[Protein-analysis] Re: Proteins Digest, Vol 24, Issue 1

Dr Engelbert Buxbaum via proteins%40net.bio.net (by engelbert_buxbaum from hotmail.com)
Sun May 6 15:23:12 EST 2007

Am 03.05.2007, 14:58 Uhr, schrieb Sai Praveen <saiprawinp from yahoo.com>:

>  I have been looking at how IR spcetroscopy can be used to study  
> secondary structure content of protein. Especially, when analysing the  
> amide I spectrum, how do we baseline correct the interferences of  
> solvent? typically water? Will DMSO help in this issue?

You would have to use pure (waterfree) DMSO since even traces of water  
would show up in the spectrum, and that would surely change the protein  
structure you wish to study.

One way of doing it is to use Attenuated Total Reflection. The IR-beam is  
send into a medium of higher optical density then the buffer under an  
angle that results in total reflection. However, under these circumstances  
the light penetrates a few nm (that is, just about the diameter of a  
protein molecule) into the medium (evanescent field). The protein is  
immobilised at the buffer/medium interface. Since the protein  
concentration there is much higher than that of water interference by  
water is reduced, even though the protein is fully hydrated. Part of the  
story is also that modern IR-spectrometers use Fourier-Transform  
spectroscopy, resuling in much sharper peaks than the conventional types.

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