CNS vs. XPLOR starting and ending Temps

Monika Ivancic ivancicm at
Sun Nov 12 18:37:56 EST 2000

I have been performing structure calculations on a drug bound DNA molecule
using NOE constraints and have been using CNS.  I have a couple of
questions about the difference between XPLOR and CNS NMR structure
calculations and would very much appreciate your input.

Most of the structures I've seen publish use XPLOR and with those the
starting temperature for a simulated annealing run is usually 2,000K.
However in CNS, the starting temp in 'anneal.inp' is suggested to be
20,000K for DNA molecules and 50,000K for proteins.  Does anyone know why
such a big difference in XPLOR vs. CNS starting temps?  (When I talk to
the crystallographers here & tell them I'm using such a high T, they think
I'm crazy)

Also, the CNS version of 'anneal.inp' has the final temperature for the
slow cooling portion set at 0K, while most published structures end at
300K.  Why is CNS using 0K for the final temp?  I am aware that this T can
be changed to a more desired value, if necessary.

Thank you in advance for your help,


Monika Ivancic                        email: ivancicm at
Biochemistry and Biophysics Dept.
Oregon State University
Corvallis, OR 97331


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