. Author manuscript; available in PMC: 2009 Jun 1.

Published in final edited form as: Chem Res Toxicol. 2008 May 22;21(6):1295–1303. doi: 10.1021/tx800059j

Table 1.

Spectral constants and relative binding efficiencies for PCB 136 atropisomers with mouse hepatic microsomal P450 enzymes^a

Spectral parameter	(+)-PCB 136	(-)-PCB 136	(±)-PCB 136
Hepatic microsomes from NF-treated mice^b
ΔA_max (absorbance unit/nmol P450)	0.011	0.005	0.008
K_s^app (μM)	9.2	2.9	4.2
ΔA_max/K_s^app (absorbance unit/nmol P450/M)	1200	1900	2000
Hepatic microsomes from PB-treated mice^c
ΔA_max (absorbance unit/nmol P450)	0.028 ± 0.002	0.020 ± 0.002	0.027 ± 0.001
K_s^app (μM)	8.2 ± 0.70	5.6 ± 1.0	7.0 ± 0.60
ΔA_max/K_s^app (absorbance unit/nmol P450/M)	3500 ± 450	3800 ± 480	3900 ± 430
Hepatic microsomes from DEX-treated mice^c
ΔA_max (absorbance unit/nmol P450)	0.026 ± 0.001	0.017 ± 0.001	0.020 ± 0.001
K_s^app (μM)	24 ± 5.4	7.6 ± 1.4	12 ± 2.8
ΔA_max/K_s^app (absorbance unit/nmol P450/M)	1200 ± 240	2400 ± 450	1800 ± 380
Hepatic microsomes from CO-treated mice^b
ΔA_max (absorbance unit/nmol P450)	0.012	0.010	0.012
K_s^app (μM)	9.7	21	10
ΔA_max/K_s^app (absorbance unit/nmol P450/M)	1200	450	1200

Maximal absorbance change (ΔA_max), apparent spectral dissociation constant (K_s^app) and relative binding efficiency (ΔA_max/K_s^app) values were obtained for hepatic microsomes prepared from NF, PB, DEX and CO-treated female mice as described in Experimental Procedures.

Single measurement.

Mean ± SE of three determinations.