AMP and p-OH-METH binding.

<p>(a) Electron density of the ligands: Left panel: A view showing the electron density (2Fo-Fc) of AMP. Right panel: A 2Fo-Fc map of p-OH-METH. The contours are drawn at 1.2 σ level. (b) A comparison of the binding modes of the two metabolites with METH. Left panel: A superposition of AMP (pink) with METH (blue). The antibody binds both AMP and METH in a similar manner, but there is a shift in the position of the nitrogen atom which forms hydrogen bonds with Glu H101 of the V_H chain and His H89 of the V_L chain. The hydrogen bond distances indicate that in the AMP structure they are much weaker. Right panel: p-OH-METH: The geometry of the binding pocket is the same in the METH structure and the hydrogen bonds are of comparable strength as in the METH structure.