Building and Testing of a MUHEG Capped Quantum Dot Lead Biosensor Specific Against Mercury Quenching
Gerlach, Gary F., II
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Lead the believed oldest known metal presents many problems when introduced into the body. The toxicity of lead arises from its ability to mimic other biologically important metals. Despite the prevalence of lead toxicity and available resources many fundamental questions about the biochemical processes responsible for lead toxicity remain unanswered. Towards this aim a biosensor was designed and constructed to detect subcellular distribution of lead ion. Biosensors have recently emerged as analytical devices that couple a biomolecular recognition event with a physicochemical detection element providing analyte detection. The functional specific design of metalloproteins was selected to represent the backbone reporter element of the biosensor. Optical physicochemical detection was emitted from quantum dots and measured through fluorescence spectroscopy. The selectively designed lead-binding metalloprotein (PbBP) was modified with a redox active ruthenium(II) metal complex at its amino-terminus. When lead ion is bound to PbBP a conformational change results, allowing the metal complex to donate an electron to the quantum dot attached at the carboxyl-terminus. The electron transferred to the quantum dot decreases the fluorescence emitted, supplying a measurable response known as the quench to be analyzed. Previous experiments have seen an undesirable 90 % quenching responses due to mercury ion presence. In addressing this problem a novel (l-Mercaptoundec-ll-yl)hexa(ethylene glycol) quantum dot capping group (MUHEG) replaced the previously used metallothionein capping group, and rectified the quenched response by ten fold.