Table 1.

Plasmids and phages used in this study.

Plasmid or phage	Relevant characteristics	λtI ΔG (kcal/mol at 37 °C)*	Reference
pKG1800	ampR, galK+, without terminator between Pgal and galK	—	McKenney et al. 1981
pUS6	ampR, galK+, with wild λtI terminator between Pgal and galK	−18.2	Schmeissner et al. 1984a
pMC+32	3′ deletion +32 in λtI	−18.2	This work
pMC+22	3′ deletion +22 in λtI	−18.2	This work
pMC+3	3′ deletion +3 in λtI	−18.2	This work
pMC−9	3′ deletion −9 in λtI	−15.6	This work
pMC−15	3′ deletion −15 in λtI	−2.1	This work
pMC−34	3′ deletion −34 in λtI	0.0	This work
pMS−106	5′ deletion −106 in λtI	−18.2	This work
pMS−92	5′ deletion −92 in λtI	−18.2	This work
pMS−64	5′ deletion −64 in λtI	−18.2	This work
pMS−37	5′ deletion −37 in λtI	−15.0	This work
pMS−32	5′ deletion −32 in λtI	−1.5	This work
pMS−31	5′ deletion −31 in λtI	−0.3	This work
pMS1	Point mutation in the λtI stem	−12.0	Montanez et al. 1986
M13mp8	Lac I′	—	Zinder and Boeke 1982

^*Stability was calculated considering that the stretch of uridines was forming a hybrid with the DNA strand.