|
Register | Sign In |
|
QuickSearch
EvC Forum active members: 64 (9164 total) |
| |
ChatGPT | |
Total: 916,902 Year: 4,159/9,624 Month: 1,030/974 Week: 357/286 Day: 13/65 Hour: 0/0 |
Thread ▼ Details |
|
Thread Info
|
|
|
Author | Topic: Excellent paper-peptide self assembly | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
You gave three links, one of which you yourself seemed hesistant about. So I looked at the other two.
One, about polar bears (http://www.springerlink.com/app/home/main.asp?wasp=6a86b7...), led to a site where one must pay to access the articles. I am not going to pay to look for your evidence: that’s your responsibility. The second link, about "various possibilities" (http://www.endeav.org/evolut/chiral/chiralit.htm) had an interesting abstract about the the Coriolis force, but the actual article didn’t seem to say what you think it might have. Here’s a quote, with emphasis added.
quote: The impression I get from skimming the article is that the authors are claiming that AFTER LIFE WAS ALREADY WELL ESTABLISHED AND EVOLVED TO THE LEVEL OF PLANTS AND PROTOZOA, rotation of the Earth could have influenced chirality of LARGE-SCALE SUPERSTRUCTURES, which could have then, the postulate, been backfed down the chain of hierarchical structures to ultimately influence the selection of monomer chirality. One problem with this theory is that it goes against the mainstream view which holds that homochirality is required for life to arise. Also, the article (which appears to be written by a foreigner who doesn’t speak English exceptionally well) doesn’t seem to have actually demonstrated the reverse flow of chirality it proposes (though I admit I didn’t carefully read it - but their use of the word postulate in terms of this part does indicate the lack of experimental support). [This message has been edited by DNAunion, 11-16-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: 1) It does not mean that it WILL HAVE dramatic effects. Maybe the effects would be dramatic, maybe the effects would be slight, maybe the effects would be negligible. 2) Exactly what chiral catalyst are you proposing for generating an enantiomeric excess of left-handed amino acids and/or right-handed ribose? Or is this going to remain some unnamed mystery catalyst? 3) How did your as-of-yet unidentified chiral catalyst come to be present preferentially in one chiral form? 4) How did your as-of-yet unidentified chiral catalyst maintain its chiral preference over an extended period of time? Was there some other chiral catalyst making it?
quote: Can you see how, since racemization is a spontaneous process — which leads away from enantiomerically pure mixtures and towards racemic ones — a slight excess of one enantiomer could be lost? Can you see how enantiomeric cross inhibition could result in the locking up of some of the slight enatiomeric excess in molecules whose growth was still poisoned by inclusion of both enantiomers?
quote: Aren’t you forgetting about enantiomeric cross-inhibition? That phenomenon deals with polymerization, not monomer formation, so your catalyst is helpless here. Just having a slight excess of one chiral form of a monomer does not mean that only that one enantiomer would be incorporated into growing polymers: the probability for both enantiomers being incorporated at some point would still be high and enantiomeric cross inhibition would greatly retard the production of polymers. Or does your mystery catalyst not only preferentially make one chiral form of monomers, but also, as if by magic, also serve as a polymerase, and one that ensures that only one chiral form gets incorporated into growing polymer chains? That would be one fantatstic catalyst! Leaving out magical molecules, we are still left with enantiomeric cross inhibition and the associated difficulty of polymer formation (and the locking up of some of the slight enantiomeric excess in growth-stunted molecules). With a low production rate of polymers (and a non-zero background rate of hydrolysis), the chances of hitting upon a useful catalyst is greatly reduced, and the chances of the amplification you are hoping for follow along.
quote: If everything you presented was unavoidable and non-problematic, sure. But mostly what you’ve done is paint an oversimplified, rosy picture; it’s devoid of nasty details (like spontaneous racemization, poisoning of polymer formation by enantiomeric cross inhibition, and the locking up of some of the enantiomeric excess in growth-stunted molecules) that always seem to get in the way of such speculations; it relies upon unidentified, mysterious catalysts; and it has not been demonstrated experimentally.
