Describing change in conf. of helix

[Yoram Puius]

Hi all.

A fellow in our lab is working on two crystal structures in which a particular
helix is moved _and_ rotated with respect to the other.  Naturally, this is
only slightly problematic for aligning the structures (you just align on the
rest of the molecule).

However, we need some way of quantifying the difference between the helix.
Ideally, we'd like a program analogous to Fred Richards' DDMP, but with
some sort of vectorial approach.  If we could calculate a difference in 
the azimuth of the helix, that would be nice.

Any ideas?  `Obvious' software packages I haven't heard about?  Any info would
be greatly appreciated, because it would prevent me from writing the
home-grown software.

-- 
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Yoram A. Puius                            Albert Einstein College of Medicine
puius at telico.bioc.aecom.yu.edu            Department of Biochemistry
M.D.-Ph.D.    Class of 1999 [?]           Bronx, NY  10461
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	I do not know which to prefer,/ The beauty of inflections/ 
    Or the beauty of innuendoes,/ The blackbird whistling/ Or just after.
					- Wallace Stevens