(1) All three enzymes showed a marked preference for adenine over guanine nucleotides .(2) Purine salvage pathway allows interconversion of bases, nucleosides and nucleotides .(3) It has been reported that lanthanides are able to bind to DNA, RNA and nucleotides in vitro.(4) This package contains a number of substitution models for nucleotides and RNA base pairs.(5) This strategy is based on the attachment of some cytidine nucleotides to nascent cDNA first strands by reverse transcriptase.