Lanthanide induced shifts by Lu3+, Yb3+, Tm3+, Er3+, Ho3+, and Dy3+ in NAcAsp (0.14 M in D2O, pH 5) are observed for ten magnetic sites (1H and 13C). The averaged binding constant for 1:1 complexes is 72 M−1 (for chloride solutions of ca. 0.05 M). Determination of the pseudo-contact geometrical factors (under axial symmetry approximation) requires taking into account a contact term and discarding the Tm3+ results. Data from the Asp residue are in agreement with 6 structures of this residue such that chelation occurs through the two carboxylates. Oβ−… Cα′ length seems to be the main factor while COOα− orientation is a minor one. The entire set of results is consistent with only three structures where the nitrogen atom is far from the carboxylates, and the Cα—N rotamers have extended conformations. Three oxygen atoms (two from the COOβ− group) appear to be involved in the chelation. However, the data do not exclude another minor conformational species.