What is the Biggest Non-Repeating Molecule?

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What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Mon Aug 08, 2016 3:44 pm UTC

I know that molecules like DNA and carbon chains can be huge. However, both of these have repeating groups, so they do not count. By biggest I am talking in terms of volume, mass, length and/or number of atoms. What if we limit the answers to molecules that have been successfully synthesized?

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Re: What is the Biggest Non-Repeating Molecule?

Postby p1t1o » Mon Aug 08, 2016 4:16 pm UTC

Well anything with a repeating carbon backbone is out, anything crystalline is out, I think the answer is going to be a surprisingly small molecule.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Soupspoon » Mon Aug 08, 2016 4:48 pm UTC

I think "non-repeating" as part of the question is problematic. Something can be not translationarily self-similar but still 'repeat' its components, at a trivial level.

But to avoid all confusion, perhaps start with a single polyvalent 'backbone' element (one benzene ring?... or something polycyclicly aromatic like a coronene, but certainly no more repetitious and possibly itself 'gltched' to not be rotationally similar) and then add on different polyvalent elements to the periphery in unique ways, etc, until forced to close se off branches with terminating units in order to neither repeat nor destabilise adjacent branchings.

For the ultimate non-repeating structure, though, how many single representative atoms of any given element can be fit into a molecule? (Start with an Si-C core, perhaps... Can we make that Si-C-Ge, or Ge-Si-C? That's beyond what I ever did in chemistry, myself...) Mathematically it seems work-out-able, although goodness knows what temperatures and pressures would support the stability of all bonds, and then there's unintended cross-linking/group-switching/polymerisation if you're synthesising many such molecules in the same (sufficientlt inert or intangible) 'container'.

That aside, it reminds me of my asking my dad "what's the biggest number in the world? ", when I was much younger. Although in this case its possible that there is an answer, if amorphous masses are allowable. However incalcuably complicated they may be.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Mon Aug 08, 2016 7:44 pm UTC

(CH2)-(CF2)-[CH2]2-(CF2)-[CH2]3... seems to be an infinite nonrepeating molecule. Theoretically it could be synthesized at any arbitrary length under the proper conditions, right?

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Re: What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Thu Aug 18, 2016 8:54 am UTC

Is the very beginning of that molecule suppose to be CH3; if so then I think that you are right. What if we limit the answer to molecules that have been synthesized?

Soupspoon wrote:That aside, it reminds me of my asking my dad "what's the biggest number in the world? ", when I was much younger.

You say that like it's a bad thing.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Soupspoon » Thu Aug 18, 2016 10:45 am UTC

jewish_scientist wrote:
Soupspoon wrote:That aside, it reminds me of my asking my dad "what's the biggest number in the world? ", when I was much younger.

You say that like it's a bad thing.

He never told me what it was, though!!!!

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Re: What is the Biggest Non-Repeating Molecule?

Postby Shufflepants » Thu Aug 18, 2016 7:31 pm UTC

What counts as a "repeating group"? Does CH3 not count because we repeated hydrogen twice? At what point do you count DNA to be repeating i.e. what's the largest chain of DNA that you count as being non-repeating? Do we only get 1 usage of each nucleotide? So, we could make AGTC, but AGTCG wouldn't count because we already used G? Or does it still count because we never used a G next to a C. In that case could we make something like AAGGTTCCATACGCTGT where there's at most 1 occurrence of each nucleotide to the left or right of each nucleotide.

The only rigorous definition of repetition I've normally seen is just if something is periodic. That is something is only repetition if you can choose some proper subset of the whole and repeat just that pattern over and over again to recover the original. But with that definition we would allow virtually every naturally occurring piece of DNA in existence.

Also, how would you count quasicrystals which are 3 dimensionally aperiodic https://en.wikipedia.org/wiki/Quasicrystal
For those there are macroscopic molecules that are aperiodic.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Thu Aug 18, 2016 8:38 pm UTC

Maybe a more interesting question is what is the biggest synthetic molecule, repeating or otherwise, that was synthesized without the use of any enzymes.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Sizik » Fri Aug 19, 2016 2:27 am UTC

Eebster the Great wrote:Maybe a more interesting question is what is the biggest synthetic molecule, repeating or otherwise, that was synthesized without the use of any enzymes.


Do silicon crystals count?
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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Fri Aug 19, 2016 3:17 am UTC

I don't think covalent crystals are typically called "molecules." It does become a bit ambiguous when you get into stuff like carbon nanotubes though.

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Re: What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Thu Aug 25, 2016 11:12 pm UTC

Shufflepants wrote:What counts as a "repeating group"? Does CH3 not count because we repeated hydrogen twice? At what point do you count DNA to be repeating i.e. what's the largest chain of DNA that you count as being non-repeating? Do we only get 1 usage of each nucleotide? So, we could make AGTC, but AGTCG wouldn't count because we already used G? Or does it still count because we never used a G next to a C. In that case could we make something like AAGGTTCCATACGCTGT where there's at most 1 occurrence of each nucleotide to the left or right of each nucleotide.


Eebster the Great's molecule has 3 parts; CH3 CH2 and CH2FH2. The largest of those is made of 6 atoms, which is small enough that I would consider it trivial. This has a picture of the structure of each nucleotide, excluding the carbohydrate backbone. It is clear that a single nucleotide is made up of vastly more than 6 atoms, which is why I do not consider it trivial. This means that the biggest molecule you could make would be AGTC or a similar sequence. Anything bigger and a non-trivial part is used twice. I am not sure exactly where the cut-off point is for what is trivial and what is not; I am sure that it would be closer to CH2FH2 than a nucleotide.

The only rigorous definition of repetition I've normally seen is just if something is periodic. That is something is only repetition if you can choose some proper subset of the whole and repeat just that pattern over and over again to recover the original. But with that definition we would allow virtually every naturally occurring piece of DNA in existence.

If a non-trivial subset can be found in at least 2 places in a molecule, I would count that as a repetition. In other words, there must be no translation, rotational or reflexive symmetry, excluding reflections that change the chirality a.k.a. handiness.

Also, how would you count quasicrystals which are 3 dimensionally aperiodic https://en.wikipedia.org/wiki/Quasicrystal
For those there are macroscopic molecules that are aperiodic.

Wikipedia says that certain quasicrystals, called icosahedral quasicrystals, are "aperiodic in all directions". However this article says that icosahedral quasicrystals have rotational symmetry. Almost all references are better than wikipedia; therefor quasicrystals are not allowed.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Fri Aug 26, 2016 11:14 am UTC

Rotational symmetry does not prevent a crystal from being aperiodic. Periodicity is essentially just translational symmetry. After all, a helium atom is highly rotationally symmetric, but I wouldn't call it "periodic."

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Re: What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Tue Aug 30, 2016 7:51 am UTC

Eebster the Great wrote:Rotational symmetry does not prevent a crystal from being aperiodic. Periodicity is essentially just translational symmetry. After all, a helium atom is highly rotationally symmetric, but I wouldn't call it "periodic."

Your right; that was my mistake. However, a picture of the cross-section of the crystal shows some repeated parts. For example, I noticed 3 red hexagons surrounding pentagons that they have no bonds with. Of course, a cross-section of a 3D molecule is inherently inaccurate; it is reasonable to argue that the units that these hexagons and pentagons are part of differ in ways not shown in this illustration.

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Re: What is the Biggest Non-Repeating Molecule?

Postby jaap » Tue Aug 30, 2016 8:17 am UTC

jewish_scientist wrote:
Eebster the Great wrote:Rotational symmetry does not prevent a crystal from being aperiodic. Periodicity is essentially just translational symmetry. After all, a helium atom is highly rotationally symmetric, but I wouldn't call it "periodic."