quote: In a non-biological and undirected setting? Because having an enantiomeric excess of amino acids and/or nucleotides (the sugar moieties) is not the equilibrium state, and therefore, undirected processes will tend to bring any discrepancies back in line — back towards equilibrium. After all, racemization (of amino acids and ribose) is a thermodynamically spontaneous process, whereas resolution is not. Sure, if one ASSUMES into existence some somehow-enantiomerically enriched catalyst that can be maintained, somehow, in its enantiomerically enriched state over some extended period, and that can generate enantiomeric excesses in amino acids and/or ribose, and one also assumes into existence some other unidentified polymerase catalyst that preferentially selects the enantiomer that is present in slightly greater quantity (and also assumes anything else I’ve forgotten here), then sure, one can imagine an increase towards homochirality could occur. But even given all of that, homochirality is not assured.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Rei Member (Idle past 7042 days) Posts: 1546 From: Iowa City, IA Joined: |
quote: Fair enough.
quote: DNAunion, prophet of the God of the Gaps.
quote: Are you familiar with a Wimshurst Machine? It's a neat electrostatic generator that uses induction to generate power. That is, an imbalance in the charges of the plate is amplified by the process. A curious thing about it is which terminal ends up positively charged and which one ends up negatively charged: it's random. What happens is, it is essentially impossible to have the two disks have precisely the same charge on them. However minutely different the charge is, it gets amplified with each pass. That is exactly what I am suggesting in this case. A slight imbalance of one catalyst, over long-term iterative processes, leads to a major imbalance of end products. Play "God of the Gaps" all you want, but don't fail to address the meat of the issue.
quote:quote: Only if you have a completely pure solution - i.e., free from chiral catalytic influences. When the catalysts are chiral, an imbalance in the ratios betwen catalysts will lead to an imbalance in the end products. When your next line of catalysts are the ones produced from the previous go-round, you get a further imbalance. And a further imbalance, and further, etc.
quote: As I pointed out and referenced earlier, only certain types of chemical synthesis suffer from cross-inhibition.
quote: Arent you forgetting about enantiomeric cross-inhibition?[/quote] Aren't you forgetting my reference? Furthermore, I should add, cross-inhibition is only a problem when you're trying to build a *specific* chemical, through a *specific* pathway, under which the pathway works in a chirally pure solution but has inhibition in a chirally imbalanced solution. Here, we're talking about a near incomprehensive number of different chemicals in the same solution. This sort of pathway inhibition is virtually irrelevant. Let me put it another way. You you're specifically trying to spell the word "AUSTRALOPITHECUS". However, so long as the K key exists, whenever you try to type O-P-I, the K attaches intstead of an I, inhibiting the process. Ok, but what if you first created AUSTRALOP, and ITHECUS, and then joined them? What if you created AUST, RALO, PITH, and ECUS, and joined them? What if HOMOHABILUS functioned the same or nearly the same as AUSTRALOPITHECUS? Etc. Your strict laboratory synthesis analogy is about as unlike a prebiotic earth as you can get, where you have countless different types of reactions going on at once. The more different routes something can take, the less relevant a certain route being inhibited is; in fact, for every route that you have inhibited, odds are you're creating a new possible route. And, as I mentioned before, even in a laboratory synthesis environment, cross inhibition is not always an issue.
quote: Look, do you see me making fun of you? I could likewise start sentences with, "Does your invisible friend in the sky ... ".
quote: That's a given, now isn't it, in most cases with a chiral catalyst?
quote: You're one to speak.
quote: I'm not discussing a specific catalyst, just catalysts. DNA, don't be a pain: you know very well that if we knew the exact route that abiogenesis took (even if it were your "poof, here's life!" method), there would be nothing to discuss. We're here to discuss theories as to what could lead to enantioselective properties, not trade insults over the gaps in our knowledge.
quote: Where do you get a low production rate of polymers from?
quote: There have been a number of theories on the rates of hydrolysis versus polymerization, with varying "wet" and "dry" theories. One such theory involves an in-between, with early polymer forming in the gaps between clay particles.
quote:quote: Why do you expect spontaneous racemization when you're using chiral reactants?
quote: A non-issue - see above. You can poison specific polymers in a laboratory style environment, but you have yet to evidence that it poisons polymer formation in general.
quote: How do you conclude that this would occur?
quote: Once again, introducing the "God of the Gaps!" I can just picture creationists in the 1800s now... "You say that the earth is billions of years old... and yet, we know of no way that the sun could be more than a few millions of years old - the best that you can come up with for its energy is "gravitational collapse". What, is there some "mystery, magical energy source" powering it that we don't know of? That has not been demonstrated experimentally.". The God of the Gaps is continually being forced to move into a new gap. Are you sure you want him in this one? That is why we discuss possibilities, not absolutes, when we're discussing gaps in scientific knowledge. Shoving a God wherever you see a gap is not a good plan for advancing human knowlege.
