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If we want to design a bilayer from Myristic acid (14 carbon fatty acid). The average bond length between C-C is 1.5 A. What will be average thickness of the membrane?

Edited to include the OP attempt that was posted in a comment:

There are 13 C-C bonds in Myristic acid, 13*1.5=19.5A. 1A=o.1nm.. so 19.5A=1.95nm, so the average thickness would be 1.95nm. As membrane is bilayer it will be 3.9nm

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closed as off-topic by MattDMo, Chris, jarlemag, WYSIWYG, leonardo Mar 27 '14 at 21:45

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up vote 1 down vote accepted

Lewis & Engelman (1983) Lipid bilayer thickness varies linearly with acyl chain length in fluid phosphatidylcholine vesicles. J. Mol. Biol. 166: 211 - 217.

Table 1 and Figure 3 have the information that you need. For C14:0 the thickness of the hydrocarbon bilayer is given as 23 Å. Just in case this is homework, I'll leave you to convert that to nm.

added later

Just to follow up on the comments, as hinted at by Shigeta, if you wanted to calculate an estimated bilayer thickness you would have to take into account the C-C-C bond angle which for tetrahedral carbon is 109.46°.

Thus the distance between two C atoms in an extended C chain is 2 x 1.5 x sin(109.46/2) = 2.45 Å

For C14:0 the length is then 6.5 x 2.45 = 15.9 Å (from methyl C to carbonyl C).

Therefore, calculated bilayer thickness = 31.8 Å plus any distance between the two C chains in the centre of the bilayer. This is still a lot bigger than the reported 23 Å.

Clearly the bilayer does not consist of extended hydrocarbon chains. The chains are presumably partially collapsed (on average) and may also interdigitate to some extent.

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I want to ask one thing that if we are not provided with the information about the thickness of membrane in any table or a graph then can we are capable to calculate the Membrane thickness according to some data that is provided in Question such as C-C bond length? As I have tried it tell me whether it is correct or not? :/ There are 13 C-C bonds in Myristic acid, 13*1.5=19.5A. 1A=o.1nm.. so 19.5A=1.95nm, so the average thickness would be 1.95nm. As membrane is bilayer it will be 3.9nm. – katherinebridges Mar 26 '14 at 15:40
notice how your answer is ~70% longer than the actual answer? Because the chains are flexible its not that simple. You might calculate the average length of the chain in the membrane given all the reasonable bond angles the chain might take, probably by molecular dynamics. its not straightforward. Even if you built a model of the molecule you'd find that the bond angles of the extended chain gave a length at least 30% shorter than your end to end number. The table cited here is the actual answer, from a measurement of membranes and so even better than that. – shigeta Mar 26 '14 at 18:49

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