Your right; that was my mistake. However, a picture of the cross-section of the crystal shows some repeated parts. For example, I noticed 3 red hexagons surrounding pentagons that they have no bonds with. Of course, a cross-section of a 3D molecule is inherently inaccurate; it is reasonable to argue that the units that these hexagons and pentagons are part of differ in ways not shown in this illustration.

Aperiodic also does not mean that no part of it ever occurs anywhere else. In fact, in a Penrose tiling any finite patch of tiles, however large, can be found an infinite number of times - just not at regular translational intervals. I think this is true for perfect quasi-crystals as well.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Tue Aug 30, 2016 5:34 pm UTC

It must be true for at least some patches of arbitrarily large size, since there are only finitely many of any given size. Of course, that doesn't prove it must be true for all patches of finite size, and for quasicrystals I'm not actually sure that is true (though it certainly is for Penrose tilings). Either way, you're never going to get an aperiodic tiling with no repeats at any scale for pigeonhole reasons.

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Re: What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Mon Sep 05, 2016 6:56 am UTC

jaap wrote:Aperiodic also does not mean that no part of it ever occurs anywhere else.

I understand that. What I am asking is not for the largest aperiodic molecule; rather the largest non-repeating molecule.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Mon Sep 05, 2016 9:58 pm UTC

You haven't explained what "non-repeating" means or why rotational symmetry is a type of repetition.

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Re: What is the Biggest Non-Repeating Molecule?

Postby jackar56 » Fri Jan 27, 2017 7:03 am UTC

Back bone in DNA should be non repeating.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Penitent87 » Mon Feb 27, 2017 12:30 pm UTC

Perhaps some consideration of 'compressibility' would be useful?

I'm no expert on biology or chemistry (far from it), but if DNA has only four fundamental units, then in some sense its compressibility might be quite large. Similarly for long hydrocarbons.

What I mean to say is: while DNA contains an extremely large amount of information, perhaps the ratio of information to number of atoms is not that high compared to some molecules.

Maybe the OP can give some threshold for the molecules he's allowing?

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Re: What is the Biggest Non-Repeating Molecule?

Postby Xanthir » Mon Feb 27, 2017 10:00 pm UTC

"Lots of information" and "high compressibility" are literally opposites. DNA is very different from long hydrocarbons in this respect; a full and accurate formula for a DNA strand can't be compressed well (because it contains a lot of information), while a full formula for a long hydrocarbon is often extremely small and simple.
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Re: What is the Biggest Non-Repeating Molecule?

Postby Elmach » Tue Feb 28, 2017 5:26 am UTC

I agree that DNA has more information; I disagree that it can't be compressed well.
EDIT: Now I think I disagree - the difference is that DNA/RNA/proteins tend to be larger.

Given a single strand of DNA, you need some number of bits to explain ATCG, and then you just need less than* 2 bits/325 amu, or 0.005 bits/amu ((average molecular mass of a nucleotide)/((log base 2 4) bits)]178.3 amu/bit) for the actual encoding of the molecule. A double helix would take less than* 2 bits/650 amu or .00028 bits/amu (356.7 amu/bit)

Compare to proteins, which take 4.32 bits/136.90 amu ~ 0.0315 bits/amu (31.68 amu/bit)

By this metric, for sufficiently long DNA and proteins, it seems that DNA holds less information than protein. (This calculation neglects secondary and tertiary structure.)


* this calculation assumes that the distribution of ATCG / amino acids is uniform - any non-uniformity decreases this number.

Of course, as you've mentioned, hydrocarbons take significantly less information. The largest hydrocarbon synthesized (as of 1993) is C1398H1278 - and I have no idea how to figure out the bits/amu of this molecule. Actually, it looks like that paper claims that there is a lot of information in hydrocarbons...

