Electron Paramagnetic Resonance and Electron Spin Echo Studies of Co2+ Coordination by Nicotinamide Adenine Dinucleotide (NAD+) in Water Solution

• Published in: Applied magnetic resonance 2013-07, Vol.44 (7), p.817-826
• Main Authors: Hoffmann, Stanisław K., Goslar, Janina, Lijewski, Stefan
• Format: Article
• Language: English
• Subjects: Adenine; Adenosine; Atoms and Molecules in Strong Fields; Cobalt; Coordination; Electron paramagnetic resonance; Electron spin; Electrons; Enzymes; Fourier transforms; Hydrogen bonds; Laser Matter Interaction; Ligands; Low temperature; Magnetic fields; Nicotinamide; Nicotinamide adenine dinucleotide; Nitrogen atoms; Organic Chemistry; Oxygen; Phosphates; Physical Chemistry; Physics; Physics and Astronomy; Solid State Physics; Spectroscopy/Spectrometry; Spectrum analysis; Symmetry; Temperature
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-013-0444-z

Co 2+ 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(H 2 O) 6 complexes. EPR spin-Hamiltonian parameters of the Co/NAD + complex at 6 K are g z  = 2.01, g x  = 2.38, g y  = 3.06, A z  = 94 × 10 −4  cm −1 , A x  = 33 × 10 −4  cm −1 and A y  = 71 × 10 −4  cm −1 . They indicate the low-spin Co 2+ configuration with S  = 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, Co 2+ ion is coordinated in pseudo-tetrahedral geometry by four nitrogen atoms of adenine rings of two NAD + molecules.