PMC

(A) Key silicone features of the A160 valve. (B) Normal diaphragm and distorted diaphragm with loss of elasticity and blister. Effect on O-ring after absorbing moisture and losing elasticity. (C) Valve with normal function. (D) Valve with gap in seal, allowing continuous flow.

Assays of triR-lacZ expression in various mutants. Expression of triR was assayed using pIJ7878 (triR-lacZ) introduced into the wild-type strain A34 (filled diamonds), the rhiR mutant A160 (filled squares), the bisR mutant A549 (open squares), the triR mutant A627 (filled triangles), and the cinI mutant A664 (open triangles). OD₆₀₀s measured using strain A34 are represented by open diamonds, and the growth rates of all the strains were similar.

Expression of rhiI-lacZ and rhiA-lacZ. The expression of rhiI-lacZ (pIJ7794) (A) or rhiA-lacZ (pIJ1769) (B) was analyzed by measuring β-galactosidase throughout growth of strains A34 (wild type), 8401 (strain A34 lacking pRL1JI), A160 (rhiR1::Tn5), and A721 (rhiI15::Tn5). The growth curves (OD₆₀₀) shown as broken lines correspond to those obtained with A34/pIJ7794 or A34/pIJ1769; the growth of the other strains was very similar. LSD, least significant difference.

Base triples, annotated using the symbols of Leontis and Westhof (13). (A) Minor groove AGC triple, from entry 1jj2. A2291 and G2289 form a trans Watson–Crick/Sugar Edge pair; G2289 and C2281 are Watson–Crick paired. A2291 is the least-paired base, base N, because of the Watson–Crick pair between G2289 and C2281. The G2289–C2281 pair is base pair N–1 because base A2291 lies in the minor groove. (B) S-turn GUA triple, from entry 1jj2. U176 and G175 form a cis Hoogsteen/Sugar Edge pair; U176 and A160 form a trans Watson–Crick/Hoogsteen pair. G175 is the least-paired base, base N, because there is only one hydrogen bond in the G175·U176 pair, while there are two hydrogen bonds in the U176·A160 pair. The U176·A160 pair is base pair N+1 because base G175 lies in the major groove. (C) Symmetric triple from entry 1j5e. A411 and A430 form a trans Watson–Crick/Hoogsteen pair, as do A430 and A414. Here it is difficult to identify a least-paired base, since the A411·A430 and A430·A414 pairs both involve two hydrogen bonds and no two bases form a Watson–Crick/Watson–Crick pair.