Park , C . B . , Yi , K . S . , Matsuzaki , K . , Kim , M . S . & Kim , S . C . Structure - activity analysis of buforin II , a histone H 2 A - derived antimicrobial peptide : the proline hinge is responsible for the cell - penetrating ability of buforin II . Proc . Natl . Acad . Sci . USA 97 , 8245 - 8250 ( 2000 ) . Paxinos G , Watson C . The Rat Brain in Stereotaxic Coordinates . 2 nd ed . San Diego , Calif . : Academic ; 1986 .