Table 1.

in vitro thermodynamic parameters for the binding of different hydrocarbons to TodS and their capacity to induce expression from P_todX in vivo

Compound	Binding parameters to TodS in vitro		β-Gal expression, Miller units
	KD, μM	ΔH, kcal/mol
Benzene and singly substituted benzene derivatives
Benzene	0.76 ± 0.1	−11.0 ± 0.2	79 ± 3*
Toluene	0.69 ± 0.1	−5.5 ± 0.1	333 ± 55*
Ethylbenzene	3.1 ± 0.1	−3.6 ± 0.1	15 ± 2*
Propylbenzene	18 ± 2	−2.7 ± 0.4	2 ± 1*
Butylbenzene	81 ± 4	−5.4 ± 0.1	2 ± 1*
Styrene	0.58 ± 0.1	−12.4 ± 0.3	129 ± 42*
Nitrobenzene	6.6 ± 0.1	−7.3 ± 0.9	141 ± 20*
Chlorobenzene	1.2 ± 0.1	−9.9 ± 0.4	92 ± 5*
Fluorobenzene	1.2 ± 0.1	−5.3 ± 0.1	111 ± 22
Disubstituted benzene derivatives
o-Xylene	0.58 ± 0.1	−9.4 ± 0.1	2 ± 1*
m-Xylene	1.2 ± 0.1	−9.0 ± 0.1	34 ± 2*
p-Xylene	0.76 ± 0.1	−10.1 ± 0.1	88 ± 18*
o-Chlorotoluene	0.73 ± 0.1	−6.7 ± 0.2	2 ± 1†
m-Chlorotoluene	8.3 ± 0.1	−11.0 ± 2	186 ± 12*
p-Chlorotoluene	0.29 ± 0.1	−8.9 ± 0.1	146 ± 32*
o-Toluidine	3.2 ± 0.2	−28.7 ± 2.5	17 ± 4*
m-Toluidine	8.6 ± 0.7	−7.3 ± 0.8	52 ± 16*
p-Toluidine	11 ± 1	−20.7 ± 3	63 ± 14*
Catechol	16 ± 4	−1.6 ± 0.6	13 ± 2
TMB isomers
1,2,3-TMB	0.58 ± 0.1	−4.2 ± 0.1	0*
1,2,4-TMB	1.9 ± 0.2	−2.6 ± 0.1	0*
1,3,5-TMB	133 ± 20	−3.2 ± 1.6	0*
Biaromatics
1-naphthol	2.1 ± 0.1	−12.4 ± 0,3	0
2,3-dihydroxynaphthalene	7.5 ± 0.3	−15.1 ± 0.3	0

*Data were initially reported in ref. 13.

^†No binding to TodS or transcription stimulation was observed for 1-hexanol, cyclohexane, benzamide, benzoate, anthracene, or naringenine.