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Re: What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Tue Feb 28, 2017 1:24 pm UTC

jewish_scientist wrote:I know that molecules like DNA and carbon chains can be huge. However, both of these have repeating groups, so they do not count.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Elmach » Tue Feb 28, 2017 4:24 pm UTC

As other people have mentioned, non-repeating isn't well defined yet; nevertheless, the hydrocarbon mentioned in my last post is not a carbon chain.

I propose that a metric you want is information per unit mass or information per atom.

Although this molecule has multiple (CH3-)s and probably many (CH3CH2-)s, the higher structure of this molecule is (probably) fractal. I believe this molecule has many branches and maybe many loops.

Each time a carbon is added, it can replace any of the hydrogens - that's 1278 possibilities for the final molecule - or any pair of hydrogens - that's about half a million possibilities. While there may be smaller molecules with a higher information to atom ratio, I believe this is close to being the winner for large molecules.

However, to answer your question, I would need to know

How small of a structure must not be repeated? That is, what is the largest part of a molecule that can be repeated?

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Tue Feb 28, 2017 6:41 pm UTC

Surely a monatomic gas has at least as much "information per atom" as any other chemical.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Elmach » Tue Feb 28, 2017 8:19 pm UTC

My use of "information" was only dealing with the structure of the molecule - that is, the bonds between atoms - not including position/momentum, flexing, etc. Thus, I believe I would measure a monatomic gas as having 0 bits/atom (plus a header saying that all molecules are atoms). Alternatively, each molecule has one atom, and there is only one way that can happen (plus a few bits to define which atom)

Of course, that does mean that H2 has 1 bit/2 atoms, which for a molecule, is significantly higher than any other molecule I have posted - 0.5 bits/atom and 0.5 bits/amu. Actually, I believe H2 would also have 0 bits for bonding, because there is only one way to have a molecule with two atoms.

Of course, that means that CO2 has three possibilities, so 1.58 bits/3 atoms or 1.58 bit/44 amu, which is actually lower than proteins higher than the other molecules I have posted. (The three ways are OCO, COO, and all three bonded somehow.

I finally managed to get average number of atoms in an amino acid (19.20), so I can say that proteins would have 4.32 bits/19.20 atoms = 0.225 bits/atom.

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Re: What is the Biggest Non-Repeating Molecule?

Postby WibblyWobbly » Tue Feb 28, 2017 8:46 pm UTC

Elmach: sorry for butting into your conversation for a stupid question, but I'd be interested to know how you come to calculate "information" in molecules such as DNA and proteins (and hydrocarbons, for that matter). If you're OK with explaining it to me, feel free either here or in PM.

On another side, though, while I have yet to read the full article you post for largest hydrocarbon, the abstract mentions the structures are dendrimeric - usually, dendrimers are highly symmetric molecules; whether or not certain forms of symmetry should be regarded as repetition in a molecular structure is still debatable, but if so, how does that figure into your calculation?

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Re: What is the Biggest Non-Repeating Molecule?

Postby Elmach » Tue Feb 28, 2017 10:56 pm UTC

I am not sure if I even have a consistent definition.

Edit: The definition I was intending to use was how many bits it takes to represent the molecule - I do not know how to make this exact except for sufficiently large repeating molecules. This should be roughly equal to the length of the shortest program that can print the structural formula of the molecule. For large molecules, they can usually be deconstructed into two parts: a O(1) program part that explains what nucleotides/amino acids are and how they connect, and an O(n) input part that lists what connects.

For sufficiently large, repeating molecules, I take the log base 2 of the number of possibilities, and assume everything else is O(1), and get around that by saying "I said sufficiently large."

This is just an easy upper bound for this concept.

The problem is that I don't have a definition for the O(1) part (which doesn't depend on length).

Alternatively: if you have most of a sufficiently long DNA molecule, it takes at most two bits per base pair (there are four different ways you can extend it on one end, log2 4 is 2) to know the rest of the molecule. For a protein, you would need 4.32 bits per amino acid (there are twenty amino acids, log2 20 is 4.32).



