---

Biochip Assays and Discovery of Small Molecule Inhibitors

The surface chemistries we have developed for modeling ECM offer important benefits to biochip research. The use of inert surfaces, the development of a range of well-controlled methods for immobilizing biomolecules and our recent development of mass spectrometry methods for identifying interactions on the biochips have combined to give a system that is applicable to a broad range of bioassays.63, 90 This approach allows the label-free and chip-based determination of kinase, protease, methyltransferase, glycosyltransferase and other enzyme activities.67, 84, 92 Further, these assays can be adopted for high throughput screening for the purpose of developing reagents for use in chemical biology. We have reported inhibitors of the two anthrax toxins, lethal factor and edema factor.82, 87

Figure 5.  Examples of enzyme assays on SAMs using MALDI MS as the detection method. (A) A carbohydrate immobilized to a SAM is glycosylated with a galactosyltransferase and subsequently deglycosylated with a glycosidase. (B) MALDI MS spectrum of the monosaccharide-tethered SAM shown in A. (C) MALDI MS spectrum of the SAM after the glycosylation reaction. The increase in m/z value corresponds to the addition of galactose. (D) Src tyrosine kinase phosphorylates the immobilized peptide substrate. The modification is apparent by the 80 dalton increase in molecular weight corresponding to phosphate incorporation. (E) A similar example, but instead using the serine/threonine kinase PKA.

---