1. Developmental Therapeutics Branch and Laboratory of Molecular Pharmacology, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892, USA.
2. Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois, Rockford, IL 61107, USA.
3. Collaborative Protein Technology Resource, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
4. Advanced Imaging and Microscopy Resource, National Institute of Biomedical Imaging and Bioengineering, NIH, MD 20892, USA.