A protein assumes {HEAD ~ a neutral charge} when {TAIL ~ the pH} of the environment is equivalent to pI of the protein 
when
A protein assumes { HEAD ~ a neutral charge } when { TAIL ~ the pH } of the environment is equivalent to pI of the protein
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH