r-Inosine is historically considered a universal base, and it is therefore widely used to create degenerate positions in a nucleotide chain. However, Inosine is structurally a guanosine lacking its 2-amino group. Inosine has been shown to bind preferentially to dC and dA, and less strongly to dT and dG. Typically, Inosine is used at the third position of a codon, so to create “degenerate” PCR primers and probes that will anneal to degenerate target DNA sequences. However, as written above, Inosine binds preferentially to dC and dA, especially when it is placed at the third position of a codon. Therefore, it is advisable to mix Inosine-primers with non-Inosine primers, so to ensure sufficient diversity in the PCR products. The base Inosine in RNA has been recognized to be essential for protein translation.

ModifiedBasis r inosine

Metabion offers r-Inosine in its RNA portfolio. Click here

MW 330.19 g/mol
Extinction coefficient (260 nm) 7.5 mM-1cm-1


F.H. Martin, M.M. Castro, F. Aboul-ela, I. Tinoco Jr. Base pairing involving deoxyinosine: implications for probe design. Nucleic Acids Res. 13, 1985, 8927–8938.

I. Alseth, B. Dalhus, M. Bjørås. Inosine in DNA and RNA. Curr. Op. Gen.& Dev. 26, 2014, 116-123.

E. Ben-Dov, O.H. Shapiro, N. Siboni, A. Kushmaro. Advantage of Using Inosine at the 3’ Termini of 16S rRNA Gene Universal Primers for the Study of Microbial Diversity. Appl. Environ. Microb. (2006), 72: 6902-6906.

A.A. Su, L. Randau. A-to-I and C-to-U editing within transfer RNAs. Biochemistry (Mosc). 76, 2011, 932–937

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