variant cell lines 5-mt-21 , -26 and -27 showed a low degree of resistance to 5-mt , when grown on a selective medium and were cross-resistant to parafluorophenylalanine and 3-fluorotyrosine , analogues of phenylalanine and tyrosine .
C0030137
parafluorophenylalanine
C0031453
phenylalanine