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DNA is known to have a double-helical structure. Do any other molecules have this structure?

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    $\begingroup$ Probably also interesting to ask: was their molecular structure known before that of DNA? $\endgroup$ Commented Aug 13, 2017 at 19:25
  • $\begingroup$ Double Stranded RNA Actin Filament Collagen protein Starch is kind of similar too $\endgroup$
    – doc0ab
    Commented Aug 24, 2017 at 16:41

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A few examples:


Starch

A polymer of glucose that can form a double helix and functions primarily as energy storage in plants.

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f-Actin

Filamentous actin forms a helical structure with two strands of polymerized g-actin. This is a structural component of the cytoskeleton.

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Coiled Coil

Protein motif with a helical structure formed by two (or more) α-helices. Coiled coils are found in a diverse range of proteins from structural proteins like keratin to transcription factors like c-Fos.

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Gramicidin

A peptide-based antibiotic that has been shown to form membrane spanning double helices.

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[image source]

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Yes, double-stranded RNA as found in some viruses.

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    $\begingroup$ Do you know of any other such molecule? RNA is very similar to DNA, but is there a molecule that is very different from DNA and yet still has a double helix structure? $\endgroup$ Commented Aug 11, 2017 at 16:29
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    $\begingroup$ Yes, I thought you'd be only half satisfied with this answer. I do not know of any other molecules (but I am not a good chemist) but the answer may depend upon how different the structure of a molecule can be until you start considering its structure to really be different. $\endgroup$
    – Remi.b
    Commented Aug 11, 2017 at 16:34
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The structural protein collagen consists of a triple helix of polypeptides. Whether this answers the question is arguable—you could say that the triple helix contains double helices. In any case, depending on what prompted your question, I thought it might be an interesting structure to consider.

Collagen-like peptide triple helix consisting of three peptide molecules (orange, blue, purple)

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