Unsustainable DNA molecule when unfolded to be in a line

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    Dna Line Molecule
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Discussion Overview

The discussion revolves around the thermodynamic implications of unfolding a DNA molecule into a linear configuration, which some participants suggest could be close to one meter long. The conversation explores the feasibility of such a configuration existing over time, touching on concepts from thermodynamics and molecular physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant mentions that Constantino Tsalis suggested an unfolded DNA molecule could be close to one meter long but posits that thermodynamically, this configuration may be impossible to sustain.
  • Another participant discusses the scale of DNA, noting that with billions of base pairs and a single unit dimension of about one nanometer, the unraveled length could indeed reach several meters.
  • Concerns are raised about the energy stored in the chain and its ability to break bonds, with one participant arguing that thermal energy, rather than the weight of the chain, is responsible for potential bond breakage.
  • A metaphor comparing the DNA chain to an extremely long strand of overcooked spaghetti is used to illustrate the scale and challenges of maintaining such a configuration.

Areas of Agreement / Disagreement

Participants express differing views on the factors that would lead to the instability of a long, unfolded DNA molecule. There is no consensus on the specific thermodynamic principles that would govern this scenario.

Contextual Notes

Participants discuss the implications of bond strength and thermal energy without resolving the underlying assumptions about molecular behavior and thermodynamic principles.

Who May Find This Useful

Individuals interested in molecular biology, thermodynamics, and the physical properties of biomolecules may find this discussion relevant.

DaTario
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Hello,

Some years ago I have heard from the brazilian physicist, Constantino Tsalis, that the DNA molecule, if unfolded and made to lay in a line, will be close to one meter long. But he said that thermodynamically this configuration could be taken as an impossibility, for no such long and linear molecule could exist for long time. Is there any clear principle in thermodynamics that put the things in this terms?

Best Regards,

DaTario
 
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DaTario said:
close to one meter long.
Numbers that get thrown around for DNA run on the order of magnitude of billions of base pairs. Dimension of a single unit at one nm isn't too bad (ten atoms). That works out to an unraveled length of the order of one to couple meters.
Base units (including the ribose chains) run 25-30 atoms each. 3 x1010 times three degrees of freedom per atom is a heat capacity of 1011kB. Bond energies for organic compounds are of the order of four to five hundred kJ/mol. That works out to a maximum chain length of a few hundred atoms before there is sufficient energy stored in two sections of the chain to pull bonds apart if the situation is such that bond strength is the only thing holding the chain together.
 
Sorry, but are you considering that the weight of the chain is the responsible for the breaking?

best wishes,

DaTario
 
DaTario said:
that the weight of the chain is the responsible for the breaking?
Not the weight, but the thermal energy in some length of the chain is sufficient to break bonds. Or, the bond is of insufficient strength to play "crack the whip" with the lengths of the chain to either side.
 
If you try imagining the scale that we're talking about, a meter-long chain of nanometer-sized units... That's like a single strand of overcooked angel-hair spaghetti several hundreds of kilometers long.
 
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Nugatory said:
overcooked angel-hair spaghetti several hundreds of kilometers long.
And King Kong trying to use it for a jump rope. Perfect analogy.
 
Ok, thank you a lot to both. The analogy was very nice.

Best Regards,

DaTario
 

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