Table 1.

Basic cap structures used in IVT mRNA modification [24,26,30,34,35,36,37,38].

Type of Cap	Structure	Capping Enzymes	Capping Stage
Cap 0	m7G-ppp-N-p	Vaccinia Capping Enzyme (VCE)	Separate stage
Cap 1	m7G-ppp-N2’-Me-Op	Vaccinia Capping Enzyme (VCE) and mRNA cap 2′O-methyltransferase (MTase)	Two separate stages
Anti-Reverse Cap Analog (ARCA)	3′-O-Me-m7G5′-ppp-5′G	RNA polymerases of bacteriophages T3, T7 or SP6	Сo-transcriptionally
CleanCap® Reagent AG 3′OMe	m7G3′-O-Me-ppp-A2′-O-Me-p-G	RNA polymerases of bacteriophages T3, T7 or SP6	Сo-transcriptionally
CleanCap® Reagent AG	m7G-ppp-A2′-O-Me-p-G	RNA polymerases of bacteriophages T3, T7 or SP6	Сo-transcriptionally
CleanCap® Reagent AU	m7G-ppp-A2′-O-Me-p-U	RNA polymerases of bacteriophages T3, T7 or SP6	Сo-transcriptionally

Abbreviations: p is a phosphate, N is any nucleotide, m7G is 7 methyl guanosine, O is oxygen, and Me is a methyl group.