As before {HEAD ~ application} of a DC field cause {TAIL ~ leuco} and reducing groups to become distal whereas application of a reverse DC field or AC field brings into random contact the leuco and reducing groups 
cause
As before { HEAD ~ application } of a DC field cause { TAIL ~ leuco } and reducing groups to become distal whereas application of a reverse DC field or AC field brings into random contact the leuco and reducing groups
OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH