Computational studies of histidine radicals.

 Dear All,
 I am looking for any computational studies (particularly, but not
 necesssarily, DFT )which have been carried out on histidine radicals (neutral,
 cationic and +2 charged) or on related  truncated species, such as
 I am particularly interested in calculated vibrational frequencies and/or
 mode assignments for these species.
 If anyone could point me in a useful direction I would be most grateful.
 Darryl A. Ellson
 Darryl A. Ellson - Molecular Design & Simulation Laboratory.
 Dept. Chemistry, UMIST, Manchester. UK. M60 1QD
 Tel: 0161-236-3311 x4476    Fax: 0161-236-7677
    |_o_|   "Unless I am very much mistaken... I AM very much mistaken
  []=(_)=[] (M.Walker)