Ca Cb chemical shifts as restraints

Ricard A. Rodriguez rarodrig at
Mon Dec 3 12:18:50 EST 2001

Hi all,

I'm quite new using CNS. I've been trying to obtain a low resolution structure

for a 20 kD protein. I've encountered some problems when including, Ca and

Cb chemical shifts as restraints for the CNS calculation.

The input file seems to be correct, but in the generated structures nearly all

restraints are violated. Also in the output i get the next message for most

of the residues:

 The following Ca or Cb delta secondary
shifts are greater than the cutoff (-99.99 = no expectation):
(Ca) (obsCa) (rcoilCa) (obsdeltaCa) (calcdeltaCa) (deltadeltaCa)
     (obsCb) (rcoilCb) (obsdeltaCb) (calcdeltaCb) (deltadeltaCb)
class C1
    8   GLU CA   55.00 56.40 -1.40-99.99-99.99 33.68 29.70  3.98-99.99-99.99
    9   GLN CA   57.50 56.10  1.40-99.99-99.99 29.19 28.40  0.79-99.99-99.99

it seems that the program doesnt read well the random coil values from the

libraries, but anyway i dont know how to solve it.

If anyone has the answer i'd be very grateful.

Thanks in advance.

Ricard A. Rodríguez
Dept. Química Orgànica (Unitat 10)
Universitat de Barcelona
C/ Martí i Franqués 1-11
08028 Barcelona

Tel: 34-93-4021261
Fax: 34-93-3397878
email: rarodrig at

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