[An efficient and accurate method for counting target molecules in phage-display peptide library].

The phage titer of samples representing the low,intermediate and high phage number was respectively determined by the double-layer agar plate(DLAP) method and real-time PCR assay.The two methods accurately measured the titer of samples.The plaques from about 1/3 double-agar layer plates could be used to determine the phage titer.The DLAP experiment should repeat 10 times with 10 μl sample each time,while the within-assay coefficient variation(CV) was 4.93%-30.38%.At the same time,the real-time PCR assay only repeated 3 times with 1 μl phage each time,while CV for within-assay ranged from 0.02% to 0.25%.Results indicated that real-time PCR is a simple and quick method for determining bacteriophage titer.