The question about symmetries in the hydrocarbon is important, and I do not know the answer. I know that you should subtract some number of bits for each symmetry (two-fold symmetry is one bit, 4-fold is two bits, n-fold is log2 n.) but I have no idea how to count them. This is probably significant.

Edit: correction- subtract a bit for every pair of ways you can get the same molecule using the same program with different inputs.

I also have not read the article, but that statement made me remember that most hydrocarbons are not linear, and is what made m convinced that hydrocarbons have a high information density. Without reading the article, I would assume that the molecule was grown similar to how snowflakes are grown, so although there would be approximate symmetries, I suspect that there would be enough different similar molecules that this is a significant winner.


Edit: sorry about the nonlinear nature of this post. I wrote this on mobile.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Eebster the Great » Wed Mar 01, 2017 5:43 am UTC

DNA and proteins are much more complicated than you give them credit for. For instance, proteins usually include disulfide bridges within and between chains, so there is more to them than just the primary sequence. They also may contain charges or form salts, polymers, salts of polymers, ligand complexes, and even more complicated compounds. Nucleotides in DNA can contain extra methyl gropus, and methylation patterns affect transcription. Their pattern of hydrogen bonding changes depending on their quaternary structure. And they may be bonded to other biomolecules such as histones, spindle fibers, or of course enzymes. A lot actually happens in these macromolecules that you can't just dismiss as irrelevant.

On the topic of monatomic gases, you say "a few bits to define which atom." But there is only one atom. So that is a few bits per atom, which surely puts it above anything else you have listed so far. My point is that you are not calculating anything resembling length but rather compressibility, in which case longer molecules will almost surely be more compressible than shorter ones. In other words, it is almost the opposite of what the OP was looking for.

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Re: What is the Biggest Non-Repeating Molecule?

Postby WibblyWobbly » Wed Mar 01, 2017 4:22 pm UTC

Eebster the Great wrote:DNA and proteins are much more complicated than you give them credit for. For instance, proteins usually include disulfide bridges within and between chains, so there is more to them than just the primary sequence. They also may contain charges or form salts, polymers, salts of polymers, ligand complexes, and even more complicated compounds. Nucleotides in DNA can contain extra methyl gropus, and methylation patterns affect transcription. Their pattern of hydrogen bonding changes depending on their quaternary structure. And they may be bonded to other biomolecules such as histones, spindle fibers, or of course enzymes. A lot actually happens in these macromolecules that you can't just dismiss as irrelevant.

This seems very important to me, and should not be discounted. Among other factors, pH is an important aspect to consider, as it can drastically change the charge distributions around a number of residues, greatly altering the higher-order (secondary and up) structure of proteins with the same primary structure. And that becomes even more important when you look at proteins whose residues protonate or deprotonate near physiological pH (histidine is the big one here, I think) but may not stay in a given protonation state as the chemical environment shifts. And nucleotide/amino acid distributions are certainly nowhere near uniform, but this doesn't seem (to me) to lead to a conclusion that less information is actually encoded (because of some of the aforementioned reasons), so there's a significant amount more going on than ATCG frequency or amino acid sequences.

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Re: What is the Biggest Non-Repeating Molecule?

Postby jewish_scientist » Wed Mar 01, 2017 5:55 pm UTC

The cut off point for where something goes from trivial to non-trivial in size is arbitrary, so I am just going to pick 20 atoms as the limit, inclusive. This person calculates the every nucleotide base should have ~34 atoms. 34 > 20, so a base is big enough to be non-trivial. Consider the molecule ACTGX, where X represents a base. No matter what base you decide X should be, it has already been used. Therefor, the largest molecule you can make using DNA is ~170 atoms. If there really is no larger non-repeating molecule, I would be pretty disappointed.

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Re: What is the Biggest Non-Repeating Molecule?