quote:quote: One could apply that exact same argument toward the weather. Having turbulence in the atmosphere is not an equilibrium state, and so the world should balance itself out toward a simple constant atmospheric Coriolis flow. Does it? Part of the nature of iterative processes is that errors magnify themselves tremendously. Take a class on chaos theory some time, then get back to me.
quote: Explain?
quote: It's a given. No mixture is ever exactly even.
quote: Or whatever early life was based on, which may have nothing to do with life as we know it today.
quote: Why are you requiring two catalysts, again? And why must one of them be a polymerase (assuming that you mean according to current usage of the term, DNA and RNA polymerases, although you could be meaning it in a general sense)?
quote: Actually, given that, it is assured. Given that differences amplify themselves over time, as they are observed to do in many systems, then it is assured. The question is whether they amplify themselves in this particular system. Next week I'll look to see if I can find any studies on the subject; you do your research as well. Of course, remember, we're not talking about a laboratory synthesis environment with a single iteration. We're talking about an environment in which the products of the first reaction are involved in the second, and those products in the third, etc, for billions upon billions of iterations. ------------------"Illuminant light, illuminate me."
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Tokyojim Inactive Member |
DNAunion,
I've wondered about the exact same thing you brought up here in this post (#25) for a long time. I'm sure it has been mentioned on this site before, but I haven't read it. I've been reading this thread with interest. I don't understand everything I read, but I'm learning. Anyway, here is what I'm referring to: _____________________________________________________________________ DNAunion writes:One thing that has to kept in mind is that 10^48 40-mers existing at one time would have a mass comparable to the Earth's. Let's not focus on the "weight" right now (or the amount of resources that would go into making such a library) but rather on the distribution of so many molecules - or even a fraction of them. For one 40-mer to replicate the other, the molecules can't arise one in "the Pacific Ocean" and the other in "the Indian Ocean": they'd never meet. Even if both arose on opposite shores of "the Indian Ocean" they'd never encounter one another. In fact, even if they sprung up just a mile apart the probability that they would meet is close to 0. And although it gets harder to "calculate", even if two partners arose just 10 yards away from each other it seems very unlikely that one would happen to come into contact with the other. Further, let's not forget that polymers tend to hydrolyze in water (we could get more technical, but that's the general idea). So there is a time limit on how long they have to wonder about looking for their partner. One's arising at time X and the other's arising at time X + 10,000 years (even if in the exact same spot where the other "host" would be) is going to do no good at all. So not only would a pair of RNA replicases have to arise in almost the same exact microscopic volume, but they would also have to arise at almost exactly the same time." ____________________________________________________________________ It is absolutely amazing to me that OOL scientists and others, in spite of the seemingly insurmountable odds and lack of evidence, can have so much faith in chance. The fact that these DNA replicases must be formed at EXACTLY THE SAME TIME AND THE SAME PLACE is something that we don't hear very much. DNAunion explained it very well and no one responded to it. From a layman's perspective, this is too much to actually expect people to honestly believe. Yet, scientists would have us believe that the fact that life has arisen by chance is all but certain. The only thing that is not yet known is exactly how that happened. And the problem of chirality is only one of a number of very difficult problems for OOL scientists. Of course scientists can say that it is only a matter of time until we understand everything. That is simply a statement of faith without any empirical evidence at all. Perhaps they will find that the problems only get worse for OOL scientists the more they learn. It certainly seems that so far as we look back on history, that this has been the case. Scientists of Darwin's era didn't need much faith to believe in spontaneous generation, but problems like chirality have greatly increased the odds against spontaneous generation. That one of these RNA replicases could even be produced at all is questionable, but even if it could have arisen by chance or been produced by some means, what would preserve it or keep it from continuing to react and change into another form that would make it unusable? The fact that new theories limit the area of the supposed "organic soup" to small areas around thermal vents, etc. makes the formation of these RNA replicases an even more fantastically improbable event. I'm sorry, but if scientists really want me to swallow their "scientific" theories, they have to do better than that. It's too much for my little brain to actually believe. Anyway, I'm learning a lot from this thread. Thanks.Tokyojim
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
First of all, I think Rei is being disingenuous.
