AL
components fi t together and then click into the ANSI-standard plate perimeter. This design can be used to avoid edge eff ects in cell culture, or to isolate reagents and waste.
Consistent measurement of cell confluence is essential to cell culture QC and signal nor- malization. Tecan introduced the Spark20M microplate reader for label-free cell-analysis imaging for cell counting and viability analysis, especially during long run assays. Spark software enables the scientist to count specific locations or regions in the well with either kinetic or endpoint modes. Since it is label-free, complications from labels and transfection are avoided.
Second harmonic generation Small-molecule drugs can change the higher
order structure of target proteins. Biodesy, Inc. (South San Francisco, Calif.) introduced a second harmonic generation (SHG) platform that measures ligand-induced conformational changes. Biodesy explained that SGH arises when a protein receptor is covalently labeled with a fl uorescent dye via an amine or thiol linker. The protein is tethered to a lipid bi- layer on a detection cell via a histamine tag. The dyes generate second harmonic light when illuminated with a femtosecond laser. Fluorescence intensity is a strong function of the average angular orientation of the dye. Even sub-Angstrom shifts produce a detect- able signal change. SHG is insensitive to mass or primary structure. Biodesy reported that SHG is suitable for testing potential ligands, including antibody/antigen interactions.
Dr. Charles Wartchow of the Novartis Institutes for Biomedical Research (Cambridge, Mass.) evaluated the SHG platform for binding pep- tide and protein fragments. Wartchow pointed out that the SHG is different from more tradi- tional binding assays such as surface plasmon resonance (SPR), since the binding must involve a change in the conformation of the target. Wartchow and colleagues were interested in evaluating drug libraries, and thought that the SHG-sensitive conforma- tional change could be related to a possible mechanism of action (MOA). In a blinded study, results obtained for SHG were compared with
2-D nuclear magnetic resonance (NMR) and X-ray crystallography. A Venn diagram of three overlapping circles (one each for SHG, NMR and X-ray) had significant numbers in all regions, which suggests that each technique is complementary and useful in lead discovery. Wartchow concluded that SHG is useful in screening fragments with therapeutic targets that induce conformational change.
SLAS2017 will be held February 4–8 at the Walter E. Washington Convention Center in Washington, D.C. Monitor
www.SLAS2017.org for the latest information.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail:
rlsteven@yahoo.com
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AMERICAN LABORATORY 19 APRIL 2016
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