A water soluble calcium-sodium based coordination polymer: selective release of calcium at specific binding sites on proteinsElectronic supplementary information (ESI) available: Detailed experimental procedures include synthesis, crystallographic data, bond lengths, bond angle data, MALDI-TOF mass spectrum, NMR spectra, UV-vis and emission spectra of Ca/Na-1, comparison of M-crystallin titration using Ca/Na-1 and CaCl2 as the titrant, and thermodynamic parameters of M-crystallin-Ca/Na-1 complex

A calcium-sodium based water soluble coordination complex [{Ca 4 Na(EGTA) 2 (H 2 O) 13 } n ·NO 3 ] (EGTA = ethylene bis(oxyethylenenitrilo)tetraaceticacid), henceforth named Ca/Na-1, has been synthesized hydrothermally and characterized using spectroscopic and single crystal X-ray diffraction techniques. Single crystal X-ray diffraction of the assembly affirms a two dimensional self assembled net-like supramolecular structure. The complex serves as a biological mimic of a calcium buffer and dispenses felicitous amounts of Ca 2+ ions at the binding sites on proteins, as shown by SEM imaging and MALDI-TOF spectroscopy. The thermodynamics of binding has also been measured by isothermal titration calorimetry. Protein conformational changes have been characterized by NMR spectroscopy. A calcium-sodium based water soluble coordination complex, [{Ca 4 Na(EGTA) 2 (H 2 O) 13 } n ·NO 3 ] (EGTA = ethylene bis(oxyethylenenitrilo)tetraaceticacid), has been synthesized hydrothermally and characterized using spectroscopic and single crystal X-ray diffraction techniques.