g_fg2cg -pfg fg.top -pcg cg.top -c fg.gro -n 1 -o cg.gro
g_fg2cg -pfg fg.top -pcg cg.top -c fg.xtc -n 1 -o fg2cg.xtc


 make_ndx -f cg.gro -o angle

a GL1| a C1A|a D2A
a C1A|a D2A|a D3A
a D2A|a D3A|a C4A
a C1A|a D2A|a D3A|a C4A


g_angle -f fg2cg.xtc -type angle -n angle.ndx -od fg2cg_ang{1,2,3}.xvg
g_angle -f fg2cg.xtc -type dihedral  -n angle.ndx -od fg2cg_dih1.xvg
