Small Molecule Probes For Redox Events In Living Cells

The fluorescence-based assays have been developed quickly in recent years due to their easy handling, high sensitivity, and non-destructiveness to samples. A large number of fluorescent probes are widely used for measurement of diverse biological molecules, such as enzymes, reactive oxygen/nitrogen species, cations, and anions. To explore the cellular redox events, we designed and synthesized a series of fluorescent probes based on naphthalimide,8-aminoquinoline or coumarin scaffold, and applied them in detection of thioredoxin reductase （TrxR）, Zn²⁺, H2S, and glutathione （GSH）. All fluorescent probes can be performed in living cells with high sensitivity and selectivity. The results are summarized as follows:Chapter 1. A general introduction of flurescence probes was presented, and the recent development of probes for Zn²⁺, H2S, and various enzymes were reviewed.Chapter 2. The naphthalimide-based fluorescence probes, NSS-1, NSS-2, and NSS-3, were rationally designed and synthesized for thioredoxin reductase. It was demonstrated that NSS-1 could be selectively triggered on by TrxR both in vitro and in living cells.Chapter 3. The carboxamidoquinoline-based fluorescent Zn²⁺ probes, BEAQA and PMQA, were designed and synthesized. Both ligand could selectively recognize Zn²⁺over other tested cations. Furthermore, BEAQA and PMQA were successfully applied in imaging Zn²⁺ in living cells. Interestingly, PMQA displays totally different binding mode toward Zn²⁺ and Cu²⁺, which might be informative for designing novel selective zinc probes without suffering from the copper interference.Chapter 4. Diethyl 2,2’-（2-oxo-2-（quinolin-8-ylamino）ethylazanediyl）diacetate （DOQED）, an aminoquinoline-based fluorescent probe, was synthesized, and successfully applied in detection of Cu²⁺ and S22- in aqueous buffered solution. The emission signal of DOQED was selectively quenched by Cu²⁺, and was exclusively recovered by subsequent addition of S2-. Thus, The DOQED-Cu²⁺ complex might be a potential turn-on probe for H2S, a biological signaling molecule.Chapter 5. A series of compounds containing sulfoxide scaffold was synthesized and characterized. Preliminary results reveal compound CNBF-SO-Me responds to biothiols, such as GSH, cysteine, and homocysteine, quickly but with poor selectivity, while compound Nap-SO-Me shows fairly good selectivity towards GSH and was successfully applied in imaging GSH in living cells.