Gly phi constraints

Kristy Downing kristy at
Wed Nov 15 11:34:09 EST 1995

Dear All,

I have extracted coupling constants corresponding to Gly HA1-HN and HA2-HN from
a HNHA experiment, and I would now like to use this information to derive
backbone phi constraints.  I have two questions:

(i) How do the couplings relate to the phi angle?  For example, if one HA-HN
coupling constant is 4.0 Hz and the other is 7.4 Hz, what equation do I use to
derive phi?  (If anyone knows of a reference, I would be very grateful!)

(ii) Are glycine phi constraints encoded the same way in X-PLOR as other
backbone torsion angle constraints, i.e., using the atoms of C(i-1), N, CA, and

Thanks very much,

Kristy Downing
Dr. A. Kristina Downing			
Oxford University			tel.	01865-275956
Department of Biochemistry		fax.	01865-275253
Oxford  OX1 3QU  ENGLAND		e-mail: kristy at

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