5' adapter comprising an internal 5′-5′ linkage

Abstract

This disclosure provides, among other things, a 5' adapter of the formula 3′*—X—(5′5′)—Y—3′, where: 3′* is a blocked 3′ end, X is a synthetic sequence, (5′5′) is an internal 5′-5′ linkage, Y is an adapter sequence, and 3′ is a hydroxylated 3′ end. In use, sequence X hybridizes to sequence X′ in a population of RNA molecules of formula R—X′, which increases the efficiency of ligation of the 5′ adapter to the nucleic acid molecules.