title: Electron Paramagnetic Resonance and Electron Spin Echo Studies of Co2+Coordination by Nicotinamide Adenine Dinucleotide (NAD+) in Water Solution.
abstract: Co2+binding to the nicotinamide adenine dinucleotide (NAD+) molecule in water solution was studied by electron paramagnetic resonance (EPR) and electron spin echo at low temperatures. Cobalt is coordinated by NAD+when the metal is in excess only, but even in such conditions, the Co/NAD+complexes coexist with Co(H2O)6complexes. EPR spin-Hamiltonian parameters of the Co/NAD+complex at 6 K aregz= 2.01,gx= 2.38,gy= 3.06,Az= 94 × 10-4cm-1,Ax= 33 × 10-4cm-1andAy= 71 × 10-4cm-1. They indicate the low-spin Co2+configuration withS= 1/2. Electron spin echo envelope modulation spectroscopy with Fourier transform of the modulated spin echo decay shows a strong coordination by nitrogen atoms and excludes the coordination by phosphate and/or amide groups. Thus, Co2+ion is coordinated in pseudo-tetrahedral geometry by four nitrogen atoms of adenine rings of two NAD+molecules.
authors.affiliation: Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, Poland.
authors.forename: Stanisław K
authors.initials: SK
authors.lastname: Hoffmann
authors.forename: Janina
authors.initials: J
authors.lastname: Goslar
authors.forename: Stefan
authors.initials: S
authors.lastname: Lijewski