[gmx-users] What does column 'cgnr'(in topology file) mean?

[Zhenting Gao]

Hi  gmx-users,              

[ atoms ]        
;   nr      type  resnr resid  atom  cgnr   charge     mass        
     1        OM     1  GDP     O2B     1   -0.941   15.9994        
     2         P     1  GDP      PB     1   1.334    30.9738        
     3        OM     1  GDP     O3B     1   -0.975   15.9994        
     4        OM     1  GDP     O1B     1   -1.043   15.9994        
     5        OA     1  GDP     O3A     2   -0.482   15.9994        
........        

What does column 'cgnr'(in topology file) mean?        
How should I assign the number for 'cgnr'?        

Thanks.        

　　　　　　　                 
　　　　　　　　　　                 

Yours sincerely,                 
Zhenting Gao                 
zhentg at 163.com                  
2004-11-3           

------------------------------------                 
Drug Discovery and Design Center,                 
Shanghai Institute of Materia Medica,                 
Chinese Academy of Science                 
P.R. China               
URL http://www.dddc.ac.cn/group/zhentg.htm