yl 1 1 3 3 tetramethyluroniumhexafluorophosphate hbtu the side chain protecting groups were lys boc asp obut ser but cys trt and asn trt the protected peptidyl resin was treated with 20 piperidine in dimethylformamide the cleavage and separation of the protecting groups were obtained by treatment with 90 trifluoroacetic acid 5 ethane dithiol 2 5 thioanisole and 2 5 phenol v v v at room temperature for 2 5 hours all of the products were precipitated in ether and purified by preparative hplc shimazu lc 8a shimazu duisburg germany on a ymc ods a 7a s 7 u03bcm reverse phase hplc column 20 u00d7 250 mm using 0 1 trifluoroacetic acid in water a and 60 acetonitrile in water b as an eluting agent the peptides were eluted with a linear gradient of 25 b to 60 b at a flow rate of 10 ml min within 40 minutes the fractions corresponding to the purified conjugate were lyophilized sequences of individual molecules and the complete bimodular construct were characterized by analytical hplc shimadzu lc 10 and laser desorption mass spectroscopy finnigan vision 2000 finnigan mat san jose calif u s a as described below the sequence of the pna directed against an ampicillin resistance was as follows h 2 n attgttagatttcat cooh seq id no 1 this is a sequence which can hybridize with the region of position 86 to position 100 of the pdna of pbr322 genebank accession number j01749 the sequence of the pna used against the kanamycin resistance.