- Symmetrical stabilization of bound Ca2+ ions in a cooperative pair of EF-hands through hydrogen bonding of coordinating water molecules in calbindin D(9k). Fast, J., Håkansson, M., Muranyi, A., Gippert, G.P., Thulin, E., Evenäs, J., Svensson, L.A., Linse, S. Biochemistry (2001)