Postby WibblyWobbly » Wed Mar 01, 2017 6:23 pm UTC

jewish_scientist wrote:The cut off point for where something goes from trivial to non-trivial in size is arbitrary, so I am just going to pick 20 atoms as the limit, inclusive. This person calculates the every nucleotide base should have ~34 atoms. 34 > 20, so a base is big enough to be non-trivial. Consider the molecule ACTGX, where X represents a base. No matter what base you decide X should be, it has already been used. Therefor, the largest molecule you can make using DNA is ~170 atoms. If there really is no larger non-repeating molecule, I would be pretty disappointed.

I feel like saying that a non-repeating nucleotide sequence can't have more than one of any nucleotide is a little like saying a non-repeating decimal can't have more than one 5. But pi is non-repeating and non-terminating, and it has more than one of any digit in it; that doesn't make it repeating. And Eebster's methylene-difluoromethylene chain from earlier is just a decimal like 0.301101110..., where 3 = methyl, 0 = difluoromethylene, and 1 = methylene. It makes for a non-repeating, non-terminating decimal, but how is having a chain of just methylene and difluoromethylene that much different from one that has just adenine and thymine (ATATTATTTATTTT..., never mind the C and G)?

The arbitrariness is problematic. What do you mean by trivial vs. non-trivial? Why not limit yourself to codons instead of nucleotides? Then you can make sequences 192 nucleotides (64*3) in length without any codon being repeated. Or, if I could get you to set the number of atoms at 30, all of the proteinogenic amino acids become trivial, while nucleotides stay non-trivial. But at least there are 20 or 21 such amino acids you can use, so now you've got a lot more than 4 elements to work with. And if triviality means we can put amino acids together and consider that molecule, the titin protein has up to ~36,000 amino acid residues, which average 19-20 atoms each, for a total molecular weight of nearly 4,000,000 g/mol. But it will use some amino acids more than once.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Liri » Thu Mar 02, 2017 1:57 pm UTC

WibblyWobbly wrote:But it will use some amino acids more than once.

That's an amusing understatement.

Yeah, if your cutoff point for trivial is arbitrary, you might as well raise it to allow for nucleotides/amino acids/codons/etc.

Unless this biochemistry rabbit hole isn't the one you're looking for. But if you *do* want to follow it, you'll probably never find the same segment of DNA twice with identical methylation patterns, identical nucleosome locations, identical histone modifications, identical chromatin status, etc - in which case you're looking at the genomes of fern species, which have a tendency to duplicate and reduplicate (it's likely one of the reasons they look so similar today as they did hundreds of millions of years ago [little chance of every copy of a gene getting mutated and fixed in the population]).
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Re: What is the Biggest Non-Repeating Molecule?

Postby WibblyWobbly » Thu Mar 02, 2017 4:14 pm UTC

Liri wrote:
WibblyWobbly wrote:But it will use some amino acids more than once.

That's an amusing understatement.

I'm well known for my subtle and understated humor.

Liri wrote:Yeah, if your cutoff point for trivial is arbitrary, you might as well raise it to allow for nucleotides/amino acids/codons/etc.

Unless this biochemistry rabbit hole isn't the one you're looking for. But if you *do* want to follow it, you'll probably never find the same segment of DNA twice with identical methylation patterns, identical nucleosome locations, identical histone modifications, identical chromatin status, etc - in which case you're looking at the genomes of fern species, which have a tendency to duplicate and reduplicate (it's likely one of the reasons they look so similar today as they did hundreds of millions of years ago [little chance of every copy of a gene getting mutated and fixed in the population]).

Now, see, you're an actual biologist/biochemist, aren't you? I'm just a physicist with a background in polymers pretending to be a biochemist/biomaterials scientist on TV. (Not actually on TV) There are perhaps a hundred things I'd love to pick your brain about, but this probably isn't the time or place.

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Re: What is the Biggest Non-Repeating Molecule?

Postby Liri » Thu Mar 02, 2017 5:24 pm UTC

Yeah, biologist, and I am always happy to talk shop.
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Re: What is the Biggest Non-Repeating Molecule?

