Synthesis and design of fluorescence ligands to act as sensor for zinc

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Wei Gan (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Robert Hancock

Abstract: Design and synthesis of ligands to detect low concentrations of Zn2+ in various systems are being explored worldwide. The purpose of this research is to synthesize and study fluorescent sensors for Zn2+ in nervous system by utilizing CHEF (Chelation Enhanced Fluorescence) effect. TQA, a known compound, was synthesized and characterized. It is small and hydrophobic, which may allow it to cross the blood-brain barrier. The quinolyl groups provide good fluorescent properties. Ni2+, Cu2+, Cd2+, Pb2+ were selected to compare the selectivity of the designed ligand for Zn2+. It was shown that TQA does have CHEF effect with Zn 2+ and Cd2+ (of which Zn2+-ligand complex is 10 times stronger in terms of fluorescence intensity) and has no CHEF effect with Ni2+, Cu2+, Pb2+. The drawback of TQA is that its solubility in water is too low (only 10-5 M in 50% methanol/water) to test its pKa and formation constants with metals ions above. DQPMA, also a known compound, and DQPEA were synthesized and characterized to improve the selectivity and solubility of sensors. Three aspects characterizing the ligands were explored in this work. Crystals of Zn2+- DQPEA and Cd2+-DQPEA were grown and their crystal structures were determined. The pKa’s of DQPMA and DQPEA were then determined by potentiometry and NMR. Finally, the formation constants of DQPMA and DQPEA with the metal ions above were determined by polarography and fluorescence techniques. It was proved in this study that the selectivities of the sensors, DQPMA and DQPEA, for small metal ions such as Zn2+ over big metal ions such as Cd2+do increase when one of chelate ring increases from the five membered (Zn2+-DQPMA) to the six membered (Zn2+-DQPEA).

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Ligands (Biochemistry), Ligands--Synthesis, Zinc--Research
Zinc -- Research
Ligands (Biochemistry)
Ligands -- Synthesis

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