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