For what it is worth, SHELXL sets the S-H distance to 1.20A. As with other bonds to hydrogen, this allows for apparent shortening to fit the electron distribution and also librational effects. An S-H distance determined by neutron diffraction would be longer.
George Prof. George M. Sheldrick FRS Dept. Structural Chemistry, University of Goettingen, Tammannstr. 4, D37077 Goettingen, Germany Tel. +49-551-39-3021 or -3068 Fax. +49-551-39-2582 On Mon, 20 Aug 2007, Juergen J. Mueller wrote: > 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 > >
