2.6. Generation of quantification standards
A fragment of 348 bp of M gene of PPRV contain-ing the real time RT-PCR primers binding sites wereamplified using the primer pair M4F (forward primer): 5-CCAGGTAAGGGTCATCGATCC-3(99–119) and M4R (reverseprimer): 5-AAGCGGGACTAGGTTGACTGCA-3(426–447) (In housedesigned). The RT-PCR product was cloned into T&A cloningvector according to the manufacturer’s instructions. Plasmid DNAwas recovered from the transformed Escherichia coli BL-21 cellsusing AxyPrep Plasmid Miniprep Kit (Axygen Biosciences). TheOD value of the plasmid DNA standard concentrations was mea-sured at 260 nm/280 nm on Thermo Scientific NanoDropTM1000Spectrophotometer (NanoDrop Technologies, LLC, Wilmington,DE, USA). Plasmid copy number was calculated using the for-mula described by Adams (2006). The concentration of theobtained plasmid DNA was 95 ng/l which equates 2.88 × 1010copies/l.