CD/helix/hydrogen bond

Frank Fuerst ffrank at rz.uni-potsdam.de
Mon May 14 03:32:57 EST 2001

Jens Kaalby Thomsen <jkt at hemulen.dk> wrote:

>Is the hydrogen bond itself important for the CD spectrum of an alpha-helix 
>in a protein? Or does the signal only depend on bond angles? 

It depends on the 3-dimensional (electronical) environment of the
peptide bonds. Thus, the torsion angles (not the bond angles, which
are rather invariable) are the main determinant of the CD signal.

Of course also the formation of an h-bond changes the electronic
environment, and therefore the statement "CD-signal is independent on
h-bonds" is wrong in a strict sense.

>So the 
>(hypothetical) question is:
>Would an alpha helix which has the correct angles but NO hydrogen bonds 
>give the CD spectrum of a native hydrogen bonded alpha-helix?

In practice, I'm quite sure you wouldn't see anything. Fortunately, I
can't think of an experiment to falsify this statement :-)

Bye, Frank
>> Mus ich maunten? wie geth es?
> Das verraet Dir man mount
Was muss man rauchen, um so einen Schwachsinn parsen zu können?
[ein DAU, Regina V. Kappes und Robin S. Socha in dcoulmisc]

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