The inside cover picture shows a mapping technique by Y. Taguchi, L. A. Hohsfield, G. S. Baron et al. (see p. 1597 ff.). Tetracysteine (TC) motifs bind fluorescent biarsenical dyes (FlAsH). Positions where FlAsH/TC insertion into PrP inhibits trypsin cleavage are detected by SDS-PAGE, thus localizing points of contact between PrP and trypsin. Thanks to Darrell Hurt (BCBB, NIAID) and Austin Athman for graphics assistance.