What I have been discussing in this thread has clearly been nucleotides, amino acids, and their polymers — the main molecules involved in OOL discussions. The first 14 posts in this thread, by everyone, were limited to amino acids/peptides: because Rei, in an OOL-related thread, spoke of enantiomers in general (step one in her plan to divert the topic?), at post 15 I replied and started discussing nucleotides also. But based on Rei’s statements lately, apparently Rei has been trying to slip her own ideas into the discussions without actually saying so, with her hidden agenda causing confusion. For example, I’ve pointed out and fully supported enantiomeric cross inhibition numerous times in relation to nucleotides and amino acids: the molecules being discussed. But Rei keeps acting like, and indeed stating that, enantiomeric cross inhibition isn’t a problem. Is she deaf, dumb, and blind? Well, if we assume she’s not, our options are limited. One of them is that Rei, unlike me, has stopped talking about just amino acids, nucleotides, and their polymers and has implicitly injected in some other molecules (what, quartz?) into the discussion, without actually mentioning them. I think it only fair that Rei stick to the topic others are discussing and stop trying to change them. Or at the very least, Rei should stop playing games and actually state what she is talking about. *********************************
quote: Please learn to use appropriate terms: it helps communication. Chirally imbalanced? Do you mean a solution with an enantiomeric excess? Such a solution would be out of equilibrium and thus imbalanced. Or do you mean a racemic mixture, even though a racemic mixture is just about perfectly balanced, with 50% L and 50% D? Does your term chirally pure mean that it is a pure solution containing just the two chiral forms? If on the other hand you mean that only one enantiomer is present you should use the term enantiomerically pure. You see, an enantiomer is ONE of TWO chiral forms of a molecule, so if you mean only ONE enantiomer is present, then enantiomer is the correct word to convert into an adverb. ***********************************
quote: No, and I don’t need to be, since a Wimshurst Machine isn’t a nucleotide or an amino acid or polymers made of these monomers.
quote: And yet you’ve failed to answer any of these questions, as well as others:
quote: All you are offering is speculation: you have no catalyst in hand and you have no experimental confirmation either. PS: Wimshurst Machines don’t count.
quote: quote: To lend some support to my last statement there, I’ll quote from an OOL book.
quote: Looks like Rei is facing a bigger problem than she thinks.
quote: quote: Yeah, and those being discussed being among them!!! So don’t pretend that what you said earlier, or now, has countered my last point — it still stands.
quote: quote: quote: Nope, because you’ve given none that are relevant. You’ve provided no reference that shows that enantiomeric cross inhibition would not be a problem for nucleotides and/or amino acids, whereas I supplied what, a dozen, that showed it would be.
quote: Yeah, like the ones believed to have been involved in the OOL, like amino acids and nucleotides. Please don’t change the subject.
quote: quote: ENANTIOMERIC CROSS-INHIBITION It is a problem that prebiotic syntheses of polynucleotides and polypeptides would face, stunting the growth of chains and leading to low production rate of polymers.
quote: quote: quote: Why do you expect chiral reactants in the first place? (That’s poor terminology, but I stuck with your phrasing) And why do you expect a small presence of a chiral catalyst to stop a spontaneous process like racemization from occurring?
quote: quote: A real issue for nucleotides and amino acidssee above and the dozen or so quotes I provided from OOL researchers. Please stick to the subject being discussed.
quote: Go back and read the quotes I posted and/or research it yourselfI think you’re confused.
quote: quote: Simple reasoning. Let’s look at the general idea of enantiomeric cross inhibition in nucleotides while looking at an average chain. Under racemic conditions (D/L = 1.0), the average chain starts to elongate but by the third monomer it has both enantiomers in it and so stops growing. Being so short, it won’t likely have any complex, useful function. Thus, the nucleotides in that chain are basically locked up in a useless molecule. Having a slight enantiomeric excess (instead of D/L = 1.0) might cause the average chain to incorporate one or two additional monomers, but would still quickly end up with both enantiomers. That chain too (being something like 4 or 5 monomers in length) is also not likely to be able to carry out any complex, useful function and so the nucleotides in it — which include the slight enantiomeric excess - are basically locked up in a useless molecule. Thus, enantiomeric cross inhibition would/could lock up some of the enantiomeric excess in growth-stunted molecules.
quote: quote: quote: Too bad for you that we’re not talking about weather. What we are talking about is amino acids and nucleotides, and there is a thermodynamically spontaneous process, called racemization, that leads towards the equilibrium state of a racemic mixture. Here, I’ll repeat a quote form you.
