Similarly, when the pH of the environment falls below the pH of the protein, {HEAD ~ the protein} has {TAIL ~ a net positive charge} 
has
Similarly , when the pH of the environment falls below the pH of the protein , { HEAD ~ the protein } has { TAIL ~ a net positive charge }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL