General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Two fluorescent probes, m-PSP and p-PSP, for sulfite and/or sulfide were constructed by connecting a pyridinium ion to a coumarin fluorophore through an a,b-unsaturated ketone. The presence of the pyridinium salt promoted the nucleophilic addition of sulfite and sulfide to the a,b-unsaturated ketone, which could be visualized by dramatic changes in the solution's color and fluorescence intensity. Both probes exhibit good selectivity (the selectivity coefficients toward major interferences are less than 0.07) and high sensitivity for sulfite and sulfide over biothiols and other potential analytes. The detection limits of m-PSP for the analysis of sulfite and sulfide are calculated to 8.5 Â 10 À7 M and 2.7 Â 10 À7 M, respectively. Living cell imaging results indicate that both probes can be applied in biological systems.

Two fluorescent probes STP1–2 for GSH and mercapto-containing proteins were designed. Both probes have potential application in fluorescence imaging of GSH within living cells.