The photocrosslinking can use a sensitizer and {HEAD ~ exposure} to {TAIL ~ light} to achieve crosslinking 
to
The photocrosslinking can use a sensitizer and { HEAD ~ exposure } to { TAIL ~ light } to achieve crosslinking
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH