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Author Topic:   Abiogenesis - Or Better Living Through Chemistry
Rrhain
Member (Idle past 659 days)
Posts: 6349
From: San Diego, CA, USA
Joined: 05-03-2003


Message 52 of 85 (64105)
11-03-2003 7:09 AM
Reply to: Message 51 by DNAunion
11-02-2003 8:13 PM


Re: sadistics
DNAunion writes:

quote:
The calculation implicitly relies upon homochirality.

But achieving homochirality isn't a problem:

NAI News Article: One-Handed Life

------------------
Rrhain
WWJD? JWRTFM!


This message is a reply to:
 Message 51 by DNAunion, posted 11-02-2003 8:13 PM DNAunion has responded

Replies to this message:
 Message 53 by DNAunion, posted 11-03-2003 8:49 AM Rrhain has responded

  
Rrhain
Member (Idle past 659 days)
Posts: 6349
From: San Diego, CA, USA
Joined: 05-03-2003


Message 56 of 85 (64218)
11-03-2003 6:20 PM
Reply to: Message 53 by DNAunion
11-03-2003 8:49 AM


Re: sadistics
DNAunion responds to me:

quote:
quote:
But achieving homochirality isn't a problem:

/*DNAunion*/ Wrong. That article does not demonstrate how homochirality can originate...the "self-replicating" molecules themsevles start out chirally pure: they then select the correct enantiomeric forms.


First, it was a start to more research. Not the sole piece of information.

Second, you're ignoring an important point in the paper: Mutations get corrected:

They further discovered that if they added "mutant" peptide templates with a single incorrectly handed molecule, these would not make more mutant templates. They would instead correct the mistake and catalyze the formation of new molecules with the correct composition.

It seems you're simplifying.

Here's some more analysis of that paper:

Biochemistry: Single-handed cooperation

Synthetic polymers are simpler than biological systems and provide a model for understanding the origin of homochirality in biomolecules. One proposal stems from observations that polymers made from building blocks of random handedness will contain mixtures of right- and left-handed blocks so complex that no two polymers will have identical stereochemistry. All the polymers will be chiral, but if one exists, it is unlikely that its mirror image will too. For small polymers consisting of only a few building blocks, the number of possible combinations of right- and left-handed blocks is small, and the mirror images are easily formed. However, for a polymer comprising 20 building blocks there are almost a million possibilities, and an enormous number of blocks would be required to build all the possible mirror images. Biological molecules often have over 100 building blocks, pushing the limits of available materials and making it extremely unlikely that a molecule and its mirror image can be prepared in the same batch. If the sample of polymers contained some that were self-replicating, it is reasonable that the most efficient one will emerge, and only this homochiral polymer will exist.

quote:
Also, the calculation I was referencing dealt with polynucleotides, not peptides.

Is there some reason to assume that chirality in polynucleotides would not have similar methods of establishment compared to peptides?

quote:
By the way, there are other problems with using that paper to support origin of life, as in, "See, this is how life arose".

Nobody is saying that. Is there a particular reason why you are assuming that the work into how life could have arisen necessarily means that what is found is the precise method about how it actually did? As the second link I just provided states, "The origin of one-handedness in biological molecules is not yet clear."

The point is that there are ways to achieve homochirality. We should not simply claim that because something is difficult for us right now means that it will never be possible to figure out. Too many times we have claimed something to be impossible (like the synthesis of organic compounds from inorganic reagents) only to find out that it is quite possible.

quote:
For example, despite the misleading term used by the authors and others, the peptides do not self-replicate.

Incorrect. Did you read the article?

For the "template" peptides to replicate, the correctly-handed components in the mixture would have to stick to the correct location on the peptides and then link up, forming exact copies of the template molecules, and this is exactly what they observed.

What do you think "For the 'template' peptides to replicate" means?

Not only did the results show that the peptides favored the synthesis of correct duplicates, but the duplicates auto-catalyzed the reaction, speeding it up.

What do you think "the peptides favored the synthesis of correct duplicates" means?

------------------
Rrhain
WWJD? JWRTFM!


