From chemistry-request $#at#$ ccl.net Fri Jun 14 20:57:08 1991
Date: Fri, 14 Jun 91 20:09:31 EDT
From: shenkin #at# avogadro.barnard.columbia.edu (Peter S. Shenkin)
To: Shaun Black <BLACK ":at:" OHSTPHRM.PHARMACY.OHIO-STATE.EDU>,
Subject: Re:  Poly-Ala
Status: R


Gee, a real SCIENCE discussion on this list!  I love it!

Shaun D. Black          | Bitnet: black #at# ohstphrm.bitnet writes:
> It is my recollection that poly-Ala is only sparingly soluble in water,
> but enough can be gotten into solution to do a CD spectrum and see that it
> is alpha helical.  Poly-Gly will probably be more soluble in water, but
> only because it likely unfolds and hydrogen bonds with the solvent.  My
> bet is for "random coil" in water.  It's not clear to me what the entropic
> considerations would be, net....

In aqueous solution entropic changes in the solvent are important.  I'm almost
sure poly-ALA is helical in CCl4.  If poly-GLY is a random coil in that 
solvent, my guess is that its greater chain entropy (greater allowed region in 
the Ramachandran plot is responsible).  I admit that this is a supposition on 
top of a supposition, so maybe someone out there who knows can comment.

>                           ....More discussion on this would be interesting.

Always glad to add my $.02    :-)

	-P.
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Peter S. Shenkin, Department of Chemistry, Barnard College, New York, NY 10027
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