PAHs (Polycyclic Aromatic Hydrocarbons) and the Origins of Life. Alexander Karol Padden Murphy Scott Pruessing

Transcription

1 PAHs (Polycyclic Aromatic Hydrocarbons) and the Origins of Life Alexander Karol Padden Murphy Scott Pruessing

2 What Are PAHs? PAHS are very stable organic molecules made up of only carbon and hydrogen PAHS are planer and are made up of rings that are fused together PAHS is an acronym for "polycyclic aromatic hydrocarbons" The polycyclic refers to fact that they are multiple rings of carbon atoms The "aromatic" refers to the kinds of strong chemical bonds that exist between the carbon atoms. The "hydrocarbon" refers to atomic composition, which is hydrogen and carbon.

3 What Are PAHs?? (Cont.) PAHs have many different types and isomers of hydrogen and carbon PAHs commonly range from three to seven member rings, but most often have five or six PAHs with more than six rings are large while those with more than six are called small PAHs decrease in solubility as the ring number increases, so as a result they are more commonly found in oils and sediments.

4 Where are PAHs found on Earth? On Earth, PAHs are formed by the partial combustion of carbon products PAHS are lipophilic,, and are therefore commonly found in oils and fats. Examples where PAHs are found: Coal Diesel Fats Wood Edible Oils Tobacco Most PAHs have no use, and are often known carcinogens. Some PAHs are used to make: Medicines Plastics Pesticides Mothballs Dyes Anabolic Steroids

5 PAHs outside of Earth The NASA Spitzer Space Telescope detects PAHs in two ways IRAC (Infrared Array Camera) IRS (Infrared Spectrograph) PAHs have been found to exist in the red spectral rays of a dying nebula Two types of PAHs, Anthracene and Pyrene, were found to occur in the Red Rectangle nebula 1000 light years from Earth.

6 Theory Time Everything from here on out based in fact, but is theory Emerging Field as we have just been decoding the Human genome Theories very recent

7 RNA World Hypothesis that RNA was the formation of life Contains genetic information Acts as a ribozyme,, similar to an enzyme

8 Formation Theory Nucleic acids floating around in the primordial soup Most formed bonds weak and break up Some base pairs have catalytic sequencing causing them to hold together together and grow longer

9 Formation Theory RNA can self replicate Formed a natural selection process More efficient RNA lived and procreated Developed proteins, dna,, lipids, carbohydrates, and other molecules

10 Problems There are many problems with the formation theory RNA is fragile and would likely not form on its own Nucleotides must be activated to form RNA, doesn t t happen autonomously Nucleotides do not stack well on their own

11 PAH World Theory for the formation of RNA PAHs are a likely constituent of the primordial soup PAHs are amphiphilic and tend to stack with each other with a separation of.034nm. RNA and DNA bases have a separation of.034nm. Coincidence?

12 PAH World (Cont.) PAHs stack hydrophilic end out. Molecules attach to them, but PAHs swivel around each other and dislodge these molecules. Pyrimidines and Purines can stay attached because they are flat and do not dislodge each other.

13 PAH World (Cont.) Pyrimidines and Purines (Nucleic Bases) also are amphiphilic and line up in stacks. Makes a scaffold for nucleic acid backbones to form. Change in acidity would allow the chain to break off and form RNA.

14 Conclusion PAHs are known to be found both in the interstellar medium and here on Earth. PAHs may have been the molecules that first formed RNA. The idea of a PAH based initiation to the RNA world is very appealing but as of yet untested.

15 References // info/profiles/74.html shtml