Abstract: Preparation of 13C/15N-labeled DNA oligomers using the polymerase chain reaction (PCR). A PCR based method for uniform (13C/15N)-labeling of DNA duplexes is described. Multiple copies of a blunt-ended duplex are cloned into a plasmid, each copy containing the sequence of interest and restriction Hinc II sequences at both the 5′ and 3′ ends. PCR using bi-directional primers and uniformly 13C/15N-labeled dNTP precursors generates labeled DNA duplexes containing multiple copies of the sequence of interest. Twenty-four cycles of PCR, followed by restriction and purification, gave the uniformly 13C/15N-labeled duplex sequence with a 30% yield. Such labeled duplexes find significant applications in multinuclear magnetic resonance spectroscopy.

Abstract: A G.sub.1 phase kinase inhibitor is applied in a low concentration to a population of normal and transformed mammalian cells. The concentration of G.sub.1 phase kinase inhibitor is selected to reversibly arrest normal mammalian cells in the G.sub.1 cell cycle without arresting growth of transformed cells. The transformed cells may then be selectively identified and/or cloned for research or diagnostic purposes. The transformed cells may also be selectively killed by therapeutic agents that do not affect normal cells in the G.sub.1 phase, suggesting that such G.sub.1 phase kinase inhibitors may form an effective adjuvant for use with chemotherapeutic agents in cancer therapy for optimizing the killing dose of chemotherapeutic agents while minimizing undesirable side effects on normal cells.