimental DesignSealed apparatusBoiled waterH2O
vapor mixed with gasesSparked electricity through the gas chamber
for 1 weekGas passed through condenserReturned to water flaskFig.
1. Miller, 1953
waterGassescondenserelectrodeb. Experimental Design -
DiscussWhat does the presence of water simulate?Why is the water
boiled?What does the gas-filled chamber simulate?Why did Miller use
the particular gas mixture he did?What do the electrical sparks
simulate?What happens in the condenser? What atmospheric process is
simulated?Fig. 1. Miller, 1953
waterGassescondenserelectrodeWhich gas in Millers experiment
would provide the C necessary to make organic
compounds?AmmoniaWaterHydrogenMethane
Analytical MethodSamples were removed from the apparatus after 1
week of constant heating & sparkingSamples were analyzed by
size separationE. Analytical Methodpaper chromatography
Figure 2. Miller, 1953Method: Paper ChromatographyPaper
chromatographySolvent 1Paper chromatographySolvent 2Stain with
ninhydrin a chemical that turns blue-purple when it reacts with NH2
groupsSolvent 1Solvent 2Paper chromatographyPaper
chromatographyNinhydrin-stained chromatogramSolvent 1Solvent 2F.
Results
Solvent 1Solvent 2red lines indicate migration of compounds in
solvent 2241. How many amine-containing compounds were found?
In his 1953 paper, Miller reported non-biotic synthesis of which
compounds?
FormaldehydeHydrocarbonsAmino acidsHydrogen cyanide
Carefully examine the text of Figure 4.2 and find the
error.26Which 2 amino acids are most abundant in Millers
samples?
AB-alanine-alanineAspartic acid-amino-butyric acidglycine
Draw an inference: Which statement is a reasonable conclusion
based on Millers results?Life formed from ammonia, methane,
hydrogen gas and water.The first cells were formed from methane and
ammonia.Amino acids could have been produced from ammonia, methane,
H2 and H2O.Proteins and lipids could have been produced from
inorganic reactants (NH3, CH4, H2, H2O).
Miller repeated his experiment without electrical sparks.
Predict the results he obtained.More complex products formed.The
same as the first experiment: a few amino acids formed.No products
formed.
EpilogueMiller saved a set of dried samples (extracts) from a
1958 expt.In 2008, a research group used more sensitive modern
techniques to detect organic cpds in the samples.New analysis of
old samplesCompoundMolar Ratio (glycine = 1.0)*Glycine1.0Alanine2.7
x 10-2-alanine0.003Serine1.0 x 10-4-amino-isobutyric acid1.1 x
10-3-amino-isobutyric acid3.2 x 10-5-amino-butyric acid7.0 x
10-4-amino-butyric acid5.0 x 10-4-amino-butyric acid5.0 x
-10-4Aspartic acid6.0 x 10-4Valine3.3 x 10-5Why are there no units
for concentration?What kinds of molecules were detected by the more
sensitive analysis?CompoundMolar Ratio (glycine =
1.0)*Glycine1.0Alanine2.7 x 10-2-alanine0.003Serine1.0 x
10-4-amino-isobutyric acid1.1 x 10-3-amino-isobutyric acid3.2 x
10-5-amino-butyric acid7.0 x 10-4-amino-butyric acid5.0 x
10-4-amino-butyric acid5.0 x -10-4Aspartic acid6.0 x 10-4Valine3.3
x 10-5
Hydrogen cyanideHydrocarbonsAmino
acidsProteinsPhospholipidsNucleic acidsWhich 3 compounds were most
abundant in the new analysis?CompoundMolar Ratio (glycine =
1.0)*Glycine1.0Alanine2.7 x 10-2-alanine0.003Serine1.0 x
10-4-amino-isobutyric acid1.1 x 10-3-amino-isobutyric acid3.2 x
10-5-amino-butyric acid7.0 x 10-4-amino-butyric acid5.0 x
10-4-amino-butyric acid5.0 x -10-4Aspartic acid6.0 x 10-4Valine3.3
x 10-5PhospholipidsValineGlycineAspartic acidAlanine-alanineNucleic
acids
Experimental DesignAdd labels to this figure from Millers 1953
paper.
Fig. 1. Miller, 1953Apparatus 2