. 2004 Jun 4;5:71. doi: 10.1186/1471-2105-5-71

Table 2.

Stacking grammar specifications.

		Parameters
Grammar	NT	Total	Tied	C. elegans LSU Memory (MB)	Notes
G2	2	287(281)	283(278)	53.2	ambiguous
G7	5	341(326)	289(281)	128	min 1 nt loop; no lone pairs; no ε string
G8	4	347(334)	287(280)	103	min 1 nt loop; no lone pairs
G6^S	3	282(276)	282(276)	79.4	min 2 nt loop; no ε string

Stacking adds to grammars more nonterminals (NT) and total (free) parameters. This translates into increased memory requirements, as shown by the folding of C. elegans large subunit ribosomal RNA (3662 nucleotides). It also may introduce other restrictions such as not permitting lone pairs.