title: Field- and temperature-dependent 13C NMR studies of the EDTA-Zn2+ complex: insight into structure and dynamics via relaxation measurements.
abstract: The relaxation rates for the three different carbon types in EDTA (carbonyl, CH2 central, and CH2 lateral) were measured with and without Zn(2+) 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; dipole-dipole) to the total relaxation rate for each carbon to be determined. Temperature studies allowed for determination of the activation energy (Ea) for the motions of each carbon type. The most surprising result was the observation that the τ(c) decreases significantly for the lateral carbon upon addition of Zn(2+) 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 τ(c) increases for the lateral carbon upon addition of Zn(2+) under strongly basic conditions.
authors.affiliation: Department of Chemistry, East Carolina University , Greenville, North Carolina 27858, United States.
authors.forename: Sriramya
authors.initials: S
authors.lastname: Garapati
authors.forename: Colin S
authors.initials: CS
authors.lastname: Burns
authors.forename: A A
authors.initials: AA
authors.lastname: Rodriguez