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ANALYTICAL CURRENTS Affinity beads for drug receptors
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NH 2 H O NH 2 OH
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SGNEGDE beads O
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CH2CHCH2-O-(CH2)2OCH2CHCH2 O O
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Drug-fixed beads
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Preparation of drug-fixed latex beads. (Adapted with permission. Copyright 2000 Nature America.)
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drance. The latex bead is also designed with a small diameter, which maximizes the surface area; a hydrophilic surface to minimize nonspecific protein binding; and appropriate chemical stability to couple ligands in organic solvents. To demonstrate the method, the beads were coupled with an immunosuppressive drug in one experiment and an anti-inflammatory drug in another. During both experiments, the bead fished out binding proteins from cytoplasmic material, showing high binding efficiency. (Nature Biotechnol. 2000, 18, 877–881)
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Determining whether a candidate drug is worth pursuing is often a matter of knowing to which proteins it will bind. Hiroshi Handa and colleagues from the Tokyo Institute of Technology, Nihon University School of Medicine, Mitsubishi Chemical Corp., University of Tokyo, and Keio University (all in Japan) have developed a simple approach for identifying drug receptors on the basis of affinity purification. Their approach uses latex beads with the drug of interest bound to the surface, which then is used to capture the specific receptor protein. Like a collection of flagpoles, the latex beads are covered with a divalent epoxide spacer that distances the bound drug from the latex surface and reduces potential problems with steric hin-
High-throughput catalyst screening The multimillion-dollar catalytic gasprocessing industry has created a demand for new heterogeneous catalysts. Although combinatorial assays can produce large numbers of potential cata-
lysts, such methods typically produce too many candidates, creating the need for high-throughput screening methods. Edward S. Yeung and Hui Su of Iowa State University/Ames Laboratory have turned to laser-induced fluorescence imaging (LIFI) with micrometerscale spatial resolution and millisecond temporal resolution as an alternative to more traditional methods, such as IR thermography, for screening large numbers of potential catalysts. LIFI is capable of screening multiple arrays of catalyst formulations simultaneously, making it easier to determine the best combination of catalyst and reaction conditions. LIFI relies on the fact that the formation and destruction of chemical bonds Fluorescence imaging of reaction products (color added) on top of an array of vanadium pentoxide wells. change the fluorescent prop-
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erties of molecules. The region directly above the catalytic surface is simply irradiated with a laser, and the fluorescence intensity of a particular product or reactant is monitored using a CCD camera. In this way, the catalytic activity can be followed as a function of time and space. To demonstrate the technique, the researchers monitored the catalytic activity of vanadium pentoxide during the oxidation of napthalene to naphthoquinone, which is an important reaction in industry. In addition, they investigated differences in the S/N between LIFI and IR thermography for an array of vanadium pentoxide wells, which were 400 µm in diameter, 400-µm deep, and spaced 400-µm apart. During experiments conducted between 330 and 370 °C, lower temperatures favored LIFI, whereas temperatures >350 °C favored IR thermography. (J. Am. Chem. Soc. 2000, 122, 7422–7423)
