Proline cis/trans isomerisation

Simon Brocklehurst smb18 at
Wed Oct 27 08:57:11 EST 1993

bjd12 at (Ben Davis) writes:

>	I'm working on the NMR structure of a 40 residue peptide that contains
> three prolines. Does anyone know 
>	(a) what ratio of cis:trans proline do you expect for a random coil, and

      This question is not full resolved as far as I know.  It seems
that the ratio of cis:trans in a largely unstructured chain depends on the 
LENGTH of the peptide. The longer the peptide, the greater the pecentage
of trans peptide bonds.  The ratio may also depend on the nature of the
sequence.  The bottom line is probably that, once you get beyond about 10-15
residues, probably >95% X-pro peptide bonds are trans.
      Check out e.g. 
     Green, J.D.F. et al., (1992) J. Biol. Chem. 267, 23484-23488
 and Deber, C .M. et al., (1970) JACS 92, 6191-6198

>	(b) how far (typically) does the cis:trans isomerisation affect the
>chemical shifts observed in other residues
      Which nuclei do you mean???

   As an aside, could I ask how many, if any, disulphides your peptide has?

Simon M. Brocklehurst
Cambridge Centre for Molecular Recognition
Department of Biochemistry
University of Cambridge

E-mail: smb18 at

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