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Figure 2.
Fig. 2. Electrostatic and shape complementarity of the hapten 1
in (A) the EP2-25C10 and (B) the EP2-19G2 antibody-combining
site. Slices through the center of the binding sites are shown.
The heavy and light chains are colored in blue and green,
respectively. The electrostatic potential was calculated in APBS
(30) and mapped onto the surface with the color code ranging
from –30 kT/e (bright red) to +30 kT/e (dark blue). Both
binding pockets are highly apolar, but strongly differ in their
depth and penetration of the variable antibody domain. (C)
Crystal structure of purple-fluorescent antibody EP2-25C10 in
complex with 1 (yellow). The 2F[o] – F[c] electron density map
around hapten 1 is contoured at 1.5  . (D) Crystal
structure of the blue-emissive antibody EP2-19G2 in complex with
1 (yellow) (4). Trp^H103 undergoes parallel  -stacking with 1 and
forms a charge-transfer complex in the excited state. In
contrast, stilbene 1 in EP2-25C10 does not engage in any -stacking
interactions with tryptophan.
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