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Unformatted text preview: Fluorescent Probes for Chemical Transformations on the Single-Molecule Level G REGOR J UNG , A LEXANDER S CHMITT , M ICHAELA J ACOB , AND B ABETTE H INKELDEY Saarland University, Biophysical Chemistry, Saarbruecken, Germany We highlight our recent achievements in the design of fluorescent dyes for the investigation of chem- ical reactions on the single-molecule level. These fluorophores are tailored to undergo changes in their photophysical properties upon chemical transformations. Three examples are presented: electrophilic aromatic substitution, phosphoester cleavage, and oxidation of double-bonds. Thin- layer chromatography and fluorescence correlation spectroscopy are used to separate and char- acterize the different reaction products, respectively. We are planning to develop more fluorescent synthons which enable us to perform single-molecule chemistry of various reactions. Key words: single-molecule; fluorescence correlation spectroscopy; alkaline phosphatase; Bodipy; self-calibrating; high-throughput screening; dihydroxylation Introduction Synthetic chemical products have entered everyday life worldwide. Their industrial production with an annual conversion of hundreds of tons is founded on highly selective chemical reactions. For these efficien- cies to have become realized, mechanistic descriptions were elaborated in research laboratories by numerous stereochemical, thermodynamic, and kinetic investiga- tions. The essence of those efforts is a reaction mecha- nism in which a standard substrate molecule undergoes the transformation to the product molecule. Hence, chemists are destined to think on the level of single molecules, although the experiments they carry out are typically done with a huge number of molecules. Evi- dently, there is a concentration gap between perception and performance of chemistry which we would like to overcome. In the past three decades, researchers have made the observation of single molecules feasible. Scan- ning probe microscopies, patch-clamp techniques, and fluorescence-based techniques are widespread methods to follow the behavior and fate of indi- vidual molecules. Most versatile for the transfer to real chemistry might be fluorescence-based detec- tion schemes in combination with confocal microscopy. In this article, we present our efforts toward the visu- alization of chemical reactions on the single-molecule Address for correspondence: Gregor Jung, Saarland University, Bio- physical Chemistry, Campus, Building B2 2, Saarbruecken, DE 66123. email@example.com level by initially designing fluorescent probes for that purpose. Beyond its aesthetics (seeing is believing), study- ing reactions of individual molecules is expected to help in understanding side reactions. While bimolecu- lar reaction sequences are hardly synchronizable and, hence, reactive and short-living intermediates are of- ten hidden in ensemble investigations, such transient structures appear as fluorescing or dark species in...
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This note was uploaded on 07/11/2010 for the course SPECTOGRAP 545 taught by Professor Gdf during the Spring '10 term at AIB College of Business.
- Spring '10