quote: Please stick to the subject.
quote: Your posts are evidence of that! :-)
quote: Take a class on biochemistry some time, then get back to me.
quote: quote: The driving force behind racemization - towards equilibrium/racemic mixtures - is entropic (enthalpy remains constant). Going in the opposite direction — towards homochirality — has a positive delta G associated with it (because of the decrease in entropy) and thus is not spontaneous.
quote: Please don’t, you’ve gotten too far off topic already. [This message has been edited by DNAunion, 11-16-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Rei Member (Idle past 7042 days) Posts: 1546 From: Iowa City, IA Joined: |
DNAunion:
You're back to your old habits of A) splitting up individual posts into multiple, making it very hard to reply to, and B) focusing on personal attacks. If you keep this up, I will cease to respond in this thread. You have been warned; don't expect another warning.
quote: It's implicit in your line of argument. Because, by your line of argument, if not every reaction receives a high degree (or any degree at all, in the case of many reactions) of cross inhibition, then it's not a problem: it only poses problems for *particular pathways* to develop early life. There are countless possible pathways. Your argument, unless all reactions have the same degree of inhibition, is thus near useless.
quote: Now we're back to the GL? Nice try at a dodge there, but this conversation wasn't on the subject of the GL. Let me ask you a question - since you seem to have this huge problem with the concept of how much of a sample size has been observed: What percentage of possible proteins have we looked at that are the length of the GL to test to see whether they're ever self replicating? The ghadiri ligase is, what, 32 amino acids long? We're looking at 4.29e41 possible combinations here for a protein of that length. You have a very serious problem with the concept of the percentage of total sample size observed that you have displayed again and again, and it gets very frustrating. Please quit pretending that we have observed even a tiny, remotely statistically significant percentage of total possibilities. Even in our proportionally tiny percentage of self replicators that we have observed, there are going to be countless different ways such a protein can be formed. Given this, the odds that there will be routes with no cross inhibition seem to be almost a given.
quote: You seem to accept evolution (just not abiogenesis), right? If that is the case, then look at what an undirected process has accomplished since then (or do you believe in "directed evolution"?) "Synthesized in the lab, not in nature". Ah. Just assuming that there are 10 tons of chemicals and solvents involved in brand new, documented organic chemistry expierments being conducted each year on the subject of abiogenesis (not likely, but let's be nice. ), Earth's oceans alone (0.04% of Earth's mass) have a mass of 1.35 quintillion metric tons (1,350,000,000,000,000,000 metric tons). Even assuming that only 0.1% of the oceans were involved (and that nothing on land was involved), that's still giving a volume of 1,350,000,000,000,000 metric tons of reactants operating for a billion years. That is *Far Better* than in a lab. Of course, you won't accept that, because in your worldview, only directed things achieve amazing results, right?
quote: Why? It has preposterously more possible chances in nature to occur. Unless you feel there is some sort of laboratory situation that cannot occur in nature - and if so, please name it.
quote: That one was about hijacking earlier, much simpler forms of life. The sample concept presented was in selective growth of clays, in which different types of crystals compete with each other for further mineral deposits. Deposits of organic material on the surface of the crystals could aid in such selection, and these deposits would likely be chiral (corresponding to the type of crystal substrate they're growing on). Eventually, with a much greater range of possible chemistry, the organic component took over. Again, though, I think such a concept is still too speculative, and I'd like to see more research done on whether it is possible for different clays to have competitive selection.
quote: It must have changed since I looked at it then, because I was able to access the full text the other day for free. I'll summarize: the distribution of a number of organic pesticides has been found to be chirally imbalanced in the world's oceans, leading to a chiral imbalance in wildlife.
