Dr. Brent's team is seeking to identify and study proteins that control functions such as self-renewal, differentiation and senescence in mammalian embryonic stem cells. They are using peptide aptamer technology, which employs synthetic molecules that narrowly target proteins. This project involved constructing a set of lentiviral vectors, derived from HIV, to deliver and express libraries of peptide aptamers inside mouse and human embryonic stem cells. The researchers planned to test this system in mouse cells at The Molecular Sciences Institute and in human cells at the lab of Dr. Brent's collaborator, Dr. James Thomson at the University of Wisconsin. They will be looking for embryonic stem cells that exhibit "interesting" phenotypes, Dr. Brent said, particularly those that show self-renewal. After determining that aptamers caused the observed phenotype, they will try to identify the proteins that interacted with the aptamers to produce that effect. Much of the work supported by this award was for technology development, providing new tools for delving into the intricacies of the cell's lifespan.