Thus, {TAIL ~ the sequence} may be in {HEAD ~ a cell free solution} or placed in a different cellular environment 
Thus , { TAIL ~ the sequence } may be in { HEAD ~ a cell free solution } or placed in a different cellular environment
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH