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