Frank N. Chang
Office: Department of Biology
301 Bio-Life Building
Phone: (215) 204-8843
Even though the human genome contains only about 22,000 genes, but due to post-translational modifications and differential mRNA splicing, the total number of distinct proteins is likely close to one million. This level of complexity presents unique challenges in terms of separation techniques. In particular, hydrophobic proteins such as integral membrane proteins that play important roles in signal transduction and other biological processes are difficult to characterize by currently available analytical approaches. Proteomic profiles generated from two-dimensional gel electrophoresis are known to lack highly hydrophobic proteins. Additionally, proteins also form complexes with their partners and such protein-protein interactions are critical not only to biological functions but also disease progression. It has been estimated that 650,000 protein-protein interactions exist in humans and at present only less than 0.3% of the interactions among human proteins are identified. Current methods for detecting protein interactions such as co-immunoprecipitation, pull-down assays, tandem affinity purification or yeast two-hybrid screen are inadequate. A new approach that can directly isolate protein complexes without relying on tags or other manipulations is required. To address this need, my laboratory has developed a novel electrophoretic method employing protein-blotting membrane as a supporting matrix rather than using polyacrylamide gel. By carrying electrophoresis directly on PVDF membrane we have eliminated both 2-D polyacrylamide gel electrophoresis and subsequent blotting steps. Both proteins (such as hydrophobic proteins) and their complexes are separated into distinct spots. Using this method we have identified serum markers associated with different stages of breast cancer. Markers for other cancers are also discovered.
Chang FN, Yonan CR. System and methods for electrophoretic separation of proteins on protein binding membranes. U.S Patent 7,326,326, (2008).
Ma, B and F.N. Chang. Purification and cloning of a Delta class glutathione S-transferase displaying high peroxidase activity isolated from the German cockroach Blattella germanica. FEBS Journal 274:1793-1803, (2007).