The relaxation rates for the three different carbon types in EDTA (carbonyl, CH2 central, and CH2 lateral) were measured with and without Zn2+ as a function of field strength and temperature. The use of different field strengths in combination with NOE measurements allowed for the contribution of each relaxation mechanism (chemical shift anisotropy; spin rotation; dipoledipole) to the total relaxation rate for each carbon to be determined. Temperature studies allowed for determination of the activation energy (E-a) for the motions of each carbon type. The most surprising result was the observation that the tc decreases significantly for the lateral carbon upon addition of Zn2+ at neutral pH, going from 54 to 8.6 ps at 298 K. This appears to be a pH-dependent phenomenon as other reports indicate that tau(c) increases for the lateral carbon upon addition of Zn2+ under strongly basic conditions.