Connolly Molecular Surface Area (CMA, the contact surface created when a probe

sphere (radius = 1.4 A+, the size of H20), representing the solvent, is rolled over the

molecular shape), the Connolly Solvent-Excluded Volume (CSV, the volume contained

within the contact molecular surface, or that volume of space that the probe is excluded

from by collisions with the atoms of the molecule), the ovality (the ratio of the Molecular

Surface Area to the Minimum Surface Area, which is the surface area of a sphere having

a volume equal to CSV of the molecule), and dihedral angle (the angle formed between

the planes of the two rings, which is related to the extent of coplanarity of the molecule).

ACD/ILab software (Advanced Chemistry Development, Ontario, Canada) was used to

predict log P, log D (at pH 7.0), and the pKa (of the phenolic group).

 Kinetic analysis. Duplicate values were employed for the rate of conjugate

formation at each substrate concentration to calculate kinetic parameters using Prism v4.0

(GraphPad Software, Inc., San Diego, CA). Equations used to fit the data were the

Michaelis-Menten hyperbola for one-site binding and the Hill plot for positive

cooperativity.

 Results

 The kinetics for UDPGA were analyzed for the glucuronidation of three

representative OH-PCBs (Table 4-1). Saturating concentrations of UDPGA were higher

in liver than in intestine (Figure 4-2). The glucuronidation of most of the OH-PCBs tested

followed Michaelis-Menten kinetics (Figure 4-3A). In the case of the glucuronidation of

4'OHCB35 by liver and 4'OHCBll2 by proximal intestine, the data fitted the Hill plot

(Figure 4-3B).