Postby gmalivuk » Sat Mar 04, 2017 4:29 pm UTC

jewish_scientist wrote:
jewish_scientist wrote:I know that molecules like DNA and carbon chains can be huge. However, both of these have repeating groups, so they do not count.
Yes, we know you've declared DNA and things with carbon chains not to count.

The problem is that you haven't given any consistent definition of "non-repeating" that implies they don't count, which means it remains impossible to actually answer your question in the way you apparently want (because you haven't defined all your terms).
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Re: What is the Biggest Non-Repeating Molecule?

Postby Liri » Mon Mar 06, 2017 2:20 am UTC

I think the most interesting/worthwhile interpretation would be the molecule that uses the largest number of atoms of different elements, with each being used only once. There's a clear cap on the possible answer and it can be easily visualized. You could expand it to allow multiple hydrogen atoms if you want, but it wouldn't make much of a difference.

edit: yeah honestly p1t1o's post at the very top is what I would go with, and yeah, it wouldn't be very large
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Re: What is the Biggest Non-Repeating Molecule?

Postby madaco » Wed Mar 08, 2017 7:02 am UTC

[Edit: I am writing this in order] To try to get at the idea of "repeating" which is [edit: maybe] meant,

I get the impression that they don't want the molecule to be a chain of "blocks" where each "block" is from some structured family. (By a "block" I mean something like a DNA base pair, or an amino acid, or a simpler sort of thing)

Or maybe the problem wouldn't be with the families being "structured" so much as, the families being such that a chain of blocks from the families could be extended arbitrarily far?

Like, if there was some pattern that a molecule followed, but such that there was a (chemistry based) limit to how big a molecule could be while following that pattern, the largest size for that pattern would be counted as valid (provided it didn't fit into any other pattern that could be extended arbitrarily far? Or at least, not very far into such a pattern.)

Just trying to guess at possible meanings / variations that might have an interesting answer

I don't know chemistry so I'm not sure whether these could be a good interpretation/variation of the idea/question
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Re: What is the Biggest Non-Repeating Molecule?

Postby roderik » Fri Mar 17, 2017 4:25 pm UTC

Biggest synthesised would probably end up as some random polymer, potentially with some funky groups randomly placed inside it.
The restrictions you have though... I'm not sure even what those are supposed to mean in this context.

I suppose giant polymers tend to have repeating parts in orders that may or may not be random. But... at some point what is the difference between another CH2 group in between stuff, something larger in between stuff, or just a specific atom being bonded in the same way all over the structure?

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Re: What is the Biggest Non-Repeating Molecule?

Postby Katsuray » Fri Mar 17, 2017 10:44 pm UTC

Could not a (theoretical) crystal with impurities (placed in a descetized fractal pattern within the lattice) reach an arbitrary volume? The pattern of placement would repeat but an exact repetition across a volume should escape observation (unless similarity is sufficient to be called repetition).

There would likely be matching segments, but if segments count as repetition (which it seems you are advocating for), aren't we talking about a molecule made up of single-atom contributions from the elements?

AKA, whats the biggest element ( Oganesson )?

jewish_scientist wrote:What if we limit the answers to molecules that have been successfully synthesized?


That might disqualify the impurity fractal (as well as any theoretical heavy element combinations).

Liri wrote:edit: yeah honestly p1t1o's post at the very top is what I would go with, and yeah, it wouldn't be very large


p1t1o wrote:Well anything with a repeating carbon backbone is out, anything crystalline is out, I think the answer is going to be a surprisingly small molecule.


I guess my vote is for monoatomic Oganesson, at least for the mass category (with these constraints on repetition).

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Re: What is the Biggest Non-Repeating Molecule?

Postby Liri » Sat Mar 18, 2017 12:40 am UTC

Katsuray wrote:I guess my vote is for monoatomic Oganesson, at least for the mass category (with these constraints on repetition).

monatomic means, by definition, not a molecule
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