[gmx-users] how to select head groups of lipid within 10 angstrom of protein

[SHAHEE ISLAM]

Hi,
I am trying to calculate the angle between P and N vector of my lipid
(popc+popg) with regards to the z axis to see how the protein is affecting
the membrane. I am using this command, but it does not working
gmx select -f *.xtc -s *.tpr -select POPG & name P* N* within 1.0 of
Protein -oi number.dat
but the problem is, when the command is running only
  gmx select -f *.xtc -s *.tpr -select POPG
this command.
Can anyone please guide me what i am doing wrong.
Thanking you
Shahee