Coordination to Divalent Cations by Calcium-Binding Proteins
Fourier-transform infrared spectroscopy (FTIR) is a powerful tool for examining the metal coordination of the side chain COO− groups of Glu and Asp on Ca2+-binding proteins in solution. The behavior of COO− symmetric stretch can be investigated by using protein samples in H2O solution. However, it is difficult to obtain information about the behavior of the COO− antisymmetric stretch in H2O solution, because the COO− antisymmetric stretching band overlaps with the amide II band. Therefore, to obtain reliable infrared spectra in the region of COO− antisymmetric stretch, exchangeable protons in the protein should be completely deuterated by incubating the apoprotein dissolved in D2O under mild heating conditions.
Key wordsFTIR Coordination structure Carboxylate group Synthetic peptide analogue HD exchange
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