This message is a reply to:
 Message 53 by DNAunion, posted 11-03-2003 8:49 AM DNAunion has responded

Replies to this message:
 Message 59 by NosyNed, posted 11-04-2003 12:38 AM Rrhain has not yet responded
 Message 60 by DNAunion, posted 11-04-2003 12:46 AM Rrhain has responded
 Message 61 by DNAunion, posted 11-04-2003 12:57 AM Rrhain has not yet responded
 Message 62 by DNAunion, posted 11-04-2003 1:05 AM Rrhain has not yet responded
 Message 63 by DNAunion, posted 11-04-2003 1:32 AM Rrhain has not yet responded

  
Rrhain
Member (Idle past 659 days)
Posts: 6349
From: San Diego, CA, USA
Joined: 05-03-2003


Message 64 of 85 (64859)
11-07-2003 5:59 AM
Reply to: Message 60 by DNAunion
11-04-2003 12:46 AM


Re: sadistics
DNAunion responds to me:

quote:
quote:
First, it was a start to more research. Not the sole piece of information.

First, it was THE ONLY paper you gave as support.


That's because I am not here to do your homework for you. The field of biochemistry that looks at self-replicating molecules and studies things such as homochirality and auto-catalysation is a huge area of research. Since you seem to be stating that something is a physical problem on a fundamental basis, the response is merely to show you that it isn't a fundamental problem.

It may be a specific problem for a specific proposed method, but that is a separate question. That is, the question of what 2 + 2 equals in the specific is quite different from the question of whether or not addition exists in the first place.

quote:
Ignoring something completely irrelevant to the discussion does not make one guilty of “ignoring” something, despite your insinuation.

What makes you think it is irrelevant? Do you not think that a process that actively suppresses non-homochiral molecules is important to the question of how homochirality came about?

quote:
That such “mutations” are corrected is completely irrelevant as to the ORIGIN of homochirality

Why? Other than your say so, why?

quote:
also completely irrelevant to whether or not the GL is a self-replicator (which was my point).

And what evidence, other than your say so, shows that it is not a self-replicator?

You seem to be playing a game. You claim that X is not seen. When shown an example of X, you then claim that it isn't an example of Y and hope to high heaven that nobody notices that you didn't ask for Y in the first place.

quote:
So why should I need to address such an irrelevant point?

Because your mere assertion that it is irrelevant is not sufficient to show that it is.

------------------
Rrhain
WWJD? JWRTFM!


This message is a reply to:
 Message 60 by DNAunion, posted 11-04-2003 12:46 AM DNAunion has responded

Replies to this message:
 Message 65 by DNAunion, posted 11-08-2003 12:56 AM Rrhain has responded

  
Rrhain
Member (Idle past 659 days)
Posts: 6349
From: San Diego, CA, USA
Joined: 05-03-2003


Message 66 of 85 (65703)
11-10-2003 9:03 PM
Reply to: Message 65 by DNAunion
11-08-2003 12:56 AM


Re: sadistics
DNAunion responds to me:

quote:
Ah, so your argument has already run out of steam

Incorrect.

The argument is still there. I, however, do not wish to do all the heavy lifting. If you cannot be bothered to get off your ass, then you shouldn't be surprised to find that you don't have all the information.

quote:
and that that one paper did not support your "contradiction" of me.

Incorrect.

You claimed it didn't support self-replication, despite the fact that the paper directly talks about the molecules self-replicating.

And if you can't even be bothered to read the information that I do provide you, then there is very little point in providing you with more.

------------------
Rrhain
WWJD? JWRTFM!


This message is a reply to:
 Message 65 by DNAunion, posted 11-08-2003 12:56 AM DNAunion has responded

Replies to this message:
 Message 67 by NosyNed, posted 11-10-2003 10:11 PM Rrhain has not yet responded
 Message 68 by DNAunion, posted 11-11-2003 11:03 PM Rrhain has responded

  
Rrhain
Member (Idle past 659 days)
Posts: 6349
From: San Diego, CA, USA
Joined: 05-03-2003


Message 70 of 85 (66514)
11-14-2003 5:06 PM
Reply to: Message 68 by DNAunion
11-11-2003 11:03 PM


Re: sadistics
DNAunion responds to me:

quote:
You can point out that the authors label the GL as self-replicating until you turn blue in the face, but it won't change the fact that it can't.

You can whine that the GL isn't self-replicating until you turn blue in the face, but it won't change the fact that it does.

------------------
Rrhain
WWJD? JWRTFM!


This message is a reply to:
 Message 68 by DNAunion, posted 11-11-2003 11:03 PM DNAunion has responded

Replies to this message:
 Message 71 by DNAunion, posted 11-14-2003 10:36 PM Rrhain has not yet responded

  
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