Developing an optical chemosensor for phosphate anions Nearly all aspects of cell life are regulated by reversible protein phosphorylation.  The attachment and removal of a phosphate group from a protein can have profound effects on the protein's activities and properties.  If an optical chemosensor can be constructed for detection of phosphate ions, we will have another tool with which to study cellular mechanics.  Towards this end we have prepared a series of fluorescein derivatives (1-4) functionalized with polyamines via amide linkages.  These are purified by semi-preparative HPLC, characterized by NMR and MS, and tested for phosphate activity using UV-vis absorbance and fluorescence emission spectroscopy.