Dear Juergen, I did a quick check in the CSD and found SG-H bondlengths between 0.587 and 1.338 Ang. for various cysteine derivatives. The most common values where around 1.33 Ang. but the average may be around 1.1 or 1.2 Ang. I did not work out any statistics. It seems that the SG-H distance is either experimentally not very well defined (there were quite a few entries with this hydrogen missing) or it might be very sensitive to e.g. (ionization).
I hope this helps. Best regards, Herman -----Ursprüngliche Nachricht----- Von: CCP4 bulletin board [mailto:[EMAIL PROTECTED] Im Auftrag von Juergen J. Mueller Gesendet: Montag, 20. August 2007 15:31 An: [email protected] Betreff: [ccp4bb] Posting again: Is the H-bond length in CYS.cif library correct? Dear all, using refmac5 to provide H-atoms for a known protein structure the distance between CYS-CG and HG is defined to 1.34 Ang. in CYS.cif. This distance has been critisiced by a non-CCP4 program by * Poor covalent bond length of 1.33954 for hydrogen atom HG. In an other library-file CSH.cif the same distance is defined to 1.1 Ang. WHATIF uses 1.0 Ang. What is the most correct one? Could the CCP4-people comment on this? (Of course I know hydrogens will not be refined but they are neccessary for some modeling programs). Thank you, Juergen
