I found in this website that the dimension of a nucleotide is 0.34 nm. Is there any experimental paper confirming this statement?

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    $\begingroup$ This site might be able to help you: en.m.wikipedia.org/wiki/…. If you are collecting facts at Yahoo Answers, why not ask the people who posted there where they got their numbers? $\endgroup$ – RosieF Oct 27 '16 at 23:38
  • $\begingroup$ What exactly do you mean by dimension? The molecule is not circular; do you mean the longest dimension? or the van der Waals radius? $\endgroup$ – WYSIWYG Oct 28 '16 at 5:34
  • $\begingroup$ I know it is not circular, rather a flattish molecule with different conformations; but a sphere is still a good approximation. Van der Waals is probably the best measure. $\endgroup$ – Gigiux Oct 28 '16 at 22:19

If you want experimental papers, we should be precise about what we're measuring. "The dimension of a nucleotide" is rather imprecise, as a nucleotide is a rather oblong, knobbly thing.

0.34 nm is a relevant measurement related to nucleotides, but it's specifically the distance between consecutive bases in a standard B-form DNA helix - that is, what's the spacing between the "rungs" on a DNA ladder.

This measurement can be confirmed by several experiments, primarily those involving X-ray or neutron crystallography or scattering. For example, both the Wilkins and Franklin papers that were published back-to-back with the famous Watson & Crick DNA structure paper referrence the strong 0.34 nm reflections from X-ray fiber diffraction which Watson & Crick reference as the spacing of the bases in their model of DNA structure. Other papers have confirmed the measurement. This 1983 Biomed Biochim Acta paper uses wide-angle X-ray scattering to find it. Additionally, there are a large number of structures in the Protein Databank which contain DNA structures - these have been determined by a number of different approaches (X-ray crystallography, neutron diffraction, NMR, electron microscopy, etc.) and all of which are consistent with the 0.34 nm average spacing of base pairs. (Modulo minor structure-to-structure variations.)

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  • $\begingroup$ this is for a polymer of nucleotides, how big is an individual nucleotide though? $\endgroup$ – Gigiux Oct 28 '16 at 22:21
  • $\begingroup$ It's for an individual nucleotide within a polymer, yes. But if that doesn't work for you, how do you want to measure it? As mentioned, a nucleotide is a rather oblong knobbly thing - the size depends on which direction you're measuring it in. Additionally, molecules don't have well-defined surfaces, being made mostly of electron clouds. There's conventions for the standard surface, but if you want experimental references, you have to specify an experimentally measurable distance. $\endgroup$ – R.M. Oct 28 '16 at 23:13

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