quote: And here's a quite with my emphasis added
quote: You continually ignore the frequent use of the word "and" in the text, taking only from one side. The model seems to postulate both on the level of lifeforms *and* on biochemistry itself. Let me add again that a chiral imbalance is not needed, as I have discussed in the first part of this post. But if it was, here's yet another way it could have occurred - a film at the surface of the water, which deals with the water/air border (how many possible methods do you need?) Of course, knowing your love of quotes, you'd probably just ignore the article and extract an out of context quote, such as "Theories on the emergence of the homochiral biopolymers of life at prebiotic times suggest the involvement of enantioselective reactions starting from heterochiral mixtures of alpha-amino acid and nucleic acid precursors (1-7). Polymerization reactions of racemates in isotropic media would lead, however, to formation of polymers comprising a random sequence of left (S)- and right (R)-handed repeat units in a binomial distribution (8). Thus, the probability of obtaining oligomers with homochiral sequence will become negligible with increasing length (9-11)." to try and convince people who don't know better. Almost any assembly that occurs on a two dimensional inorganic surface would be expected to be subject to the chiral influences of that surface. And, as I stated before, that is not even necessary, since any chiral imbalance or influence would be expected to imbalance the system as a whole, especially any that gets closer to self replication
quote: Thank you for being so mature Do most people you debate with end up getting sick of you in the process and leaving? If so, you shouldn't be surprised.
quote: There is absolutely no necessity that the first forms of life had to have been based on what life currently is based on. That is why we need to discuss enantioisomers in general.
quote: In limited cases; it takes about 5 minutes of searching to dig up a process in which there is *no* or *minimal* cross inhibition. And, as I've mentioned several times, that's only relevant for a particular route of creating a particular molecule - neither of which we are discussing when talking about abiogenesis. There are near countless possibilities under each category (routes and molecules) that can work just fine.
quote: Yes.
quote: No. "chirally pure" - Google SearchIf you'd rather I use the term enantiomerically pure, that's fine, so long as we're on the same page. quote: Do you realize how bullheaded you look when you deliberately ignore what a person is saying? Did you even read the analogy?
quote: 2) Exactly what method are you proposing for your deity generating an enantiomeric excess of left-handed amino acids and/or right-handed ribose? Or is this going to remain some unnamed mystery god-magic? 3) How did your as-of-yet unidentified god-magic come to create preferentially one chiral form? 4) How did your as-of-yet unidentified god-magic maintain the chiral preference over an extended period of time? Was there some other chiral catalyst making it? That said (turning it back on yourself), and with me pointing out yet again that we have looked at such a tiny percentage of the sample size that it's about as deceptive as you can get to ask for an exact route, I will repeat what you quite obviously did not read in your skipping over my analogy (and my entire discussion about how synthesis of a product with varying purity of reactants generally has the production rate of the end product fall off faster than the purity of the reactants - why should I even bother when you don't read what I write?): There always is an imbalance, even if incredibly small. In most real-world applications, imbalances tend to magnify themselves when subjected to iterative processes instead of converging.
quote: And don't pretend that what *I* said - that the odds of it being a particular self replicator that we discover, and having been made through the exact process that we make it - are so small as to make them essentially zero. The number of possibilities out there makes it incredibly likely that the first self replicator is *not* something that we have ever observed, and that even if it was, it would *not* be produced through the route that we produced it.
quote: Yes, I know, you have far more time for this than I do. Is that something to really be proud of? Again, why are you insistant that DNA and/or RNA had to be first? I would expect the first life to be a simple ligase that makes broken copies of itself (anything that is "close" to itself increases the odds of random interactions producing another copy of itself). This would be replaced by a ligase that makes correct copies of itself with correct source material, and broken copies of itself with incorrect source materials. This would be replaced by a ligase that either itself can handle a wider range of source materials, or can also create another ligase that creates correct and/or broken copies of the source materials; etc. This progresses until you have a fairly stable hypercycle. DNA or RNA would be a later introduction to the system. "RNA world" is a fairly old concept (1967, I believe); it had some reinvigoration in the early 1980s with the discovery of catalytic RNA molecules, but is anything but universally accepted.
quote:quote:quote: ... which effects *some* pathways for *some* molecules, but not *other* pathways, and not on *other* molecules, out of tredecillions of possibilities molecules with, perhaps, quindecillions of possible assembly methods, for something merely as long as GL.
quote: 1) Inorganic substrates (incuding the water/air boundary - any 2d substrate will do).2) *Any* level of imbalance should get magnified. quote: Not stop. Produce a mixture with an enantiomeric excess.
quote: You just claimed that you're not trying to state that all synthesis has enantiomeric cross inhibition. Are you saying that, now?
quote: Wrong. In a laboratory environment, that may happen when you're dealing with a very limited set of very pure reactants, but in the real world, those chemicals are not going to stay short for long. There are too many things that could possibly react with them to either tear them apart or attach new things to them. You're dealing with your directed, single pathway logic again. That's not at all what is proposed with abiogenesis.
