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TFE in inducing alpha-helix formation in proteins


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#1 vivlee

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Posted 30 October 2012 - 05:24 PM

Hi all,

I have been doing TFE titraion on polypeptides at 4 degrees celcius using CD, and noticed its varying effects on different polypeptides. It was effective in inducing alpha-helical structure formation in one polypeptide but not another. One of the peptide I tested was a 16mer and the other is a 32mer, the 16mer is a part of the 32mer. Does the length of the peptide influence the effect of TFE, since TFE showed its effect on the 32mer but not the 16mer (even at 80%TFE)? Any other possible reason for the difference in TFE effects on the two mers I tested?

Thanks!

#2 HOYAJM

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Posted 01 November 2012 - 07:11 AM

Shorter peptides are less likely to exhibit secondary structure. Secondary structure prediction programs often require at least 20AA peptides to predict any secondary structure. Short peptides tend to have unordered structure and this could be why you observed alpha-helical formation in the 32mer

#3 vivlee

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Posted 01 November 2012 - 05:58 PM

Shorter peptides are less likely to exhibit secondary structure. Secondary structure prediction programs often require at least 20AA peptides to predict any secondary structure. Short peptides tend to have unordered structure and this could be why you observed alpha-helical formation in the 32mer


Not even with the addition of TFE will it show secondary structure? I found that low temperature has some minor effect, but still more apparent as random coiling. Thanks for your help nonetheless!

#4 HOYAJM

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Posted 02 November 2012 - 08:36 AM

Here is a link to a study that might help you out. Im not sure what solvent you were using, but it seems that in certain situations, different solvents might be more likely to allow helix formation. They used methanol, ethanol, acetonitrile, and 1,1,1,3,3,3-hexafluoroisopropanol to produce secondary structure when water as a solvent did not. Give it a try to see if solvent has an influence.

http://www.pnas.org/content/89/10/4462




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