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| Author | Topic: Abiogenesis | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
OK, DNAUnion, you asked for details, well here we go:
quote: Wow. Chill, man! Don't get mad here. I am not just a reference babbler and I'll try to prove it!  Let's start with autocatalyzing RNA. You say this don't exist. Let's find out. First let's make sure we have our terms defined.autocatalysis: Self-catalysis; catalysis of a substance by one of its own products, as of silver oxide by the silver formed by reduction of a small portion of it. RNA (ribonucleic acid): A polymeric constituent of all living cells and many viruses, consisting of a long, usually single-stranded chain of alternating phosphate and ribose units with the bases adenine, guanine, cytosine, and uracil bonded to the ribose. The structure and base sequence of RNA are determinants of protein synthesis and the transmission of genetic information.OK, what was originally thought was that "DNA makes RNA makes protein." Obviously, if all three of these are needed at the same time for life, it causes problems for abiogenesis. However, we now know that certain things do not need DNA but instead reverse transcribe their RNA. So we can illiminate DNA from that formula. Can we also illiminate proteins? Well, we also now know that RNA can do the function of proteins and act as an enzyme (this was proved by Nobel Prize-winning researcher Thomas R. Cech). Enter the term ribozyme. ribozyme: An RNA segment that has the ability to catalyze the cleavage and formation of covalent bonds in RNA strands at specific sites. Back to autoctalysing RNA: autocatalyzing ribozymes DO exist. Let me give an example (and I'll give the details): the hammerhead ribozyme. Hammerhead ribozymes are small, catalytic RNAs that undergo self-cleavage of their own backbone to produce two RNA products. All hammerhead ribozymes contain three base-paired stems and a highly conserved core of residues required for cleavage. The cleavage reaction proceeds by an attack of a 2' hydroxyl oxygen of a catalytic site cytosine on the phosphorus atom attached to the 3' carbon of the same residue, breaking the sugar phosphate backbone and producing a 2', 3' cyclic phosphate. As for protein ribonucleases, a metal ion bound in the active site (Mg++) stabilizes the ionized form of the 2' hydroxyl oxygen, promoting the catalytic attack. The hammerhead ribozyme coordinates Mg++ in the proper geometry to stabilize the trigonal bipyramid intermediate formed by attack of the 2-OH on the phosphate. The end products are a 2,3 cyclic phosphate and a 5-OH. Now regarding self replicating peptides, uh, well first the details : There have been several self-replicating peptides discovered. The one I referenced was a 32-amino-acid peptide, folded into an alpha-helix and having a structure based on a region of the yeast transcription factor GCN4, can autocatalyse its own synthesis by accelerating the amino-bond condensation of 15- and 17-amino-acid fragments in solution. It uses a single-stranded DNA hexamer and its two trimer fragments) are based on a polymer catalysing its own formation from two fragments. Now you say this does not have any application for abiogenisis. I say it does. Self replicating peptides DO exist. I admit that they were not *formed* by some abiogenesis expirement, but they *exist* which is what I was saying. Currently, our knowledge of abiogenesis is like a puzzel. We have most of the pieces, we just have not put them together (and made life). Self replicating peptides ARE one of the pieces. Before we discovered self replicating peptides, we needed some way for amino acids to reproduce....and we did not have a way. The discovery of self-replicating peptides was in a way confirmation of a prediction that abiogensis theories made. If you think not, you should explain why not. Regarding RNA comING from peptide nucleic acids. I have not looked into that yet, but that will be the next thing I do, I will post the details that I find. BTW, DNAUnion, thanks for challenging me on this. You forced me to look things up and I learned alot. Unfortunately for you, even after doing the research, my conclusion remains the same. Note that if I had done the research and not found things to support my statements, I would have withdrawn them. I will post on peptide nucleic acids soon. I have not tryed to find anything about it yet.....Till then --Black P.S. I didn't get all the details. Want more? Ask me....or do the research yourself  [This message has been edited by Black, 04-01-2004]
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
quote: But things have happened since that time. Ever here of peptidyl transferase? Peptidyl transferase catalyzes the synthesisof peptide bonds in vitro using substrates much smaller than the aminoacyl and peptidyl tRNAs that are the ribo-some’s normal fare. How does it work? The reaction that occurs when peptide bonds form on theribosome is a simple one: the aminolysis of an ester bond.The nucleophilic -amino group of the amino acid moietyof an aminoacyl tRNA bound to the so-called A site of thepeptidyl transferase center attacks the electrophilic carbonylcarbon of the ester bond linking the peptide moiety of apeptidyl tRNA bound to the so-called P site of the peptidyltransferase center. The resulting anionic, tetrahedral carbonintermediate subsequently rearranges to yield a dischargedtRNA bound to the P site, and an A-site bound tRNA joinedby an ester bond to a peptide that is one amino acid longerthan it was before the reaction occurred.
quote: It was based on a protein found in nature, an alpha-helical coiled coil.
quote: No, intelligent researchers are not needed 3.5-4 billion years ago. The reason is simple: the researchers were simulating natural processes. These peptides could have been synthesised naturally.  An animated cartoon showing the self-replication process with the 32 residue peptidic template [GRAY] which binds a 15 residue nucleophilic fragment [RED] and a 17 residue electrophilic fragment [BLUE] which catalyses the thioester bond formation [YELLOW] hence catalyzing it's own formation. A 32-residue alpha-helical peptide [GRAY; template] based on the leucine zipper motif of GCN4 is shown to act autocatalytically in templating its own synthesis by accelerating the thioester-promoted amide bond condensation of a 15-residue [RED;nucleophilic] and 17-residue [BLUE; electrophilic] constitutional peptide fragments in neutral and dilute aqueous solutions. The self-replicating process displays parabolic growth and is goverend by square-root law kinetics in the initial period of product formation. Self-replication.
quote: No, its not a misplaced paragraph. Its what was published in Nature.
quote: You are right, Pentium 4 CPUs exist. So why aren't I bringing them up in this discussion? Because, as you said, they have nothing to do with abiogenesis. But self-replicating peptides do because they are kind of like one of the predictions of abiogenesis theories. Regarding RNA from peptide nucleic acids...I find that the evidence supports what I said before. PNA consists of N-(2-aminoethyl)glycine (AEG) and the adenine, uracil, guanine, and cytosine-N-acetic acids. AEG is produced directly in electric discharge reactions from CH4, N2, NH3, and H2O. Electric discharges also produce ethylenediamine, as do NH4CN polymerizations. AEG is produced from the robust Strecker synthesis with ethylenediamine. The NH4CN polymerization in the presence of glycine leads to the adenine and guanine-N 9-acetic acids, and the cytosine and uracil-N 1-acetic acids are produced in high yield from the reaction of cyanoacetaldehyde with hydantoic acid, rather than urea. RNA may be polymerized using the PNA as template accounts for enzymatic activities including PNA replication. So now let's review: Amino acids form naturally, as predicted by abiogenesis theories. If synthesised correctly, peptides (chains of amino acids) can self-replicate, as predicted by abiogenesis theories. The substances to create PNA (the precursor to RNA) form naturally, etc., as predicted by abiogenesis theories. RNA can do the function of DNA, as predicted by abiogenesis theories. RNA can act as a catalyst, as predicted by abiogenesis theories. RNA can do auto-catalysis, as predicted by abiogenesis theories. These things were required for abiogenesis...and now we know they are true. These are the pieces of the puzzel. I put them together....and come to the conclusion that abiogensis is possible....and is probably what happened! --Black
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
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Black Member (Idle past 5205 days) Posts: 77 Joined: |
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