quote: Racemization in peptide assembly when a ligase or the subunits has an enantioisomeric excess? How? Again, there will always be minute excesses, so you have to show that the ratios *converge* instead of *diverging* when there's an excess, in an iterative process (i.e., when the results of one process become the reactants in the next).
quote: Ah, finally an applicable quote. And my response? It's already been shown to occur. Sorry, there! Asymmetric autocatalysis and amplification of enantiomeric excess of a chiral molecule
quote: quote:quote: So typical. You respond to a point with offhand dismissal. Here I am, trying to answer each and every one of your points, and you ignore me with a wave of your hand on 2/3 of the things that I write. By the way, I have taken classes on both. (Preparing for another insult from you...)
quote: How is there a decrease in entropy? And need I mention that the trend of increasing entropy only is law inside closed systems? P.S. - Seing as you're so fond of quotes, allow me to turn your favorite old argument back on yourself. If all of these scientists are so sure that there's some sort of problem with abiogenesis, why do they believe in it? ------------------"Illuminant light, illuminate me."
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: Are you really that dense? Or are you just being dishonest? I just don't know anymore. YOU were the one who referenced the GL: it was YOUR statement I was replying to. Here, look at the actual exchange.
quote: quote: The quote you posted is from a paper on the Ghadiri Ligase...the "GL". [This message has been edited by DNAunion, 11-17-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: Sorry, but considering your general ad hom attitude and propensity for dishonesty, I am not about to take your word for it. If you've got the actual goods, present them. [This message has been edited by DNAunion, 11-17-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: So are you claiming that inorganic structures are biochemistry? YOU did highlight that part. Or are you referring to the supermolecular structures and formations? That doesn't work. First, those shouldn't be considered to be discussing biochemistry - carefully reread the clause you highlighted (of course you will disingenuous and stretch things beyond reason to try to make it somehow biochemical). Second, I already discussed superstructures in the following, which you so dishonestly omitted.
quote: So in other words, you have absolutely no point. You just PRETEND to have a point hoping to score some cheap rhetoric points. [This message has been edited by DNAunion, 11-17-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: Gee, if it’s so simple, then why haven’t you done so already? Let me try to head off ANOTHER of your predictable tricks. My statements, which you claim to be countering and therefore should stick to discussing, deal with prebiotically plausible methods of creating templated polymers from monomer additions, and with the pools of monomers being racemic.
quote: Wrong, on both counts. Enantiomeric cross inhibition is a problem for prebiotic polymerization of nucleotides. If that has nothing to do with abiogenesis, then what does? And, what are all of those OOL researchers I quoted talking about if not abiogenesis? Here, let me present those quotes to you again...why not try reading them this time?
quote: quote: quote: quote: quote: quote: quote: quote: quote: [This message has been edited by DNAunion, 11-17-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: Rei, can you read? Look back at my statement you are replying to.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: And you thing ripping molecules apart and somehow attaching various other things to them is beneficial? Do those things happen to your hypothetical catatlysts that arise? Are they torn apart? Do they get inactivated by having various other things attached to them?
quote: Wrong. I am dealing with experiments conducted by scientists attempting to explain abiogenesis. [This message has been edited by DNAunion, 11-17-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: quote: quote: quote: It's not my job to educate you. If you don't understand something, try reading a book.
quote: Wrong. It is possible for entropy to decrease in a closed system. However, total entropy cannot decrease in an isolated system. [This message has been edited by DNAunion, 11-18-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: What would you suggest as an alternative? [This message has been edited by DNAunion, 11-18-2003]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DNAunion Inactive Member |
quote: First of all, this experiment involved neither amino acids nor nucleotides (nor ribose). Second, no mention is made of whether or not all of the compounds involved are prebiotically plausible. If they aren’t, this paper has no direct bearing on the origin of life. Third, as always, we have to remember that this occurred in a lab. That is, what steps were taken to prevent unwanted side reactions? Were any other goal-oriented steps used? If so, how prebiotically plausible were those steps? If they rise to the level of illegitimate investigator interference then this paper has no direct bearing on the origin of life. However, I must admit, I am quite intrigued. I would like to see the experiment performed on amino acids and nucleotides, using prebiotically plausible molecules and conditions. [This message has been edited by DNAunion, 11-18-2003]
|
|
|
Do Nothing Button
Copyright 2001-2023 by EvC Forum, All Rights Reserved
Version 4.2
Innovative software from Qwixotic © 2024