title: mus musculus: adult male retina
design: 1) Filter small RNA: Separate RNA segment of different size by PAGE gel, select 18-30nt stripe and recycle. 2) 3' adaptorligation: link 5-adenylated, 3-blocked single-stranded DNA adapter to 3' of selected small RNAs in step (1). 3) Reverseprimer annealing: The RT primer is added to (2) system, and is crossed to the RNA 3' and excessive free 3' adapter . 4) 5'adaptor ligation: 5' adaptor is linked to 5' end of the product in step (3). Since the connection attached to the single-strandedmolecule first, but not connected to 3' adaptor and RT primer hybrid chain. It greatly reduce the self-ligation. 5) Strand cDNAsynthesis: reverse extend of the RT primer in step (3) to synthetise strand cDNA. 6) PCR amplification: use high-pingpolymerase to amplify cDNA, enrich cDNA with both 3' and 5' adaptor. 7) Library fragment selection: Separate PCR productof 100~120bp by PAGE gel to eliminate primer-dimer and other byproducts. 8) Library quantitative and pooling cyclization.